diff --git a/README.md b/README.md
index d21e558360c..053d036411e 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 [![Build Status](https://travis-ci.org/Microsoft/TypeScript.svg?branch=master)](https://travis-ci.org/Microsoft/TypeScript)
 [![npm version](https://badge.fury.io/js/typescript.svg)](https://www.npmjs.com/package/typescript)
-[![Downloads](https://img.shields.io/npm/dm/TypeScript.svg)](https://www.npmjs.com/package/typescript)
+[![Downloads](https://img.shields.io/npm/dm/typescript.svg)](https://www.npmjs.com/package/typescript)
 
 # TypeScript
 
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index b2ad2151bb6..27b3067278c 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -1414,6 +1414,7 @@ namespace ts {
                     if (isObjectLiteralOrClassExpressionMethod(node)) {
                         return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike | ContainerFlags.IsObjectLiteralOrClassExpressionMethod;
                     }
+                    // falls through
                 case SyntaxKind.Constructor:
                 case SyntaxKind.FunctionDeclaration:
                 case SyntaxKind.MethodSignature:
@@ -1715,7 +1716,7 @@ namespace ts {
                         declareModuleMember(node, symbolFlags, symbolExcludes);
                         break;
                     }
-                // fall through.
+                    // falls through
                 default:
                     if (!blockScopeContainer.locals) {
                         blockScopeContainer.locals = createMap<Symbol>();
@@ -2009,6 +2010,7 @@ namespace ts {
                         bindBlockScopedDeclaration(<Declaration>parentNode, SymbolFlags.TypeAlias, SymbolFlags.TypeAliasExcludes);
                         break;
                     }
+                    // falls through
                 case SyntaxKind.ThisKeyword:
                     if (currentFlow && (isExpression(node) || parent.kind === SyntaxKind.ShorthandPropertyAssignment)) {
                         node.flowNode = currentFlow;
@@ -2184,7 +2186,7 @@ namespace ts {
                     if (!isFunctionLike(node.parent)) {
                         return;
                     }
-                    // Fall through
+                    // falls through
                 case SyntaxKind.ModuleBlock:
                     return updateStrictModeStatementList((<Block | ModuleBlock>node).statements);
             }
@@ -2401,7 +2403,7 @@ namespace ts {
         }
 
         function lookupSymbolForName(name: string) {
-            return (container.symbol && container.symbol.exports && container.symbol.exports.get(name)) || container.locals.get(name);
+            return (container.symbol && container.symbol.exports && container.symbol.exports.get(name)) || (container.locals && container.locals.get(name));
         }
 
         function bindPropertyAssignment(functionName: string, propertyAccessExpression: PropertyAccessExpression, isPrototypeProperty: boolean) {
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 37de59ce195..0447e42ed64 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -349,7 +349,7 @@ namespace ts {
             TypeofNEHostObject = 1 << 13, // typeof x !== "xxx"
             EQUndefined = 1 << 14,        // x === undefined
             EQNull = 1 << 15,             // x === null
-            EQUndefinedOrNull = 1 << 16,  // x == undefined / x == null
+            EQUndefinedOrNull = 1 << 16,  // x === undefined / x === null
             NEUndefined = 1 << 17,        // x !== undefined
             NENull = 1 << 18,             // x !== null
             NEUndefinedOrNull = 1 << 19,  // x != undefined / x != null
@@ -727,7 +727,7 @@ namespace ts {
             if (declarationFile !== useFile) {
                 if ((modulekind && (declarationFile.externalModuleIndicator || useFile.externalModuleIndicator)) ||
                     (!compilerOptions.outFile && !compilerOptions.out)) {
-                    // nodes are in different files and order cannot be determines
+                    // nodes are in different files and order cannot be determined
                     return true;
                 }
                 // declaration is after usage
@@ -745,7 +745,7 @@ namespace ts {
                     // still might be illegal if declaration and usage are both binding elements (eg var [a = b, b = b] = [1, 2])
                     const errorBindingElement = getAncestor(usage, SyntaxKind.BindingElement) as BindingElement;
                     if (errorBindingElement) {
-                        return getAncestorBindingPattern(errorBindingElement) !== getAncestorBindingPattern(declaration) ||
+                        return findAncestor(errorBindingElement, isBindingElement) !== findAncestor(declaration, isBindingElement) ||
                             declaration.pos < errorBindingElement.pos;
                     }
                     // or it might be illegal if usage happens before parent variable is declared (eg var [a] = a)
@@ -760,11 +760,19 @@ namespace ts {
 
 
             // declaration is after usage, but it can still be legal if usage is deferred:
-            // 1. inside a function
-            // 2. inside an instance property initializer, a reference to a non-instance property
-            // 3. inside a static property initializer, a reference to a static method in the same class
+            // 1. inside an export specifier
+            // 2. inside a function
+            // 3. inside an instance property initializer, a reference to a non-instance property
+            // 4. inside a static property initializer, a reference to a static method in the same class
+            // or if usage is in a type context:
+            // 1. inside a type query (typeof in type position)
+            if (usage.parent.kind === SyntaxKind.ExportSpecifier) {
+                // export specifiers do not use the variable, they only make it available for use
+                return true;
+            }
+
             const container = getEnclosingBlockScopeContainer(declaration);
-            return isUsedInFunctionOrInstanceProperty(usage, declaration, container);
+            return isInTypeQuery(usage) || isUsedInFunctionOrInstanceProperty(usage, declaration, container);
 
             function isImmediatelyUsedInInitializerOfBlockScopedVariable(declaration: VariableDeclaration, usage: Node): boolean {
                 const container = getEnclosingBlockScopeContainer(declaration);
@@ -794,12 +802,10 @@ namespace ts {
             }
 
             function isUsedInFunctionOrInstanceProperty(usage: Node, declaration: Node, container?: Node): boolean {
-                let current = usage;
-                while (current) {
+                return !!findAncestor(usage, current => {
                     if (current === container) {
-                        return false;
+                        return "quit";
                     }
-
                     if (isFunctionLike(current)) {
                         return true;
                     }
@@ -821,20 +827,7 @@ namespace ts {
                             }
                         }
                     }
-
-                    current = current.parent;
-                }
-                return false;
-            }
-
-            function getAncestorBindingPattern(node: Node): BindingPattern {
-                while (node) {
-                    if (isBindingPattern(node)) {
-                        return node;
-                    }
-                    node = node.parent;
-                }
-                return undefined;
+                });
             }
         }
 
@@ -896,6 +889,7 @@ namespace ts {
                     case SyntaxKind.SourceFile:
                         if (!isExternalOrCommonJsModule(<SourceFile>location)) break;
                         isInExternalModule = true;
+                        // falls through
                     case SyntaxKind.ModuleDeclaration:
                         const moduleExports = getSymbolOfNode(location).exports;
                         if (location.kind === SyntaxKind.SourceFile || isAmbientModule(location)) {
@@ -1256,15 +1250,7 @@ namespace ts {
          * Return false if 'stopAt' node is reached or isFunctionLike(current) === true.
          */
         function isSameScopeDescendentOf(initial: Node, parent: Node, stopAt: Node): boolean {
-            if (!parent) {
-                return false;
-            }
-            for (let current = initial; current && current !== stopAt && !isFunctionLike(current); current = current.parent) {
-                if (current === parent) {
-                    return true;
-                }
-            }
-            return false;
+            return parent && !!findAncestor(initial, n => n === stopAt || isFunctionLike(n) ? "quit" : n === parent);
         }
 
         function getAnyImportSyntax(node: Node): AnyImportSyntax {
@@ -1273,10 +1259,7 @@ namespace ts {
                     return <ImportEqualsDeclaration>node;
                 }
 
-                while (node && node.kind !== SyntaxKind.ImportDeclaration) {
-                    node = node.parent;
-                }
-                return <ImportDeclaration>node;
+                return findAncestor(node, n => n.kind === SyntaxKind.ImportDeclaration) as ImportDeclaration;
             }
         }
 
@@ -1932,6 +1915,7 @@ namespace ts {
                         if (!isExternalOrCommonJsModule(<SourceFile>location)) {
                             break;
                         }
+                        // falls through
                     case SyntaxKind.ModuleDeclaration:
                         if (result = callback(getSymbolOfNode(location).exports)) {
                             return result;
@@ -2137,11 +2121,8 @@ namespace ts {
             return { accessibility: SymbolAccessibility.Accessible };
 
             function getExternalModuleContainer(declaration: Node) {
-                for (; declaration; declaration = declaration.parent) {
-                    if (hasExternalModuleSymbol(declaration)) {
-                        return getSymbolOfNode(declaration);
-                    }
-                }
+                const node = findAncestor(declaration, hasExternalModuleSymbol);
+                return node && getSymbolOfNode(node);
             }
         }
 
@@ -2885,10 +2866,7 @@ namespace ts {
 
         function getTypeAliasForTypeLiteral(type: Type): Symbol {
             if (type.symbol && type.symbol.flags & SymbolFlags.TypeLiteral) {
-                let node = type.symbol.declarations[0].parent;
-                while (node.kind === SyntaxKind.ParenthesizedType) {
-                    node = node.parent;
-                }
+                const node = findAncestor(type.symbol.declarations[0].parent, n => n.kind !== SyntaxKind.ParenthesizedType);
                 if (node.kind === SyntaxKind.TypeAliasDeclaration) {
                     return getSymbolOfNode(node);
                 }
@@ -3652,7 +3630,7 @@ namespace ts {
                             // If the binding pattern is empty, this variable declaration is not visible
                             return false;
                         }
-                    // Otherwise fall through
+                        // falls through
                     case SyntaxKind.ModuleDeclaration:
                     case SyntaxKind.ClassDeclaration:
                     case SyntaxKind.InterfaceDeclaration:
@@ -3683,7 +3661,8 @@ namespace ts {
                             // Private/protected properties/methods are not visible
                             return false;
                         }
-                    // Public properties/methods are visible if its parents are visible, so const it fall into next case statement
+                        // Public properties/methods are visible if its parents are visible, so:
+                        // falls through
 
                     case SyntaxKind.Constructor:
                     case SyntaxKind.ConstructSignature:
@@ -3831,8 +3810,7 @@ namespace ts {
         }
 
         function getDeclarationContainer(node: Node): Node {
-            node = getRootDeclaration(node);
-            while (node) {
+            node = findAncestor(getRootDeclaration(node), node => {
                 switch (node.kind) {
                     case SyntaxKind.VariableDeclaration:
                     case SyntaxKind.VariableDeclarationList:
@@ -3840,13 +3818,12 @@ namespace ts {
                     case SyntaxKind.NamedImports:
                     case SyntaxKind.NamespaceImport:
                     case SyntaxKind.ImportClause:
-                        node = node.parent;
-                        break;
-
+                        return false;
                     default:
-                        return node.parent;
+                        return true;
                 }
-            }
+            });
+            return node && node.parent;
         }
 
         function getTypeOfPrototypeProperty(prototype: Symbol): Type {
@@ -7918,8 +7895,10 @@ namespace ts {
             // Starting with the parent of the symbol's declaration, check if the mapper maps any of
             // the type parameters introduced by enclosing declarations. We just pick the first
             // declaration since multiple declarations will all have the same parent anyway.
-            let node: Node = symbol.declarations[0];
-            while (node) {
+            return !!findAncestor(symbol.declarations[0], node => {
+                if (node.kind === SyntaxKind.ModuleDeclaration || node.kind === SyntaxKind.SourceFile) {
+                    return "quit";
+                }
                 switch (node.kind) {
                     case SyntaxKind.FunctionType:
                     case SyntaxKind.ConstructorType:
@@ -7966,13 +7945,8 @@ namespace ts {
                             }
                         }
                         break;
-                    case SyntaxKind.ModuleDeclaration:
-                    case SyntaxKind.SourceFile:
-                        return false;
                 }
-                node = node.parent;
-            }
-            return false;
+            });
         }
 
         function isTopLevelTypeAlias(symbol: Symbol) {
@@ -8197,7 +8171,8 @@ namespace ts {
         function isSignatureAssignableTo(source: Signature,
             target: Signature,
             ignoreReturnTypes: boolean): boolean {
-            return compareSignaturesRelated(source, target, ignoreReturnTypes, /*reportErrors*/ false, /*errorReporter*/ undefined, compareTypesAssignable) !== Ternary.False;
+            return compareSignaturesRelated(source, target, /*checkAsCallback*/ false, ignoreReturnTypes, /*reportErrors*/ false,
+                /*errorReporter*/ undefined, compareTypesAssignable) !== Ternary.False;
         }
 
         type ErrorReporter = (message: DiagnosticMessage, arg0?: string, arg1?: string) => void;
@@ -8207,6 +8182,7 @@ namespace ts {
          */
         function compareSignaturesRelated(source: Signature,
             target: Signature,
+            checkAsCallback: boolean,
             ignoreReturnTypes: boolean,
             reportErrors: boolean,
             errorReporter: ErrorReporter,
@@ -8249,9 +8225,23 @@ namespace ts {
             const sourceParams = source.parameters;
             const targetParams = target.parameters;
             for (let i = 0; i < checkCount; i++) {
-                const s = i < sourceMax ? getTypeOfParameter(sourceParams[i]) : getRestTypeOfSignature(source);
-                const t = i < targetMax ? getTypeOfParameter(targetParams[i]) : getRestTypeOfSignature(target);
-                const related = compareTypes(s, t, /*reportErrors*/ false) || compareTypes(t, s, reportErrors);
+                const sourceType = i < sourceMax ? getTypeOfParameter(sourceParams[i]) : getRestTypeOfSignature(source);
+                const targetType = i < targetMax ? getTypeOfParameter(targetParams[i]) : getRestTypeOfSignature(target);
+                const sourceSig = getSingleCallSignature(getNonNullableType(sourceType));
+                const targetSig = getSingleCallSignature(getNonNullableType(targetType));
+                // In order to ensure that any generic type Foo<T> is at least co-variant with respect to T no matter
+                // how Foo uses T, we need to relate parameters bi-variantly (given that parameters are input positions,
+                // they naturally relate only contra-variantly). However, if the source and target parameters both have
+                // function types with a single call signature, we known we are relating two callback parameters. In
+                // that case it is sufficient to only relate the parameters of the signatures co-variantly because,
+                // similar to return values, callback parameters are output positions. This means that a Promise<T>,
+                // where T is used only in callback parameter positions, will be co-variant (as opposed to bi-variant)
+                // with respect to T.
+                const callbacks = sourceSig && targetSig && !sourceSig.typePredicate && !targetSig.typePredicate &&
+                    (getFalsyFlags(sourceType) & TypeFlags.Nullable) === (getFalsyFlags(targetType) & TypeFlags.Nullable);
+                const related = callbacks ?
+                    compareSignaturesRelated(targetSig, sourceSig, /*checkAsCallback*/ true, /*ignoreReturnTypes*/ false, reportErrors, errorReporter, compareTypes) :
+                    !checkAsCallback && compareTypes(sourceType, targetType, /*reportErrors*/ false) || compareTypes(targetType, sourceType, reportErrors);
                 if (!related) {
                     if (reportErrors) {
                         errorReporter(Diagnostics.Types_of_parameters_0_and_1_are_incompatible,
@@ -8283,7 +8273,11 @@ namespace ts {
                     }
                 }
                 else {
-                    result &= compareTypes(sourceReturnType, targetReturnType, reportErrors);
+                    // When relating callback signatures, we still need to relate return types bi-variantly as otherwise
+                    // the containing type wouldn't be co-variant. For example, interface Foo<T> { add(cb: () => T): void }
+                    // wouldn't be co-variant for T without this rule.
+                    result &= checkAsCallback && compareTypes(targetReturnType, sourceReturnType, /*reportErrors*/ false) ||
+                        compareTypes(sourceReturnType, targetReturnType, reportErrors);
                 }
 
             }
@@ -8714,7 +8708,7 @@ namespace ts {
                 if (maybeTypeOfKind(target, TypeFlags.Object) && !(getObjectFlags(target) & ObjectFlags.ObjectLiteralPatternWithComputedProperties)) {
                     const isComparingJsxAttributes = !!(source.flags & TypeFlags.JsxAttributes);
                     if ((relation === assignableRelation || relation === comparableRelation) &&
-                        (target === globalObjectType || (!isComparingJsxAttributes && isEmptyObjectType(target)))) {
+                        (isTypeSubsetOf(globalObjectType, target) || (!isComparingJsxAttributes && isEmptyObjectType(target)))) {
                         return false;
                     }
                     for (const prop of getPropertiesOfObjectType(source)) {
@@ -9251,7 +9245,7 @@ namespace ts {
              * See signatureAssignableTo, compareSignaturesIdentical
              */
             function signatureRelatedTo(source: Signature, target: Signature, reportErrors: boolean): Ternary {
-                return compareSignaturesRelated(source, target, /*ignoreReturnTypes*/ false, reportErrors, reportError, isRelatedTo);
+                return compareSignaturesRelated(source, target, /*checkAsCallback*/ false, /*ignoreReturnTypes*/ false, reportErrors, reportError, isRelatedTo);
             }
 
             function signaturesIdenticalTo(source: Type, target: Type, kind: SignatureKind): Ternary {
@@ -10416,19 +10410,9 @@ namespace ts {
             // TypeScript 1.0 spec (April 2014): 3.6.3
             // A type query consists of the keyword typeof followed by an expression.
             // The expression is restricted to a single identifier or a sequence of identifiers separated by periods
-            while (node) {
-                switch (node.kind) {
-                    case SyntaxKind.TypeQuery:
-                        return true;
-                    case SyntaxKind.Identifier:
-                    case SyntaxKind.QualifiedName:
-                        node = node.parent;
-                        continue;
-                    default:
-                        return false;
-                }
-            }
-            Debug.fail("should not get here");
+            return !!findAncestor(
+                node,
+                n => n.kind === SyntaxKind.TypeQuery ? true : n.kind === SyntaxKind.Identifier || n.kind === SyntaxKind.QualifiedName ? false : "quit");
         }
 
         // Return the flow cache key for a "dotted name" (i.e. a sequence of identifiers
@@ -10934,7 +10918,7 @@ namespace ts {
         // we defer subtype reduction until the evolving array type is finalized into a manifest
         // array type.
         function addEvolvingArrayElementType(evolvingArrayType: EvolvingArrayType, node: Expression): EvolvingArrayType {
-            const elementType = getBaseTypeOfLiteralType(getTypeOfExpression(node));
+            const elementType = getBaseTypeOfLiteralType(getContextFreeTypeOfExpression(node));
             return isTypeSubsetOf(elementType, evolvingArrayType.elementType) ? evolvingArrayType : getEvolvingArrayType(getUnionType([evolvingArrayType.elementType, elementType]));
         }
 
@@ -11651,15 +11635,11 @@ namespace ts {
         }
 
         function getControlFlowContainer(node: Node): Node {
-            while (true) {
-                node = node.parent;
-                if (isFunctionLike(node) && !getImmediatelyInvokedFunctionExpression(node) ||
-                    node.kind === SyntaxKind.ModuleBlock ||
-                    node.kind === SyntaxKind.SourceFile ||
-                    node.kind === SyntaxKind.PropertyDeclaration) {
-                    return node;
-                }
-            }
+            return findAncestor(node.parent, node =>
+                isFunctionLike(node) && !getImmediatelyInvokedFunctionExpression(node) ||
+                node.kind === SyntaxKind.ModuleBlock ||
+                node.kind === SyntaxKind.SourceFile ||
+                node.kind === SyntaxKind.PropertyDeclaration);
         }
 
         // Check if a parameter is assigned anywhere within its declaring function.
@@ -11676,15 +11656,7 @@ namespace ts {
         }
 
         function hasParentWithAssignmentsMarked(node: Node) {
-            while (true) {
-                node = node.parent;
-                if (!node) {
-                    return false;
-                }
-                if (isFunctionLike(node) && getNodeLinks(node).flags & NodeCheckFlags.AssignmentsMarked) {
-                    return true;
-                }
-            }
+            return !!findAncestor(node.parent, node => isFunctionLike(node) && !!(getNodeLinks(node).flags & NodeCheckFlags.AssignmentsMarked));
         }
 
         function markParameterAssignments(node: Node) {
@@ -11856,15 +11828,7 @@ namespace ts {
         }
 
         function isInsideFunction(node: Node, threshold: Node): boolean {
-            let current = node;
-            while (current && current !== threshold) {
-                if (isFunctionLike(current)) {
-                    return true;
-                }
-                current = current.parent;
-            }
-
-            return false;
+            return !!findAncestor(node, n => n === threshold ? "quit" : isFunctionLike(n));
         }
 
         function checkNestedBlockScopedBinding(node: Identifier, symbol: Symbol): void {
@@ -11916,8 +11880,8 @@ namespace ts {
         }
 
         function isAssignedInBodyOfForStatement(node: Identifier, container: ForStatement): boolean {
-            let current: Node = node;
             // skip parenthesized nodes
+            let current: Node = node;
             while (current.parent.kind === SyntaxKind.ParenthesizedExpression) {
                 current = current.parent;
             }
@@ -11938,15 +11902,7 @@ namespace ts {
 
             // at this point we know that node is the target of assignment
             // now check that modification happens inside the statement part of the ForStatement
-            while (current !== container) {
-                if (current === container.statement) {
-                    return true;
-                }
-                else {
-                    current = current.parent;
-                }
-            }
-            return false;
+            return !!findAncestor(current, n => n === container ? "quit" : n === container.statement);
         }
 
         function captureLexicalThis(node: Node, container: Node): void {
@@ -12128,12 +12084,7 @@ namespace ts {
         }
 
         function isInConstructorArgumentInitializer(node: Node, constructorDecl: Node): boolean {
-            for (let n = node; n && n !== constructorDecl; n = n.parent) {
-                if (n.kind === SyntaxKind.Parameter) {
-                    return true;
-                }
-            }
-            return false;
+            return !!findAncestor(node, n => n === constructorDecl ? "quit" : n.kind === SyntaxKind.Parameter);
         }
 
         function checkSuperExpression(node: Node): Type {
@@ -12159,10 +12110,7 @@ namespace ts {
                 // class B {
                 //     [super.foo()]() {}
                 // }
-                let current = node;
-                while (current && current !== container && current.kind !== SyntaxKind.ComputedPropertyName) {
-                    current = current.parent;
-                }
+                const current = findAncestor(node, n => n === container ? "quit" : n.kind === SyntaxKind.ComputedPropertyName);
                 if (current && current.kind === SyntaxKind.ComputedPropertyName) {
                     error(node, Diagnostics.super_cannot_be_referenced_in_a_computed_property_name);
                 }
@@ -12766,13 +12714,8 @@ namespace ts {
         }
 
         function getContextualMapper(node: Node) {
-            while (node) {
-                if (node.contextualMapper) {
-                    return node.contextualMapper;
-                }
-                node = node.parent;
-            }
-            return identityMapper;
+            node = findAncestor(node, n => !!n.contextualMapper);
+            return node ? node.contextualMapper : identityMapper;
         }
 
         // If the given type is an object or union type, if that type has a single signature, and if
@@ -17122,10 +17065,12 @@ namespace ts {
             return type;
         }
 
-        // Returns the type of an expression. Unlike checkExpression, this function is simply concerned
-        // with computing the type and may not fully check all contained sub-expressions for errors.
-        // A cache argument of true indicates that if the function performs a full type check, it is ok
-        // to cache the result.
+        /**
+         * Returns the type of an expression. Unlike checkExpression, this function is simply concerned
+         * with computing the type and may not fully check all contained sub-expressions for errors.
+         * A cache argument of true indicates that if the function performs a full type check, it is ok
+         * to cache the result.
+         */
         function getTypeOfExpression(node: Expression, cache?: boolean) {
             // Optimize for the common case of a call to a function with a single non-generic call
             // signature where we can just fetch the return type without checking the arguments.
@@ -17142,6 +17087,21 @@ namespace ts {
             return cache ? checkExpressionCached(node) : checkExpression(node);
         }
 
+        /**
+         * Returns the type of an expression. Unlike checkExpression, this function is simply concerned
+         * with computing the type and may not fully check all contained sub-expressions for errors.
+         * It is intended for uses where you know there is no contextual type,
+         * and requesting the contextual type might cause a circularity or other bad behaviour.
+         * It sets the contextual type of the node to any before calling getTypeOfExpression.
+         */
+        function getContextFreeTypeOfExpression(node: Expression) {
+            const saveContextualType = node.contextualType;
+            node.contextualType = anyType;
+            const type = getTypeOfExpression(node);
+            node.contextualType = saveContextualType;
+            return type;
+        }
+
         // Checks an expression and returns its type. The contextualMapper parameter serves two purposes: When
         // contextualMapper is not undefined and not equal to the identityMapper function object it indicates that the
         // expression is being inferentially typed (section 4.15.2 in spec) and provides the type mapper to use in
@@ -17610,7 +17570,7 @@ namespace ts {
         function checkObjectTypeForDuplicateDeclarations(node: TypeLiteralNode | InterfaceDeclaration) {
             const names = createMap<boolean>();
             for (const member of node.members) {
-                if (member.kind == SyntaxKind.PropertySignature) {
+                if (member.kind === SyntaxKind.PropertySignature) {
                     let memberName: string;
                     switch (member.name.kind) {
                         case SyntaxKind.StringLiteral:
@@ -19011,8 +18971,7 @@ namespace ts {
 
         // this function will run after checking the source file so 'CaptureThis' is correct for all nodes
         function checkIfThisIsCapturedInEnclosingScope(node: Node): void {
-            let current = node;
-            while (current) {
+            findAncestor(node, current => {
                 if (getNodeCheckFlags(current) & NodeCheckFlags.CaptureThis) {
                     const isDeclaration = node.kind !== SyntaxKind.Identifier;
                     if (isDeclaration) {
@@ -19021,15 +18980,13 @@ namespace ts {
                     else {
                         error(node, Diagnostics.Expression_resolves_to_variable_declaration_this_that_compiler_uses_to_capture_this_reference);
                     }
-                    return;
+                    return true;
                 }
-                current = current.parent;
-            }
+            });
         }
 
         function checkIfNewTargetIsCapturedInEnclosingScope(node: Node): void {
-            let current = node;
-            while (current) {
+            findAncestor(node, current => {
                 if (getNodeCheckFlags(current) & NodeCheckFlags.CaptureNewTarget) {
                     const isDeclaration = node.kind !== SyntaxKind.Identifier;
                     if (isDeclaration) {
@@ -19038,10 +18995,9 @@ namespace ts {
                     else {
                         error(node, Diagnostics.Expression_resolves_to_variable_declaration_newTarget_that_compiler_uses_to_capture_new_target_meta_property_reference);
                     }
-                    return;
+                    return true;
                 }
-                current = current.parent;
-            }
+            });
         }
 
         function checkCollisionWithCapturedSuperVariable(node: Node, name: Identifier) {
@@ -19225,19 +19181,20 @@ namespace ts {
                                 return;
                             }
                             // - parameter is wrapped in function-like entity
-                            let current = n;
-                            while (current !== node.initializer) {
-                                if (isFunctionLike(current.parent)) {
-                                    return;
-                                }
-                                // computed property names/initializers in instance property declaration of class like entities
-                                // are executed in constructor and thus deferred
-                                if (current.parent.kind === SyntaxKind.PropertyDeclaration &&
-                                    !(hasModifier(current.parent, ModifierFlags.Static)) &&
-                                    isClassLike(current.parent.parent)) {
-                                    return;
-                                }
-                                current = current.parent;
+                            if (findAncestor(
+                                n,
+                                current => {
+                                    if (current === node.initializer) {
+                                        return "quit";
+                                    }
+                                    return isFunctionLike(current.parent) ||
+                                        // computed property names/initializers in instance property declaration of class like entities
+                                        // are executed in constructor and thus deferred
+                                        (current.parent.kind === SyntaxKind.PropertyDeclaration &&
+                                         !(hasModifier(current.parent, ModifierFlags.Static)) &&
+                                         isClassLike(current.parent.parent));
+                                    })) {
+                                return;
                             }
                             // fall through to report error
                         }
@@ -20035,18 +19992,17 @@ namespace ts {
         function checkLabeledStatement(node: LabeledStatement) {
             // Grammar checking
             if (!checkGrammarStatementInAmbientContext(node)) {
-                let current = node.parent;
-                while (current) {
-                    if (isFunctionLike(current)) {
-                        break;
-                    }
-                    if (current.kind === SyntaxKind.LabeledStatement && (<LabeledStatement>current).label.text === node.label.text) {
-                        const sourceFile = getSourceFileOfNode(node);
-                        grammarErrorOnNode(node.label, Diagnostics.Duplicate_label_0, getTextOfNodeFromSourceText(sourceFile.text, node.label));
-                        break;
-                    }
-                    current = current.parent;
-                }
+                findAncestor(node.parent,
+                             current => {
+                                 if (isFunctionLike(current)) {
+                                     return "quit";
+                                 }
+                                 if (current.kind === SyntaxKind.LabeledStatement && (<LabeledStatement>current).label.text === node.label.text) {
+                                     const sourceFile = getSourceFileOfNode(node);
+                                     grammarErrorOnNode(node.label, Diagnostics.Duplicate_label_0, getTextOfNodeFromSourceText(sourceFile.text, node.label));
+                                     return true;
+                                 }
+                             });
             }
 
             // ensure that label is unique
@@ -20531,7 +20487,7 @@ namespace ts {
                             errorMessage = Diagnostics.Class_0_defines_instance_member_accessor_1_but_extended_class_2_defines_it_as_instance_member_function;
                         }
 
-                        error(derived.valueDeclaration.name, errorMessage, typeToString(baseType), symbolToString(base), typeToString(type));
+                        error(derived.valueDeclaration.name || derived.valueDeclaration, errorMessage, typeToString(baseType), symbolToString(base), typeToString(type));
                     }
                 }
             }
@@ -21045,7 +21001,7 @@ namespace ts {
                         }
                         break;
                     }
-                    // fallthrough
+                    // falls through
                 case SyntaxKind.ClassDeclaration:
                 case SyntaxKind.EnumDeclaration:
                 case SyntaxKind.FunctionDeclaration:
@@ -21680,6 +21636,7 @@ namespace ts {
                             if (!isExternalOrCommonJsModule(<SourceFile>location)) {
                                 break;
                             }
+                            // falls through
                         case SyntaxKind.ModuleDeclaration:
                             copySymbols(getSymbolOfNode(location).exports, meaning & SymbolFlags.ModuleMember);
                             break;
@@ -21691,7 +21648,8 @@ namespace ts {
                             if (className) {
                                 copySymbol(location.symbol, meaning);
                             }
-                        // fall through; this fall-through is necessary because we would like to handle
+                        // falls through
+                        // this fall-through is necessary because we would like to handle
                         // type parameter inside class expression similar to how we handle it in classDeclaration and interface Declaration
                         case SyntaxKind.ClassDeclaration:
                         case SyntaxKind.InterfaceDeclaration:
@@ -21980,7 +21938,7 @@ namespace ts {
                             return sig.thisParameter;
                         }
                     }
-                    // fallthrough
+                    // falls through
 
                 case SyntaxKind.SuperKeyword:
                     const type = isPartOfExpression(node) ? getTypeOfExpression(<Expression>node) : getTypeFromTypeNode(<TypeNode>node);
@@ -22008,7 +21966,7 @@ namespace ts {
                     if (isInJavaScriptFile(node) && isRequireCall(node.parent, /*checkArgumentIsStringLiteral*/ false)) {
                         return resolveExternalModuleName(node, <LiteralExpression>node);
                     }
-                // Fall through
+                    // falls through
 
                 case SyntaxKind.NumericLiteral:
                     // index access
@@ -22299,11 +22257,7 @@ namespace ts {
                             const symbolIsUmdExport = symbolFile !== referenceFile;
                             return symbolIsUmdExport ? undefined : symbolFile;
                         }
-                        for (let n = node.parent; n; n = n.parent) {
-                            if (isModuleOrEnumDeclaration(n) && getSymbolOfNode(n) === parentSymbol) {
-                                return <ModuleDeclaration | EnumDeclaration>n;
-                            }
-                        }
+                        return findAncestor(node.parent, n => isModuleOrEnumDeclaration(n) && getSymbolOfNode(n) === parentSymbol) as ModuleDeclaration | EnumDeclaration;
                     }
                 }
             }
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 23751186677..358b910f2f2 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -224,6 +224,25 @@ namespace ts {
         }
         return undefined;
     }
+    /**
+     * Iterates through the parent chain of a node and performs the callback on each parent until the callback
+     * returns a truthy value, then returns that value.
+     * If no such value is found, it applies the callback until the parent pointer is undefined or the callback returns "quit"
+     * At that point findAncestor returns undefined.
+     */
+    export function findAncestor(node: Node, callback: (element: Node) => boolean | "quit"): Node {
+        while (node) {
+            const result = callback(node);
+            if (result === "quit") {
+                return undefined;
+            }
+            else if (result) {
+                return node;
+            }
+            node = node.parent;
+        }
+        return undefined;
+    }
 
     export function zipWith<T, U>(arrayA: T[], arrayB: U[], callback: (a: T, b: U, index: number) => void): void {
         Debug.assert(arrayA.length === arrayB.length);
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 5f7076c949d..a1200b6a072 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -3197,6 +3197,10 @@
         "category": "Message",
         "code": 6181
     },
+    "Scoped package detected, looking in '{0}'": {
+        "category": "Message",
+        "code": "6182"
+    },
 
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index 1603f08bb5f..d511b31b331 100644
--- a/src/compiler/moduleNameResolver.ts
+++ b/src/compiler/moduleNameResolver.ts
@@ -378,7 +378,7 @@ namespace ts {
                     directoryPathMap.set(parent, result);
                     current = parent;
 
-                    if (current == commonPrefix) {
+                    if (current === commonPrefix) {
                         break;
                     }
                 }
@@ -954,10 +954,25 @@ namespace ts {
                 }
                 nodeModulesAtTypesExists = false;
             }
-            return loadModuleFromNodeModulesFolder(Extensions.DtsOnly, moduleName, nodeModulesAtTypes, nodeModulesAtTypesExists, failedLookupLocations, state);
+            return loadModuleFromNodeModulesFolder(Extensions.DtsOnly, mangleScopedPackage(moduleName, state), nodeModulesAtTypes, nodeModulesAtTypesExists, failedLookupLocations, state);
         }
     }
 
+    /** For a scoped package, we must look in `@types/foo__bar` instead of `@types/@foo/bar`. */
+    function mangleScopedPackage(moduleName: string, state: ModuleResolutionState): string {
+        if (startsWith(moduleName, "@")) {
+            const replaceSlash = moduleName.replace(ts.directorySeparator, "__");
+            if (replaceSlash !== moduleName) {
+                const mangled = replaceSlash.slice(1); // Take off the "@"
+                if (state.traceEnabled) {
+                    trace(state.host, Diagnostics.Scoped_package_detected_looking_in_0, mangled);
+                }
+                return mangled;
+            }
+        }
+        return moduleName;
+    }
+
     function tryFindNonRelativeModuleNameInCache(cache: PerModuleNameCache | undefined, moduleName: string, containingDirectory: string, traceEnabled: boolean, host: ModuleResolutionHost): SearchResult<Resolved> {
         const result = cache && cache.get(containingDirectory);
         if (result) {
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 08144e79299..93aa13bd415 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -57,7 +57,7 @@ namespace ts {
         // The visitXXX functions could be written as local functions that close over the cbNode and cbNodeArray
         // callback parameters, but that causes a closure allocation for each invocation with noticeable effects
         // on performance.
-        const visitNodes: (cb: (node: Node | Node[]) => T, nodes: Node[]) => T = cbNodeArray ? visitNodeArray : visitEachNode;
+        const visitNodes: (cb: ((node: Node) => T) | ((node: Node[]) => T), nodes: Node[]) => T = cbNodeArray ? visitNodeArray : visitEachNode;
         const cbNodes = cbNodeArray || cbNode;
         switch (node.kind) {
             case SyntaxKind.QualifiedName:
@@ -3573,6 +3573,7 @@ namespace ts {
                     if (isAwaitExpression()) {
                         return parseAwaitExpression();
                     }
+                    // falls through
                 default:
                     return parseIncrementExpression();
             }
@@ -3606,8 +3607,8 @@ namespace ts {
                     if (sourceFile.languageVariant !== LanguageVariant.JSX) {
                         return false;
                     }
-                // We are in JSX context and the token is part of JSXElement.
-                // Fall through
+                    // We are in JSX context and the token is part of JSXElement.
+                    // falls through
                 default:
                     return true;
             }
@@ -6571,7 +6572,8 @@ namespace ts {
                                     indent += scanner.getTokenText().length;
                                     break;
                                 }
-                                // FALLTHROUGH otherwise to record the * as a comment
+                                // record the * as a comment
+                                // falls through
                             default:
                                 state = JSDocState.SavingComments; // leading identifiers start recording as well
                                 pushComment(scanner.getTokenText());
@@ -6797,6 +6799,7 @@ namespace ts {
                                     break;
                                 case SyntaxKind.Identifier:
                                     canParseTag = false;
+                                    break;
                                 case SyntaxKind.EndOfFileToken:
                                     break;
                             }
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index f2d44adb1f1..0971adfc098 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -557,7 +557,7 @@ namespace ts {
             // combine results of resolutions and predicted results
             let j = 0;
             for (let i = 0; i < result.length; i++) {
-                if (result[i] == predictedToResolveToAmbientModuleMarker) {
+                if (result[i] === predictedToResolveToAmbientModuleMarker) {
                     result[i] = undefined;
                 }
                 else {
@@ -930,20 +930,22 @@ namespace ts {
          */
         function shouldReportDiagnostic(diagnostic: Diagnostic) {
             const { file, start } = diagnostic;
-            const lineStarts = getLineStarts(file);
-            let { line } = computeLineAndCharacterOfPosition(lineStarts, start);
-            while (line > 0) {
-                const previousLineText = file.text.slice(lineStarts[line - 1], lineStarts[line]);
-                const result = ignoreDiagnosticCommentRegEx.exec(previousLineText);
-                if (!result) {
-                    // non-empty line
-                    return true;
+            if (file) {
+                const lineStarts = getLineStarts(file);
+                let { line } = computeLineAndCharacterOfPosition(lineStarts, start);
+                while (line > 0) {
+                    const previousLineText = file.text.slice(lineStarts[line - 1], lineStarts[line]);
+                    const result = ignoreDiagnosticCommentRegEx.exec(previousLineText);
+                    if (!result) {
+                        // non-empty line
+                        return true;
+                    }
+                    if (result[3]) {
+                        // @ts-ignore
+                        return false;
+                    }
+                    line--;
                 }
-                if (result[3]) {
-                    // @ts-ignore
-                    return false;
-                }
-                line--;
             }
             return true;
         }
@@ -967,8 +969,7 @@ namespace ts {
                                 diagnostics.push(createDiagnosticForNode(node, Diagnostics._0_can_only_be_used_in_a_ts_file, "?"));
                                 return;
                             }
-
-                        // Pass through
+                            // falls through
                         case SyntaxKind.MethodDeclaration:
                         case SyntaxKind.MethodSignature:
                         case SyntaxKind.Constructor:
@@ -1048,7 +1049,7 @@ namespace ts {
                                 diagnostics.push(createDiagnosticForNodeArray(nodes, Diagnostics.type_parameter_declarations_can_only_be_used_in_a_ts_file));
                                 return;
                             }
-                            // pass through
+                            // falls through
                         case SyntaxKind.VariableStatement:
                             // Check modifiers
                             if (nodes === (<ClassDeclaration | FunctionLikeDeclaration | VariableStatement>parent).modifiers) {
@@ -1096,7 +1097,8 @@ namespace ts {
                                 if (isConstValid) {
                                     continue;
                                 }
-                                // Fallthrough to report error
+                                // to report error,
+                                // falls through
                             case SyntaxKind.PublicKeyword:
                             case SyntaxKind.PrivateKeyword:
                             case SyntaxKind.ProtectedKeyword:
@@ -1364,7 +1366,7 @@ namespace ts {
 
                 // If the file was previously found via a node_modules search, but is now being processed as a root file,
                 // then everything it sucks in may also be marked incorrectly, and needs to be checked again.
-                if (file && sourceFilesFoundSearchingNodeModules.get(file.path) && currentNodeModulesDepth == 0) {
+                if (file && sourceFilesFoundSearchingNodeModules.get(file.path) && currentNodeModulesDepth === 0) {
                     sourceFilesFoundSearchingNodeModules.set(file.path, false);
                     if (!options.noResolve) {
                         processReferencedFiles(file, isDefaultLib);
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index 41c48700a9a..406405600f1 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -308,6 +308,7 @@ namespace ts {
                     if (text.charCodeAt(pos) === CharacterCodes.lineFeed) {
                         pos++;
                     }
+                    // falls through
                 case CharacterCodes.lineFeed:
                     result.push(lineStart);
                     lineStart = pos;
@@ -454,6 +455,7 @@ namespace ts {
                       if (text.charCodeAt(pos + 1) === CharacterCodes.lineFeed) {
                           pos++;
                       }
+                      // falls through
                   case CharacterCodes.lineFeed:
                       pos++;
                       if (stopAfterLineBreak) {
@@ -625,6 +627,7 @@ namespace ts {
                     if (text.charCodeAt(pos + 1) === CharacterCodes.lineFeed) {
                         pos++;
                     }
+                    // falls through
                 case CharacterCodes.lineFeed:
                     pos++;
                     if (trailing) {
@@ -1072,7 +1075,7 @@ namespace ts {
                     if (pos < end && text.charCodeAt(pos) === CharacterCodes.lineFeed) {
                         pos++;
                     }
-                    // fall through
+                    // falls through
                 case CharacterCodes.lineFeed:
                 case CharacterCodes.lineSeparator:
                 case CharacterCodes.paragraphSeparator:
@@ -1459,6 +1462,7 @@ namespace ts {
                         // This fall-through is a deviation from the EcmaScript grammar. The grammar says that a leading zero
                         // can only be followed by an octal digit, a dot, or the end of the number literal. However, we are being
                         // permissive and allowing decimal digits of the form 08* and 09* (which many browsers also do).
+                        // falls through
                     case CharacterCodes._1:
                     case CharacterCodes._2:
                     case CharacterCodes._3:
diff --git a/src/compiler/transformers/module/system.ts b/src/compiler/transformers/module/system.ts
index cde4fcad57e..5711d9f1116 100644
--- a/src/compiler/transformers/module/system.ts
+++ b/src/compiler/transformers/module/system.ts
@@ -479,8 +479,8 @@ namespace ts {
                                 // module is imported only for side-effects, no emit required
                                 break;
                             }
+                            // falls through
 
-                        // fall-through
                         case SyntaxKind.ImportEqualsDeclaration:
                             Debug.assert(importVariableName !== undefined);
                             // save import into the local
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index b32a7be30d9..8981da65ba3 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -30,7 +30,7 @@ namespace ts {
     }
 
     function reportEmittedFiles(files: string[]): void {
-        if (!files || files.length == 0) {
+        if (!files || files.length === 0) {
             return;
         }
 
@@ -282,7 +282,7 @@ namespace ts {
                     // When the configFileName is just "tsconfig.json", the watched directory should be
                     // the current directory; if there is a given "project" parameter, then the configFileName
                     // is an absolute file name.
-                    directory == "" ? "." : directory,
+                    directory === "" ? "." : directory,
                     watchedDirectoryChanged, /*recursive*/ true);
             }
         }
@@ -334,7 +334,7 @@ namespace ts {
                         // When the configFileName is just "tsconfig.json", the watched directory should be
                         // the current directory; if there is a given "project" parameter, then the configFileName
                         // is an absolute file name.
-                        directory == "" ? "." : directory,
+                        directory === "" ? "." : directory,
                         watchedDirectoryChanged, /*recursive*/ true);
                 }
             }
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 3b4b87c956f..f34c15ee346 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -674,6 +674,7 @@ namespace ts {
                 // At this point, node is either a qualified name or an identifier
                 Debug.assert(node.kind === SyntaxKind.Identifier || node.kind === SyntaxKind.QualifiedName || node.kind === SyntaxKind.PropertyAccessExpression,
                     "'node' was expected to be a qualified name, identifier or property access in 'isPartOfTypeNode'.");
+                // falls through
             case SyntaxKind.QualifiedName:
             case SyntaxKind.PropertyAccessExpression:
             case SyntaxKind.ThisKeyword:
@@ -783,6 +784,7 @@ namespace ts {
                     if (operand) {
                         traverse(operand);
                     }
+                    return;
                 case SyntaxKind.EnumDeclaration:
                 case SyntaxKind.InterfaceDeclaration:
                 case SyntaxKind.ModuleDeclaration:
@@ -1000,7 +1002,7 @@ namespace ts {
                     if (!includeArrowFunctions) {
                         continue;
                     }
-                // Fall through
+                    // falls through
                 case SyntaxKind.FunctionDeclaration:
                 case SyntaxKind.FunctionExpression:
                 case SyntaxKind.ModuleDeclaration:
@@ -1059,6 +1061,7 @@ namespace ts {
                     if (!stopOnFunctions) {
                         continue;
                     }
+                    // falls through
                 case SyntaxKind.PropertyDeclaration:
                 case SyntaxKind.PropertySignature:
                 case SyntaxKind.MethodDeclaration:
@@ -1258,7 +1261,7 @@ namespace ts {
                 if (node.parent.kind === SyntaxKind.TypeQuery || isJSXTagName(node)) {
                     return true;
                 }
-            // fall through
+                // falls through
             case SyntaxKind.NumericLiteral:
             case SyntaxKind.StringLiteral:
             case SyntaxKind.ThisKeyword:
@@ -1940,7 +1943,7 @@ namespace ts {
                 if (node.asteriskToken) {
                     flags |= FunctionFlags.Generator;
                 }
-                // fall through
+                // falls through
             case SyntaxKind.ArrowFunction:
                 if (hasModifier(node, ModifierFlags.Async)) {
                     flags |= FunctionFlags.Async;
@@ -4428,7 +4431,7 @@ namespace ts {
             newEndN = Math.max(newEnd2, newEnd2 + (newEnd1 - oldEnd2));
         }
 
-        return createTextChangeRange(createTextSpanFromBounds(oldStartN, oldEndN), /*newLength:*/ newEndN - oldStartN);
+        return createTextChangeRange(createTextSpanFromBounds(oldStartN, oldEndN), /*newLength*/ newEndN - oldStartN);
     }
 
     export function getTypeParameterOwner(d: Declaration): Declaration {
@@ -4604,7 +4607,7 @@ namespace ts {
      */
     export function getParseTreeNode<T extends Node>(node: Node, nodeTest?: (node: Node) => node is T): T;
     export function getParseTreeNode(node: Node, nodeTest?: (node: Node) => boolean): Node {
-        if (node == undefined || isParseTreeNode(node)) {
+        if (node === undefined || isParseTreeNode(node)) {
             return node;
         }
 
diff --git a/src/compiler/visitor.ts b/src/compiler/visitor.ts
index 297d2cc0dde..7850155ed25 100644
--- a/src/compiler/visitor.ts
+++ b/src/compiler/visitor.ts
@@ -322,7 +322,7 @@ namespace ts {
                     nodesVisitor((<UnionOrIntersectionTypeNode>node).types, visitor, isTypeNode));
 
             case SyntaxKind.ParenthesizedType:
-                Debug.fail("not implemented.");
+                throw Debug.fail("not implemented.");
 
             case SyntaxKind.TypeOperator:
                 return updateTypeOperatorNode(<TypeOperatorNode>node, visitNode((<TypeOperatorNode>node).type, visitor, isTypeNode));
@@ -885,7 +885,7 @@ namespace ts {
             return initial;
         }
 
-        const reduceNodes: (nodes: NodeArray<Node>, f: (memo: T, node: Node | NodeArray<Node>) => T, initial: T) => T = cbNodeArray ? reduceNodeArray : reduceLeft;
+        const reduceNodes: (nodes: NodeArray<Node>, f: ((memo: T, node: Node) => T) | ((memo: T, node: NodeArray<Node>) => T), initial: T) => T = cbNodeArray ? reduceNodeArray : reduceLeft;
         const cbNodes = cbNodeArray || cbNode;
         const kind = node.kind;
 
@@ -1289,6 +1289,7 @@ namespace ts {
 
             case SyntaxKind.JsxAttributes:
                 result = reduceNodes((<JsxAttributes>node).properties, cbNodes, result);
+                break;
 
             case SyntaxKind.JsxClosingElement:
                 result = reduceNode((<JsxClosingElement>node).tagName, cbNode, result);
@@ -1310,7 +1311,7 @@ namespace ts {
             // Clauses
             case SyntaxKind.CaseClause:
                 result = reduceNode((<CaseClause>node).expression, cbNode, result);
-                // fall-through
+                // falls through
 
             case SyntaxKind.DefaultClause:
                 result = reduceNodes((<CaseClause | DefaultClause>node).statements, cbNodes, result);
@@ -1344,6 +1345,7 @@ namespace ts {
             case SyntaxKind.EnumMember:
                 result = reduceNode((<EnumMember>node).name, cbNode, result);
                 result = reduceNode((<EnumMember>node).initializer, cbNode, result);
+                break;
 
             // Top-level nodes
             case SyntaxKind.SourceFile:
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index c0e950c4f38..a56d21ae345 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -2367,13 +2367,13 @@ namespace FourSlash {
 
         public verifyImportFixAtPosition(expectedTextArray: string[], errorCode?: number) {
             const ranges = this.getRanges();
-            if (ranges.length == 0) {
+            if (ranges.length === 0) {
                 this.raiseError("At least one range should be specified in the testfile.");
             }
 
             const codeFixes = this.getCodeFixActions(this.activeFile.fileName, errorCode);
 
-            if (!codeFixes || codeFixes.length == 0) {
+            if (!codeFixes || codeFixes.length === 0) {
                 this.raiseError("No codefixes returned.");
             }
 
@@ -2738,7 +2738,7 @@ namespace FourSlash {
         private assertItemInCompletionList(items: ts.CompletionEntry[], name: string, text?: string, documentation?: string, kind?: string, spanIndex?: number) {
             for (const item of items) {
                 if (item.name === name) {
-                    if (documentation != undefined || text !== undefined) {
+                    if (documentation !== undefined || text !== undefined) {
                         const details = this.getCompletionEntryDetails(item.name);
 
                         if (documentation !== undefined) {
@@ -2989,9 +2989,8 @@ ${code}
                         }
                     }
                 }
-                // TODO: should be '==='?
             }
-            else if (line == "" || lineLength === 0) {
+            else if (line === "" || lineLength === 0) {
                 // Previously blank lines between fourslash content caused it to be considered as 2 files,
                 // Remove this behavior since it just causes errors now
             }
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 2c4eef1739d..c0ef2672b27 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -1933,7 +1933,7 @@ namespace Harness {
                 }
 
                 const parentDirectory = IO.directoryName(dirName);
-                if (parentDirectory != "") {
+                if (parentDirectory !== "") {
                     createDirectoryStructure(parentDirectory);
                 }
                 IO.createDirectory(dirName);
diff --git a/src/harness/projectsRunner.ts b/src/harness/projectsRunner.ts
index f1cc992c4a7..b0efcf4c389 100644
--- a/src/harness/projectsRunner.ts
+++ b/src/harness/projectsRunner.ts
@@ -111,8 +111,7 @@ class ProjectRunner extends RunnerBase {
                 else if (url.indexOf(diskProjectPath) === 0) {
                     // Replace the disk specific path into the project root path
                     url = url.substr(diskProjectPath.length);
-                    // TODO: should be '!=='?
-                    if (url.charCodeAt(0) != ts.CharacterCodes.slash) {
+                    if (url.charCodeAt(0) !== ts.CharacterCodes.slash) {
                         url = "/" + url;
                     }
                 }
diff --git a/src/harness/sourceMapRecorder.ts b/src/harness/sourceMapRecorder.ts
index aa66d713e1c..bb5126fb352 100644
--- a/src/harness/sourceMapRecorder.ts
+++ b/src/harness/sourceMapRecorder.ts
@@ -50,11 +50,11 @@ namespace Harness.SourceMapRecorder {
                 return true;
             }
 
-            if (sourceMapMappings.charAt(decodingIndex) == ",") {
+            if (sourceMapMappings.charAt(decodingIndex) === ",") {
                 return true;
             }
 
-            if (sourceMapMappings.charAt(decodingIndex) == ";") {
+            if (sourceMapMappings.charAt(decodingIndex) === ";") {
                 return true;
             }
 
@@ -117,7 +117,7 @@ namespace Harness.SourceMapRecorder {
             }
 
             while (decodingIndex < sourceMapMappings.length) {
-                if (sourceMapMappings.charAt(decodingIndex) == ";") {
+                if (sourceMapMappings.charAt(decodingIndex) === ";") {
                     // New line
                     decodeOfEncodedMapping.emittedLine++;
                     decodeOfEncodedMapping.emittedColumn = 1;
@@ -125,7 +125,7 @@ namespace Harness.SourceMapRecorder {
                     continue;
                 }
 
-                if (sourceMapMappings.charAt(decodingIndex) == ",") {
+                if (sourceMapMappings.charAt(decodingIndex) === ",") {
                     // Next entry is on same line - no action needed
                     decodingIndex++;
                     continue;
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 81931a2de41..66d9cb087b6 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -3228,7 +3228,7 @@ namespace ts.projectSystem {
             checkNumberOfInferredProjects(projectService, 1);
 
             const configuredProject = projectService.configuredProjects[0];
-            assert.isTrue(configuredProject.getFileNames().length == 0);
+            assert.isTrue(configuredProject.getFileNames().length === 0);
 
             const inferredProject = projectService.inferredProjects[0];
             assert.isTrue(inferredProject.containsFile(<server.NormalizedPath>file1.path));
diff --git a/src/harness/unittests/versionCache.ts b/src/harness/unittests/versionCache.ts
index 17a70f59d59..ca64ea1118f 100644
--- a/src/harness/unittests/versionCache.ts
+++ b/src/harness/unittests/versionCache.ts
@@ -278,7 +278,7 @@ and grew 1cm per day`;
                 const insertString = testContent.substring(rsa[i], rsa[i] + las[i]);
                 svc.edit(ersa[i], elas[i], insertString);
                 checkText = editFlat(ersa[i], elas[i], insertString, checkText);
-                if (0 == (i % 4)) {
+                if (0 === (i % 4)) {
                     const snap = svc.getSnapshot();
                     const snapText = snap.getText(0, checkText.length);
                     assert.equal(checkText, snapText);
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index f4f1e66e1ff..d45bb283384 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -257,7 +257,7 @@ namespace ts.server {
         startWatchingContainingDirectoriesForFile(fileName: string, project: InferredProject, callback: (fileName: string) => void) {
             let currentPath = getDirectoryPath(fileName);
             let parentPath = getDirectoryPath(currentPath);
-            while (currentPath != parentPath) {
+            while (currentPath !== parentPath) {
                 if (!this.directoryWatchersForTsconfig.has(currentPath)) {
                     this.projectService.logger.info(`Add watcher for: ${currentPath}`);
                     this.directoryWatchersForTsconfig.set(currentPath, this.projectService.host.watchDirectory(currentPath, callback));
@@ -618,7 +618,7 @@ namespace ts.server {
          */
         private onConfigFileAddedForInferredProject(fileName: string) {
             // TODO: check directory separators
-            if (getBaseFileName(fileName) != "tsconfig.json") {
+            if (getBaseFileName(fileName) !== "tsconfig.json") {
                 this.logger.info(`${fileName} is not tsconfig.json`);
                 return;
             }
@@ -1033,7 +1033,7 @@ namespace ts.server {
                 const scriptKind = propertyReader.getScriptKind(f);
                 const hasMixedContent = propertyReader.hasMixedContent(f, this.hostConfiguration.extraFileExtensions);
                 if (this.host.fileExists(rootFilename)) {
-                    const info = this.getOrCreateScriptInfoForNormalizedPath(toNormalizedPath(rootFilename), /*openedByClient*/ clientFileName == rootFilename, /*fileContent*/ undefined, scriptKind, hasMixedContent);
+                    const info = this.getOrCreateScriptInfoForNormalizedPath(toNormalizedPath(rootFilename), /*openedByClient*/ clientFileName === rootFilename, /*fileContent*/ undefined, scriptKind, hasMixedContent);
                     project.addRoot(info);
                 }
                 else {
diff --git a/src/server/project.ts b/src/server/project.ts
index b92e8e84972..09c8d74c8c7 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -643,7 +643,7 @@ namespace ts.server {
             // check if requested version is the same that we have reported last time
             if (this.lastReportedFileNames && lastKnownVersion === this.lastReportedVersion) {
                 // if current structure version is the same - return info without any changes
-                if (this.projectStructureVersion == this.lastReportedVersion && !updatedFileNames) {
+                if (this.projectStructureVersion === this.lastReportedVersion && !updatedFileNames) {
                     return { info, projectErrors: this.projectErrors };
                 }
                 // compute and return the difference
diff --git a/src/server/scriptVersionCache.ts b/src/server/scriptVersionCache.ts
index 7f09bcd549b..35266591098 100644
--- a/src/server/scriptVersionCache.ts
+++ b/src/server/scriptVersionCache.ts
@@ -79,7 +79,7 @@ namespace ts.server {
             const lm = LineIndex.linesFromText(insertedText);
             const lines = lm.lines;
             if (lines.length > 1) {
-                if (lines[lines.length - 1] == "") {
+                if (lines[lines.length - 1] === "") {
                     lines.length--;
                 }
             }
@@ -570,7 +570,7 @@ namespace ts.server {
                 }
                 if (this.checkEdits) {
                     const updatedText = this.getText(0, this.root.charCount());
-                    Debug.assert(checkText == updatedText, "buffer edit mismatch");
+                    Debug.assert(checkText === updatedText, "buffer edit mismatch");
                 }
                 return walker.lineIndex;
             }
diff --git a/src/server/server.ts b/src/server/server.ts
index 433c7e16ab1..79cfc3882ae 100644
--- a/src/server/server.ts
+++ b/src/server/server.ts
@@ -380,7 +380,7 @@ namespace ts.server {
             }
 
             this.projectService.updateTypingsForProject(response);
-            if (response.kind == ActionSet && this.socket) {
+            if (response.kind === ActionSet && this.socket) {
                 this.sendEvent(0, "setTypings", response);
             }
         }
@@ -401,7 +401,9 @@ namespace ts.server {
                 byteLength: Buffer.byteLength,
                 hrtime: process.hrtime,
                 logger,
-                canUseEvents});
+                canUseEvents,
+                globalPlugins: options.globalPlugins,
+                pluginProbeLocations: options.pluginProbeLocations});
 
             if (telemetryEnabled && typingsInstaller) {
                 typingsInstaller.setTelemetrySender(this);
diff --git a/src/server/session.ts b/src/server/session.ts
index d4dc371b16b..742f8a3c228 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -49,7 +49,7 @@ namespace ts.server {
         if (a.file < b.file) {
             return -1;
         }
-        else if (a.file == b.file) {
+        else if (a.file === b.file) {
             const n = compareNumber(a.start.line, b.start.line);
             if (n === 0) {
                 return compareNumber(a.start.offset, b.start.offset);
@@ -1128,7 +1128,7 @@ namespace ts.server {
             // getFormattingEditsAfterKeystroke either empty or pertaining
             // only to the previous line.  If all this is true, then
             // add edits necessary to properly indent the current line.
-            if ((args.key == "\n") && ((!edits) || (edits.length === 0) || allEditsBeforePos(edits, position))) {
+            if ((args.key === "\n") && ((!edits) || (edits.length === 0) || allEditsBeforePos(edits, position))) {
                 const lineInfo = scriptInfo.getLineInfo(args.line);
                 if (lineInfo && (lineInfo.leaf) && (lineInfo.leaf.text)) {
                     const lineText = lineInfo.leaf.text;
@@ -1137,10 +1137,10 @@ namespace ts.server {
                         let hasIndent = 0;
                         let i: number, len: number;
                         for (i = 0, len = lineText.length; i < len; i++) {
-                            if (lineText.charAt(i) == " ") {
+                            if (lineText.charAt(i) === " ") {
                                 hasIndent++;
                             }
-                            else if (lineText.charAt(i) == "\t") {
+                            else if (lineText.charAt(i) === "\t") {
                                 hasIndent += formatOptions.tabSize;
                             }
                             else {
@@ -1543,7 +1543,7 @@ namespace ts.server {
             const normalizedFileName = toNormalizedPath(fileName);
             const project = this.projectService.getDefaultProjectForFile(normalizedFileName, /*refreshInferredProjects*/ true);
             for (const fileNameInProject of fileNamesInProject) {
-                if (this.getCanonicalFileName(fileNameInProject) == this.getCanonicalFileName(fileName))
+                if (this.getCanonicalFileName(fileNameInProject) === this.getCanonicalFileName(fileName))
                     highPriorityFiles.push(fileNameInProject);
                 else {
                     const info = this.projectService.getScriptInfo(fileNameInProject);
@@ -1564,7 +1564,7 @@ namespace ts.server {
                 const checkList = fileNamesInProject.map(fileName => ({ fileName, project }));
                 // Project level error analysis runs on background files too, therefore
                 // doesn't require the file to be opened
-                this.updateErrorCheck(next, checkList, this.changeSeq, (n) => n == this.changeSeq, delay, 200, /*requireOpen*/ false);
+                this.updateErrorCheck(next, checkList, this.changeSeq, (n) => n === this.changeSeq, delay, 200, /*requireOpen*/ false);
             }
         }
 
diff --git a/src/server/typingsCache.ts b/src/server/typingsCache.ts
index 9379ae82d0e..a97b12ff7a8 100644
--- a/src/server/typingsCache.ts
+++ b/src/server/typingsCache.ts
@@ -61,7 +61,7 @@ namespace ts.server {
 
     function compilerOptionsChanged(opt1: CompilerOptions, opt2: CompilerOptions): boolean {
         // TODO: add more relevant properties
-        return opt1.allowJs != opt2.allowJs;
+        return opt1.allowJs !== opt2.allowJs;
     }
 
     function unresolvedImportsChanged(imports1: SortedReadonlyArray<string>, imports2: SortedReadonlyArray<string>): boolean {
diff --git a/src/server/typingsInstaller/nodeTypingsInstaller.ts b/src/server/typingsInstaller/nodeTypingsInstaller.ts
index 1018b37d90d..895a4e17cc7 100644
--- a/src/server/typingsInstaller/nodeTypingsInstaller.ts
+++ b/src/server/typingsInstaller/nodeTypingsInstaller.ts
@@ -31,7 +31,7 @@ namespace ts.server.typingsInstaller {
     }
 
     function getNPMLocation(processName: string) {
-        if (path.basename(processName).indexOf("node") == 0) {
+        if (path.basename(processName).indexOf("node") === 0) {
             return `"${path.join(path.dirname(process.argv[0]), "npm")}"`;
         }
         else {
diff --git a/src/server/utilities.ts b/src/server/utilities.ts
index 8784efff750..ffc09f29ccd 100644
--- a/src/server/utilities.ts
+++ b/src/server/utilities.ts
@@ -219,7 +219,7 @@ namespace ts.server {
         }
 
         public scheduleCollect() {
-            if (!this.host.gc || this.timerId != undefined) {
+            if (!this.host.gc || this.timerId !== undefined) {
                 // no global.gc or collection was already scheduled - skip this request
                 return;
             }
diff --git a/src/services/breakpoints.ts b/src/services/breakpoints.ts
index 1f6bec41109..e47f6d016c7 100644
--- a/src/services/breakpoints.ts
+++ b/src/services/breakpoints.ts
@@ -97,7 +97,7 @@ namespace ts.BreakpointResolver {
                         if (isFunctionBlock(node)) {
                             return spanInFunctionBlock(<Block>node);
                         }
-                    // Fall through
+                        // falls through
                     case SyntaxKind.ModuleBlock:
                         return spanInBlock(<Block>node);
 
@@ -186,6 +186,7 @@ namespace ts.BreakpointResolver {
                         if (getModuleInstanceState(node) !== ModuleInstanceState.Instantiated) {
                             return undefined;
                         }
+                        // falls through
 
                     case SyntaxKind.ClassDeclaration:
                     case SyntaxKind.EnumDeclaration:
@@ -264,7 +265,7 @@ namespace ts.BreakpointResolver {
                         // a or ...c  or d: x from
                         // [a, b, ...c] or { a, b } or { d: x } from destructuring pattern
                         if ((node.kind === SyntaxKind.Identifier ||
-                            node.kind == SyntaxKind.SpreadElement ||
+                            node.kind === SyntaxKind.SpreadElement ||
                             node.kind === SyntaxKind.PropertyAssignment ||
                             node.kind === SyntaxKind.ShorthandPropertyAssignment) &&
                             isArrayLiteralOrObjectLiteralDestructuringPattern(node.parent)) {
@@ -473,6 +474,7 @@ namespace ts.BreakpointResolver {
                         if (getModuleInstanceState(block.parent) !== ModuleInstanceState.Instantiated) {
                             return undefined;
                         }
+                        // falls through
 
                     // Set on parent if on same line otherwise on first statement
                     case SyntaxKind.WhileStatement:
@@ -582,6 +584,7 @@ namespace ts.BreakpointResolver {
                         if (getModuleInstanceState(node.parent.parent) !== ModuleInstanceState.Instantiated) {
                             return undefined;
                         }
+                        // falls through
 
                     case SyntaxKind.EnumDeclaration:
                     case SyntaxKind.ClassDeclaration:
@@ -593,7 +596,7 @@ namespace ts.BreakpointResolver {
                             // Span on close brace token
                             return textSpan(node);
                         }
-                        // fall through
+                        // falls through
 
                     case SyntaxKind.CatchClause:
                         return spanInNode(lastOrUndefined((<Block>node.parent).statements));
diff --git a/src/services/classifier.ts b/src/services/classifier.ts
index c15b65b0c39..0deff253212 100644
--- a/src/services/classifier.ts
+++ b/src/services/classifier.ts
@@ -160,7 +160,7 @@ namespace ts {
                 case EndOfLineState.InTemplateMiddleOrTail:
                     text = "}\n" + text;
                     offset = 2;
-                // fallthrough
+                    // falls through
                 case EndOfLineState.InTemplateSubstitutionPosition:
                     templateStack.push(SyntaxKind.TemplateHead);
                     break;
diff --git a/src/services/codefixes/fixAddMissingMember.ts b/src/services/codefixes/fixAddMissingMember.ts
index a808786230d..8e1d0ac2f29 100644
--- a/src/services/codefixes/fixAddMissingMember.ts
+++ b/src/services/codefixes/fixAddMissingMember.ts
@@ -14,7 +14,7 @@ namespace ts.codefix {
         //      ^^^^^^^
         const token = getTokenAtPosition(sourceFile, start);
 
-        if (token.kind != SyntaxKind.Identifier) {
+        if (token.kind !== SyntaxKind.Identifier) {
             return undefined;
         }
 
diff --git a/src/services/codefixes/fixClassSuperMustPrecedeThisAccess.ts b/src/services/codefixes/fixClassSuperMustPrecedeThisAccess.ts
index fc2be3cd0c2..2217dda8b0c 100644
--- a/src/services/codefixes/fixClassSuperMustPrecedeThisAccess.ts
+++ b/src/services/codefixes/fixClassSuperMustPrecedeThisAccess.ts
@@ -18,7 +18,7 @@ namespace ts.codefix {
 
             // figure out if the `this` access is actually inside the supercall
             // i.e. super(this.a), since in that case we won't suggest a fix
-            if (superCall.expression && superCall.expression.kind == SyntaxKind.CallExpression) {
+            if (superCall.expression && superCall.expression.kind === SyntaxKind.CallExpression) {
                 const arguments = (<CallExpression>superCall.expression).arguments;
                 for (let i = 0; i < arguments.length; i++) {
                     if ((<PropertyAccessExpression>arguments[i]).expression === token) {
diff --git a/src/services/codefixes/importFixes.ts b/src/services/codefixes/importFixes.ts
index e10794997ca..78c27a1276b 100644
--- a/src/services/codefixes/importFixes.ts
+++ b/src/services/codefixes/importFixes.ts
@@ -42,12 +42,13 @@ namespace ts.codefix {
 
                 switch (this.compareModuleSpecifiers(existingAction.moduleSpecifier, newAction.moduleSpecifier)) {
                     case ModuleSpecifierComparison.Better:
-                        // the new one is not worth considering if it is a new improt.
+                        // the new one is not worth considering if it is a new import.
                         // However if it is instead a insertion into existing import, the user might want to use
                         // the module specifier even it is worse by our standards. So keep it.
                         if (newAction.kind === "NewImport") {
                             return;
                         }
+                        // falls through
                     case ModuleSpecifierComparison.Equal:
                         // the current one is safe. But it is still possible that the new one is worse
                         // than another existing one. For example, you may have new imports from "./foo/bar"
diff --git a/src/services/codefixes/unusedIdentifierFixes.ts b/src/services/codefixes/unusedIdentifierFixes.ts
index 0daeea5df62..e1debfa4ffb 100644
--- a/src/services/codefixes/unusedIdentifierFixes.ts
+++ b/src/services/codefixes/unusedIdentifierFixes.ts
@@ -58,6 +58,8 @@ namespace ts.codefix {
                                         return deleteNodeInList(token.parent);
                                     }
                             }
+                            // TODO: #14885
+                            // falls through
 
                         case SyntaxKind.TypeParameter:
                             const typeParameters = (<DeclarationWithTypeParameters>token.parent.parent).typeParameters;
@@ -125,7 +127,7 @@ namespace ts.codefix {
 
                         case SyntaxKind.NamespaceImport:
                             const namespaceImport = <NamespaceImport>token.parent;
-                            if (namespaceImport.name == token && !(<ImportClause>namespaceImport.parent).name) {
+                            if (namespaceImport.name === token && !(<ImportClause>namespaceImport.parent).name) {
                                 const importDecl = getAncestor(namespaceImport, SyntaxKind.ImportDeclaration);
                                 return deleteNode(importDecl);
                             }
diff --git a/src/services/completions.ts b/src/services/completions.ts
index 2073b950bee..6ac3762b4c7 100644
--- a/src/services/completions.ts
+++ b/src/services/completions.ts
@@ -487,7 +487,7 @@ namespace ts.Completions {
                             // It has a left-hand side, so we're not in an opening JSX tag.
                             break;
                         }
-                        // fall through
+                        // falls through
 
                     case SyntaxKind.JsxSelfClosingElement:
                     case SyntaxKind.JsxElement:
@@ -1311,7 +1311,7 @@ namespace ts.Completions {
     }
 
     function isEqualityOperatorKind(kind: SyntaxKind) {
-        return kind == SyntaxKind.EqualsEqualsToken ||
+        return kind === SyntaxKind.EqualsEqualsToken ||
             kind === SyntaxKind.ExclamationEqualsToken ||
             kind === SyntaxKind.EqualsEqualsEqualsToken ||
             kind === SyntaxKind.ExclamationEqualsEqualsToken;
diff --git a/src/services/documentHighlights.ts b/src/services/documentHighlights.ts
index 047e665d7a5..a8afc46d736 100644
--- a/src/services/documentHighlights.ts
+++ b/src/services/documentHighlights.ts
@@ -233,7 +233,7 @@ namespace ts.DocumentHighlights {
                     if (statement.kind === SyntaxKind.ContinueStatement) {
                         continue;
                     }
-                // Fall through.
+                    // falls through
                 case SyntaxKind.ForStatement:
                 case SyntaxKind.ForInStatement:
                 case SyntaxKind.ForOfStatement:
diff --git a/src/services/findAllReferences.ts b/src/services/findAllReferences.ts
index 98e601ebb06..fd717fc546e 100644
--- a/src/services/findAllReferences.ts
+++ b/src/services/findAllReferences.ts
@@ -7,7 +7,7 @@ namespace ts.FindAllReferences {
         references: Entry[];
     }
 
-    type Definition =
+    export type Definition =
         | { type: "symbol"; symbol: Symbol; node: Node }
         | { type: "label"; node: Identifier }
         | { type: "keyword"; node: ts.Node }
@@ -20,7 +20,7 @@ namespace ts.FindAllReferences {
         node: Node;
         isInString?: true;
     }
-    interface SpanEntry {
+    export interface SpanEntry {
         type: "span";
         fileName: string;
         textSpan: TextSpan;
@@ -1234,7 +1234,7 @@ namespace ts.FindAllReferences.Core {
                 if (isObjectLiteralMethod(searchSpaceNode)) {
                     break;
                 }
-            // fall through
+                // falls through
             case SyntaxKind.PropertyDeclaration:
             case SyntaxKind.PropertySignature:
             case SyntaxKind.Constructor:
@@ -1247,7 +1247,7 @@ namespace ts.FindAllReferences.Core {
                 if (isExternalModule(<SourceFile>searchSpaceNode)) {
                     return undefined;
                 }
-            // Fall through
+                // falls through
             case SyntaxKind.FunctionDeclaration:
             case SyntaxKind.FunctionExpression:
                 break;
diff --git a/src/services/formatting/formatting.ts b/src/services/formatting/formatting.ts
index 3a4547d4597..d7c32da5e8d 100644
--- a/src/services/formatting/formatting.ts
+++ b/src/services/formatting/formatting.ts
@@ -483,9 +483,8 @@ namespace ts.formatting {
                 case SyntaxKind.MethodDeclaration:
                     if ((<MethodDeclaration>node).asteriskToken) {
                         return SyntaxKind.AsteriskToken;
-                    }/*
-                    fall-through
-                    */
+                    }
+                    // falls through
                 case SyntaxKind.PropertyDeclaration:
                 case SyntaxKind.Parameter:
                     return (<Declaration>node).name.kind;
diff --git a/src/services/outliningElementsCollector.ts b/src/services/outliningElementsCollector.ts
index 510f78c3f39..5080de2edcc 100644
--- a/src/services/outliningElementsCollector.ts
+++ b/src/services/outliningElementsCollector.ts
@@ -146,7 +146,7 @@ namespace ts.OutliningElementsCollector {
                         });
                         break;
                     }
-                // Fallthrough.
+                    // falls through
 
                 case SyntaxKind.ModuleBlock: {
                     const openBrace = findChildOfKind(n, SyntaxKind.OpenBraceToken, sourceFile);
diff --git a/src/services/services.ts b/src/services/services.ts
index 5624c48a535..8f2cbb22379 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -659,7 +659,7 @@ namespace ts {
                         if (!hasModifier(node, ModifierFlags.ParameterPropertyModifier)) {
                             break;
                         }
-                    // fall through
+                        // falls through
                     case SyntaxKind.VariableDeclaration:
                     case SyntaxKind.BindingElement: {
                         const decl = <VariableDeclaration>node;
@@ -670,6 +670,7 @@ namespace ts {
                         if (decl.initializer)
                             visit(decl.initializer);
                     }
+                        // falls through
                     case SyntaxKind.EnumMember:
                     case SyntaxKind.PropertyDeclaration:
                     case SyntaxKind.PropertySignature:
@@ -2079,7 +2080,7 @@ namespace ts {
                 if (node.parent.kind === SyntaxKind.ComputedPropertyName) {
                     return isObjectLiteralElement(node.parent.parent) ? node.parent.parent : undefined;
                 }
-            // intentionally fall through
+                // falls through
             case SyntaxKind.Identifier:
                 return isObjectLiteralElement(node.parent) &&
                     (node.parent.parent.kind === SyntaxKind.ObjectLiteralExpression || node.parent.parent.kind === SyntaxKind.JsxAttributes) &&
diff --git a/src/services/shims.ts b/src/services/shims.ts
index 37b3fbc3d94..7588e16f3dc 100644
--- a/src/services/shims.ts
+++ b/src/services/shims.ts
@@ -37,7 +37,7 @@ namespace ts {
          *
          * Or undefined value if there was no change.
          */
-        getChangeRange(oldSnapshot: ScriptSnapshotShim): string;
+        getChangeRange(oldSnapshot: ScriptSnapshotShim): string | undefined;
 
         /** Releases all resources held by this script snapshot */
         dispose?(): void;
@@ -292,8 +292,7 @@ namespace ts {
         public getChangeRange(oldSnapshot: IScriptSnapshot): TextChangeRange {
             const oldSnapshotShim = <ScriptSnapshotShimAdapter>oldSnapshot;
             const encoded = this.scriptSnapshotShim.getChangeRange(oldSnapshotShim.scriptSnapshotShim);
-            // TODO: should this be '==='?
-            if (encoded == null) {
+            if (encoded === null) {
                 return null;
             }
 
@@ -381,8 +380,7 @@ namespace ts {
 
         public getCompilationSettings(): CompilerOptions {
             const settingsJson = this.shimHost.getCompilationSettings();
-            // TODO: should this be '==='?
-            if (settingsJson == null || settingsJson == "") {
+            if (settingsJson === null || settingsJson === "") {
                 throw Error("LanguageServiceShimHostAdapter.getCompilationSettings: empty compilationSettings");
             }
             const compilerOptions = <CompilerOptions>JSON.parse(settingsJson);
@@ -416,7 +414,7 @@ namespace ts {
 
         public getLocalizedDiagnosticMessages(): any {
             const diagnosticMessagesJson = this.shimHost.getLocalizedDiagnosticMessages();
-            if (diagnosticMessagesJson == null || diagnosticMessagesJson == "") {
+            if (diagnosticMessagesJson === null || diagnosticMessagesJson === "") {
                 return null;
             }
 
diff --git a/src/services/signatureHelp.ts b/src/services/signatureHelp.ts
index 7b2abc6123c..1487bb410a5 100644
--- a/src/services/signatureHelp.ts
+++ b/src/services/signatureHelp.ts
@@ -56,7 +56,7 @@ namespace ts.SignatureHelp {
     //                break;
 
     //            case TypeScript.SyntaxKind.CommaToken:
-    //                if (stack == 0) {
+    //                if (stack === 0) {
     //                    argumentIndex++;
     //                }
 
diff --git a/src/services/textChanges.ts b/src/services/textChanges.ts
index d7056cfdca2..aa805da129a 100644
--- a/src/services/textChanges.ts
+++ b/src/services/textChanges.ts
@@ -465,7 +465,7 @@ namespace ts.textChanges {
                 change.options.indentation !== undefined
                     ? change.options.indentation
                     : change.useIndentationFromFile
-                        ? formatting.SmartIndenter.getIndentation(change.range.pos, sourceFile, formatOptions, posStartsLine || (change.options.prefix == this.newLineCharacter))
+                        ? formatting.SmartIndenter.getIndentation(change.range.pos, sourceFile, formatOptions, posStartsLine || (change.options.prefix === this.newLineCharacter))
                         : 0;
             const delta =
                 change.options.delta !== undefined
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index 815faac7417..56832b90d1f 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -441,7 +441,7 @@ namespace ts {
                 if (!(<NewExpression>n).arguments) {
                     return true;
                 }
-            // fall through
+            // falls through
             case SyntaxKind.CallExpression:
             case SyntaxKind.ParenthesizedExpression:
             case SyntaxKind.ParenthesizedType:
@@ -902,10 +902,10 @@ namespace ts {
             // Internally, we represent the end of the comment at the newline and closing '/', respectively.
             return predicate ?
                 forEach(commentRanges, c => c.pos < position &&
-                    (c.kind == SyntaxKind.SingleLineCommentTrivia ? position <= c.end : position < c.end) &&
+                    (c.kind === SyntaxKind.SingleLineCommentTrivia ? position <= c.end : position < c.end) &&
                     predicate(c)) :
                 forEach(commentRanges, c => c.pos < position &&
-                    (c.kind == SyntaxKind.SingleLineCommentTrivia ? position <= c.end : position < c.end));
+                    (c.kind === SyntaxKind.SingleLineCommentTrivia ? position <= c.end : position < c.end));
         }
 
         return false;
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignatures3.errors.txt b/tests/baselines/reference/assignmentCompatWithCallSignatures3.errors.txt
new file mode 100644
index 00000000000..0e8605efafd
--- /dev/null
+++ b/tests/baselines/reference/assignmentCompatWithCallSignatures3.errors.txt
@@ -0,0 +1,113 @@
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures3.ts(71,1): error TS2322: Type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U'.
+  Types of parameters 'y' and 'y' are incompatible.
+    Types of parameters 'arg2' and 'arg2' are incompatible.
+      Type 'Base' is not assignable to type '{ foo: string; bing: number; }'.
+        Property 'bing' is missing in type 'Base'.
+
+
+==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures3.ts (1 errors) ====
+    // these are all permitted with the current rules, since we do not do contextual signature instantiation
+    
+    class Base { foo: string; }
+    class Derived extends Base { bar: string; }
+    class Derived2 extends Derived { baz: string; }
+    class OtherDerived extends Base { bing: string; }
+    
+    var a: (x: number) => number[];
+    var a2: (x: number) => string[];
+    var a3: (x: number) => void;
+    var a4: (x: string, y: number) => string;
+    var a5: (x: (arg: string) => number) => string;
+    var a6: (x: (arg: Base) => Derived) => Base;
+    var a7: (x: (arg: Base) => Derived) => (r: Base) => Derived;
+    var a8: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived;
+    var a9: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived;
+    var a10: (...x: Derived[]) => Derived;
+    var a11: (x: { foo: string }, y: { foo: string; bar: string }) => Base;
+    var a12: (x: Array<Base>, y: Array<Derived2>) => Array<Derived>;
+    var a13: (x: Array<Base>, y: Array<Derived>) => Array<Derived>;
+    var a14: (x: { a: string; b: number }) => Object;
+    var a15: {
+        (x: number): number[];
+        (x: string): string[];
+    }
+    var a16: {
+        <T extends Derived>(x: T): number[];
+        <U extends Base>(x: U): number[];
+    }
+    var a17: {
+        (x: (a: number) => number): number[];
+        (x: (a: string) => string): string[];
+    };
+    var a18: {
+        (x: {
+            (a: number): number;
+            (a: string): string;
+        }): any[];
+        (x: {
+            (a: boolean): boolean;
+            (a: Date): Date;
+        }): any[];
+    }
+    
+    var b: <T>(x: T) => T[]; 
+    a = b; // ok
+    b = a; // ok
+    var b2: <T>(x: T) => string[]; 
+    a2 = b2; // ok 
+    b2 = a2; // ok
+    var b3: <T>(x: T) => T; 
+    a3 = b3; // ok
+    b3 = a3; // ok
+    var b4: <T, U>(x: T, y: U) => T; 
+    a4 = b4; // ok
+    b4 = a4; // ok
+    var b5: <T, U>(x: (arg: T) => U) => T; 
+    a5 = b5; // ok
+    b5 = a5; // ok
+    var b6: <T extends Base, U extends Derived>(x: (arg: T) => U) => T; 
+    a6 = b6; // ok
+    b6 = a6; // ok
+    var b7: <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => U; 
+    a7 = b7; // ok
+    b7 = a7; // ok
+    var b8: <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => U;
+    a8 = b8; // ok
+    b8 = a8; // ok
+    var b9: <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number }) => U) => (r: T) => U; 
+    a9 = b9; // ok
+    b9 = a9; // ok
+    ~~
+!!! error TS2322: Type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U'.
+!!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
+!!! error TS2322:     Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:       Type 'Base' is not assignable to type '{ foo: string; bing: number; }'.
+!!! error TS2322:         Property 'bing' is missing in type 'Base'.
+    var b10: <T extends Derived>(...x: T[]) => T; 
+    a10 = b10; // ok
+    b10 = a10; // ok
+    var b11: <T extends Base>(x: T, y: T) => T; 
+    a11 = b11; // ok
+    b11 = a11; // ok
+    var b12: <T extends Array<Base>>(x: Array<Base>, y: T) => Array<Derived>; 
+    a12 = b12; // ok
+    b12 = a12; // ok
+    var b13: <T extends Array<Derived>>(x: Array<Base>, y: T) => T; 
+    a13 = b13; // ok
+    b13 = a13; // ok
+    var b14: <T>(x: { a: T; b: T }) => T; 
+    a14 = b14; // ok
+    b14 = a14; // ok
+    var b15: <T>(x: T) => T[]; 
+    a15 = b15; // ok
+    b15 = a15; // ok
+    var b16: <T extends Base>(x: T) => number[];
+    a16 = b16; // ok
+    b16 = a16; // ok
+    var b17: <T>(x: (a: T) => T) => T[]; // ok
+    a17 = b17; // ok
+    b17 = a17; // ok
+    var b18: <T>(x: (a: T) => T) => T[]; 
+    a18 = b18; // ok
+    b18 = a18; // ok
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt b/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt
index 8d184edc085..df391b27f98 100644
--- a/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt
+++ b/tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt
@@ -1,17 +1,15 @@
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts(52,9): error TS2322: Type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
   Types of parameters 'y' and 'y' are incompatible.
-    Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-      Types of parameters 'arg2' and 'arg2' are incompatible.
-        Type '{ foo: number; }' is not assignable to type 'Base'.
-          Types of property 'foo' are incompatible.
-            Type 'number' is not assignable to type 'string'.
+    Types of parameters 'arg2' and 'arg2' are incompatible.
+      Type '{ foo: number; }' is not assignable to type 'Base'.
+        Types of property 'foo' are incompatible.
+          Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts(53,9): error TS2322: Type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
   Types of parameters 'y' and 'y' are incompatible.
-    Type '(arg2: { foo: number; }) => any' is not assignable to type '(arg2: Base) => Derived'.
-      Types of parameters 'arg2' and 'arg2' are incompatible.
-        Type 'Base' is not assignable to type '{ foo: number; }'.
-          Types of property 'foo' are incompatible.
-            Type 'string' is not assignable to type 'number'.
+    Types of parameters 'arg2' and 'arg2' are incompatible.
+      Type 'Base' is not assignable to type '{ foo: number; }'.
+        Types of property 'foo' are incompatible.
+          Type 'string' is not assignable to type 'number'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts (2 errors) ====
@@ -70,20 +68,18 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
             ~~
 !!! error TS2322: Type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
 !!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
-!!! error TS2322:     Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-!!! error TS2322:       Types of parameters 'arg2' and 'arg2' are incompatible.
-!!! error TS2322:         Type '{ foo: number; }' is not assignable to type 'Base'.
-!!! error TS2322:           Types of property 'foo' are incompatible.
-!!! error TS2322:             Type 'number' is not assignable to type 'string'.
+!!! error TS2322:     Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:       Type '{ foo: number; }' is not assignable to type 'Base'.
+!!! error TS2322:         Types of property 'foo' are incompatible.
+!!! error TS2322:           Type 'number' is not assignable to type 'string'.
             b8 = a8; // error, { foo: number } and Base are incompatible
             ~~
 !!! error TS2322: Type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
 !!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
-!!! error TS2322:     Type '(arg2: { foo: number; }) => any' is not assignable to type '(arg2: Base) => Derived'.
-!!! error TS2322:       Types of parameters 'arg2' and 'arg2' are incompatible.
-!!! error TS2322:         Type 'Base' is not assignable to type '{ foo: number; }'.
-!!! error TS2322:           Types of property 'foo' are incompatible.
-!!! error TS2322:             Type 'string' is not assignable to type 'number'.
+!!! error TS2322:     Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:       Type 'Base' is not assignable to type '{ foo: number; }'.
+!!! error TS2322:         Types of property 'foo' are incompatible.
+!!! error TS2322:           Type 'string' is not assignable to type 'number'.
     
             
             var b10: <T extends Derived>(...x: T[]) => T; 
diff --git a/tests/baselines/reference/assignmentCompatWithConstructSignatures3.errors.txt b/tests/baselines/reference/assignmentCompatWithConstructSignatures3.errors.txt
new file mode 100644
index 00000000000..995a9b67ccd
--- /dev/null
+++ b/tests/baselines/reference/assignmentCompatWithConstructSignatures3.errors.txt
@@ -0,0 +1,113 @@
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures3.ts(71,1): error TS2322: Type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U'.
+  Types of parameters 'y' and 'y' are incompatible.
+    Types of parameters 'arg2' and 'arg2' are incompatible.
+      Type 'Base' is not assignable to type '{ foo: string; bing: number; }'.
+        Property 'bing' is missing in type 'Base'.
+
+
+==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures3.ts (1 errors) ====
+    // checking assignment compatibility relations for function types. All of these are valid.
+    
+    class Base { foo: string; }
+    class Derived extends Base { bar: string; }
+    class Derived2 extends Derived { baz: string; }
+    class OtherDerived extends Base { bing: string; }
+    
+    var a: new (x: number) => number[];
+    var a2: new (x: number) => string[];
+    var a3: new (x: number) => void;
+    var a4: new (x: string, y: number) => string;
+    var a5: new (x: (arg: string) => number) => string;
+    var a6: new (x: (arg: Base) => Derived) => Base;
+    var a7: new (x: (arg: Base) => Derived) => (r: Base) => Derived;
+    var a8: new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived;
+    var a9: new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived;
+    var a10: new (...x: Derived[]) => Derived;
+    var a11: new (x: { foo: string }, y: { foo: string; bar: string }) => Base;
+    var a12: new (x: Array<Base>, y: Array<Derived2>) => Array<Derived>;
+    var a13: new (x: Array<Base>, y: Array<Derived>) => Array<Derived>;
+    var a14: new (x: { a: string; b: number }) => Object;
+    var a15: {
+        new (x: number): number[];
+        new (x: string): string[];
+    }
+    var a16: {
+        new <T extends Derived>(x: T): number[];
+        new <U extends Base>(x: U): number[];
+    }
+    var a17: {
+        new (x: new (a: number) => number): number[];
+        new (x: new (a: string) => string): string[];
+    };
+    var a18: {
+        new (x: {
+            new (a: number): number;
+            new (a: string): string;
+        }): any[];
+        new (x: {
+            new (a: boolean): boolean;
+            new (a: Date): Date;
+        }): any[];
+    }
+    
+    var b: new <T>(x: T) => T[]; 
+    a = b; // ok
+    b = a; // ok
+    var b2: new <T>(x: T) => string[]; 
+    a2 = b2; // ok 
+    b2 = a2; // ok
+    var b3: new <T>(x: T) => T; 
+    a3 = b3; // ok
+    b3 = a3; // ok
+    var b4: new <T, U>(x: T, y: U) => T; 
+    a4 = b4; // ok
+    b4 = a4; // ok
+    var b5: new <T, U>(x: (arg: T) => U) => T; 
+    a5 = b5; // ok
+    b5 = a5; // ok
+    var b6: new <T extends Base, U extends Derived>(x: (arg: T) => U) => T; 
+    a6 = b6; // ok
+    b6 = a6; // ok
+    var b7: new <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => U; 
+    a7 = b7; // ok
+    b7 = a7; // ok
+    var b8: new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => U;
+    a8 = b8; // ok
+    b8 = a8; // ok
+    var b9: new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number }) => U) => (r: T) => U; 
+    a9 = b9; // ok
+    b9 = a9; // ok
+    ~~
+!!! error TS2322: Type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U'.
+!!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
+!!! error TS2322:     Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:       Type 'Base' is not assignable to type '{ foo: string; bing: number; }'.
+!!! error TS2322:         Property 'bing' is missing in type 'Base'.
+    var b10: new <T extends Derived>(...x: T[]) => T; 
+    a10 = b10; // ok
+    b10 = a10; // ok
+    var b11: new <T extends Base>(x: T, y: T) => T; 
+    a11 = b11; // ok
+    b11 = a11; // ok
+    var b12: new <T extends Array<Base>>(x: Array<Base>, y: T) => Array<Derived>; 
+    a12 = b12; // ok
+    b12 = a12; // ok
+    var b13: new <T extends Array<Derived>>(x: Array<Base>, y: T) => T; 
+    a13 = b13; // ok
+    b13 = a13; // ok
+    var b14: new <T>(x: { a: T; b: T }) => T; 
+    a14 = b14; // ok
+    b14 = a14; // ok
+    var b15: new <T>(x: T) => T[]; 
+    a15 = b15; // ok
+    b15 = a15; // ok
+    var b16: new <T extends Base>(x: T) => number[];
+    a16 = b16; // ok
+    b16 = a16; // ok
+    var b17: new <T>(x: new (a: T) => T) => T[]; // ok
+    a17 = b17; // ok
+    b17 = a17; // ok
+    var b18: new <T>(x: new (a: T) => T) => T[]; 
+    a18 = b18; // ok
+    b18 = a18; // ok
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt b/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt
index f6e93e13f04..6b2f4a0de17 100644
--- a/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt
+++ b/tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt
@@ -1,17 +1,15 @@
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(52,9): error TS2322: Type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
   Types of parameters 'y' and 'y' are incompatible.
-    Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-      Types of parameters 'arg2' and 'arg2' are incompatible.
-        Type '{ foo: number; }' is not assignable to type 'Base'.
-          Types of property 'foo' are incompatible.
-            Type 'number' is not assignable to type 'string'.
+    Types of parameters 'arg2' and 'arg2' are incompatible.
+      Type '{ foo: number; }' is not assignable to type 'Base'.
+        Types of property 'foo' are incompatible.
+          Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(53,9): error TS2322: Type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
   Types of parameters 'y' and 'y' are incompatible.
-    Type '(arg2: { foo: number; }) => any' is not assignable to type '(arg2: Base) => Derived'.
-      Types of parameters 'arg2' and 'arg2' are incompatible.
-        Type 'Base' is not assignable to type '{ foo: number; }'.
-          Types of property 'foo' are incompatible.
-            Type 'string' is not assignable to type 'number'.
+    Types of parameters 'arg2' and 'arg2' are incompatible.
+      Type 'Base' is not assignable to type '{ foo: number; }'.
+        Types of property 'foo' are incompatible.
+          Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(77,9): error TS2322: Type 'new <T>(x: (a: T) => T) => T[]' is not assignable to type '{ new (x: { new (a: number): number; new (a?: number): number; }): number[]; new (x: { new (a: boolean): boolean; new (a?: boolean): boolean; }): boolean[]; }'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ new (a: number): number; new (a?: number): number; }' is not assignable to type '(a: any) => any'.
@@ -86,20 +84,18 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
             ~~
 !!! error TS2322: Type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
 !!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
-!!! error TS2322:     Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-!!! error TS2322:       Types of parameters 'arg2' and 'arg2' are incompatible.
-!!! error TS2322:         Type '{ foo: number; }' is not assignable to type 'Base'.
-!!! error TS2322:           Types of property 'foo' are incompatible.
-!!! error TS2322:             Type 'number' is not assignable to type 'string'.
+!!! error TS2322:     Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:       Type '{ foo: number; }' is not assignable to type 'Base'.
+!!! error TS2322:         Types of property 'foo' are incompatible.
+!!! error TS2322:           Type 'number' is not assignable to type 'string'.
             b8 = a8; // error
             ~~
 !!! error TS2322: Type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived' is not assignable to type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U'.
 !!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
-!!! error TS2322:     Type '(arg2: { foo: number; }) => any' is not assignable to type '(arg2: Base) => Derived'.
-!!! error TS2322:       Types of parameters 'arg2' and 'arg2' are incompatible.
-!!! error TS2322:         Type 'Base' is not assignable to type '{ foo: number; }'.
-!!! error TS2322:           Types of property 'foo' are incompatible.
-!!! error TS2322:             Type 'string' is not assignable to type 'number'.
+!!! error TS2322:     Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2322:       Type 'Base' is not assignable to type '{ foo: number; }'.
+!!! error TS2322:         Types of property 'foo' are incompatible.
+!!! error TS2322:           Type 'string' is not assignable to type 'number'.
     
             
             var b10: new <T extends Derived>(...x: T[]) => T; 
diff --git a/tests/baselines/reference/assignmentToExpandingArrayType.js b/tests/baselines/reference/assignmentToExpandingArrayType.js
new file mode 100644
index 00000000000..5b885b6913f
--- /dev/null
+++ b/tests/baselines/reference/assignmentToExpandingArrayType.js
@@ -0,0 +1,56 @@
+//// [assignmentToExpandingArrayType.ts]
+// Fixes exponential time/space in #14628
+let x = []
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' } // previously ran out of memory here
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+
+
+//// [assignmentToExpandingArrayType.js]
+// Fixes exponential time/space in #14628
+var x = [];
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' }; // previously ran out of memory here
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
+x[0] = { foo: 'hi' };
diff --git a/tests/baselines/reference/assignmentToExpandingArrayType.symbols b/tests/baselines/reference/assignmentToExpandingArrayType.symbols
new file mode 100644
index 00000000000..c8285706f6e
--- /dev/null
+++ b/tests/baselines/reference/assignmentToExpandingArrayType.symbols
@@ -0,0 +1,101 @@
+=== tests/cases/compiler/assignmentToExpandingArrayType.ts ===
+// Fixes exponential time/space in #14628
+let x = []
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 2, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 3, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 4, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 5, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 6, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 7, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 8, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 9, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 10, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 11, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 12, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 13, 8))
+
+x[0] = { foo: 'hi' } // previously ran out of memory here
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 14, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 15, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 16, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 17, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 18, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 19, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 20, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 21, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 22, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 23, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 24, 8))
+
+x[0] = { foo: 'hi' }
+>x : Symbol(x, Decl(assignmentToExpandingArrayType.ts, 1, 3))
+>foo : Symbol(foo, Decl(assignmentToExpandingArrayType.ts, 25, 8))
+
diff --git a/tests/baselines/reference/assignmentToExpandingArrayType.types b/tests/baselines/reference/assignmentToExpandingArrayType.types
new file mode 100644
index 00000000000..da923b23646
--- /dev/null
+++ b/tests/baselines/reference/assignmentToExpandingArrayType.types
@@ -0,0 +1,222 @@
+=== tests/cases/compiler/assignmentToExpandingArrayType.ts ===
+// Fixes exponential time/space in #14628
+let x = []
+>x : any[]
+>[] : undefined[]
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' } // previously ran out of memory here
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
+x[0] = { foo: 'hi' }
+>x[0] = { foo: 'hi' } : { foo: string; }
+>x[0] : any
+>x : any[]
+>0 : 0
+>{ foo: 'hi' } : { foo: string; }
+>foo : string
+>'hi' : "hi"
+
diff --git a/tests/baselines/reference/callSignatureAssignabilityInInheritance3.errors.txt b/tests/baselines/reference/callSignatureAssignabilityInInheritance3.errors.txt
index 2d7e795d26a..f5e05567b25 100644
--- a/tests/baselines/reference/callSignatureAssignabilityInInheritance3.errors.txt
+++ b/tests/baselines/reference/callSignatureAssignabilityInInheritance3.errors.txt
@@ -7,11 +7,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/callSign
   Types of property 'a8' are incompatible.
     Type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
       Types of parameters 'y' and 'y' are incompatible.
-        Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-          Types of parameters 'arg2' and 'arg2' are incompatible.
-            Type '{ foo: number; }' is not assignable to type 'Base'.
-              Types of property 'foo' are incompatible.
-                Type 'number' is not assignable to type 'string'.
+        Types of parameters 'arg2' and 'arg2' are incompatible.
+          Type '{ foo: number; }' is not assignable to type 'Base'.
+            Types of property 'foo' are incompatible.
+              Type 'number' is not assignable to type 'string'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/callSignatureAssignabilityInInheritance3.ts (2 errors) ====
@@ -86,11 +85,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/callSign
 !!! error TS2430:   Types of property 'a8' are incompatible.
 !!! error TS2430:     Type '<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type '(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
 !!! error TS2430:       Types of parameters 'y' and 'y' are incompatible.
-!!! error TS2430:         Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-!!! error TS2430:           Types of parameters 'arg2' and 'arg2' are incompatible.
-!!! error TS2430:             Type '{ foo: number; }' is not assignable to type 'Base'.
-!!! error TS2430:               Types of property 'foo' are incompatible.
-!!! error TS2430:                 Type 'number' is not assignable to type 'string'.
+!!! error TS2430:         Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2430:           Type '{ foo: number; }' is not assignable to type 'Base'.
+!!! error TS2430:             Types of property 'foo' are incompatible.
+!!! error TS2430:               Type 'number' is not assignable to type 'string'.
                 a8: <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U; // error, type mismatch
             }
     
diff --git a/tests/baselines/reference/checkJsFiles_noErrorLocation.errors.txt b/tests/baselines/reference/checkJsFiles_noErrorLocation.errors.txt
new file mode 100644
index 00000000000..758b295a49d
--- /dev/null
+++ b/tests/baselines/reference/checkJsFiles_noErrorLocation.errors.txt
@@ -0,0 +1,25 @@
+tests/cases/compiler/a.js(14,5): error TS2424: Class 'A' defines instance member function 'foo', but extended class 'B' defines it as instance member property.
+
+
+==== tests/cases/compiler/a.js (1 errors) ====
+    // @ts-check
+    class A {
+      constructor() {
+    
+      }
+      foo() {
+        return 4;
+      }
+    }
+    
+    class B extends A {
+      constructor() {
+        super();
+        this.foo = () => 3;
+        ~~~~~~~~~~~~~~~~~~
+!!! error TS2424: Class 'A' defines instance member function 'foo', but extended class 'B' defines it as instance member property.
+      }
+    }
+    
+    const i = new B();
+    i.foo();
\ No newline at end of file
diff --git a/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.errors.txt b/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.errors.txt
index 086372aac17..7bd76159391 100644
--- a/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.errors.txt
+++ b/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.errors.txt
@@ -7,11 +7,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/construc
   Types of property 'a8' are incompatible.
     Type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
       Types of parameters 'y' and 'y' are incompatible.
-        Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-          Types of parameters 'arg2' and 'arg2' are incompatible.
-            Type '{ foo: number; }' is not assignable to type 'Base'.
-              Types of property 'foo' are incompatible.
-                Type 'number' is not assignable to type 'string'.
+        Types of parameters 'arg2' and 'arg2' are incompatible.
+          Type '{ foo: number; }' is not assignable to type 'Base'.
+            Types of property 'foo' are incompatible.
+              Type 'number' is not assignable to type 'string'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/constructSignatureAssignabilityInInheritance3.ts (2 errors) ====
@@ -76,11 +75,10 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/construc
 !!! error TS2430:   Types of property 'a8' are incompatible.
 !!! error TS2430:     Type 'new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U' is not assignable to type 'new (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived'.
 !!! error TS2430:       Types of parameters 'y' and 'y' are incompatible.
-!!! error TS2430:         Type '(arg2: Base) => Derived' is not assignable to type '(arg2: { foo: number; }) => any'.
-!!! error TS2430:           Types of parameters 'arg2' and 'arg2' are incompatible.
-!!! error TS2430:             Type '{ foo: number; }' is not assignable to type 'Base'.
-!!! error TS2430:               Types of property 'foo' are incompatible.
-!!! error TS2430:                 Type 'number' is not assignable to type 'string'.
+!!! error TS2430:         Types of parameters 'arg2' and 'arg2' are incompatible.
+!!! error TS2430:           Type '{ foo: number; }' is not assignable to type 'Base'.
+!!! error TS2430:             Types of property 'foo' are incompatible.
+!!! error TS2430:               Type 'number' is not assignable to type 'string'.
                 a8: new <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: number; }) => U) => (r: T) => U; // error, type mismatch
             }
     
diff --git a/tests/baselines/reference/covariantCallbacks.errors.txt b/tests/baselines/reference/covariantCallbacks.errors.txt
new file mode 100644
index 00000000000..55c69c89728
--- /dev/null
+++ b/tests/baselines/reference/covariantCallbacks.errors.txt
@@ -0,0 +1,132 @@
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts(12,5): error TS2322: Type 'P<A>' is not assignable to type 'P<B>'.
+  Type 'A' is not assignable to type 'B'.
+    Property 'b' is missing in type 'A'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts(17,5): error TS2322: Type 'Promise<A>' is not assignable to type 'Promise<B>'.
+  Type 'A' is not assignable to type 'B'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts(30,5): error TS2322: Type 'AList1' is not assignable to type 'BList1'.
+  Types of property 'forEach' are incompatible.
+    Type '(cb: (item: A) => void) => void' is not assignable to type '(cb: (item: B) => void) => void'.
+      Types of parameters 'cb' and 'cb' are incompatible.
+        Types of parameters 'item' and 'item' are incompatible.
+          Type 'A' is not assignable to type 'B'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts(43,5): error TS2322: Type 'AList2' is not assignable to type 'BList2'.
+  Types of property 'forEach' are incompatible.
+    Type '(cb: (item: A) => boolean) => void' is not assignable to type '(cb: (item: A) => void) => void'.
+      Types of parameters 'cb' and 'cb' are incompatible.
+        Type 'void' is not assignable to type 'boolean'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts(56,5): error TS2322: Type 'AList3' is not assignable to type 'BList3'.
+  Types of property 'forEach' are incompatible.
+    Type '(cb: (item: A) => void) => void' is not assignable to type '(cb: (item: A, context: any) => void) => void'.
+      Types of parameters 'cb' and 'cb' are incompatible.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts(69,5): error TS2322: Type 'AList4' is not assignable to type 'BList4'.
+  Types of property 'forEach' are incompatible.
+    Type '(cb: (item: A) => A) => void' is not assignable to type '(cb: (item: B) => B) => void'.
+      Types of parameters 'cb' and 'cb' are incompatible.
+        Types of parameters 'item' and 'item' are incompatible.
+          Type 'A' is not assignable to type 'B'.
+
+
+==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts (6 errors) ====
+    // Test that callback parameters are related covariantly
+    
+    interface P<T> {
+        then(cb: (value: T) => void): void;
+    };
+    
+    interface A { a: string }
+    interface B extends A { b: string }
+    
+    function f1(a: P<A>, b: P<B>) {
+        a = b;
+        b = a;  // Error
+        ~
+!!! error TS2322: Type 'P<A>' is not assignable to type 'P<B>'.
+!!! error TS2322:   Type 'A' is not assignable to type 'B'.
+!!! error TS2322:     Property 'b' is missing in type 'A'.
+    }
+    
+    function f2(a: Promise<A>, b: Promise<B>) {
+        a = b;
+        b = a;  // Error
+        ~
+!!! error TS2322: Type 'Promise<A>' is not assignable to type 'Promise<B>'.
+!!! error TS2322:   Type 'A' is not assignable to type 'B'.
+    }
+    
+    interface AList1 {
+        forEach(cb: (item: A) => void): void;
+    }
+    
+    interface BList1 {
+        forEach(cb: (item: B) => void): void;
+    }
+    
+    function f11(a: AList1, b: BList1) {
+        a = b;
+        b = a;  // Error
+        ~
+!!! error TS2322: Type 'AList1' is not assignable to type 'BList1'.
+!!! error TS2322:   Types of property 'forEach' are incompatible.
+!!! error TS2322:     Type '(cb: (item: A) => void) => void' is not assignable to type '(cb: (item: B) => void) => void'.
+!!! error TS2322:       Types of parameters 'cb' and 'cb' are incompatible.
+!!! error TS2322:         Types of parameters 'item' and 'item' are incompatible.
+!!! error TS2322:           Type 'A' is not assignable to type 'B'.
+    }
+    
+    interface AList2 {
+        forEach(cb: (item: A) => boolean): void;
+    }
+    
+    interface BList2 {
+        forEach(cb: (item: A) => void): void;
+    }
+    
+    function f12(a: AList2, b: BList2) {
+        a = b;
+        b = a;  // Error
+        ~
+!!! error TS2322: Type 'AList2' is not assignable to type 'BList2'.
+!!! error TS2322:   Types of property 'forEach' are incompatible.
+!!! error TS2322:     Type '(cb: (item: A) => boolean) => void' is not assignable to type '(cb: (item: A) => void) => void'.
+!!! error TS2322:       Types of parameters 'cb' and 'cb' are incompatible.
+!!! error TS2322:         Type 'void' is not assignable to type 'boolean'.
+    }
+    
+    interface AList3 {
+        forEach(cb: (item: A) => void): void;
+    }
+    
+    interface BList3 {
+        forEach(cb: (item: A, context: any) => void): void;
+    }
+    
+    function f13(a: AList3, b: BList3) {
+        a = b;
+        b = a;  // Error
+        ~
+!!! error TS2322: Type 'AList3' is not assignable to type 'BList3'.
+!!! error TS2322:   Types of property 'forEach' are incompatible.
+!!! error TS2322:     Type '(cb: (item: A) => void) => void' is not assignable to type '(cb: (item: A, context: any) => void) => void'.
+!!! error TS2322:       Types of parameters 'cb' and 'cb' are incompatible.
+    }
+    
+    interface AList4 {
+        forEach(cb: (item: A) => A): void;
+    }
+    
+    interface BList4 {
+        forEach(cb: (item: B) => B): void;
+    }
+    
+    function f14(a: AList4, b: BList4) {
+        a = b;
+        b = a;  // Error
+        ~
+!!! error TS2322: Type 'AList4' is not assignable to type 'BList4'.
+!!! error TS2322:   Types of property 'forEach' are incompatible.
+!!! error TS2322:     Type '(cb: (item: A) => A) => void' is not assignable to type '(cb: (item: B) => B) => void'.
+!!! error TS2322:       Types of parameters 'cb' and 'cb' are incompatible.
+!!! error TS2322:         Types of parameters 'item' and 'item' are incompatible.
+!!! error TS2322:           Type 'A' is not assignable to type 'B'.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/covariantCallbacks.js b/tests/baselines/reference/covariantCallbacks.js
new file mode 100644
index 00000000000..4678c13bf15
--- /dev/null
+++ b/tests/baselines/reference/covariantCallbacks.js
@@ -0,0 +1,101 @@
+//// [covariantCallbacks.ts]
+// Test that callback parameters are related covariantly
+
+interface P<T> {
+    then(cb: (value: T) => void): void;
+};
+
+interface A { a: string }
+interface B extends A { b: string }
+
+function f1(a: P<A>, b: P<B>) {
+    a = b;
+    b = a;  // Error
+}
+
+function f2(a: Promise<A>, b: Promise<B>) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList1 {
+    forEach(cb: (item: A) => void): void;
+}
+
+interface BList1 {
+    forEach(cb: (item: B) => void): void;
+}
+
+function f11(a: AList1, b: BList1) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList2 {
+    forEach(cb: (item: A) => boolean): void;
+}
+
+interface BList2 {
+    forEach(cb: (item: A) => void): void;
+}
+
+function f12(a: AList2, b: BList2) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList3 {
+    forEach(cb: (item: A) => void): void;
+}
+
+interface BList3 {
+    forEach(cb: (item: A, context: any) => void): void;
+}
+
+function f13(a: AList3, b: BList3) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList4 {
+    forEach(cb: (item: A) => A): void;
+}
+
+interface BList4 {
+    forEach(cb: (item: B) => B): void;
+}
+
+function f14(a: AList4, b: BList4) {
+    a = b;
+    b = a;  // Error
+}
+
+
+//// [covariantCallbacks.js]
+"use strict";
+// Test that callback parameters are related covariantly
+;
+function f1(a, b) {
+    a = b;
+    b = a; // Error
+}
+function f2(a, b) {
+    a = b;
+    b = a; // Error
+}
+function f11(a, b) {
+    a = b;
+    b = a; // Error
+}
+function f12(a, b) {
+    a = b;
+    b = a; // Error
+}
+function f13(a, b) {
+    a = b;
+    b = a; // Error
+}
+function f14(a, b) {
+    a = b;
+    b = a; // Error
+}
diff --git a/tests/baselines/reference/exportBinding.js b/tests/baselines/reference/exportBinding.js
new file mode 100644
index 00000000000..5059c5356a3
--- /dev/null
+++ b/tests/baselines/reference/exportBinding.js
@@ -0,0 +1,19 @@
+//// [exportBinding.ts]
+export { x }
+const x = 'x'
+
+export { Y as Z }
+class Y {}
+
+
+//// [exportBinding.js]
+"use strict";
+exports.__esModule = true;
+var x = 'x';
+exports.x = x;
+var Y = (function () {
+    function Y() {
+    }
+    return Y;
+}());
+exports.Z = Y;
diff --git a/tests/baselines/reference/exportBinding.symbols b/tests/baselines/reference/exportBinding.symbols
new file mode 100644
index 00000000000..cb3b58a5776
--- /dev/null
+++ b/tests/baselines/reference/exportBinding.symbols
@@ -0,0 +1,14 @@
+=== tests/cases/conformance/es6/modules/exportBinding.ts ===
+export { x }
+>x : Symbol(x, Decl(exportBinding.ts, 0, 8))
+
+const x = 'x'
+>x : Symbol(x, Decl(exportBinding.ts, 1, 5))
+
+export { Y as Z }
+>Y : Symbol(Z, Decl(exportBinding.ts, 3, 8))
+>Z : Symbol(Z, Decl(exportBinding.ts, 3, 8))
+
+class Y {}
+>Y : Symbol(Y, Decl(exportBinding.ts, 3, 17))
+
diff --git a/tests/baselines/reference/exportBinding.types b/tests/baselines/reference/exportBinding.types
new file mode 100644
index 00000000000..e2553ba1eaa
--- /dev/null
+++ b/tests/baselines/reference/exportBinding.types
@@ -0,0 +1,15 @@
+=== tests/cases/conformance/es6/modules/exportBinding.ts ===
+export { x }
+>x : "x"
+
+const x = 'x'
+>x : "x"
+>'x' : "x"
+
+export { Y as Z }
+>Y : typeof Y
+>Z : typeof Y
+
+class Y {}
+>Y : Y
+
diff --git a/tests/baselines/reference/jsFileClassPropertyInitalizationInObjectLiteral.symbols b/tests/baselines/reference/jsFileClassPropertyInitalizationInObjectLiteral.symbols
new file mode 100644
index 00000000000..6cb2e235ce2
--- /dev/null
+++ b/tests/baselines/reference/jsFileClassPropertyInitalizationInObjectLiteral.symbols
@@ -0,0 +1,15 @@
+=== tests/cases/compiler/foo.js ===
+module.exports = function () {
+>module : Symbol(export=, Decl(foo.js, 0, 0))
+>exports : Symbol(export=, Decl(foo.js, 0, 0))
+
+  class A { }
+>A : Symbol(A, Decl(foo.js, 0, 30))
+
+  return {
+    c: A.b = 1,
+>c : Symbol(c, Decl(foo.js, 2, 10))
+>A : Symbol(A, Decl(foo.js, 0, 30))
+  }
+};
+
diff --git a/tests/baselines/reference/jsFileClassPropertyInitalizationInObjectLiteral.types b/tests/baselines/reference/jsFileClassPropertyInitalizationInObjectLiteral.types
new file mode 100644
index 00000000000..fc1fad7f861
--- /dev/null
+++ b/tests/baselines/reference/jsFileClassPropertyInitalizationInObjectLiteral.types
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/foo.js ===
+module.exports = function () {
+>module.exports = function () {  class A { }  return {    c: A.b = 1,  }} : () => { [x: string]: any; c: number; }
+>module.exports : any
+>module : any
+>exports : any
+>function () {  class A { }  return {    c: A.b = 1,  }} : () => { [x: string]: any; c: number; }
+
+  class A { }
+>A : A
+
+  return {
+>{    c: A.b = 1,  } : { [x: string]: any; c: number; }
+
+    c: A.b = 1,
+>c : number
+>A.b = 1 : 1
+>A.b : any
+>A : typeof A
+>b : any
+>1 : 1
+  }
+};
+
diff --git a/tests/baselines/reference/library-reference-scoped-packages.js b/tests/baselines/reference/library-reference-scoped-packages.js
new file mode 100644
index 00000000000..3019008c16b
--- /dev/null
+++ b/tests/baselines/reference/library-reference-scoped-packages.js
@@ -0,0 +1,11 @@
+//// [tests/cases/conformance/references/library-reference-scoped-packages.ts] ////
+
+//// [index.d.ts]
+export const y = 0;
+
+//// [a.ts]
+/// <reference types="@beep/boop" />
+
+
+//// [a.js]
+/// <reference types="@beep/boop" />
diff --git a/tests/baselines/reference/library-reference-scoped-packages.symbols b/tests/baselines/reference/library-reference-scoped-packages.symbols
new file mode 100644
index 00000000000..60ccaab89d2
--- /dev/null
+++ b/tests/baselines/reference/library-reference-scoped-packages.symbols
@@ -0,0 +1,7 @@
+=== /a.ts ===
+/// <reference types="@beep/boop" />
+No type information for this code.
+No type information for this code.=== /node_modules/@types/beep__boop/index.d.ts ===
+export const y = 0;
+>y : Symbol(y, Decl(index.d.ts, 0, 12))
+
diff --git a/tests/baselines/reference/library-reference-scoped-packages.trace.json b/tests/baselines/reference/library-reference-scoped-packages.trace.json
new file mode 100644
index 00000000000..54dcf95fe50
--- /dev/null
+++ b/tests/baselines/reference/library-reference-scoped-packages.trace.json
@@ -0,0 +1,12 @@
+[
+    "======== Resolving type reference directive '@beep/boop', containing file '/a.ts', root directory 'types'. ========",
+    "Resolving with primary search path 'types'.",
+    "Directory 'types/@beep' does not exist, skipping all lookups in it.",
+    "Looking up in 'node_modules' folder, initial location '/'.",
+    "Scoped package detected, looking in 'beep__boop'",
+    "File '/node_modules/@types/beep__boop.d.ts' does not exist.",
+    "File '/node_modules/@types/beep__boop/package.json' does not exist.",
+    "File '/node_modules/@types/beep__boop/index.d.ts' exist - use it as a name resolution result.",
+    "Resolving real path for '/node_modules/@types/beep__boop/index.d.ts', result '/node_modules/@types/beep__boop/index.d.ts'.",
+    "======== Type reference directive '@beep/boop' was successfully resolved to '/node_modules/@types/beep__boop/index.d.ts', primary: false. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-scoped-packages.types b/tests/baselines/reference/library-reference-scoped-packages.types
new file mode 100644
index 00000000000..bbb3062d98b
--- /dev/null
+++ b/tests/baselines/reference/library-reference-scoped-packages.types
@@ -0,0 +1,8 @@
+=== /a.ts ===
+/// <reference types="@beep/boop" />
+No type information for this code.
+No type information for this code.=== /node_modules/@types/beep__boop/index.d.ts ===
+export const y = 0;
+>y : 0
+>0 : 0
+
diff --git a/tests/baselines/reference/optionalFunctionArgAssignability.errors.txt b/tests/baselines/reference/optionalFunctionArgAssignability.errors.txt
index 024c5c1ea2b..1898db92463 100644
--- a/tests/baselines/reference/optionalFunctionArgAssignability.errors.txt
+++ b/tests/baselines/reference/optionalFunctionArgAssignability.errors.txt
@@ -1,8 +1,7 @@
 tests/cases/compiler/optionalFunctionArgAssignability.ts(7,1): error TS2322: Type '<U>(onFulFill?: (value: number) => U, onReject?: (reason: any) => U) => Promise<U>' is not assignable to type '<U>(onFulfill?: (value: string) => U, onReject?: (reason: any) => U) => Promise<U>'.
   Types of parameters 'onFulFill' and 'onFulfill' are incompatible.
-    Type '(value: string) => any' is not assignable to type '(value: number) => any'.
-      Types of parameters 'value' and 'value' are incompatible.
-        Type 'number' is not assignable to type 'string'.
+    Types of parameters 'value' and 'value' are incompatible.
+      Type 'number' is not assignable to type 'string'.
 
 
 ==== tests/cases/compiler/optionalFunctionArgAssignability.ts (1 errors) ====
@@ -16,7 +15,6 @@ tests/cases/compiler/optionalFunctionArgAssignability.ts(7,1): error TS2322: Typ
     ~
 !!! error TS2322: Type '<U>(onFulFill?: (value: number) => U, onReject?: (reason: any) => U) => Promise<U>' is not assignable to type '<U>(onFulfill?: (value: string) => U, onReject?: (reason: any) => U) => Promise<U>'.
 !!! error TS2322:   Types of parameters 'onFulFill' and 'onFulfill' are incompatible.
-!!! error TS2322:     Type '(value: string) => any' is not assignable to type '(value: number) => any'.
-!!! error TS2322:       Types of parameters 'value' and 'value' are incompatible.
-!!! error TS2322:         Type 'number' is not assignable to type 'string'.
+!!! error TS2322:     Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2322:       Type 'number' is not assignable to type 'string'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/overloadOnConstNoAnyImplementation.errors.txt b/tests/baselines/reference/overloadOnConstNoAnyImplementation.errors.txt
index 0573c6ed79e..aa7bbf77239 100644
--- a/tests/baselines/reference/overloadOnConstNoAnyImplementation.errors.txt
+++ b/tests/baselines/reference/overloadOnConstNoAnyImplementation.errors.txt
@@ -1,8 +1,11 @@
+tests/cases/compiler/overloadOnConstNoAnyImplementation.ts(1,10): error TS2394: Overload signature is not compatible with function implementation.
 tests/cases/compiler/overloadOnConstNoAnyImplementation.ts(9,8): error TS2345: Argument of type '1' is not assignable to parameter of type 'string'.
 
 
-==== tests/cases/compiler/overloadOnConstNoAnyImplementation.ts (1 errors) ====
+==== tests/cases/compiler/overloadOnConstNoAnyImplementation.ts (2 errors) ====
     function x1(a: number, cb: (x: 'hi') => number);
+             ~~
+!!! error TS2394: Overload signature is not compatible with function implementation.
     function x1(a: number, cb: (x: 'bye') => number);
     function x1(a: number, cb: (x: string) => number) {
         cb('hi');
diff --git a/tests/baselines/reference/overloadOnConstNoAnyImplementation2.errors.txt b/tests/baselines/reference/overloadOnConstNoAnyImplementation2.errors.txt
index 24047578ec6..a090f370863 100644
--- a/tests/baselines/reference/overloadOnConstNoAnyImplementation2.errors.txt
+++ b/tests/baselines/reference/overloadOnConstNoAnyImplementation2.errors.txt
@@ -1,3 +1,4 @@
+tests/cases/compiler/overloadOnConstNoAnyImplementation2.ts(6,5): error TS2394: Overload signature is not compatible with function implementation.
 tests/cases/compiler/overloadOnConstNoAnyImplementation2.ts(12,18): error TS2345: Argument of type '1' is not assignable to parameter of type 'string'.
 tests/cases/compiler/overloadOnConstNoAnyImplementation2.ts(18,9): error TS2345: Argument of type '(x: "bye") => number' is not assignable to parameter of type '(x: "hi") => number'.
   Types of parameters 'x' and 'x' are incompatible.
@@ -7,13 +8,15 @@ tests/cases/compiler/overloadOnConstNoAnyImplementation2.ts(21,9): error TS2345:
     Type '"hi"' is not assignable to type 'number'.
 
 
-==== tests/cases/compiler/overloadOnConstNoAnyImplementation2.ts (3 errors) ====
+==== tests/cases/compiler/overloadOnConstNoAnyImplementation2.ts (4 errors) ====
     interface I {
         x1(a: number, callback: (x: 'hi') => number);
     }
     
     class C {
         x1(a: number, callback: (x: 'hi') => number);
+        ~~
+!!! error TS2394: Overload signature is not compatible with function implementation.
         x1(a: number, callback: (x: string) => number) {
             callback('hi');
             callback('bye');
diff --git a/tests/baselines/reference/promisePermutations.errors.txt b/tests/baselines/reference/promisePermutations.errors.txt
index e5e7f2109a9..8b46f18666f 100644
--- a/tests/baselines/reference/promisePermutations.errors.txt
+++ b/tests/baselines/reference/promisePermutations.errors.txt
@@ -31,16 +31,16 @@ tests/cases/compiler/promisePermutations.ts(110,19): error TS2345: Argument of t
 tests/cases/compiler/promisePermutations.ts(111,19): error TS2345: Argument of type '(cb: <T>(a: T) => T) => Promise<string>' is not assignable to parameter of type '(value: string) => IPromise<string>'.
   Types of parameters 'cb' and 'value' are incompatible.
     Type 'string' is not assignable to type '<T>(a: T) => T'.
-tests/cases/compiler/promisePermutations.ts(117,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations.ts(120,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations.ts(121,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+tests/cases/compiler/promisePermutations.ts(117,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations.ts(120,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations.ts(121,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
 tests/cases/compiler/promisePermutations.ts(122,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
-tests/cases/compiler/promisePermutations.ts(126,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+tests/cases/compiler/promisePermutations.ts(126,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
 tests/cases/compiler/promisePermutations.ts(129,11): error TS2453: The type argument for type parameter 'U' cannot be inferred from the usage. Consider specifying the type arguments explicitly.
   Type argument candidate 'IPromise<number>' is not a valid type argument because it is not a supertype of candidate 'IPromise<string>'.
     Type 'string' is not assignable to type 'number'.
-tests/cases/compiler/promisePermutations.ts(132,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations.ts(133,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+tests/cases/compiler/promisePermutations.ts(132,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations.ts(133,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
 tests/cases/compiler/promisePermutations.ts(134,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
 tests/cases/compiler/promisePermutations.ts(137,11): error TS2453: The type argument for type parameter 'U' cannot be inferred from the usage. Consider specifying the type arguments explicitly.
   Type argument candidate 'IPromise<number>' is not a valid type argument because it is not a supertype of candidate 'IPromise<string>'.
@@ -51,9 +51,8 @@ tests/cases/compiler/promisePermutations.ts(152,12): error TS2453: The type argu
     Types of property 'then' are incompatible.
       Type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }' is not assignable to type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }'.
         Types of parameters 'success' and 'onfulfilled' are incompatible.
-          Type '(value: number) => any' is not assignable to type '(value: string) => IPromise<any>'.
-            Types of parameters 'value' and 'value' are incompatible.
-              Type 'string' is not assignable to type 'number'.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'string' is not assignable to type 'number'.
 tests/cases/compiler/promisePermutations.ts(156,21): error TS2345: Argument of type '{ (x: number): IPromise<number>; (x: string): IPromise<string>; }' is not assignable to parameter of type '(value: number) => IPromise<string>'.
   Type 'IPromise<number>' is not assignable to type 'IPromise<string>'.
     Type 'number' is not assignable to type 'string'.
@@ -67,9 +66,8 @@ tests/cases/compiler/promisePermutations.ts(160,21): error TS2345: Argument of t
     Types of property 'then' are incompatible.
       Type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }' is not assignable to type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }'.
         Types of parameters 'onfulfilled' and 'success' are incompatible.
-          Type '(value: string) => IPromise<any>' is not assignable to type '(value: number) => any'.
-            Types of parameters 'value' and 'value' are incompatible.
-              Type 'number' is not assignable to type 'string'.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'number' is not assignable to type 'string'.
 
 
 ==== tests/cases/compiler/promisePermutations.ts (33 errors) ====
@@ -241,15 +239,15 @@ tests/cases/compiler/promisePermutations.ts(160,21): error TS2345: Argument of t
     var nPromise: (x: any) => Promise<number>;
     var r8a = r8.then(testFunction8, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var r8b = r8.then(nIPromise, nIPromise, nIPromise).then(nIPromise, nIPromise, nIPromise); // ok
     var s8: Promise<number>;
     var s8a = s8.then(testFunction8, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var s8b = s8.then(testFunction8P, testFunction8P, testFunction8P); // error
                       ~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
     var s8c = s8.then(testFunction8P, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
@@ -258,7 +256,7 @@ tests/cases/compiler/promisePermutations.ts(160,21): error TS2345: Argument of t
     var r9: IPromise<number>;
     var r9a = r9.then(testFunction9, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var r9b = r9.then(sIPromise, sIPromise, sIPromise); // ok
     var r9c = r9.then(nIPromise, nIPromise, nIPromise); // ok
     var r9d = r9.then(testFunction, sIPromise, nIPromise); // ok
@@ -270,10 +268,10 @@ tests/cases/compiler/promisePermutations.ts(160,21): error TS2345: Argument of t
     var s9: Promise<number>;
     var s9a = s9.then(testFunction9, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var s9b = s9.then(testFunction9P, testFunction9P, testFunction9P); // error
                       ~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
     var s9c = s9.then(testFunction9P, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
@@ -307,9 +305,8 @@ tests/cases/compiler/promisePermutations.ts(160,21): error TS2345: Argument of t
 !!! error TS2453:     Types of property 'then' are incompatible.
 !!! error TS2453:       Type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }' is not assignable to type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }'.
 !!! error TS2453:         Types of parameters 'success' and 'onfulfilled' are incompatible.
-!!! error TS2453:           Type '(value: number) => any' is not assignable to type '(value: string) => IPromise<any>'.
-!!! error TS2453:             Types of parameters 'value' and 'value' are incompatible.
-!!! error TS2453:               Type 'string' is not assignable to type 'number'.
+!!! error TS2453:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2453:             Type 'string' is not assignable to type 'number'.
     var s10g = s10.then(testFunctionP, nIPromise, sIPromise).then(sPromise, sIPromise, sIPromise); // ok
     
     var r11: IPromise<number>;
@@ -335,9 +332,8 @@ tests/cases/compiler/promisePermutations.ts(160,21): error TS2345: Argument of t
 !!! error TS2345:     Types of property 'then' are incompatible.
 !!! error TS2345:       Type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }' is not assignable to type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }'.
 !!! error TS2345:         Types of parameters 'onfulfilled' and 'success' are incompatible.
-!!! error TS2345:           Type '(value: string) => IPromise<any>' is not assignable to type '(value: number) => any'.
-!!! error TS2345:             Types of parameters 'value' and 'value' are incompatible.
-!!! error TS2345:               Type 'number' is not assignable to type 'string'.
+!!! error TS2345:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2345:             Type 'number' is not assignable to type 'string'.
     
     var r12 = testFunction12(x => x);
     var r12a = r12.then(testFunction12, testFunction12, testFunction12); // ok
diff --git a/tests/baselines/reference/promisePermutations2.errors.txt b/tests/baselines/reference/promisePermutations2.errors.txt
index 26fec6b2fd1..32df80e20f1 100644
--- a/tests/baselines/reference/promisePermutations2.errors.txt
+++ b/tests/baselines/reference/promisePermutations2.errors.txt
@@ -31,16 +31,16 @@ tests/cases/compiler/promisePermutations2.ts(109,19): error TS2345: Argument of
 tests/cases/compiler/promisePermutations2.ts(110,19): error TS2345: Argument of type '(cb: <T>(a: T) => T) => Promise<string>' is not assignable to parameter of type '(value: string) => IPromise<string>'.
   Types of parameters 'cb' and 'value' are incompatible.
     Type 'string' is not assignable to type '<T>(a: T) => T'.
-tests/cases/compiler/promisePermutations2.ts(116,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations2.ts(119,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations2.ts(120,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+tests/cases/compiler/promisePermutations2.ts(116,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations2.ts(119,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations2.ts(120,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
 tests/cases/compiler/promisePermutations2.ts(121,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
-tests/cases/compiler/promisePermutations2.ts(125,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+tests/cases/compiler/promisePermutations2.ts(125,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
 tests/cases/compiler/promisePermutations2.ts(128,11): error TS2453: The type argument for type parameter 'U' cannot be inferred from the usage. Consider specifying the type arguments explicitly.
   Type argument candidate 'IPromise<number>' is not a valid type argument because it is not a supertype of candidate 'IPromise<string>'.
     Type 'string' is not assignable to type 'number'.
-tests/cases/compiler/promisePermutations2.ts(131,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations2.ts(132,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+tests/cases/compiler/promisePermutations2.ts(131,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations2.ts(132,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
 tests/cases/compiler/promisePermutations2.ts(133,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
 tests/cases/compiler/promisePermutations2.ts(136,11): error TS2453: The type argument for type parameter 'U' cannot be inferred from the usage. Consider specifying the type arguments explicitly.
   Type argument candidate 'IPromise<number>' is not a valid type argument because it is not a supertype of candidate 'IPromise<string>'.
@@ -51,9 +51,8 @@ tests/cases/compiler/promisePermutations2.ts(151,12): error TS2453: The type arg
     Types of property 'then' are incompatible.
       Type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }' is not assignable to type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }'.
         Types of parameters 'success' and 'onfulfilled' are incompatible.
-          Type '(value: number) => any' is not assignable to type '(value: string) => IPromise<any>'.
-            Types of parameters 'value' and 'value' are incompatible.
-              Type 'string' is not assignable to type 'number'.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'string' is not assignable to type 'number'.
 tests/cases/compiler/promisePermutations2.ts(155,21): error TS2345: Argument of type '{ (x: number): IPromise<number>; (x: string): IPromise<string>; }' is not assignable to parameter of type '(value: number) => IPromise<string>'.
   Type 'IPromise<number>' is not assignable to type 'IPromise<string>'.
     Type 'number' is not assignable to type 'string'.
@@ -67,9 +66,8 @@ tests/cases/compiler/promisePermutations2.ts(159,21): error TS2345: Argument of
     Types of property 'then' are incompatible.
       Type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }' is not assignable to type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }'.
         Types of parameters 'onfulfilled' and 'success' are incompatible.
-          Type '(value: string) => IPromise<any>' is not assignable to type '(value: number) => any'.
-            Types of parameters 'value' and 'value' are incompatible.
-              Type 'number' is not assignable to type 'string'.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'number' is not assignable to type 'string'.
 
 
 ==== tests/cases/compiler/promisePermutations2.ts (33 errors) ====
@@ -240,15 +238,15 @@ tests/cases/compiler/promisePermutations2.ts(159,21): error TS2345: Argument of
     var nPromise: (x: any) => Promise<number>;
     var r8a = r8.then(testFunction8, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var r8b = r8.then(nIPromise, nIPromise, nIPromise).then(nIPromise, nIPromise, nIPromise); // ok
     var s8: Promise<number>;
     var s8a = s8.then(testFunction8, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var s8b = s8.then(testFunction8P, testFunction8P, testFunction8P); // error
                       ~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
     var s8c = s8.then(testFunction8P, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
@@ -257,7 +255,7 @@ tests/cases/compiler/promisePermutations2.ts(159,21): error TS2345: Argument of
     var r9: IPromise<number>;
     var r9a = r9.then(testFunction9, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var r9b = r9.then(sIPromise, sIPromise, sIPromise); // ok
     var r9c = r9.then(nIPromise, nIPromise, nIPromise); // ok
     var r9d = r9.then(testFunction, sIPromise, nIPromise); // error
@@ -269,10 +267,10 @@ tests/cases/compiler/promisePermutations2.ts(159,21): error TS2345: Argument of
     var s9: Promise<number>;
     var s9a = s9.then(testFunction9, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var s9b = s9.then(testFunction9P, testFunction9P, testFunction9P); // error
                       ~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
     var s9c = s9.then(testFunction9P, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
@@ -306,9 +304,8 @@ tests/cases/compiler/promisePermutations2.ts(159,21): error TS2345: Argument of
 !!! error TS2453:     Types of property 'then' are incompatible.
 !!! error TS2453:       Type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }' is not assignable to type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }'.
 !!! error TS2453:         Types of parameters 'success' and 'onfulfilled' are incompatible.
-!!! error TS2453:           Type '(value: number) => any' is not assignable to type '(value: string) => IPromise<any>'.
-!!! error TS2453:             Types of parameters 'value' and 'value' are incompatible.
-!!! error TS2453:               Type 'string' is not assignable to type 'number'.
+!!! error TS2453:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2453:             Type 'string' is not assignable to type 'number'.
     var s10g = s10.then(testFunctionP, nIPromise, sIPromise).then(sPromise, sIPromise, sIPromise); // ok
     
     var r11: IPromise<number>;
@@ -334,9 +331,8 @@ tests/cases/compiler/promisePermutations2.ts(159,21): error TS2345: Argument of
 !!! error TS2345:     Types of property 'then' are incompatible.
 !!! error TS2345:       Type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }' is not assignable to type '{ <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => IPromise<U>, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => IPromise<U>, progress?: (progress: any) => void): IPromise<U>; <U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void): IPromise<U>; }'.
 !!! error TS2345:         Types of parameters 'onfulfilled' and 'success' are incompatible.
-!!! error TS2345:           Type '(value: string) => IPromise<any>' is not assignable to type '(value: number) => any'.
-!!! error TS2345:             Types of parameters 'value' and 'value' are incompatible.
-!!! error TS2345:               Type 'number' is not assignable to type 'string'.
+!!! error TS2345:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2345:             Type 'number' is not assignable to type 'string'.
     
     var r12 = testFunction12(x => x);
     var r12a = r12.then(testFunction12, testFunction12, testFunction12); // ok
diff --git a/tests/baselines/reference/promisePermutations3.errors.txt b/tests/baselines/reference/promisePermutations3.errors.txt
index 1354f486fcb..3d9fc1b2d26 100644
--- a/tests/baselines/reference/promisePermutations3.errors.txt
+++ b/tests/baselines/reference/promisePermutations3.errors.txt
@@ -34,16 +34,16 @@ tests/cases/compiler/promisePermutations3.ts(109,19): error TS2345: Argument of
 tests/cases/compiler/promisePermutations3.ts(110,19): error TS2345: Argument of type '(cb: <T>(a: T) => T) => Promise<string>' is not assignable to parameter of type '(value: string) => IPromise<string>'.
   Types of parameters 'cb' and 'value' are incompatible.
     Type 'string' is not assignable to type '<T>(a: T) => T'.
-tests/cases/compiler/promisePermutations3.ts(116,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations3.ts(119,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations3.ts(120,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+tests/cases/compiler/promisePermutations3.ts(116,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations3.ts(119,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations3.ts(120,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
 tests/cases/compiler/promisePermutations3.ts(121,19): error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
-tests/cases/compiler/promisePermutations3.ts(125,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+tests/cases/compiler/promisePermutations3.ts(125,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
 tests/cases/compiler/promisePermutations3.ts(128,11): error TS2453: The type argument for type parameter 'U' cannot be inferred from the usage. Consider specifying the type arguments explicitly.
   Type argument candidate 'IPromise<number>' is not a valid type argument because it is not a supertype of candidate 'IPromise<string>'.
     Type 'string' is not assignable to type 'number'.
-tests/cases/compiler/promisePermutations3.ts(131,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
-tests/cases/compiler/promisePermutations3.ts(132,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+tests/cases/compiler/promisePermutations3.ts(131,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
+tests/cases/compiler/promisePermutations3.ts(132,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
 tests/cases/compiler/promisePermutations3.ts(133,19): error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
 tests/cases/compiler/promisePermutations3.ts(136,11): error TS2453: The type argument for type parameter 'U' cannot be inferred from the usage. Consider specifying the type arguments explicitly.
   Type argument candidate 'IPromise<number>' is not a valid type argument because it is not a supertype of candidate 'IPromise<string>'.
@@ -54,9 +54,8 @@ tests/cases/compiler/promisePermutations3.ts(151,12): error TS2453: The type arg
     Types of property 'then' are incompatible.
       Type '<U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void) => IPromise<U>' is not assignable to type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }'.
         Types of parameters 'success' and 'onfulfilled' are incompatible.
-          Type '(value: number) => any' is not assignable to type '(value: string) => any'.
-            Types of parameters 'value' and 'value' are incompatible.
-              Type 'string' is not assignable to type 'number'.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'string' is not assignable to type 'number'.
 tests/cases/compiler/promisePermutations3.ts(155,21): error TS2345: Argument of type '{ (x: number): IPromise<number>; (x: string): IPromise<string>; }' is not assignable to parameter of type '(value: number) => IPromise<string>'.
   Type 'IPromise<number>' is not assignable to type 'IPromise<string>'.
     Type 'number' is not assignable to type 'string'.
@@ -70,9 +69,8 @@ tests/cases/compiler/promisePermutations3.ts(159,21): error TS2345: Argument of
     Types of property 'then' are incompatible.
       Type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }' is not assignable to type '<U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void) => IPromise<U>'.
         Types of parameters 'onfulfilled' and 'success' are incompatible.
-          Type '(value: string) => any' is not assignable to type '(value: number) => any'.
-            Types of parameters 'value' and 'value' are incompatible.
-              Type 'number' is not assignable to type 'string'.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'number' is not assignable to type 'string'.
 tests/cases/compiler/promisePermutations3.ts(165,21): error TS2345: Argument of type '{ <T>(x: T): IPromise<T>; <T>(x: T, y: T): Promise<T>; }' is not assignable to parameter of type '(value: (x: any) => any) => Promise<any>'.
   Type 'IPromise<any>' is not assignable to type 'Promise<any>'.
     Types of property 'then' are incompatible.
@@ -252,15 +250,15 @@ tests/cases/compiler/promisePermutations3.ts(165,21): error TS2345: Argument of
     var nPromise: (x: any) => Promise<number>;
     var r8a = r8.then(testFunction8, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var r8b = r8.then(nIPromise, nIPromise, nIPromise).then(nIPromise, nIPromise, nIPromise); // ok
     var s8: Promise<number>;
     var s8a = s8.then(testFunction8, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var s8b = s8.then(testFunction8P, testFunction8P, testFunction8P); // error
                       ~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
     var s8c = s8.then(testFunction8P, testFunction8, testFunction8); // error
                       ~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '<T>(x: T, cb: (a: T) => T) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
@@ -269,7 +267,7 @@ tests/cases/compiler/promisePermutations3.ts(165,21): error TS2345: Argument of
     var r9: IPromise<number>;
     var r9a = r9.then(testFunction9, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var r9b = r9.then(sIPromise, sIPromise, sIPromise); // ok
     var r9c = r9.then(nIPromise, nIPromise, nIPromise); // ok
     var r9d = r9.then(testFunction, sIPromise, nIPromise); // error
@@ -281,10 +279,10 @@ tests/cases/compiler/promisePermutations3.ts(165,21): error TS2345: Argument of
     var s9: Promise<number>;
     var s9a = s9.then(testFunction9, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => IPromise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
     var s9b = s9.then(testFunction9P, testFunction9P, testFunction9P); // error
                       ~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<number>'.
+!!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => Promise<any>'.
     var s9c = s9.then(testFunction9P, testFunction9, testFunction9); // error
                       ~~~~~~~~~~~~~~
 !!! error TS2345: Argument of type '<T>(x: T, cb: <U>(a: U) => U) => Promise<T>' is not assignable to parameter of type '(value: number) => IPromise<any>'.
@@ -318,9 +316,8 @@ tests/cases/compiler/promisePermutations3.ts(165,21): error TS2345: Argument of
 !!! error TS2453:     Types of property 'then' are incompatible.
 !!! error TS2453:       Type '<U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void) => IPromise<U>' is not assignable to type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }'.
 !!! error TS2453:         Types of parameters 'success' and 'onfulfilled' are incompatible.
-!!! error TS2453:           Type '(value: number) => any' is not assignable to type '(value: string) => any'.
-!!! error TS2453:             Types of parameters 'value' and 'value' are incompatible.
-!!! error TS2453:               Type 'string' is not assignable to type 'number'.
+!!! error TS2453:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2453:             Type 'string' is not assignable to type 'number'.
     var s10g = s10.then(testFunctionP, nIPromise, sIPromise).then(sPromise, sIPromise, sIPromise); // ok
     
     var r11: IPromise<number>;
@@ -346,9 +343,8 @@ tests/cases/compiler/promisePermutations3.ts(165,21): error TS2345: Argument of
 !!! error TS2345:     Types of property 'then' are incompatible.
 !!! error TS2345:       Type '{ <TResult1 = number, TResult2 = never>(onfulfilled?: (value: number) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>): Promise<TResult1 | TResult2>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => Promise<U>, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => Promise<U>, progress?: (progress: any) => void): Promise<U>; <U>(success?: (value: number) => U, error?: (error: any) => U, progress?: (progress: any) => void): Promise<U>; }' is not assignable to type '<U>(success?: (value: string) => U, error?: (error: any) => U, progress?: (progress: any) => void) => IPromise<U>'.
 !!! error TS2345:         Types of parameters 'onfulfilled' and 'success' are incompatible.
-!!! error TS2345:           Type '(value: string) => any' is not assignable to type '(value: number) => any'.
-!!! error TS2345:             Types of parameters 'value' and 'value' are incompatible.
-!!! error TS2345:               Type 'number' is not assignable to type 'string'.
+!!! error TS2345:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2345:             Type 'number' is not assignable to type 'string'.
     
     var r12 = testFunction12(x => x);
     var r12a = r12.then(testFunction12, testFunction12, testFunction12); // ok
diff --git a/tests/baselines/reference/promisesWithConstraints.errors.txt b/tests/baselines/reference/promisesWithConstraints.errors.txt
new file mode 100644
index 00000000000..d2c459da284
--- /dev/null
+++ b/tests/baselines/reference/promisesWithConstraints.errors.txt
@@ -0,0 +1,36 @@
+tests/cases/compiler/promisesWithConstraints.ts(15,1): error TS2322: Type 'Promise<Foo>' is not assignable to type 'Promise<Bar>'.
+  Type 'Foo' is not assignable to type 'Bar'.
+    Property 'y' is missing in type 'Foo'.
+tests/cases/compiler/promisesWithConstraints.ts(20,1): error TS2322: Type 'CPromise<Foo>' is not assignable to type 'CPromise<Bar>'.
+  Type 'Foo' is not assignable to type 'Bar'.
+
+
+==== tests/cases/compiler/promisesWithConstraints.ts (2 errors) ====
+    interface Promise<T> {
+        then<U>(cb: (x: T) => Promise<U>): Promise<U>;
+    }
+    
+    interface CPromise<T extends { x: any; }> {
+        then<U extends { x: any; }>(cb: (x: T) => Promise<U>): Promise<U>;
+    }
+    
+    interface Foo { x; }
+    interface Bar { x; y; }
+    
+    var a: Promise<Foo>;
+    var b: Promise<Bar>;
+    a = b; // ok
+    b = a; // ok
+    ~
+!!! error TS2322: Type 'Promise<Foo>' is not assignable to type 'Promise<Bar>'.
+!!! error TS2322:   Type 'Foo' is not assignable to type 'Bar'.
+!!! error TS2322:     Property 'y' is missing in type 'Foo'.
+    
+    var a2: CPromise<Foo>;
+    var b2: CPromise<Bar>;
+    a2 = b2; // ok
+    b2 = a2; // was error
+    ~~
+!!! error TS2322: Type 'CPromise<Foo>' is not assignable to type 'CPromise<Bar>'.
+!!! error TS2322:   Type 'Foo' is not assignable to type 'Bar'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/recursiveTypeComparison2.errors.txt b/tests/baselines/reference/recursiveTypeComparison2.errors.txt
index 5c1200ceec6..71f337ad15f 100644
--- a/tests/baselines/reference/recursiveTypeComparison2.errors.txt
+++ b/tests/baselines/reference/recursiveTypeComparison2.errors.txt
@@ -1,7 +1,9 @@
 tests/cases/compiler/recursiveTypeComparison2.ts(13,80): error TS2304: Cannot find name 'StateValue'.
+tests/cases/compiler/recursiveTypeComparison2.ts(30,5): error TS2322: Type 'Bus<{}>' is not assignable to type 'Bus<number>'.
+  Type '{}' is not assignable to type 'number'.
 
 
-==== tests/cases/compiler/recursiveTypeComparison2.ts (1 errors) ====
+==== tests/cases/compiler/recursiveTypeComparison2.ts (2 errors) ====
     // Before fix this would cause compiler to hang (#1170)
     
     declare module Bacon {
@@ -33,4 +35,7 @@ tests/cases/compiler/recursiveTypeComparison2.ts(13,80): error TS2304: Cannot fi
         var Bus: new <T>() => Bus<T>;
     }
     
-    var stuck: Bacon.Bus<number> = new Bacon.Bus();
\ No newline at end of file
+    var stuck: Bacon.Bus<number> = new Bacon.Bus();
+        ~~~~~
+!!! error TS2322: Type 'Bus<{}>' is not assignable to type 'Bus<number>'.
+!!! error TS2322:   Type '{}' is not assignable to type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/scopedPackages.js b/tests/baselines/reference/scopedPackages.js
new file mode 100644
index 00000000000..75606d2e1b9
--- /dev/null
+++ b/tests/baselines/reference/scopedPackages.js
@@ -0,0 +1,20 @@
+//// [tests/cases/conformance/moduleResolution/scopedPackages.ts] ////
+
+//// [index.d.ts]
+export const x: number;
+
+//// [index.d.ts]
+export const y: number;
+
+//// [z.d.ts]
+export const z: number;
+
+//// [a.ts]
+import { x } from "@cow/boy";
+import { y } from "@be/bop";
+import { z } from "@be/bop/e/z";
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
diff --git a/tests/baselines/reference/scopedPackages.symbols b/tests/baselines/reference/scopedPackages.symbols
new file mode 100644
index 00000000000..e992c4d9375
--- /dev/null
+++ b/tests/baselines/reference/scopedPackages.symbols
@@ -0,0 +1,22 @@
+=== /a.ts ===
+import { x } from "@cow/boy";
+>x : Symbol(x, Decl(a.ts, 0, 8))
+
+import { y } from "@be/bop";
+>y : Symbol(y, Decl(a.ts, 1, 8))
+
+import { z } from "@be/bop/e/z";
+>z : Symbol(z, Decl(a.ts, 2, 8))
+
+=== /node_modules/@cow/boy/index.d.ts ===
+export const x: number;
+>x : Symbol(x, Decl(index.d.ts, 0, 12))
+
+=== /node_modules/@types/be__bop/index.d.ts ===
+export const y: number;
+>y : Symbol(y, Decl(index.d.ts, 0, 12))
+
+=== /node_modules/@types/be__bop/e/z.d.ts ===
+export const z: number;
+>z : Symbol(z, Decl(z.d.ts, 0, 12))
+
diff --git a/tests/baselines/reference/scopedPackages.trace.json b/tests/baselines/reference/scopedPackages.trace.json
new file mode 100644
index 00000000000..20df3bec172
--- /dev/null
+++ b/tests/baselines/reference/scopedPackages.trace.json
@@ -0,0 +1,30 @@
+[
+    "======== Resolving module '@cow/boy' from '/a.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module '@cow/boy' from 'node_modules' folder, target file type 'TypeScript'.",
+    "File '/node_modules/@cow/boy.ts' does not exist.",
+    "File '/node_modules/@cow/boy.tsx' does not exist.",
+    "File '/node_modules/@cow/boy.d.ts' does not exist.",
+    "File '/node_modules/@cow/boy/package.json' does not exist.",
+    "File '/node_modules/@cow/boy/index.ts' does not exist.",
+    "File '/node_modules/@cow/boy/index.tsx' does not exist.",
+    "File '/node_modules/@cow/boy/index.d.ts' exist - use it as a name resolution result.",
+    "Resolving real path for '/node_modules/@cow/boy/index.d.ts', result '/node_modules/@cow/boy/index.d.ts'.",
+    "======== Module name '@cow/boy' was successfully resolved to '/node_modules/@cow/boy/index.d.ts'. ========",
+    "======== Resolving module '@be/bop' from '/a.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module '@be/bop' from 'node_modules' folder, target file type 'TypeScript'.",
+    "Scoped package detected, looking in 'be__bop'",
+    "File '/node_modules/@types/be__bop.d.ts' does not exist.",
+    "File '/node_modules/@types/be__bop/package.json' does not exist.",
+    "File '/node_modules/@types/be__bop/index.d.ts' exist - use it as a name resolution result.",
+    "Resolving real path for '/node_modules/@types/be__bop/index.d.ts', result '/node_modules/@types/be__bop/index.d.ts'.",
+    "======== Module name '@be/bop' was successfully resolved to '/node_modules/@types/be__bop/index.d.ts'. ========",
+    "======== Resolving module '@be/bop/e/z' from '/a.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module '@be/bop/e/z' from 'node_modules' folder, target file type 'TypeScript'.",
+    "Scoped package detected, looking in 'be__bop/e/z'",
+    "File '/node_modules/@types/be__bop/e/z.d.ts' exist - use it as a name resolution result.",
+    "Resolving real path for '/node_modules/@types/be__bop/e/z.d.ts', result '/node_modules/@types/be__bop/e/z.d.ts'.",
+    "======== Module name '@be/bop/e/z' was successfully resolved to '/node_modules/@types/be__bop/e/z.d.ts'. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/scopedPackages.types b/tests/baselines/reference/scopedPackages.types
new file mode 100644
index 00000000000..c876590f54a
--- /dev/null
+++ b/tests/baselines/reference/scopedPackages.types
@@ -0,0 +1,22 @@
+=== /a.ts ===
+import { x } from "@cow/boy";
+>x : number
+
+import { y } from "@be/bop";
+>y : number
+
+import { z } from "@be/bop/e/z";
+>z : number
+
+=== /node_modules/@cow/boy/index.d.ts ===
+export const x: number;
+>x : number
+
+=== /node_modules/@types/be__bop/index.d.ts ===
+export const y: number;
+>y : number
+
+=== /node_modules/@types/be__bop/e/z.d.ts ===
+export const z: number;
+>z : number
+
diff --git a/tests/baselines/reference/scopedPackagesClassic.js b/tests/baselines/reference/scopedPackagesClassic.js
new file mode 100644
index 00000000000..f42acde2306
--- /dev/null
+++ b/tests/baselines/reference/scopedPackagesClassic.js
@@ -0,0 +1,12 @@
+//// [tests/cases/conformance/moduleResolution/scopedPackagesClassic.ts] ////
+
+//// [index.d.ts]
+export const x = 0;
+
+//// [a.ts]
+import { x } from "@see/saw";
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
diff --git a/tests/baselines/reference/scopedPackagesClassic.symbols b/tests/baselines/reference/scopedPackagesClassic.symbols
new file mode 100644
index 00000000000..e0d84f44c91
--- /dev/null
+++ b/tests/baselines/reference/scopedPackagesClassic.symbols
@@ -0,0 +1,8 @@
+=== /a.ts ===
+import { x } from "@see/saw";
+>x : Symbol(x, Decl(a.ts, 0, 8))
+
+=== /node_modules/@types/see__saw/index.d.ts ===
+export const x = 0;
+>x : Symbol(x, Decl(index.d.ts, 0, 12))
+
diff --git a/tests/baselines/reference/scopedPackagesClassic.trace.json b/tests/baselines/reference/scopedPackagesClassic.trace.json
new file mode 100644
index 00000000000..c58c7d2ed10
--- /dev/null
+++ b/tests/baselines/reference/scopedPackagesClassic.trace.json
@@ -0,0 +1,9 @@
+[
+    "======== Resolving module '@see/saw' from '/a.ts'. ========",
+    "Explicitly specified module resolution kind: 'Classic'.",
+    "Scoped package detected, looking in 'see__saw'",
+    "File '/node_modules/@types/see__saw.d.ts' does not exist.",
+    "File '/node_modules/@types/see__saw/package.json' does not exist.",
+    "File '/node_modules/@types/see__saw/index.d.ts' exist - use it as a name resolution result.",
+    "======== Module name '@see/saw' was successfully resolved to '/node_modules/@types/see__saw/index.d.ts'. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/scopedPackagesClassic.types b/tests/baselines/reference/scopedPackagesClassic.types
new file mode 100644
index 00000000000..65047f2436d
--- /dev/null
+++ b/tests/baselines/reference/scopedPackagesClassic.types
@@ -0,0 +1,9 @@
+=== /a.ts ===
+import { x } from "@see/saw";
+>x : 0
+
+=== /node_modules/@types/see__saw/index.d.ts ===
+export const x = 0;
+>x : 0
+>0 : 0
+
diff --git a/tests/baselines/reference/subtypingWithCallSignatures2.types b/tests/baselines/reference/subtypingWithCallSignatures2.types
index 8ce4b566b86..86c65702b98 100644
--- a/tests/baselines/reference/subtypingWithCallSignatures2.types
+++ b/tests/baselines/reference/subtypingWithCallSignatures2.types
@@ -681,14 +681,14 @@ var r9 = foo9(r9arg1); // any
 >r9arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
 
 var r9a = [r9arg1, r9arg2];
->r9a : (<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U)[]
->[r9arg1, r9arg2] : (<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U)[]
+>r9a : ((<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U) | ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived))[]
+>[r9arg1, r9arg2] : ((<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U) | ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived))[]
 >r9arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
 >r9arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
 
 var r9b = [r9arg2, r9arg1];
->r9b : (<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U)[]
->[r9arg2, r9arg1] : (<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U)[]
+>r9b : ((<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U) | ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived))[]
+>[r9arg2, r9arg1] : ((<T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U) | ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived))[]
 >r9arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
 >r9arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
 
diff --git a/tests/baselines/reference/typeofUsedBeforeBlockScoped.js b/tests/baselines/reference/typeofUsedBeforeBlockScoped.js
new file mode 100644
index 00000000000..eebf4beae67
--- /dev/null
+++ b/tests/baselines/reference/typeofUsedBeforeBlockScoped.js
@@ -0,0 +1,19 @@
+//// [typeofUsedBeforeBlockScoped.ts]
+type T = typeof C & typeof C.s & typeof o & typeof o.n;
+class C {
+    static s = 2;
+}
+type W = typeof o.n;
+let o2: typeof o;
+let o = { n: 12 };
+
+
+//// [typeofUsedBeforeBlockScoped.js]
+var C = (function () {
+    function C() {
+    }
+    return C;
+}());
+C.s = 2;
+var o2;
+var o = { n: 12 };
diff --git a/tests/baselines/reference/typeofUsedBeforeBlockScoped.symbols b/tests/baselines/reference/typeofUsedBeforeBlockScoped.symbols
new file mode 100644
index 00000000000..5cf09a4d4d5
--- /dev/null
+++ b/tests/baselines/reference/typeofUsedBeforeBlockScoped.symbols
@@ -0,0 +1,32 @@
+=== tests/cases/compiler/typeofUsedBeforeBlockScoped.ts ===
+type T = typeof C & typeof C.s & typeof o & typeof o.n;
+>T : Symbol(T, Decl(typeofUsedBeforeBlockScoped.ts, 0, 0))
+>C : Symbol(C, Decl(typeofUsedBeforeBlockScoped.ts, 0, 55))
+>C.s : Symbol(C.s, Decl(typeofUsedBeforeBlockScoped.ts, 1, 9))
+>C : Symbol(C, Decl(typeofUsedBeforeBlockScoped.ts, 0, 55))
+>s : Symbol(C.s, Decl(typeofUsedBeforeBlockScoped.ts, 1, 9))
+>o : Symbol(o, Decl(typeofUsedBeforeBlockScoped.ts, 6, 3))
+>o.n : Symbol(n, Decl(typeofUsedBeforeBlockScoped.ts, 6, 9))
+>o : Symbol(o, Decl(typeofUsedBeforeBlockScoped.ts, 6, 3))
+>n : Symbol(n, Decl(typeofUsedBeforeBlockScoped.ts, 6, 9))
+
+class C {
+>C : Symbol(C, Decl(typeofUsedBeforeBlockScoped.ts, 0, 55))
+
+    static s = 2;
+>s : Symbol(C.s, Decl(typeofUsedBeforeBlockScoped.ts, 1, 9))
+}
+type W = typeof o.n;
+>W : Symbol(W, Decl(typeofUsedBeforeBlockScoped.ts, 3, 1))
+>o.n : Symbol(n, Decl(typeofUsedBeforeBlockScoped.ts, 6, 9))
+>o : Symbol(o, Decl(typeofUsedBeforeBlockScoped.ts, 6, 3))
+>n : Symbol(n, Decl(typeofUsedBeforeBlockScoped.ts, 6, 9))
+
+let o2: typeof o;
+>o2 : Symbol(o2, Decl(typeofUsedBeforeBlockScoped.ts, 5, 3))
+>o : Symbol(o, Decl(typeofUsedBeforeBlockScoped.ts, 6, 3))
+
+let o = { n: 12 };
+>o : Symbol(o, Decl(typeofUsedBeforeBlockScoped.ts, 6, 3))
+>n : Symbol(n, Decl(typeofUsedBeforeBlockScoped.ts, 6, 9))
+
diff --git a/tests/baselines/reference/typeofUsedBeforeBlockScoped.types b/tests/baselines/reference/typeofUsedBeforeBlockScoped.types
new file mode 100644
index 00000000000..ec8e30bb135
--- /dev/null
+++ b/tests/baselines/reference/typeofUsedBeforeBlockScoped.types
@@ -0,0 +1,35 @@
+=== tests/cases/compiler/typeofUsedBeforeBlockScoped.ts ===
+type T = typeof C & typeof C.s & typeof o & typeof o.n;
+>T : T
+>C : typeof C
+>C.s : number
+>C : typeof C
+>s : number
+>o : { n: number; }
+>o.n : number
+>o : { n: number; }
+>n : number
+
+class C {
+>C : C
+
+    static s = 2;
+>s : number
+>2 : 2
+}
+type W = typeof o.n;
+>W : number
+>o.n : number
+>o : { n: number; }
+>n : number
+
+let o2: typeof o;
+>o2 : { n: number; }
+>o : { n: number; }
+
+let o = { n: 12 };
+>o : { n: number; }
+>{ n: 12 } : { n: number; }
+>n : number
+>12 : 12
+
diff --git a/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.js b/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.js
new file mode 100644
index 00000000000..7140f13cb7b
--- /dev/null
+++ b/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.js
@@ -0,0 +1,8 @@
+//// [unknownPropertiesAreAssignableToObjectUnion.ts]
+const x: Object | string = { x: 0 };
+const y: Object | undefined = { x: 0 };
+
+
+//// [unknownPropertiesAreAssignableToObjectUnion.js]
+var x = { x: 0 };
+var y = { x: 0 };
diff --git a/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.symbols b/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.symbols
new file mode 100644
index 00000000000..f9c0b09c987
--- /dev/null
+++ b/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.symbols
@@ -0,0 +1,11 @@
+=== tests/cases/compiler/unknownPropertiesAreAssignableToObjectUnion.ts ===
+const x: Object | string = { x: 0 };
+>x : Symbol(x, Decl(unknownPropertiesAreAssignableToObjectUnion.ts, 0, 5))
+>Object : Symbol(Object, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(unknownPropertiesAreAssignableToObjectUnion.ts, 0, 28))
+
+const y: Object | undefined = { x: 0 };
+>y : Symbol(y, Decl(unknownPropertiesAreAssignableToObjectUnion.ts, 1, 5))
+>Object : Symbol(Object, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(unknownPropertiesAreAssignableToObjectUnion.ts, 1, 31))
+
diff --git a/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.types b/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.types
new file mode 100644
index 00000000000..d242cb8805c
--- /dev/null
+++ b/tests/baselines/reference/unknownPropertiesAreAssignableToObjectUnion.types
@@ -0,0 +1,15 @@
+=== tests/cases/compiler/unknownPropertiesAreAssignableToObjectUnion.ts ===
+const x: Object | string = { x: 0 };
+>x : string | Object
+>Object : Object
+>{ x: 0 } : { x: number; }
+>x : number
+>0 : 0
+
+const y: Object | undefined = { x: 0 };
+>y : Object | undefined
+>Object : Object
+>{ x: 0 } : { x: number; }
+>x : number
+>0 : 0
+
diff --git a/tests/cases/compiler/assignmentToExpandingArrayType.ts b/tests/cases/compiler/assignmentToExpandingArrayType.ts
new file mode 100644
index 00000000000..05680afa386
--- /dev/null
+++ b/tests/cases/compiler/assignmentToExpandingArrayType.ts
@@ -0,0 +1,27 @@
+// @noImplicitAny: true
+// Fixes exponential time/space in #14628
+let x = []
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' } // previously ran out of memory here
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
+x[0] = { foo: 'hi' }
diff --git a/tests/cases/compiler/checkJsFiles_noErrorLocation.ts b/tests/cases/compiler/checkJsFiles_noErrorLocation.ts
new file mode 100644
index 00000000000..a0b12c47115
--- /dev/null
+++ b/tests/cases/compiler/checkJsFiles_noErrorLocation.ts
@@ -0,0 +1,24 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+
+// @fileName: a.js
+// @ts-check
+class A {
+  constructor() {
+
+  }
+  foo() {
+    return 4;
+  }
+}
+
+class B extends A {
+  constructor() {
+    super();
+    this.foo = () => 3;
+  }
+}
+
+const i = new B();
+i.foo();
\ No newline at end of file
diff --git a/tests/cases/compiler/jsFileClassPropertyInitalizationInObjectLiteral.ts b/tests/cases/compiler/jsFileClassPropertyInitalizationInObjectLiteral.ts
new file mode 100644
index 00000000000..d8908740fd4
--- /dev/null
+++ b/tests/cases/compiler/jsFileClassPropertyInitalizationInObjectLiteral.ts
@@ -0,0 +1,10 @@
+// @allowJs: true
+// @noEmit: true
+
+// @filename: foo.js
+module.exports = function () {
+  class A { }
+  return {
+    c: A.b = 1,
+  }
+};
diff --git a/tests/cases/compiler/typeofUsedBeforeBlockScoped.ts b/tests/cases/compiler/typeofUsedBeforeBlockScoped.ts
new file mode 100644
index 00000000000..3ab1534875b
--- /dev/null
+++ b/tests/cases/compiler/typeofUsedBeforeBlockScoped.ts
@@ -0,0 +1,7 @@
+type T = typeof C & typeof C.s & typeof o & typeof o.n;
+class C {
+    static s = 2;
+}
+type W = typeof o.n;
+let o2: typeof o;
+let o = { n: 12 };
diff --git a/tests/cases/compiler/unknownPropertiesAreAssignableToObjectUnion.ts b/tests/cases/compiler/unknownPropertiesAreAssignableToObjectUnion.ts
new file mode 100644
index 00000000000..eb4209509de
--- /dev/null
+++ b/tests/cases/compiler/unknownPropertiesAreAssignableToObjectUnion.ts
@@ -0,0 +1,3 @@
+// @strictNullChecks: true
+const x: Object | string = { x: 0 };
+const y: Object | undefined = { x: 0 };
diff --git a/tests/cases/conformance/es6/modules/exportBinding.ts b/tests/cases/conformance/es6/modules/exportBinding.ts
new file mode 100644
index 00000000000..1e6b0314f0b
--- /dev/null
+++ b/tests/cases/conformance/es6/modules/exportBinding.ts
@@ -0,0 +1,5 @@
+export { x }
+const x = 'x'
+
+export { Y as Z }
+class Y {}
diff --git a/tests/cases/conformance/moduleResolution/scopedPackages.ts b/tests/cases/conformance/moduleResolution/scopedPackages.ts
new file mode 100644
index 00000000000..b604f10d7ec
--- /dev/null
+++ b/tests/cases/conformance/moduleResolution/scopedPackages.ts
@@ -0,0 +1,17 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typeRoots: types
+
+// @filename: /node_modules/@cow/boy/index.d.ts
+export const x: number;
+
+// @filename: /node_modules/@types/be__bop/index.d.ts
+export const y: number;
+
+// @filename: /node_modules/@types/be__bop/e/z.d.ts
+export const z: number;
+
+// @filename: /a.ts
+import { x } from "@cow/boy";
+import { y } from "@be/bop";
+import { z } from "@be/bop/e/z";
diff --git a/tests/cases/conformance/moduleResolution/scopedPackagesClassic.ts b/tests/cases/conformance/moduleResolution/scopedPackagesClassic.ts
new file mode 100644
index 00000000000..41b6fc09e19
--- /dev/null
+++ b/tests/cases/conformance/moduleResolution/scopedPackagesClassic.ts
@@ -0,0 +1,10 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typeRoots: types
+// @moduleResolution: classic
+
+// @filename: /node_modules/@types/see__saw/index.d.ts
+export const x = 0;
+
+// @filename: /a.ts
+import { x } from "@see/saw";
diff --git a/tests/cases/conformance/references/library-reference-scoped-packages.ts b/tests/cases/conformance/references/library-reference-scoped-packages.ts
new file mode 100644
index 00000000000..86a1ad3e93d
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-scoped-packages.ts
@@ -0,0 +1,9 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typeRoots: types
+
+// @filename: /node_modules/@types/beep__boop/index.d.ts
+export const y = 0;
+
+// @filename: /a.ts
+/// <reference types="@beep/boop" />
diff --git a/tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts b/tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts
new file mode 100644
index 00000000000..4f3e7ecda0d
--- /dev/null
+++ b/tests/cases/conformance/types/typeRelationships/assignmentCompatibility/covariantCallbacks.ts
@@ -0,0 +1,73 @@
+// @target: es2015
+// @strict: true
+
+// Test that callback parameters are related covariantly
+
+interface P<T> {
+    then(cb: (value: T) => void): void;
+};
+
+interface A { a: string }
+interface B extends A { b: string }
+
+function f1(a: P<A>, b: P<B>) {
+    a = b;
+    b = a;  // Error
+}
+
+function f2(a: Promise<A>, b: Promise<B>) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList1 {
+    forEach(cb: (item: A) => void): void;
+}
+
+interface BList1 {
+    forEach(cb: (item: B) => void): void;
+}
+
+function f11(a: AList1, b: BList1) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList2 {
+    forEach(cb: (item: A) => boolean): void;
+}
+
+interface BList2 {
+    forEach(cb: (item: A) => void): void;
+}
+
+function f12(a: AList2, b: BList2) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList3 {
+    forEach(cb: (item: A) => void): void;
+}
+
+interface BList3 {
+    forEach(cb: (item: A, context: any) => void): void;
+}
+
+function f13(a: AList3, b: BList3) {
+    a = b;
+    b = a;  // Error
+}
+
+interface AList4 {
+    forEach(cb: (item: A) => A): void;
+}
+
+interface BList4 {
+    forEach(cb: (item: B) => B): void;
+}
+
+function f14(a: AList4, b: BList4) {
+    a = b;
+    b = a;  // Error
+}
diff --git a/tslint.json b/tslint.json
index 92bfed07c95..9552d193a70 100644
--- a/tslint.json
+++ b/tslint.json
@@ -60,6 +60,8 @@
         "object-literal-surrounding-space": true,
         "no-type-assertion-whitespace": true,
         "no-in-operator": true,
+        "no-switch-case-fall-through": true,
+        "triple-equals": true,
         "jsdoc-format": true
     }
 }