diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 6bde3775b94..f8c2bc12f63 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4628,6 +4628,10 @@ namespace ts {
             if (isTypeAny(parentType)) {
                 return parentType;
             }
+            // Relax null check on ambient destructuring parameters, since the parameters have no implementation and are just documentation
+            if (strictNullChecks && declaration.flags & NodeFlags.Ambient && isParameterDeclaration(declaration)) {
+                parentType = getNonNullableType(parentType);
+            }
 
             let type: Type | undefined;
             if (pattern.kind === SyntaxKind.ObjectBindingPattern) {
@@ -4647,53 +4651,13 @@ namespace ts {
                 else {
                     // Use explicitly specified property name ({ p: xxx } form), or otherwise the implied name ({ p } form)
                     const name = declaration.propertyName || <Identifier>declaration.name;
-                    const isLate = isLateBindableName(name);
-                    const isWellKnown = isComputedPropertyName(name) && isWellKnownSymbolSyntactically(name.expression);
-                    if (!isLate && !isWellKnown && isComputedNonLiteralName(name)) {
-                        const exprType = checkExpression((name as ComputedPropertyName).expression);
-                        if (isTypeAssignableToKind(exprType, TypeFlags.ESSymbolLike)) {
-                            if (noImplicitAny) {
-                                error(declaration, Diagnostics.Type_0_cannot_be_used_to_index_type_1, typeToString(exprType), typeToString(parentType));
-                            }
-                            return anyType;
-                        }
-                        const indexerType = isTypeAssignableToKind(exprType, TypeFlags.NumberLike) && getIndexTypeOfType(parentType, IndexKind.Number) || getIndexTypeOfType(parentType, IndexKind.String);
-                        if (!indexerType && noImplicitAny && !compilerOptions.suppressImplicitAnyIndexErrors) {
-                            if (getIndexTypeOfType(parentType, IndexKind.Number)) {
-                                error(declaration, Diagnostics.Element_implicitly_has_an_any_type_because_index_expression_is_not_of_type_number);
-                            }
-                            else {
-                                error(declaration, Diagnostics.Element_implicitly_has_an_any_type_because_type_0_has_no_index_signature, typeToString(parentType));
-                            }
-                        }
-                        return indexerType || anyType;
-                    }
-
-                    // Use type of the specified property, or otherwise, for a numeric name, the type of the numeric index signature,
-                    // or otherwise the type of the string index signature.
-                    const nameType = isLate ? checkComputedPropertyName(name as ComputedPropertyName) as LiteralType | UniqueESSymbolType : undefined;
-                    const text = isLate ? getLateBoundNameFromType(nameType!) :
-                        isWellKnown ? getPropertyNameForKnownSymbolName(idText(((name as ComputedPropertyName).expression as PropertyAccessExpression).name)) :
-                        getTextOfPropertyName(name);
-
-                    // Relax null check on ambient destructuring parameters, since the parameters have no implementation and are just documentation
-                    if (strictNullChecks && declaration.flags & NodeFlags.Ambient && isParameterDeclaration(declaration)) {
-                        parentType = getNonNullableType(parentType);
-                    }
-                    if (isLate && nameType && !getPropertyOfType(parentType, text) && isTypeAssignableToKind(nameType, TypeFlags.ESSymbolLike)) {
-                        if (noImplicitAny) {
-                            error(declaration, Diagnostics.Type_0_cannot_be_used_to_index_type_1, typeToString(nameType), typeToString(parentType));
-                        }
-                        return anyType;
-                    }
-                    const declaredType = getConstraintForLocation(getTypeOfPropertyOfType(parentType, text), declaration.name);
-                    type = declaredType && getFlowTypeOfReference(declaration, declaredType) ||
-                        isNumericLiteralName(text) && getIndexTypeOfType(parentType, IndexKind.Number) ||
-                        getIndexTypeOfType(parentType, IndexKind.String);
-                    if (!type) {
-                        error(name, Diagnostics.Type_0_has_no_property_1_and_no_string_index_signature, typeToString(parentType), declarationNameToString(name));
-                        return errorType;
-                    }
+                    const exprType = isComputedPropertyName(name)
+                        ? checkComputedPropertyName(name)
+                        : isIdentifier(name)
+                            ? getLiteralType(unescapeLeadingUnderscores(name.escapedText))
+                            : checkExpression(name);
+                    const declaredType = checkIndexedAccessIndexType(getIndexedAccessType(getApparentType(parentType), exprType, name), name);
+                    type = getFlowTypeOfReference(declaration, getConstraintForLocation(declaredType, declaration.name));
                 }
             }
             else {
@@ -9360,12 +9324,16 @@ namespace ts {
             return false;
         }
 
-        function getPropertyTypeForIndexType(objectType: Type, indexType: Type, accessNode: ElementAccessExpression | IndexedAccessTypeNode | undefined, cacheSymbol: boolean, missingType: Type) {
+        function getPropertyTypeForIndexType(objectType: Type, indexType: Type, accessNode: ElementAccessExpression | IndexedAccessTypeNode | PropertyName | undefined, cacheSymbol: boolean, missingType: Type) {
             const accessExpression = accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode : undefined;
-            const propName = isTypeUsableAsLateBoundName(indexType) ? getLateBoundNameFromType(indexType) :
-                accessExpression && checkThatExpressionIsProperSymbolReference(accessExpression.argumentExpression, indexType, /*reportError*/ false) ?
-                    getPropertyNameForKnownSymbolName(idText((<PropertyAccessExpression>accessExpression.argumentExpression).name)) :
-                    undefined;
+            const propName = isTypeUsableAsLateBoundName(indexType)
+                ? getLateBoundNameFromType(indexType)
+                : accessExpression && checkThatExpressionIsProperSymbolReference(accessExpression.argumentExpression, indexType, /*reportError*/ false)
+                    ? getPropertyNameForKnownSymbolName(idText((<PropertyAccessExpression>accessExpression.argumentExpression).name))
+                    : accessNode && isPropertyName(accessNode)
+                        // late bound names are handled in the first branch, so here we only need to handle normal names
+                        ? getPropertyNameForPropertyNameNode(accessNode)
+                        : undefined;
             if (propName !== undefined) {
                 const prop = getPropertyOfType(objectType, propName);
                 if (prop) {
@@ -9386,7 +9354,7 @@ namespace ts {
                 }
                 if (everyType(objectType, isTupleType) && isNumericLiteralName(propName) && +propName >= 0) {
                     if (accessNode && everyType(objectType, t => !(<TupleTypeReference>t).target.hasRestElement)) {
-                        const indexNode = accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode.argumentExpression : accessNode.indexType;
+                        const indexNode = getIndexNodeForAccessExpression(accessNode);
                         error(indexNode, Diagnostics.Property_0_does_not_exist_on_type_1, unescapeLeadingUnderscores(propName), typeToString(objectType));
                     }
                     return mapType(objectType, t => getRestTypeOfTupleType(<TupleTypeReference>t) || undefinedType);
@@ -9401,7 +9369,7 @@ namespace ts {
                     undefined;
                 if (indexInfo) {
                     if (accessNode && !isTypeAssignableToKind(indexType, TypeFlags.String | TypeFlags.Number)) {
-                        const indexNode = accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode.argumentExpression : accessNode.indexType;
+                        const indexNode = getIndexNodeForAccessExpression(accessNode);
                         error(indexNode, Diagnostics.Type_0_cannot_be_used_as_an_index_type, typeToString(indexType));
                     }
                     else if (accessExpression && indexInfo.isReadonly && (isAssignmentTarget(accessExpression) || isDeleteTarget(accessExpression))) {
@@ -9442,7 +9410,7 @@ namespace ts {
                 return anyType;
             }
             if (accessNode) {
-                const indexNode = accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode.argumentExpression : accessNode.indexType;
+                const indexNode = getIndexNodeForAccessExpression(accessNode);
                 if (indexType.flags & (TypeFlags.StringLiteral | TypeFlags.NumberLiteral)) {
                     error(indexNode, Diagnostics.Property_0_does_not_exist_on_type_1, "" + (<LiteralType>indexType).value, typeToString(objectType));
                 }
@@ -9459,6 +9427,16 @@ namespace ts {
             return missingType;
         }
 
+        function getIndexNodeForAccessExpression(accessNode: ElementAccessExpression | IndexedAccessTypeNode | PropertyName) {
+            return accessNode.kind === SyntaxKind.ElementAccessExpression
+            ? accessNode.argumentExpression
+            : accessNode.kind === SyntaxKind.IndexedAccessType
+                ? accessNode.indexType
+                : accessNode.kind === SyntaxKind.ComputedPropertyName
+                    ? accessNode.expression
+                    : accessNode;
+        }
+
         function isGenericObjectType(type: Type): boolean {
             return maybeTypeOfKind(type, TypeFlags.InstantiableNonPrimitive | TypeFlags.GenericMappedType);
         }
@@ -9522,7 +9500,7 @@ namespace ts {
             return instantiateType(getTemplateTypeFromMappedType(objectType), templateMapper);
         }
 
-        function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode, missingType = accessNode ? errorType : unknownType): Type {
+        function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode | PropertyName, missingType = accessNode ? errorType : unknownType): Type {
             if (objectType === wildcardType || indexType === wildcardType) {
                 return wildcardType;
             }
@@ -23208,7 +23186,7 @@ namespace ts {
             forEach(node.types, checkSourceElement);
         }
 
-        function checkIndexedAccessIndexType(type: Type, accessNode: ElementAccessExpression | IndexedAccessTypeNode) {
+        function checkIndexedAccessIndexType(type: Type, accessNode: Node) {
             if (!(type.flags & TypeFlags.IndexedAccess)) {
                 return type;
             }
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 782f76b3d1f..18987466352 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -164,6 +164,13 @@ namespace ts {
             category: Diagnostics.Command_line_Options,
             description: Diagnostics.Stylize_errors_and_messages_using_color_and_context_experimental
         },
+        {
+            name: "showConfig",
+            type: "boolean",
+            category: Diagnostics.Command_line_Options,
+            isCommandLineOnly: true,
+            description: Diagnostics.Print_the_final_configuration_instead_of_building
+        },
 
         // Basic
         {
@@ -1653,6 +1660,137 @@ namespace ts {
         return false;
     }
 
+    /**
+     * Generate an uncommented, complete tsconfig for use with "--showConfig"
+     * @param configParseResult options to be generated into tsconfig.json
+     * @param configFileName name of the parsed config file - output paths will be generated relative to this
+     * @param host provides current directory and case sensitivity services
+     */
+    /** @internal */
+    export function convertToTSConfig(configParseResult: ParsedCommandLine, configFileName: string, host: { getCurrentDirectory(): string, useCaseSensitiveFileNames: boolean }): object {
+        const getCanonicalFileName = createGetCanonicalFileName(host.useCaseSensitiveFileNames);
+        const files = map(
+            filter(
+                configParseResult.fileNames,
+                !configParseResult.configFileSpecs ? _ => false : matchesSpecs(
+                    configFileName,
+                    configParseResult.configFileSpecs.validatedIncludeSpecs,
+                    configParseResult.configFileSpecs.validatedExcludeSpecs
+                )
+            ),
+            f => getRelativePathFromFile(getNormalizedAbsolutePath(configFileName, host.getCurrentDirectory()), f, getCanonicalFileName)
+        );
+        const optionMap = serializeCompilerOptions(configParseResult.options, { configFilePath: getNormalizedAbsolutePath(configFileName, host.getCurrentDirectory()), useCaseSensitiveFileNames: host.useCaseSensitiveFileNames });
+        const config = {
+            compilerOptions: {
+                ...arrayFrom(optionMap.entries()).reduce((prev, cur) => ({ ...prev, [cur[0]]: cur[1] }), {}),
+                showConfig: undefined,
+                configFile: undefined,
+                configFilePath: undefined,
+                help: undefined,
+                init: undefined,
+                listFiles: undefined,
+                listEmittedFiles: undefined,
+                project: undefined,
+            },
+            references: map(configParseResult.projectReferences, r => ({ ...r, path: r.originalPath, originalPath: undefined })),
+            files: length(files) ? files : undefined,
+            ...(configParseResult.configFileSpecs ? {
+                include: filterSameAsDefaultInclude(configParseResult.configFileSpecs.validatedIncludeSpecs),
+                exclude: configParseResult.configFileSpecs.validatedExcludeSpecs
+            } : {}),
+            compilerOnSave: !!configParseResult.compileOnSave ? true : undefined
+        };
+        return config;
+    }
+
+    function filterSameAsDefaultInclude(specs: ReadonlyArray<string> | undefined) {
+        if (!length(specs)) return undefined;
+        if (length(specs) !== 1) return specs;
+        if (specs![0] === "**/*") return undefined;
+        return specs;
+    }
+
+    function matchesSpecs(path: string, includeSpecs: ReadonlyArray<string> | undefined, excludeSpecs: ReadonlyArray<string> | undefined): (path: string) => boolean {
+        if (!includeSpecs) return _ => false;
+        const patterns = getFileMatcherPatterns(path, excludeSpecs, includeSpecs, sys.useCaseSensitiveFileNames, sys.getCurrentDirectory());
+        const excludeRe = patterns.excludePattern && getRegexFromPattern(patterns.excludePattern, sys.useCaseSensitiveFileNames);
+        const includeRe = patterns.includeFilePattern && getRegexFromPattern(patterns.includeFilePattern, sys.useCaseSensitiveFileNames);
+        if (includeRe) {
+            if (excludeRe) {
+                return path => includeRe.test(path) && !excludeRe.test(path);
+            }
+            return path => includeRe.test(path);
+        }
+        if (excludeRe) {
+            return path => !excludeRe.test(path);
+        }
+        return _ => false;
+    }
+
+    function getCustomTypeMapOfCommandLineOption(optionDefinition: CommandLineOption): Map<string | number> | undefined {
+        if (optionDefinition.type === "string" || optionDefinition.type === "number" || optionDefinition.type === "boolean") {
+            // this is of a type CommandLineOptionOfPrimitiveType
+            return undefined;
+        }
+        else if (optionDefinition.type === "list") {
+            return getCustomTypeMapOfCommandLineOption(optionDefinition.element);
+        }
+        else {
+            return (<CommandLineOptionOfCustomType>optionDefinition).type;
+        }
+    }
+
+    function getNameOfCompilerOptionValue(value: CompilerOptionsValue, customTypeMap: Map<string | number>): string | undefined {
+        // There is a typeMap associated with this command-line option so use it to map value back to its name
+        return forEachEntry(customTypeMap, (mapValue, key) => {
+            if (mapValue === value) {
+                return key;
+            }
+        });
+    }
+
+    function serializeCompilerOptions(options: CompilerOptions, pathOptions?: { configFilePath: string, useCaseSensitiveFileNames: boolean }): Map<CompilerOptionsValue> {
+        const result = createMap<CompilerOptionsValue>();
+        const optionsNameMap = getOptionNameMap().optionNameMap;
+        const getCanonicalFileName = pathOptions && createGetCanonicalFileName(pathOptions.useCaseSensitiveFileNames);
+
+        for (const name in options) {
+            if (hasProperty(options, name)) {
+                // tsconfig only options cannot be specified via command line,
+                // so we can assume that only types that can appear here string | number | boolean
+                if (optionsNameMap.has(name) && optionsNameMap.get(name)!.category === Diagnostics.Command_line_Options) {
+                    continue;
+                }
+                const value = <CompilerOptionsValue>options[name];
+                const optionDefinition = optionsNameMap.get(name.toLowerCase());
+                if (optionDefinition) {
+                    const customTypeMap = getCustomTypeMapOfCommandLineOption(optionDefinition);
+                    if (!customTypeMap) {
+                        // There is no map associated with this compiler option then use the value as-is
+                        // This is the case if the value is expect to be string, number, boolean or list of string
+                        if (pathOptions && optionDefinition.isFilePath) {
+                            result.set(name, getRelativePathFromFile(pathOptions.configFilePath, getNormalizedAbsolutePath(value as string, getDirectoryPath(pathOptions.configFilePath)), getCanonicalFileName!));
+                        }
+                        else {
+                            result.set(name, value);
+                        }
+                    }
+                    else {
+                        if (optionDefinition.type === "list") {
+                            result.set(name, (value as ReadonlyArray<string | number>).map(element => getNameOfCompilerOptionValue(element, customTypeMap)!)); // TODO: GH#18217
+                        }
+                        else {
+                            // There is a typeMap associated with this command-line option so use it to map value back to its name
+                            result.set(name, getNameOfCompilerOptionValue(value, customTypeMap));
+                        }
+                    }
+                }
+            }
+        }
+        return result;
+    }
+
     /**
      * Generate tsconfig configuration when running command line "--init"
      * @param options commandlineOptions to be generated into tsconfig.json
@@ -1664,63 +1802,6 @@ namespace ts {
         const compilerOptionsMap = serializeCompilerOptions(compilerOptions);
         return writeConfigurations();
 
-        function getCustomTypeMapOfCommandLineOption(optionDefinition: CommandLineOption): Map<string | number> | undefined {
-            if (optionDefinition.type === "string" || optionDefinition.type === "number" || optionDefinition.type === "boolean") {
-                // this is of a type CommandLineOptionOfPrimitiveType
-                return undefined;
-            }
-            else if (optionDefinition.type === "list") {
-                return getCustomTypeMapOfCommandLineOption(optionDefinition.element);
-            }
-            else {
-                return (<CommandLineOptionOfCustomType>optionDefinition).type;
-            }
-        }
-
-        function getNameOfCompilerOptionValue(value: CompilerOptionsValue, customTypeMap: Map<string | number>): string | undefined {
-            // There is a typeMap associated with this command-line option so use it to map value back to its name
-            return forEachEntry(customTypeMap, (mapValue, key) => {
-                if (mapValue === value) {
-                    return key;
-                }
-            });
-        }
-
-        function serializeCompilerOptions(options: CompilerOptions): Map<CompilerOptionsValue> {
-            const result = createMap<CompilerOptionsValue>();
-            const optionsNameMap = getOptionNameMap().optionNameMap;
-
-            for (const name in options) {
-                if (hasProperty(options, name)) {
-                    // tsconfig only options cannot be specified via command line,
-                    // so we can assume that only types that can appear here string | number | boolean
-                    if (optionsNameMap.has(name) && optionsNameMap.get(name)!.category === Diagnostics.Command_line_Options) {
-                        continue;
-                    }
-                    const value = <CompilerOptionsValue>options[name];
-                    const optionDefinition = optionsNameMap.get(name.toLowerCase());
-                    if (optionDefinition) {
-                        const customTypeMap = getCustomTypeMapOfCommandLineOption(optionDefinition);
-                        if (!customTypeMap) {
-                            // There is no map associated with this compiler option then use the value as-is
-                            // This is the case if the value is expect to be string, number, boolean or list of string
-                            result.set(name, value);
-                        }
-                        else {
-                            if (optionDefinition.type === "list") {
-                                result.set(name, (value as ReadonlyArray<string | number>).map(element => getNameOfCompilerOptionValue(element, customTypeMap)!)); // TODO: GH#18217
-                            }
-                            else {
-                                // There is a typeMap associated with this command-line option so use it to map value back to its name
-                                result.set(name, getNameOfCompilerOptionValue(value, customTypeMap));
-                            }
-                        }
-                    }
-                }
-            }
-            return result;
-        }
-
         function getDefaultValueForOption(option: CommandLineOption) {
             switch (option.type) {
                 case "number":
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 1f1ee7a6948..01aa861cabb 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1007,6 +1007,10 @@
         "category": "Error",
         "code": 1349
     },
+    "Print the final configuration instead of building.": {
+        "category": "Message",
+        "code": 1350
+    },
 
     "Duplicate identifier '{0}'.": {
         "category": "Error",
diff --git a/src/compiler/sourcemapDecoder.ts b/src/compiler/sourcemapDecoder.ts
index 28cbbe39cf5..dd0d65c8092 100644
--- a/src/compiler/sourcemapDecoder.ts
+++ b/src/compiler/sourcemapDecoder.ts
@@ -57,6 +57,7 @@ namespace ts.sourcemaps {
         fileExists(path: string): boolean;
         getCanonicalFileName(path: string): string;
         log(text: string): void;
+        useCaseSensitiveFileNames: boolean;
     }
 
     export function decode(host: SourceMapDecodeHost, mapPath: string, map: SourceMapData, program?: Program, fallbackCache = createSourceFileLikeCache(host)): SourceMapper {
@@ -79,7 +80,7 @@ namespace ts.sourcemaps {
                 // if no exact match, closest is 2's compliment of result
                 targetIndex = ~targetIndex;
             }
-            if (!maps[targetIndex] || comparePaths(loc.fileName, maps[targetIndex].sourcePath, sourceRoot) !== 0) {
+            if (!maps[targetIndex] || comparePaths(loc.fileName, maps[targetIndex].sourcePath, sourceRoot, !host.useCaseSensitiveFileNames) !== 0) {
                 return loc;
             }
             return { fileName: toPath(map.file!, sourceRoot, host.getCanonicalFileName), position: maps[targetIndex].emittedPosition }; // Closest pos
@@ -129,7 +130,7 @@ namespace ts.sourcemaps {
         }
 
         function compareProcessedPositionSourcePositions(a: ProcessedSourceMapPosition, b: ProcessedSourceMapPosition) {
-            return comparePaths(a.sourcePath, b.sourcePath, sourceRoot) ||
+            return comparePaths(a.sourcePath, b.sourcePath, sourceRoot, !host.useCaseSensitiveFileNames) ||
                 compareValues(a.sourcePosition, b.sourcePosition);
         }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index aeb310671ed..1e592ad5886 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -4556,6 +4556,7 @@ namespace ts {
         /*@internal*/ version?: boolean;
         /*@internal*/ watch?: boolean;
         esModuleInterop?: boolean;
+        /* @internal */ showConfig?: boolean;
 
         [option: string]: CompilerOptionsValue | TsConfigSourceFile | undefined;
     }
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index a969d580b86..991e403f52e 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -2921,7 +2921,6 @@ namespace ts {
         }
     }
 
-    /* @internal */
     export function getBinaryOperatorPrecedence(kind: SyntaxKind): number {
         switch (kind) {
             case SyntaxKind.BarBarToken:
@@ -6834,7 +6833,6 @@ namespace ts {
 
 /* @internal */
 namespace ts {
-    /** @internal */
     export function isNamedImportsOrExports(node: Node): node is NamedImportsOrExports {
         return node.kind === SyntaxKind.NamedImports || node.kind === SyntaxKind.NamedExports;
     }
@@ -6898,7 +6896,6 @@ namespace ts {
         getSourceMapSourceConstructor: () => <any>SourceMapSource,
     };
 
-    /* @internal */
     export function formatStringFromArgs(text: string, args: ArrayLike<string>, baseIndex = 0): string {
         return text.replace(/{(\d+)}/g, (_match, index: string) => Debug.assertDefined(args[+index + baseIndex]));
     }
@@ -6909,7 +6906,6 @@ namespace ts {
         return localizedDiagnosticMessages && localizedDiagnosticMessages[message.key] || message.message;
     }
 
-    /* @internal */
     export function createFileDiagnostic(file: SourceFile, start: number, length: number, message: DiagnosticMessage, ...args: (string | number | undefined)[]): DiagnosticWithLocation;
     export function createFileDiagnostic(file: SourceFile, start: number, length: number, message: DiagnosticMessage): DiagnosticWithLocation {
         Debug.assertGreaterThanOrEqual(start, 0);
@@ -6938,7 +6934,6 @@ namespace ts {
         };
     }
 
-    /* @internal */
     export function formatMessage(_dummy: any, message: DiagnosticMessage): string {
         let text = getLocaleSpecificMessage(message);
 
@@ -6949,7 +6944,6 @@ namespace ts {
         return text;
     }
 
-    /* @internal */
     export function createCompilerDiagnostic(message: DiagnosticMessage, ...args: (string | number | undefined)[]): Diagnostic;
     export function createCompilerDiagnostic(message: DiagnosticMessage): Diagnostic {
         let text = getLocaleSpecificMessage(message);
@@ -6970,7 +6964,6 @@ namespace ts {
         };
     }
 
-    /* @internal */
     export function createCompilerDiagnosticFromMessageChain(chain: DiagnosticMessageChain): Diagnostic {
         return {
             file: undefined,
@@ -6983,7 +6976,6 @@ namespace ts {
         };
     }
 
-    /* @internal */
     export function chainDiagnosticMessages(details: DiagnosticMessageChain | undefined, message: DiagnosticMessage, ...args: (string | undefined)[]): DiagnosticMessageChain;
     export function chainDiagnosticMessages(details: DiagnosticMessageChain | undefined, message: DiagnosticMessage): DiagnosticMessageChain {
         let text = getLocaleSpecificMessage(message);
@@ -7015,14 +7007,12 @@ namespace ts {
         return diagnostic.file ? diagnostic.file.path : undefined;
     }
 
-    /* @internal */
     export function compareDiagnostics(d1: Diagnostic, d2: Diagnostic): Comparison {
         return compareDiagnosticsSkipRelatedInformation(d1, d2) ||
             compareRelatedInformation(d1, d2) ||
             Comparison.EqualTo;
     }
 
-    /* @internal */
     export function compareDiagnosticsSkipRelatedInformation(d1: Diagnostic, d2: Diagnostic): Comparison {
         return compareStringsCaseSensitive(getDiagnosticFilePath(d1), getDiagnosticFilePath(d2)) ||
             compareValues(d1.start, d2.start) ||
@@ -7360,7 +7350,6 @@ namespace ts {
         return rootLength > 0 && rootLength === path.length;
     }
 
-    /* @internal */
     export function convertToRelativePath(absoluteOrRelativePath: string, basePath: string, getCanonicalFileName: (path: string) => string): string {
         return !isRootedDiskPath(absoluteOrRelativePath)
             ? absoluteOrRelativePath
diff --git a/src/server/protocol.ts b/src/server/protocol.ts
index aad7ba085de..e956290181a 100644
--- a/src/server/protocol.ts
+++ b/src/server/protocol.ts
@@ -2401,6 +2401,7 @@ namespace ts.server.protocol {
      */
     export interface DiagnosticEvent extends Event {
         body?: DiagnosticEventBody;
+        event: DiagnosticEventKind;
     }
 
     export interface ConfigFileDiagnosticEventBody {
@@ -2520,6 +2521,10 @@ namespace ts.server.protocol {
         maxFileSize: number;
     }
 
+    /*@internal*/
+    export type AnyEvent = RequestCompletedEvent | DiagnosticEvent | ConfigFileDiagnosticEvent | ProjectLanguageServiceStateEvent | TelemetryEvent |
+        ProjectsUpdatedInBackgroundEvent | ProjectLoadingStartEvent | ProjectLoadingFinishEvent | SurveyReadyEvent | LargeFileReferencedEvent;
+
     /**
      * Arguments for reload request.
      */
diff --git a/src/server/session.ts b/src/server/session.ts
index 49db5562992..da4808c31f6 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -576,7 +576,7 @@ namespace ts.server {
                     break;
                 case ProjectLoadingFinishEvent:
                     const { project: finishProject } = event.data;
-                    this.event<protocol.ProjectLoadingFinishEventBody>({ projectName: finishProject.getProjectName() }, ProjectLoadingStartEvent);
+                    this.event<protocol.ProjectLoadingFinishEventBody>({ projectName: finishProject.getProjectName() }, ProjectLoadingFinishEvent);
                     break;
                 case LargeFileReferencedEvent:
                     const { file, fileSize, maxFileSize } = event.data;
diff --git a/src/services/services.ts b/src/services/services.ts
index 4367bd11985..afcdc7b4f16 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1139,7 +1139,7 @@ namespace ts {
         const useCaseSensitiveFileNames = hostUsesCaseSensitiveFileNames(host);
         const getCanonicalFileName = createGetCanonicalFileName(useCaseSensitiveFileNames);
 
-        const sourceMapper = getSourceMapper(getCanonicalFileName, currentDirectory, log, host, () => program);
+        const sourceMapper = getSourceMapper(useCaseSensitiveFileNames, currentDirectory, log, host, () => program);
 
         function getValidSourceFile(fileName: string): SourceFile {
             const sourceFile = program.getSourceFile(fileName);
diff --git a/src/services/sourcemaps.ts b/src/services/sourcemaps.ts
index 1833c415be4..25e6fb9c124 100644
--- a/src/services/sourcemaps.ts
+++ b/src/services/sourcemaps.ts
@@ -13,12 +13,13 @@ namespace ts {
     }
 
     export function getSourceMapper(
-        getCanonicalFileName: GetCanonicalFileName,
+        useCaseSensitiveFileNames: boolean,
         currentDirectory: string,
         log: (message: string) => void,
         host: LanguageServiceHost,
         getProgram: () => Program,
     ): SourceMapper {
+        const getCanonicalFileName = createGetCanonicalFileName(useCaseSensitiveFileNames);
         let sourcemappedFileCache: SourceFileLikeCache;
         return { tryGetOriginalLocation, tryGetGeneratedLocation, toLineColumnOffset, clearCache };
 
@@ -56,6 +57,7 @@ namespace ts {
             return file.sourceMapper = sourcemaps.decode({
                 readFile: s => host.readFile!(s), // TODO: GH#18217
                 fileExists: s => host.fileExists!(s), // TODO: GH#18217
+                useCaseSensitiveFileNames,
                 getCanonicalFileName,
                 log,
             }, mapFileName, maps, getProgram(), sourcemappedFileCache);
@@ -105,7 +107,11 @@ namespace ts {
 
         function tryGetGeneratedLocation(info: sourcemaps.SourceMappableLocation): sourcemaps.SourceMappableLocation | undefined {
             const program = getProgram();
-            const declarationPath = getDeclarationEmitOutputFilePathWorker(info.fileName, program.getCompilerOptions(), currentDirectory, program.getCommonSourceDirectory(), getCanonicalFileName);
+            const options = program.getCompilerOptions();
+            const outPath = options.outFile || options.out;
+            const declarationPath = outPath ?
+                removeFileExtension(outPath) + Extension.Dts :
+                getDeclarationEmitOutputFilePathWorker(info.fileName, program.getCompilerOptions(), currentDirectory, program.getCommonSourceDirectory(), getCanonicalFileName);
             if (declarationPath === undefined) return undefined;
             const declarationFile = getFile(declarationPath);
             if (!declarationFile) return undefined;
diff --git a/src/testRunner/tsconfig.json b/src/testRunner/tsconfig.json
index 42edf839964..af25aba408d 100644
--- a/src/testRunner/tsconfig.json
+++ b/src/testRunner/tsconfig.json
@@ -75,6 +75,7 @@
         "unittests/reuseProgramStructure.ts",
         "unittests/session.ts",
         "unittests/semver.ts",
+        "unittests/showConfig.ts",
         "unittests/symbolWalker.ts",
         "unittests/telemetry.ts",
         "unittests/textChanges.ts",
diff --git a/src/testRunner/unittests/showConfig.ts b/src/testRunner/unittests/showConfig.ts
new file mode 100644
index 00000000000..a2b5bb10258
--- /dev/null
+++ b/src/testRunner/unittests/showConfig.ts
@@ -0,0 +1,34 @@
+namespace ts {
+    describe("showTSConfig", () => {
+        function showTSConfigCorrectly(name: string, commandLinesArgs: string[]) {
+            describe(name, () => {
+                const commandLine = parseCommandLine(commandLinesArgs);
+                const initResult = convertToTSConfig(commandLine, `/${name}/tsconfig.json`, { getCurrentDirectory() { return `/${name}`; }, useCaseSensitiveFileNames: true });
+                const outputFileName = `showConfig/${name.replace(/[^a-z0-9\-. ]/ig, "")}/tsconfig.json`;
+
+                it(`Correct output for ${outputFileName}`, () => {
+                    // tslint:disable-next-line:no-null-keyword
+                    Harness.Baseline.runBaseline(outputFileName, JSON.stringify(initResult, null, 4) + "\n");
+                });
+            });
+        }
+
+        showTSConfigCorrectly("Default initialized TSConfig", ["--showConfig"]);
+
+        showTSConfigCorrectly("Show TSConfig with files options", ["--showConfig", "file0.st", "file1.ts", "file2.ts"]);
+
+        showTSConfigCorrectly("Show TSConfig with boolean value compiler options", ["--showConfig", "--noUnusedLocals"]);
+
+        showTSConfigCorrectly("Show TSConfig with enum value compiler options", ["--showConfig", "--target", "es5", "--jsx", "react"]);
+
+        showTSConfigCorrectly("Show TSConfig with list compiler options", ["--showConfig", "--types", "jquery,mocha"]);
+
+        showTSConfigCorrectly("Show TSConfig with list compiler options with enum value", ["--showConfig", "--lib", "es5,es2015.core"]);
+
+        showTSConfigCorrectly("Show TSConfig with incorrect compiler option", ["--showConfig", "--someNonExistOption"]);
+
+        showTSConfigCorrectly("Show TSConfig with incorrect compiler option value", ["--showConfig", "--lib", "nonExistLib,es5,es2015.promise"]);
+
+        showTSConfigCorrectly("Show TSConfig with advanced options", ["--showConfig", "--declaration", "--declarationDir", "lib", "--skipLibCheck", "--noErrorTruncation"]);
+    });
+}
\ No newline at end of file
diff --git a/src/testRunner/unittests/tsserverProjectSystem.ts b/src/testRunner/unittests/tsserverProjectSystem.ts
index 9f569f46d4d..c52940a49be 100644
--- a/src/testRunner/unittests/tsserverProjectSystem.ts
+++ b/src/testRunner/unittests/tsserverProjectSystem.ts
@@ -330,12 +330,12 @@ namespace ts.projectSystem {
         return new TestSession({ ...sessionOptions, ...opts });
     }
 
-    function createSessionWithEventTracking<T extends server.ProjectServiceEvent, U extends server.ProjectServiceEvent = T>(host: server.ServerHost, eventName: T["eventName"], eventName2?: U["eventName"]) {
-        const events: (T | U)[] = [];
+    function createSessionWithEventTracking<T extends server.ProjectServiceEvent>(host: server.ServerHost, eventName: T["eventName"], ...eventNames: T["eventName"][]) {
+        const events: T[] = [];
         const session = createSession(host, {
             eventHandler: e => {
-                if (e.eventName === eventName || (eventName2 && e.eventName === eventName2)) {
-                    events.push(e as T | U);
+                if (e.eventName === eventName || eventNames.some(eventName => e.eventName === eventName)) {
+                    events.push(e as T);
                 }
             }
         });
@@ -343,6 +343,31 @@ namespace ts.projectSystem {
         return { session, events };
     }
 
+    function createSessionWithDefaultEventHandler<T extends protocol.AnyEvent>(host: TestServerHost, eventNames: T["event"] | T["event"][], opts: Partial<server.SessionOptions> = {}) {
+        const session = createSession(host, { canUseEvents: true, ...opts });
+
+        return {
+            session,
+            getEvents,
+            clearEvents
+        };
+
+        function getEvents() {
+            const outputEventRegex = /Content\-Length: [\d]+\r\n\r\n/;
+            return mapDefined(host.getOutput(), s => {
+                const e = convertToObject(
+                    parseJsonText("json.json", s.replace(outputEventRegex, "")),
+                    []
+                );
+                return (isArray(eventNames) ? eventNames.some(eventName => e.event === eventName) : e.event === eventNames) ? e as T : undefined;
+            });
+        }
+
+        function clearEvents() {
+            session.clearMessages();
+        }
+    }
+
     interface CreateProjectServiceParameters {
         cancellationToken?: HostCancellationToken;
         logger?: server.Logger;
@@ -8062,15 +8087,7 @@ namespace ts.projectSystem {
             verifyProjectsUpdatedInBackgroundEvent(createSessionWithProjectChangedEventHandler);
 
             function createSessionWithProjectChangedEventHandler(host: TestServerHost): ProjectsUpdatedInBackgroundEventVerifier {
-                const projectChangedEvents: server.ProjectsUpdatedInBackgroundEvent[] = [];
-                const session = createSession(host, {
-                    eventHandler: e => {
-                        if (e.eventName === server.ProjectsUpdatedInBackgroundEvent) {
-                            projectChangedEvents.push(e);
-                        }
-                    }
-                });
-
+                const { session, events: projectChangedEvents } = createSessionWithEventTracking<server.ProjectsUpdatedInBackgroundEvent>(host, server.ProjectsUpdatedInBackgroundEvent);
                 return {
                     session,
                     verifyProjectsUpdatedInBackgroundEventHandler,
@@ -8110,7 +8127,7 @@ namespace ts.projectSystem {
 
 
             function createSessionThatUsesEvents(host: TestServerHost, noGetErrOnBackgroundUpdate?: boolean): ProjectsUpdatedInBackgroundEventVerifier {
-                const session = createSession(host, { canUseEvents: true, noGetErrOnBackgroundUpdate });
+                const { session, getEvents, clearEvents } = createSessionWithDefaultEventHandler<protocol.ProjectsUpdatedInBackgroundEvent>(host, server.ProjectsUpdatedInBackgroundEvent, { noGetErrOnBackgroundUpdate });
 
                 return {
                     session,
@@ -8124,16 +8141,7 @@ namespace ts.projectSystem {
                             openFiles: e.data.openFiles
                         };
                     });
-                    const outputEventRegex = /Content\-Length: [\d]+\r\n\r\n/;
-                    const events: protocol.ProjectsUpdatedInBackgroundEvent[] = filter(
-                        map(
-                            host.getOutput(), s => convertToObject(
-                                parseJsonText("json.json", s.replace(outputEventRegex, "")),
-                                []
-                            )
-                        ),
-                        e => e.event === server.ProjectsUpdatedInBackgroundEvent
-                    );
+                    const events = getEvents();
                     assert.equal(events.length, expectedEvents.length, `Incorrect number of events Actual: ${map(events, e => e.body)} Expected: ${expectedEvents}`);
                     forEach(events, (actualEvent, i) => {
                         const expectedEvent = expectedEvents[i];
@@ -8141,7 +8149,7 @@ namespace ts.projectSystem {
                     });
 
                     // Verified the events, reset them
-                    session.clearMessages();
+                    clearEvents();
 
                     if (events.length) {
                         host.checkTimeoutQueueLength(noGetErrOnBackgroundUpdate ? 0 : 1); // Error checking queued only if not noGetErrOnBackgroundUpdate
@@ -9457,141 +9465,180 @@ export const x = 10;`
         const configBPath = `${projectRoot}/b/tsconfig.json`;
         const files = [libFile, aTs, configA];
 
-        function createSessionWithEventHandler(files: ReadonlyArray<File>) {
-            const host = createServerHost(files);
+        function verifyProjectLoadingStartAndFinish(createSession: (host: TestServerHost) => {
+            session: TestSession;
+            getNumberOfEvents: () => number;
+            clearEvents: () => void;
+            verifyProjectLoadEvents: (expected: [server.ProjectLoadingStartEvent, server.ProjectLoadingFinishEvent]) => void;
+        }) {
+            function createSessionToVerifyEvent(files: ReadonlyArray<File>) {
+                const host = createServerHost(files);
+                const originalReadFile = host.readFile;
+                const { session, getNumberOfEvents, clearEvents, verifyProjectLoadEvents } = createSession(host);
+                host.readFile = file => {
+                    if (file === configA.path || file === configBPath) {
+                        assert.equal(getNumberOfEvents(), 1, "Event for loading is sent before reading config file");
+                    }
+                    return originalReadFile.call(host, file);
+                };
+                const service = session.getProjectService();
+                return { host, session, verifyEvent, verifyEventWithOpenTs, service, getNumberOfEvents };
 
-            const originalReadFile = host.readFile;
-            host.readFile = file => {
-                if (file === configA.path || file === configBPath) {
-                    assert.equal(events.length, 1, "Event for loading is sent before reading config file");
+                function verifyEvent(project: server.Project, reason: string) {
+                    verifyProjectLoadEvents([
+                        { eventName: server.ProjectLoadingStartEvent, data: { project, reason } },
+                        { eventName: server.ProjectLoadingFinishEvent, data: { project } }
+                    ]);
+                    clearEvents();
                 }
-                return originalReadFile.call(host, file);
-            };
-            const { session, events } = createSessionWithEventTracking<server.ProjectLoadingStartEvent, server.ProjectLoadingFinishEvent>(host, server.ProjectLoadingStartEvent, server.ProjectLoadingFinishEvent);
-            const service = session.getProjectService();
-            return { host, session, verifyEvent, verifyEventWithOpenTs, service, events };
 
-            function verifyEvent(project: server.Project, reason: string) {
-                assert.deepEqual(events, [
-                    { eventName: server.ProjectLoadingStartEvent, data: { project, reason } },
-                    { eventName: server.ProjectLoadingFinishEvent, data: { project } }
-                ]);
-                events.length = 0;
+                function verifyEventWithOpenTs(file: File, configPath: string, configuredProjects: number) {
+                    openFilesForSession([file], session);
+                    checkNumberOfProjects(service, { configuredProjects });
+                    const project = service.configuredProjects.get(configPath)!;
+                    assert.isDefined(project);
+                    verifyEvent(project, `Creating possible configured project for ${file.path} to open`);
+                }
             }
 
-            function verifyEventWithOpenTs(file: File, configPath: string, configuredProjects: number) {
-                openFilesForSession([file], session);
-                checkNumberOfProjects(service, { configuredProjects });
-                const project = service.configuredProjects.get(configPath)!;
-                assert.isDefined(project);
-                verifyEvent(project, `Creating possible configured project for ${file.path} to open`);
-            }
-        }
+            it("when project is created by open file", () => {
+                const bTs: File = {
+                    path: bTsPath,
+                    content: "export class B {}"
+                };
+                const configB: File = {
+                    path: configBPath,
+                    content: "{}"
+                };
+                const { verifyEventWithOpenTs } = createSessionToVerifyEvent(files.concat(bTs, configB));
+                verifyEventWithOpenTs(aTs, configA.path, 1);
+                verifyEventWithOpenTs(bTs, configB.path, 2);
+            });
 
-        it("when project is created by open file", () => {
-            const bTs: File = {
-                path: bTsPath,
-                content: "export class B {}"
-            };
-            const configB: File = {
-                path: configBPath,
-                content: "{}"
-            };
-            const { verifyEventWithOpenTs } = createSessionWithEventHandler(files.concat(bTs, configB));
-            verifyEventWithOpenTs(aTs, configA.path, 1);
-            verifyEventWithOpenTs(bTs, configB.path, 2);
-        });
+            it("when change is detected in the config file", () => {
+                const { host, verifyEvent, verifyEventWithOpenTs, service } = createSessionToVerifyEvent(files);
+                verifyEventWithOpenTs(aTs, configA.path, 1);
 
-        it("when change is detected in the config file", () => {
-            const { host, verifyEvent, verifyEventWithOpenTs, service } = createSessionWithEventHandler(files);
-            verifyEventWithOpenTs(aTs, configA.path, 1);
+                host.writeFile(configA.path, configA.content);
+                host.checkTimeoutQueueLengthAndRun(2);
+                const project = service.configuredProjects.get(configA.path)!;
+                verifyEvent(project, `Change in config file detected`);
+            });
 
-            host.writeFile(configA.path, configA.content);
-            host.checkTimeoutQueueLengthAndRun(2);
-            const project = service.configuredProjects.get(configA.path)!;
-            verifyEvent(project, `Change in config file detected`);
-        });
-
-        it("when opening original location project", () => {
-            const aDTs: File = {
-                path: `${projectRoot}/a/a.d.ts`,
-                content: `export declare class A {
+            it("when opening original location project", () => {
+                const aDTs: File = {
+                    path: `${projectRoot}/a/a.d.ts`,
+                    content: `export declare class A {
 }
 //# sourceMappingURL=a.d.ts.map
 `
-            };
-            const aDTsMap: File = {
-                path: `${projectRoot}/a/a.d.ts.map`,
-                content: `{"version":3,"file":"a.d.ts","sourceRoot":"","sources":["./a.ts"],"names":[],"mappings":"AAAA,qBAAa,CAAC;CAAI"}`
-            };
-            const bTs: File = {
-                path: bTsPath,
-                content: `import {A} from "../a/a"; new A();`
-            };
-            const configB: File = {
-                path: configBPath,
-                content: JSON.stringify({
-                    references: [{ path: "../a" }]
-                })
-            };
+                };
+                const aDTsMap: File = {
+                    path: `${projectRoot}/a/a.d.ts.map`,
+                    content: `{"version":3,"file":"a.d.ts","sourceRoot":"","sources":["./a.ts"],"names":[],"mappings":"AAAA,qBAAa,CAAC;CAAI"}`
+                };
+                const bTs: File = {
+                    path: bTsPath,
+                    content: `import {A} from "../a/a"; new A();`
+                };
+                const configB: File = {
+                    path: configBPath,
+                    content: JSON.stringify({
+                        references: [{ path: "../a" }]
+                    })
+                };
 
-            const { service, session, verifyEventWithOpenTs, verifyEvent } = createSessionWithEventHandler(files.concat(aDTs, aDTsMap, bTs, configB));
-            verifyEventWithOpenTs(bTs, configB.path, 1);
+                const { service, session, verifyEventWithOpenTs, verifyEvent } = createSessionToVerifyEvent(files.concat(aDTs, aDTsMap, bTs, configB));
+                verifyEventWithOpenTs(bTs, configB.path, 1);
 
-            session.executeCommandSeq<protocol.ReferencesRequest>({
-                command: protocol.CommandTypes.References,
-                arguments: {
-                    file: bTs.path,
-                    ...protocolLocationFromSubstring(bTs.content, "A()")
-                }
+                session.executeCommandSeq<protocol.ReferencesRequest>({
+                    command: protocol.CommandTypes.References,
+                    arguments: {
+                        file: bTs.path,
+                        ...protocolLocationFromSubstring(bTs.content, "A()")
+                    }
+                });
+
+                checkNumberOfProjects(service, { configuredProjects: 2 });
+                const project = service.configuredProjects.get(configA.path)!;
+                assert.isDefined(project);
+                verifyEvent(project, `Creating project for original file: ${aTs.path} for location: ${aDTs.path}`);
             });
 
-            checkNumberOfProjects(service, { configuredProjects: 2 });
-            const project = service.configuredProjects.get(configA.path)!;
-            assert.isDefined(project);
-            verifyEvent(project, `Creating project for original file: ${aTs.path} for location: ${aDTs.path}`);
+            describe("with external projects and config files ", () => {
+                const projectFileName = `${projectRoot}/a/project.csproj`;
+
+                function createSession(lazyConfiguredProjectsFromExternalProject: boolean) {
+                    const { session, service, verifyEvent: verifyEventWorker, getNumberOfEvents } = createSessionToVerifyEvent(files);
+                    service.setHostConfiguration({ preferences: { lazyConfiguredProjectsFromExternalProject } });
+                    service.openExternalProject(<protocol.ExternalProject>{
+                        projectFileName,
+                        rootFiles: toExternalFiles([aTs.path, configA.path]),
+                        options: {}
+                    });
+                    checkNumberOfProjects(service, { configuredProjects: 1 });
+                    return { session, service, verifyEvent, getNumberOfEvents };
+
+                    function verifyEvent() {
+                        const projectA = service.configuredProjects.get(configA.path)!;
+                        assert.isDefined(projectA);
+                        verifyEventWorker(projectA, `Creating configured project in external project: ${projectFileName}`);
+                    }
+                }
+
+                it("when lazyConfiguredProjectsFromExternalProject is false", () => {
+                    const { verifyEvent } = createSession(/*lazyConfiguredProjectsFromExternalProject*/ false);
+                    verifyEvent();
+                });
+
+                it("when lazyConfiguredProjectsFromExternalProject is true and file is opened", () => {
+                    const { verifyEvent, getNumberOfEvents, session } = createSession(/*lazyConfiguredProjectsFromExternalProject*/ true);
+                    assert.equal(getNumberOfEvents(), 0);
+
+                    openFilesForSession([aTs], session);
+                    verifyEvent();
+                });
+
+                it("when lazyConfiguredProjectsFromExternalProject is disabled", () => {
+                    const { verifyEvent, getNumberOfEvents, service } = createSession(/*lazyConfiguredProjectsFromExternalProject*/ true);
+                    assert.equal(getNumberOfEvents(), 0);
+
+                    service.setHostConfiguration({ preferences: { lazyConfiguredProjectsFromExternalProject: false } });
+                    verifyEvent();
+                });
+            });
+        }
+
+        describe("when using event handler", () => {
+            verifyProjectLoadingStartAndFinish(host => {
+                const { session, events } = createSessionWithEventTracking<server.ProjectLoadingStartEvent | server.ProjectLoadingFinishEvent>(host, server.ProjectLoadingStartEvent, server.ProjectLoadingFinishEvent);
+                return {
+                    session,
+                    getNumberOfEvents: () => events.length,
+                    clearEvents: () => events.length = 0,
+                    verifyProjectLoadEvents: expected => assert.deepEqual(events, expected)
+                };
+            });
         });
 
-        describe("with external projects and config files ", () => {
-            const projectFileName = `${projectRoot}/a/project.csproj`;
+        describe("when using default event handler", () => {
+            verifyProjectLoadingStartAndFinish(host => {
+                const { session, getEvents, clearEvents } = createSessionWithDefaultEventHandler<protocol.ProjectLoadingStartEvent | protocol.ProjectLoadingFinishEvent>(host, [server.ProjectLoadingStartEvent, server.ProjectLoadingFinishEvent]);
+                return {
+                    session,
+                    getNumberOfEvents: () => getEvents().length,
+                    clearEvents,
+                    verifyProjectLoadEvents
+                };
 
-            function createSession(lazyConfiguredProjectsFromExternalProject: boolean) {
-                const { session, service, verifyEvent: verifyEventWorker, events } = createSessionWithEventHandler(files);
-                service.setHostConfiguration({ preferences: { lazyConfiguredProjectsFromExternalProject } });
-                service.openExternalProject(<protocol.ExternalProject>{
-                    projectFileName,
-                    rootFiles: toExternalFiles([aTs.path, configA.path]),
-                    options: {}
-                });
-                checkNumberOfProjects(service, { configuredProjects: 1 });
-                return { session, service, verifyEvent, events };
-
-                function verifyEvent() {
-                    const projectA = service.configuredProjects.get(configA.path)!;
-                    assert.isDefined(projectA);
-                    verifyEventWorker(projectA, `Creating configured project in external project: ${projectFileName}`);
+                function verifyProjectLoadEvents(expected: [server.ProjectLoadingStartEvent, server.ProjectLoadingFinishEvent]) {
+                    const actual = getEvents().map(e => ({ eventName: e.event, data: e.body }));
+                    const mappedExpected = expected.map(e => {
+                        const { project, ...rest } = e.data;
+                        return { eventName: e.eventName, data: { projectName: project.getProjectName(), ...rest } };
+                    });
+                    assert.deepEqual(actual, mappedExpected);
                 }
-            }
-
-            it("when lazyConfiguredProjectsFromExternalProject is false", () => {
-                const { verifyEvent } = createSession(/*lazyConfiguredProjectsFromExternalProject*/ false);
-                verifyEvent();
-            });
-
-            it("when lazyConfiguredProjectsFromExternalProject is true and file is opened", () => {
-                const { verifyEvent, events, session } = createSession(/*lazyConfiguredProjectsFromExternalProject*/ true);
-                assert.equal(events.length, 0);
-
-                openFilesForSession([aTs], session);
-                verifyEvent();
-            });
-
-            it("when lazyConfiguredProjectsFromExternalProject is disabled", () => {
-                const { verifyEvent, events, service } = createSession(/*lazyConfiguredProjectsFromExternalProject*/ true);
-                assert.equal(events.length, 0);
-
-                service.setHostConfiguration({ preferences: { lazyConfiguredProjectsFromExternalProject: false } });
-                verifyEvent();
             });
         });
     });
@@ -10481,13 +10528,15 @@ declare class TestLib {
                 TestFSWithWatch.getTsBuildProjectFile(project, "index.ts"),
             ];
         }
-        it("does not error on container only project", () => {
-            const project = "container";
-            const containerLib = getProjectFiles("container/lib");
-            const containerExec = getProjectFiles("container/exec");
-            const containerCompositeExec = getProjectFiles("container/compositeExec");
-            const containerConfig = TestFSWithWatch.getTsBuildProjectFile(project, "tsconfig.json");
-            const files = [libFile, ...containerLib, ...containerExec, ...containerCompositeExec, containerConfig];
+
+        const project = "container";
+        const containerLib = getProjectFiles("container/lib");
+        const containerExec = getProjectFiles("container/exec");
+        const containerCompositeExec = getProjectFiles("container/compositeExec");
+        const containerConfig = TestFSWithWatch.getTsBuildProjectFile(project, "tsconfig.json");
+        const files = [libFile, ...containerLib, ...containerExec, ...containerCompositeExec, containerConfig];
+
+        function createHost() {
             const host = createServerHost(files);
 
             // ts build should succeed
@@ -10495,6 +10544,12 @@ declare class TestLib {
             solutionBuilder.buildAllProjects();
             assert.equal(host.getOutput().length, 0);
 
+            return host;
+        }
+
+        it("does not error on container only project", () => {
+            const host = createHost();
+
             // Open external project for the folder
             const session = createSession(host);
             const service = session.getProjectService();
@@ -10521,6 +10576,30 @@ declare class TestLib {
                 assert.deepEqual(semanticDiagnostics, []);
             });
         });
+
+        it("can successfully find references with --out options", () => {
+            const host = createHost();
+            const session = createSession(host);
+            openFilesForSession([containerCompositeExec[1]], session);
+            const service = session.getProjectService();
+            checkNumberOfProjects(service, { configuredProjects: 1 });
+            const locationOfMyConst = protocolLocationFromSubstring(containerCompositeExec[1].content, "myConst");
+            const response = session.executeCommandSeq<protocol.RenameRequest>({
+                command: protocol.CommandTypes.Rename,
+                arguments: {
+                    file: containerCompositeExec[1].path,
+                    ...locationOfMyConst
+               }
+            }).response as protocol.RenameResponseBody;
+
+
+            const myConstLen = "myConst".length;
+            const locationOfMyConstInLib = protocolLocationFromSubstring(containerLib[1].content, "myConst");
+            assert.deepEqual(response.locs, [
+                { file: containerCompositeExec[1].path, locs: [{ start: locationOfMyConst, end: { line: locationOfMyConst.line, offset: locationOfMyConst.offset + myConstLen } }] },
+                { file: containerLib[1].path, locs: [{ start: locationOfMyConstInLib, end: { line: locationOfMyConstInLib.line, offset: locationOfMyConstInLib.offset + myConstLen } }] }
+            ]);
+        });
     });
 
     describe("tsserverProjectSystem duplicate packages", () => {
diff --git a/src/tsc/tsc.ts b/src/tsc/tsc.ts
index ec2d029e60a..549f79f9025 100644
--- a/src/tsc/tsc.ts
+++ b/src/tsc/tsc.ts
@@ -132,6 +132,11 @@ namespace ts {
         const commandLineOptions = commandLine.options;
         if (configFileName) {
             const configParseResult = parseConfigFileWithSystem(configFileName, commandLineOptions, sys, reportDiagnostic)!; // TODO: GH#18217
+            if (commandLineOptions.showConfig) {
+                // tslint:disable-next-line:no-null-keyword
+                sys.write(JSON.stringify(convertToTSConfig(configParseResult, configFileName, sys), null, 4) + sys.newLine);
+                return sys.exit(ExitStatus.Success);
+            }
             updateReportDiagnostic(configParseResult.options);
             if (isWatchSet(configParseResult.options)) {
                 reportWatchModeWithoutSysSupport();
@@ -142,6 +147,11 @@ namespace ts {
             }
         }
         else {
+            if (commandLineOptions.showConfig) {
+                // tslint:disable-next-line:no-null-keyword
+                sys.write(JSON.stringify(convertToTSConfig(commandLine, combinePaths(sys.getCurrentDirectory(), "tsconfig.json"), sys), null, 4) + sys.newLine);
+                return sys.exit(ExitStatus.Success);
+            }
             updateReportDiagnostic(commandLineOptions);
             if (isWatchSet(commandLineOptions)) {
                 reportWatchModeWithoutSysSupport();
diff --git a/tests/baselines/reference/ES5For-of27.errors.txt b/tests/baselines/reference/ES5For-of27.errors.txt
index 0c839859930..837a11cf7ee 100644
--- a/tests/baselines/reference/ES5For-of27.errors.txt
+++ b/tests/baselines/reference/ES5For-of27.errors.txt
@@ -1,13 +1,13 @@
-tests/cases/conformance/statements/for-ofStatements/ES5For-of27.ts(1,11): error TS2459: Type 'number' has no property 'x' and no string index signature.
-tests/cases/conformance/statements/for-ofStatements/ES5For-of27.ts(1,21): error TS2459: Type 'number' has no property 'y' and no string index signature.
+tests/cases/conformance/statements/for-ofStatements/ES5For-of27.ts(1,11): error TS2339: Property 'x' does not exist on type 'Number'.
+tests/cases/conformance/statements/for-ofStatements/ES5For-of27.ts(1,21): error TS2339: Property 'y' does not exist on type 'Number'.
 
 
 ==== tests/cases/conformance/statements/for-ofStatements/ES5For-of27.ts (2 errors) ====
     for (var {x: a = 0, y: b = 1} of [2, 3]) {
               ~
-!!! error TS2459: Type 'number' has no property 'x' and no string index signature.
+!!! error TS2339: Property 'x' does not exist on type 'Number'.
                         ~
-!!! error TS2459: Type 'number' has no property 'y' and no string index signature.
+!!! error TS2339: Property 'y' does not exist on type 'Number'.
         a;
         b;
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/ES5For-of29.errors.txt b/tests/baselines/reference/ES5For-of29.errors.txt
index e669b070222..c23ff1af211 100644
--- a/tests/baselines/reference/ES5For-of29.errors.txt
+++ b/tests/baselines/reference/ES5For-of29.errors.txt
@@ -1,13 +1,13 @@
-tests/cases/conformance/statements/for-ofStatements/ES5For-of29.ts(1,13): error TS2459: Type 'number' has no property 'x' and no string index signature.
-tests/cases/conformance/statements/for-ofStatements/ES5For-of29.ts(1,23): error TS2459: Type 'number' has no property 'y' and no string index signature.
+tests/cases/conformance/statements/for-ofStatements/ES5For-of29.ts(1,13): error TS2339: Property 'x' does not exist on type 'Number'.
+tests/cases/conformance/statements/for-ofStatements/ES5For-of29.ts(1,23): error TS2339: Property 'y' does not exist on type 'Number'.
 
 
 ==== tests/cases/conformance/statements/for-ofStatements/ES5For-of29.ts (2 errors) ====
     for (const {x: a = 0, y: b = 1} of [2, 3]) {
                 ~
-!!! error TS2459: Type 'number' has no property 'x' and no string index signature.
+!!! error TS2339: Property 'x' does not exist on type 'Number'.
                           ~
-!!! error TS2459: Type 'number' has no property 'y' and no string index signature.
+!!! error TS2339: Property 'y' does not exist on type 'Number'.
         a;
         b;
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/ES5For-of35.errors.txt b/tests/baselines/reference/ES5For-of35.errors.txt
index 8c43d959888..c22dc96e42d 100644
--- a/tests/baselines/reference/ES5For-of35.errors.txt
+++ b/tests/baselines/reference/ES5For-of35.errors.txt
@@ -1,13 +1,13 @@
-tests/cases/conformance/statements/for-ofStatements/ES5For-of35.ts(1,13): error TS2459: Type 'number' has no property 'x' and no string index signature.
-tests/cases/conformance/statements/for-ofStatements/ES5For-of35.ts(1,23): error TS2459: Type 'number' has no property 'y' and no string index signature.
+tests/cases/conformance/statements/for-ofStatements/ES5For-of35.ts(1,13): error TS2339: Property 'x' does not exist on type 'Number'.
+tests/cases/conformance/statements/for-ofStatements/ES5For-of35.ts(1,23): error TS2339: Property 'y' does not exist on type 'Number'.
 
 
 ==== tests/cases/conformance/statements/for-ofStatements/ES5For-of35.ts (2 errors) ====
     for (const {x: a = 0, y: b = 1} of [2, 3]) {
                 ~
-!!! error TS2459: Type 'number' has no property 'x' and no string index signature.
+!!! error TS2339: Property 'x' does not exist on type 'Number'.
                           ~
-!!! error TS2459: Type 'number' has no property 'y' and no string index signature.
+!!! error TS2339: Property 'y' does not exist on type 'Number'.
         a;
         b;
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index ccc9557e948..b5ef0cac750 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -7486,6 +7486,7 @@ declare namespace ts.server.protocol {
      */
     interface DiagnosticEvent extends Event {
         body?: DiagnosticEventBody;
+        event: DiagnosticEventKind;
     }
     interface ConfigFileDiagnosticEventBody {
         /**
diff --git a/tests/baselines/reference/blockScopedBindingUsedBeforeDef.errors.txt b/tests/baselines/reference/blockScopedBindingUsedBeforeDef.errors.txt
index 042f5e6de4f..4f04f2babc5 100644
--- a/tests/baselines/reference/blockScopedBindingUsedBeforeDef.errors.txt
+++ b/tests/baselines/reference/blockScopedBindingUsedBeforeDef.errors.txt
@@ -1,23 +1,32 @@
 tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts(2,12): error TS2448: Block-scoped variable 'a' used before its declaration.
+tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts(2,12): error TS2538: Type 'any' cannot be used as an index type.
 tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts(5,12): error TS2448: Block-scoped variable 'a' used before its declaration.
+tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts(5,12): error TS2538: Type 'any' cannot be used as an index type.
 tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts(8,7): error TS2448: Block-scoped variable 'b' used before its declaration.
+tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts(8,7): error TS2538: Type 'any' cannot be used as an index type.
 
 
-==== tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts (3 errors) ====
+==== tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts (6 errors) ====
     // 1:
     for (let {[a]: a} of [{ }]) continue;
                ~
 !!! error TS2448: Block-scoped variable 'a' used before its declaration.
 !!! related TS2728 tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts:2:16: 'a' is declared here.
+               ~
+!!! error TS2538: Type 'any' cannot be used as an index type.
     
     // 2:
     for (let {[a]: a} = { }; false; ) continue;
                ~
 !!! error TS2448: Block-scoped variable 'a' used before its declaration.
 !!! related TS2728 tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts:5:16: 'a' is declared here.
+               ~
+!!! error TS2538: Type 'any' cannot be used as an index type.
     
     // 3:
     let {[b]: b} = { };
           ~
 !!! error TS2448: Block-scoped variable 'b' used before its declaration.
-!!! related TS2728 tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts:8:11: 'b' is declared here.
\ No newline at end of file
+!!! related TS2728 tests/cases/compiler/blockScopedBindingUsedBeforeDef.ts:8:11: 'b' is declared here.
+          ~
+!!! error TS2538: Type 'any' cannot be used as an index type.
\ No newline at end of file
diff --git a/tests/baselines/reference/computedPropertiesInDestructuring1.errors.txt b/tests/baselines/reference/computedPropertiesInDestructuring1.errors.txt
index d2d63a48174..31b938fb3fb 100644
--- a/tests/baselines/reference/computedPropertiesInDestructuring1.errors.txt
+++ b/tests/baselines/reference/computedPropertiesInDestructuring1.errors.txt
@@ -1,33 +1,63 @@
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(3,7): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(8,7): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(10,8): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(11,8): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(14,15): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(15,15): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(16,16): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(17,16): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
 tests/cases/compiler/computedPropertiesInDestructuring1.ts(20,8): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(20,8): error TS2538: Type 'any' cannot be used as an index type.
+tests/cases/compiler/computedPropertiesInDestructuring1.ts(21,8): error TS2538: Type 'any' cannot be used as an index type.
 tests/cases/compiler/computedPropertiesInDestructuring1.ts(21,12): error TS2339: Property 'toExponential' does not exist on type 'string'.
 tests/cases/compiler/computedPropertiesInDestructuring1.ts(33,4): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
 tests/cases/compiler/computedPropertiesInDestructuring1.ts(34,5): error TS2365: Operator '+' cannot be applied to types '1' and '{}'.
 
 
-==== tests/cases/compiler/computedPropertiesInDestructuring1.ts (4 errors) ====
+==== tests/cases/compiler/computedPropertiesInDestructuring1.ts (14 errors) ====
     // destructuring in variable declarations
     let foo = "bar";
     let {[foo]: bar} = {bar: "bar"};
+          ~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     
     let {["bar"]: bar2} = {bar: "bar"};
     
     let foo2 = () => "bar";
     let {[foo2()]: bar3} = {bar: "bar"};
+          ~~~~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     
     let [{[foo]: bar4}] = [{bar: "bar"}];
+           ~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     let [{[foo2()]: bar5}] = [{bar: "bar"}];
+           ~~~~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     
     function f1({["bar"]: x}: { bar: number }) {}
     function f2({[foo]: x}: { bar: number }) {}
+                  ~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     function f3({[foo2()]: x}: { bar: number }) {}
+                  ~~~~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     function f4([{[foo]: x}]: [{ bar: number }]) {}
+                   ~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     function f5([{[foo2()]: x}]: [{ bar: number }]) {}
+                   ~~~~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     
     // report errors on type errors in computed properties used in destructuring
     let [{[foo()]: bar6}] = [{bar: "bar"}];
            ~~~~~
 !!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+           ~~~~~
+!!! error TS2538: Type 'any' cannot be used as an index type.
     let [{[foo.toExponential()]: bar7}] = [{bar: "bar"}];
+           ~~~~~~~~~~~~~~~~~~~
+!!! error TS2538: Type 'any' cannot be used as an index type.
                ~~~~~~~~~~~~~
 !!! error TS2339: Property 'toExponential' does not exist on type 'string'.
     
diff --git a/tests/baselines/reference/computedPropertiesInDestructuring1_ES6.errors.txt b/tests/baselines/reference/computedPropertiesInDestructuring1_ES6.errors.txt
index fa4d29cf426..610b8e56ab3 100644
--- a/tests/baselines/reference/computedPropertiesInDestructuring1_ES6.errors.txt
+++ b/tests/baselines/reference/computedPropertiesInDestructuring1_ES6.errors.txt
@@ -1,34 +1,64 @@
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(3,7): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(9,7): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(11,8): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(12,8): error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(15,15): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(16,15): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(17,16): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(18,16): error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
 tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(21,8): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(21,8): error TS2538: Type 'any' cannot be used as an index type.
+tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(22,8): error TS2538: Type 'any' cannot be used as an index type.
 tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(22,12): error TS2339: Property 'toExponential' does not exist on type 'string'.
 tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(34,4): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
 tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts(35,5): error TS2365: Operator '+' cannot be applied to types '1' and '{}'.
 
 
-==== tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts (4 errors) ====
+==== tests/cases/compiler/computedPropertiesInDestructuring1_ES6.ts (14 errors) ====
     // destructuring in variable declarations
     let foo = "bar";
     let {[foo]: bar} = {bar: "bar"};
+          ~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     
     let {["bar"]: bar2} = {bar: "bar"};
     let {[11]: bar2_1} = {11: "bar"};
     
     let foo2 = () => "bar";
     let {[foo2()]: bar3} = {bar: "bar"};
+          ~~~~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     
     let [{[foo]: bar4}] = [{bar: "bar"}];
+           ~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     let [{[foo2()]: bar5}] = [{bar: "bar"}];
+           ~~~~~~
+!!! error TS2537: Type '{ bar: string; }' has no matching index signature for type 'string'.
     
     function f1({["bar"]: x}: { bar: number }) {}
     function f2({[foo]: x}: { bar: number }) {}
+                  ~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     function f3({[foo2()]: x}: { bar: number }) {}
+                  ~~~~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     function f4([{[foo]: x}]: [{ bar: number }]) {}
+                   ~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     function f5([{[foo2()]: x}]: [{ bar: number }]) {}
+                   ~~~~~~
+!!! error TS2537: Type '{ bar: number; }' has no matching index signature for type 'string'.
     
     // report errors on type errors in computed properties used in destructuring
     let [{[foo()]: bar6}] = [{bar: "bar"}];
            ~~~~~
 !!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+           ~~~~~
+!!! error TS2538: Type 'any' cannot be used as an index type.
     let [{[foo.toExponential()]: bar7}] = [{bar: "bar"}];
+           ~~~~~~~~~~~~~~~~~~~
+!!! error TS2538: Type 'any' cannot be used as an index type.
                ~~~~~~~~~~~~~
 !!! error TS2339: Property 'toExponential' does not exist on type 'string'.
     
diff --git a/tests/baselines/reference/computedPropertiesInDestructuring2.errors.txt b/tests/baselines/reference/computedPropertiesInDestructuring2.errors.txt
new file mode 100644
index 00000000000..da858e47c89
--- /dev/null
+++ b/tests/baselines/reference/computedPropertiesInDestructuring2.errors.txt
@@ -0,0 +1,8 @@
+tests/cases/compiler/computedPropertiesInDestructuring2.ts(2,7): error TS2537: Type '{}' has no matching index signature for type 'string'.
+
+
+==== tests/cases/compiler/computedPropertiesInDestructuring2.ts (1 errors) ====
+    let foo2 = () => "bar";
+    let {[foo2()]: bar3} = {};
+          ~~~~~~
+!!! error TS2537: Type '{}' has no matching index signature for type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/computedPropertiesInDestructuring2_ES6.errors.txt b/tests/baselines/reference/computedPropertiesInDestructuring2_ES6.errors.txt
new file mode 100644
index 00000000000..529cc2ebef8
--- /dev/null
+++ b/tests/baselines/reference/computedPropertiesInDestructuring2_ES6.errors.txt
@@ -0,0 +1,8 @@
+tests/cases/compiler/computedPropertiesInDestructuring2_ES6.ts(2,7): error TS2537: Type '{}' has no matching index signature for type 'string'.
+
+
+==== tests/cases/compiler/computedPropertiesInDestructuring2_ES6.ts (1 errors) ====
+    let foo2 = () => "bar";
+    let {[foo2()]: bar3} = {};
+          ~~~~~~
+!!! error TS2537: Type '{}' has no matching index signature for type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/declarationsAndAssignments.errors.txt b/tests/baselines/reference/declarationsAndAssignments.errors.txt
index 46536d6fff0..3ae6d587da5 100644
--- a/tests/baselines/reference/declarationsAndAssignments.errors.txt
+++ b/tests/baselines/reference/declarationsAndAssignments.errors.txt
@@ -15,8 +15,8 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(67,9): e
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(68,9): error TS2461: Type '{ 0: number; 1: number; }' is not an array type.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(73,11): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(73,14): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(74,11): error TS2459: Type 'undefined[]' has no property 'a' and no string index signature.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(74,14): error TS2459: Type 'undefined[]' has no property 'b' and no string index signature.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(74,11): error TS2339: Property 'a' does not exist on type 'undefined[]'.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(74,14): error TS2339: Property 'b' does not exist on type 'undefined[]'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(106,17): error TS2322: Type '{ y: boolean; }' is not assignable to type '{ x: any; y?: boolean; }'.
   Property 'x' is missing in type '{ y: boolean; }'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,6): error TS2322: Type 'string' is not assignable to type 'number'.
@@ -133,9 +133,9 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,9):
 !!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
         var { a, b } = [];  // Error
               ~
-!!! error TS2459: Type 'undefined[]' has no property 'a' and no string index signature.
+!!! error TS2339: Property 'a' does not exist on type 'undefined[]'.
                  ~
-!!! error TS2459: Type 'undefined[]' has no property 'b' and no string index signature.
+!!! error TS2339: Property 'b' does not exist on type 'undefined[]'.
     }
     
     function f11() {
diff --git a/tests/baselines/reference/definiteAssignmentOfDestructuredVariable.types b/tests/baselines/reference/definiteAssignmentOfDestructuredVariable.types
index 96d632736dd..fb40a9b492e 100644
--- a/tests/baselines/reference/definiteAssignmentOfDestructuredVariable.types
+++ b/tests/baselines/reference/definiteAssignmentOfDestructuredVariable.types
@@ -18,20 +18,20 @@ class C<T extends Options> {
 >method : () => void
 
         let { a, b } = this.foo;
->a : T["a"]
->b : T["b"]
+>a : { [P in keyof T]: T[P]; }["a"]
+>b : { [P in keyof T]: T[P]; }["b"]
 >this.foo : { [P in keyof T]: T[P]; }
 >this : this
 >foo : { [P in keyof T]: T[P]; }
 
         !(a && b);
 >!(a && b) : false
->(a && b) : T["b"]
->a && b : T["b"]
->a : T["a"]
->b : T["b"]
+>(a && b) : { [P in keyof T]: T[P]; }["b"]
+>a && b : { [P in keyof T]: T[P]; }["b"]
+>a : { [P in keyof T]: T[P]; }["a"]
+>b : { [P in keyof T]: T[P]; }["b"]
 
         a;
->a : T["a"]
+>a : { [P in keyof T]: T[P]; }["a"]
     }
 }
diff --git a/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.errors.txt b/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.errors.txt
index 6a5c50021db..100ce2d9a08 100644
--- a/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.errors.txt
+++ b/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/destructuredLateBoundNameHasCorrectTypes.ts(11,7): error TS2459: Type '{ prop: string; }' has no property '[notPresent]' and no string index signature.
+tests/cases/compiler/destructuredLateBoundNameHasCorrectTypes.ts(11,8): error TS2339: Property 'prop2' does not exist on type '{ prop: string; }'.
 
 
 ==== tests/cases/compiler/destructuredLateBoundNameHasCorrectTypes.ts (1 errors) ====
@@ -13,6 +13,6 @@ tests/cases/compiler/destructuredLateBoundNameHasCorrectTypes.ts(11,7): error TS
     const notPresent = "prop2";
     
     let { [notPresent]: computed2 } = { prop: "b" };
-          ~~~~~~~~~~~~
-!!! error TS2459: Type '{ prop: string; }' has no property '[notPresent]' and no string index signature.
+           ~~~~~~~~~~
+!!! error TS2339: Property 'prop2' does not exist on type '{ prop: string; }'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.js b/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.js
new file mode 100644
index 00000000000..3fe1f2febcc
--- /dev/null
+++ b/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.js
@@ -0,0 +1,16 @@
+//// [destructuredMaappedTypeIsNotImplicitlyAny.ts]
+function foo<T extends string>(key: T, obj: { [_ in T]: number }) {
+    const { [key]: bar } = obj; // Element implicitly has an 'any' type because type '{ [_ in T]: number; }' has no index signature.
+    bar; // bar : any
+
+    // Note: this does work:
+    const lorem = obj[key];
+}
+
+//// [destructuredMaappedTypeIsNotImplicitlyAny.js]
+function foo(key, obj) {
+    var _a = key, bar = obj[_a]; // Element implicitly has an 'any' type because type '{ [_ in T]: number; }' has no index signature.
+    bar; // bar : any
+    // Note: this does work:
+    var lorem = obj[key];
+}
diff --git a/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.symbols b/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.symbols
new file mode 100644
index 00000000000..93bd2be6638
--- /dev/null
+++ b/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.symbols
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/destructuredMaappedTypeIsNotImplicitlyAny.ts ===
+function foo<T extends string>(key: T, obj: { [_ in T]: number }) {
+>foo : Symbol(foo, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 0))
+>T : Symbol(T, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 13))
+>key : Symbol(key, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 31))
+>T : Symbol(T, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 13))
+>obj : Symbol(obj, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 38))
+>_ : Symbol(_, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 47))
+>T : Symbol(T, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 13))
+
+    const { [key]: bar } = obj; // Element implicitly has an 'any' type because type '{ [_ in T]: number; }' has no index signature.
+>key : Symbol(key, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 31))
+>bar : Symbol(bar, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 1, 11))
+>obj : Symbol(obj, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 38))
+
+    bar; // bar : any
+>bar : Symbol(bar, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 1, 11))
+
+    // Note: this does work:
+    const lorem = obj[key];
+>lorem : Symbol(lorem, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 5, 9))
+>obj : Symbol(obj, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 38))
+>key : Symbol(key, Decl(destructuredMaappedTypeIsNotImplicitlyAny.ts, 0, 31))
+}
diff --git a/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.types b/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.types
new file mode 100644
index 00000000000..493eabe1e2a
--- /dev/null
+++ b/tests/baselines/reference/destructuredMaappedTypeIsNotImplicitlyAny.types
@@ -0,0 +1,21 @@
+=== tests/cases/compiler/destructuredMaappedTypeIsNotImplicitlyAny.ts ===
+function foo<T extends string>(key: T, obj: { [_ in T]: number }) {
+>foo : <T extends string>(key: T, obj: { [_ in T]: number; }) => void
+>key : T
+>obj : { [_ in T]: number; }
+
+    const { [key]: bar } = obj; // Element implicitly has an 'any' type because type '{ [_ in T]: number; }' has no index signature.
+>key : T
+>bar : { [_ in T]: number; }[T]
+>obj : { [_ in T]: number; }
+
+    bar; // bar : any
+>bar : { [_ in T]: number; }[T]
+
+    // Note: this does work:
+    const lorem = obj[key];
+>lorem : { [_ in T]: number; }[T]
+>obj[key] : { [_ in T]: number; }[T]
+>obj : { [_ in T]: number; }
+>key : T
+}
diff --git a/tests/baselines/reference/destructuringObjectBindingPatternAndAssignment3.errors.txt b/tests/baselines/reference/destructuringObjectBindingPatternAndAssignment3.errors.txt
index 33344b9b5eb..5a906d7d43e 100644
--- a/tests/baselines/reference/destructuringObjectBindingPatternAndAssignment3.errors.txt
+++ b/tests/baselines/reference/destructuringObjectBindingPatternAndAssignment3.errors.txt
@@ -1,8 +1,8 @@
 tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(2,7): error TS1005: ',' expected.
 tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(3,5): error TS2322: Type '{ i: number; }' is not assignable to type 'string | number'.
   Type '{ i: number; }' is not assignable to type 'number'.
-tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(3,6): error TS2459: Type 'string | number' has no property 'i' and no string index signature.
-tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(4,6): error TS2459: Type 'string | number | {}' has no property 'i1' and no string index signature.
+tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(3,6): error TS2339: Property 'i' does not exist on type 'string | number'.
+tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(4,6): error TS2339: Property 'i1' does not exist on type 'string | number | {}'.
 tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(5,12): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
 tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(5,21): error TS2353: Object literal may only specify known properties, and 'f212' does not exist in type '{ f21: any; }'.
 tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAssignment3.ts(6,7): error TS1005: ':' expected.
@@ -20,10 +20,10 @@ tests/cases/conformance/es6/destructuring/destructuringObjectBindingPatternAndAs
 !!! error TS2322: Type '{ i: number; }' is not assignable to type 'string | number'.
 !!! error TS2322:   Type '{ i: number; }' is not assignable to type 'number'.
          ~
-!!! error TS2459: Type 'string | number' has no property 'i' and no string index signature.
+!!! error TS2339: Property 'i' does not exist on type 'string | number'.
     var {i1}: string | number| {} = { i1: 2 };
          ~~
-!!! error TS2459: Type 'string | number | {}' has no property 'i1' and no string index signature.
+!!! error TS2339: Property 'i1' does not exist on type 'string | number | {}'.
     var { f2: {f21} = { f212: "string" } }: any = undefined;
                ~~~
 !!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
diff --git a/tests/baselines/reference/destructuringParameterProperties5.errors.txt b/tests/baselines/reference/destructuringParameterProperties5.errors.txt
index 44e013fad0b..fa57ae150a0 100644
--- a/tests/baselines/reference/destructuringParameterProperties5.errors.txt
+++ b/tests/baselines/reference/destructuringParameterProperties5.errors.txt
@@ -1,7 +1,7 @@
 tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(5,17): error TS1187: A parameter property may not be declared using a binding pattern.
-tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(5,27): error TS2459: Type 'ObjType1' has no property 'x1' and no string index signature.
-tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(5,31): error TS2459: Type 'ObjType1' has no property 'x2' and no string index signature.
-tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(5,35): error TS2459: Type 'ObjType1' has no property 'x3' and no string index signature.
+tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(5,27): error TS2339: Property 'x1' does not exist on type 'ObjType1'.
+tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(5,31): error TS2339: Property 'x2' does not exist on type 'ObjType1'.
+tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(5,35): error TS2339: Property 'x3' does not exist on type 'ObjType1'.
 tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(7,29): error TS2339: Property 'x1' does not exist on type 'C1'.
 tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(7,40): error TS2339: Property 'x2' does not exist on type 'C1'.
 tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(7,51): error TS2339: Property 'x3' does not exist on type 'C1'.
@@ -22,11 +22,11 @@ tests/cases/conformance/es6/destructuring/destructuringParameterProperties5.ts(1
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS1187: A parameter property may not be declared using a binding pattern.
                               ~~
-!!! error TS2459: Type 'ObjType1' has no property 'x1' and no string index signature.
+!!! error TS2339: Property 'x1' does not exist on type 'ObjType1'.
                                   ~~
-!!! error TS2459: Type 'ObjType1' has no property 'x2' and no string index signature.
+!!! error TS2339: Property 'x2' does not exist on type 'ObjType1'.
                                       ~~
-!!! error TS2459: Type 'ObjType1' has no property 'x3' and no string index signature.
+!!! error TS2339: Property 'x3' does not exist on type 'ObjType1'.
             var foo: any = x1 || x2 || x3 || y || z;
             var bar: any = this.x1 || this.x2 || this.x3 || this.y || this.z;
                                 ~~
diff --git a/tests/baselines/reference/downlevelLetConst16.errors.txt b/tests/baselines/reference/downlevelLetConst16.errors.txt
index 905d1a607e8..955c79378fe 100644
--- a/tests/baselines/reference/downlevelLetConst16.errors.txt
+++ b/tests/baselines/reference/downlevelLetConst16.errors.txt
@@ -1,9 +1,9 @@
 tests/cases/compiler/downlevelLetConst16.ts(151,15): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
 tests/cases/compiler/downlevelLetConst16.ts(164,17): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
 tests/cases/compiler/downlevelLetConst16.ts(195,14): error TS2461: Type 'undefined' is not an array type.
-tests/cases/compiler/downlevelLetConst16.ts(202,15): error TS2459: Type 'undefined' has no property 'a' and no string index signature.
+tests/cases/compiler/downlevelLetConst16.ts(202,15): error TS2339: Property 'a' does not exist on type 'undefined'.
 tests/cases/compiler/downlevelLetConst16.ts(216,16): error TS2461: Type 'undefined' is not an array type.
-tests/cases/compiler/downlevelLetConst16.ts(223,17): error TS2459: Type 'undefined' has no property 'a' and no string index signature.
+tests/cases/compiler/downlevelLetConst16.ts(223,17): error TS2339: Property 'a' does not exist on type 'undefined'.
 
 
 ==== tests/cases/compiler/downlevelLetConst16.ts (6 errors) ====
@@ -216,7 +216,7 @@ tests/cases/compiler/downlevelLetConst16.ts(223,17): error TS2459: Type 'undefin
     function foo9() {
         for (let {a: x} of []) {
                   ~
-!!! error TS2459: Type 'undefined' has no property 'a' and no string index signature.
+!!! error TS2339: Property 'a' does not exist on type 'undefined'.
             use(x);
         }
         use(x);
@@ -241,7 +241,7 @@ tests/cases/compiler/downlevelLetConst16.ts(223,17): error TS2459: Type 'undefin
     function foo12() {
         for (const {a: x} of []) {
                     ~
-!!! error TS2459: Type 'undefined' has no property 'a' and no string index signature.
+!!! error TS2339: Property 'a' does not exist on type 'undefined'.
             use(x);
         }
         use(x);
diff --git a/tests/baselines/reference/for-inStatementsDestructuring2.errors.txt b/tests/baselines/reference/for-inStatementsDestructuring2.errors.txt
index 7589610a64e..5d80cf26ebc 100644
--- a/tests/baselines/reference/for-inStatementsDestructuring2.errors.txt
+++ b/tests/baselines/reference/for-inStatementsDestructuring2.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/conformance/statements/for-inStatements/for-inStatementsDestructuring2.ts(1,10): error TS2491: The left-hand side of a 'for...in' statement cannot be a destructuring pattern.
-tests/cases/conformance/statements/for-inStatements/for-inStatementsDestructuring2.ts(1,11): error TS2459: Type 'string' has no property 'a' and no string index signature.
-tests/cases/conformance/statements/for-inStatements/for-inStatementsDestructuring2.ts(1,14): error TS2459: Type 'string' has no property 'b' and no string index signature.
+tests/cases/conformance/statements/for-inStatements/for-inStatementsDestructuring2.ts(1,11): error TS2339: Property 'a' does not exist on type 'String'.
+tests/cases/conformance/statements/for-inStatements/for-inStatementsDestructuring2.ts(1,14): error TS2339: Property 'b' does not exist on type 'String'.
 
 
 ==== tests/cases/conformance/statements/for-inStatements/for-inStatementsDestructuring2.ts (3 errors) ====
@@ -8,6 +8,6 @@ tests/cases/conformance/statements/for-inStatements/for-inStatementsDestructurin
              ~~~~~~
 !!! error TS2491: The left-hand side of a 'for...in' statement cannot be a destructuring pattern.
               ~
-!!! error TS2459: Type 'string' has no property 'a' and no string index signature.
+!!! error TS2339: Property 'a' does not exist on type 'String'.
                  ~
-!!! error TS2459: Type 'string' has no property 'b' and no string index signature.
\ No newline at end of file
+!!! error TS2339: Property 'b' does not exist on type 'String'.
\ No newline at end of file
diff --git a/tests/baselines/reference/jsdocParamTag2.errors.txt b/tests/baselines/reference/jsdocParamTag2.errors.txt
index e19140b3f9d..cbf6140ee7d 100644
--- a/tests/baselines/reference/jsdocParamTag2.errors.txt
+++ b/tests/baselines/reference/jsdocParamTag2.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/conformance/jsdoc/0.js(56,20): error TS8024: JSDoc '@param' tag has name 'obj', but there is no parameter with that name.
-tests/cases/conformance/jsdoc/0.js(61,19): error TS2459: Type 'string' has no property 'a' and no string index signature.
-tests/cases/conformance/jsdoc/0.js(61,22): error TS2459: Type 'string' has no property 'b' and no string index signature.
+tests/cases/conformance/jsdoc/0.js(61,19): error TS2339: Property 'a' does not exist on type 'String'.
+tests/cases/conformance/jsdoc/0.js(61,22): error TS2339: Property 'b' does not exist on type 'String'.
 tests/cases/conformance/jsdoc/0.js(63,20): error TS8024: JSDoc '@param' tag has name 'y', but there is no parameter with that name.
 
 
@@ -69,9 +69,9 @@ tests/cases/conformance/jsdoc/0.js(63,20): error TS8024: JSDoc '@param' tag has
      */
     function bad1(x, {a, b}) {}
                       ~
-!!! error TS2459: Type 'string' has no property 'a' and no string index signature.
+!!! error TS2339: Property 'a' does not exist on type 'String'.
                          ~
-!!! error TS2459: Type 'string' has no property 'b' and no string index signature.
+!!! error TS2339: Property 'b' does not exist on type 'String'.
     /**
      * @param {string} y - here, y's type gets ignored but obj's is fine
                        ~
diff --git a/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.errors.txt b/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.errors.txt
index 2e926ac1b83..edba02d2939 100644
--- a/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.errors.txt
+++ b/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.errors.txt
@@ -1,16 +1,16 @@
-tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(2,15): error TS7017: Element implicitly has an 'any' type because type '{ prop: string; }' has no index signature.
-tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(13,15): error TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'.
-tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(21,15): error TS2536: Type 'unique symbol' cannot be used to index type '{ [idx: number]: string; }'.
-tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(23,15): error TS2536: Type 'unique symbol' cannot be used to index type '{ [idx: string]: string; }'.
-tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(25,16): error TS2536: Type 'symbol' cannot be used to index type '{ [idx: number]: string; }'.
-tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(27,16): error TS2536: Type 'symbol' cannot be used to index type '{ [idx: string]: string; }'.
+tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(2,7): error TS2537: Type '{ prop: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(13,7): error TS2537: Type '{ [idx: number]: string; }' has no matching index signature for type 'string'.
+tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(21,7): error TS2538: Type 'unique symbol' cannot be used as an index type.
+tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(23,7): error TS2538: Type 'unique symbol' cannot be used as an index type.
+tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(25,7): error TS2538: Type 'symbol' cannot be used as an index type.
+tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(27,7): error TS2538: Type 'symbol' cannot be used as an index type.
 
 
 ==== tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts (6 errors) ====
     let named = "foo";
     let {[named]: prop} = {prop: "foo"};
-                  ~~~~
-!!! error TS7017: Element implicitly has an 'any' type because type '{ prop: string; }' has no index signature.
+          ~~~~~
+!!! error TS2537: Type '{ prop: string; }' has no matching index signature for type 'string'.
     void prop;
     
     const numIndexed: {[idx: number]: string} = null as any;
@@ -22,8 +22,8 @@ tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(27,16): error TS2
     let symed2 = Symbol();
     
     let {[named]: prop2} = numIndexed;
-                  ~~~~~
-!!! error TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'.
+          ~~~~~
+!!! error TS2537: Type '{ [idx: number]: string; }' has no matching index signature for type 'string'.
     void prop2;
     let {[numed]: prop3} = numIndexed;
     void prop3;
@@ -32,18 +32,18 @@ tests/cases/compiler/lateBoundDestructuringImplicitAnyError.ts(27,16): error TS2
     let {[numed]: prop5} = strIndexed;
     void prop5;
     let {[symed]: prop6} = numIndexed;
-                  ~~~~~
-!!! error TS2536: Type 'unique symbol' cannot be used to index type '{ [idx: number]: string; }'.
+          ~~~~~
+!!! error TS2538: Type 'unique symbol' cannot be used as an index type.
     void prop6;
     let {[symed]: prop7} = strIndexed;
-                  ~~~~~
-!!! error TS2536: Type 'unique symbol' cannot be used to index type '{ [idx: string]: string; }'.
+          ~~~~~
+!!! error TS2538: Type 'unique symbol' cannot be used as an index type.
     void prop7;
     let {[symed2]: prop8} = numIndexed;
-                   ~~~~~
-!!! error TS2536: Type 'symbol' cannot be used to index type '{ [idx: number]: string; }'.
+          ~~~~~~
+!!! error TS2538: Type 'symbol' cannot be used as an index type.
     void prop8;
     let {[symed2]: prop9} = strIndexed;
-                   ~~~~~
-!!! error TS2536: Type 'symbol' cannot be used to index type '{ [idx: string]: string; }'.
+          ~~~~~~
+!!! error TS2538: Type 'symbol' cannot be used as an index type.
     void prop9;
\ No newline at end of file
diff --git a/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.types b/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.types
index 92d2c4c662c..60c220095ad 100644
--- a/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.types
+++ b/tests/baselines/reference/lateBoundDestructuringImplicitAnyError.types
@@ -87,12 +87,12 @@ void prop6;
 
 let {[symed]: prop7} = strIndexed;
 >symed : unique symbol
->prop7 : any
+>prop7 : string
 >strIndexed : { [idx: string]: string; }
 
 void prop7;
 >void prop7 : undefined
->prop7 : any
+>prop7 : string
 
 let {[symed2]: prop8} = numIndexed;
 >symed2 : symbol
@@ -105,10 +105,10 @@ void prop8;
 
 let {[symed2]: prop9} = strIndexed;
 >symed2 : symbol
->prop9 : any
+>prop9 : string
 >strIndexed : { [idx: string]: string; }
 
 void prop9;
 >void prop9 : undefined
->prop9 : any
+>prop9 : string
 
diff --git a/tests/baselines/reference/nonPrimitiveAccessProperty.errors.txt b/tests/baselines/reference/nonPrimitiveAccessProperty.errors.txt
index 0a6dfa66b86..c584dba6462 100644
--- a/tests/baselines/reference/nonPrimitiveAccessProperty.errors.txt
+++ b/tests/baselines/reference/nonPrimitiveAccessProperty.errors.txt
@@ -1,5 +1,5 @@
 tests/cases/conformance/types/nonPrimitive/nonPrimitiveAccessProperty.ts(3,3): error TS2339: Property 'nonExist' does not exist on type 'object'.
-tests/cases/conformance/types/nonPrimitive/nonPrimitiveAccessProperty.ts(5,7): error TS2459: Type 'object' has no property 'destructuring' and no string index signature.
+tests/cases/conformance/types/nonPrimitive/nonPrimitiveAccessProperty.ts(5,7): error TS2339: Property 'destructuring' does not exist on type '{}'.
 
 
 ==== tests/cases/conformance/types/nonPrimitive/nonPrimitiveAccessProperty.ts (2 errors) ====
@@ -11,6 +11,6 @@ tests/cases/conformance/types/nonPrimitive/nonPrimitiveAccessProperty.ts(5,7): e
     
     var { destructuring } = a; // error
           ~~~~~~~~~~~~~
-!!! error TS2459: Type 'object' has no property 'destructuring' and no string index signature.
+!!! error TS2339: Property 'destructuring' does not exist on type '{}'.
     var { ...rest } = a; // ok
     
\ No newline at end of file
diff --git a/tests/baselines/reference/objectRest.errors.txt b/tests/baselines/reference/objectRest.errors.txt
index dfea8b96b96..48d8bd3f328 100644
--- a/tests/baselines/reference/objectRest.errors.txt
+++ b/tests/baselines/reference/objectRest.errors.txt
@@ -1,9 +1,13 @@
+tests/cases/conformance/types/rest/objectRest.ts(7,12): error TS2339: Property '0' does not exist on type 'String'.
+tests/cases/conformance/types/rest/objectRest.ts(7,20): error TS2339: Property '1' does not exist on type 'String'.
+tests/cases/conformance/types/rest/objectRest.ts(43,8): error TS2537: Type '{ a: number; b: string; }' has no matching index signature for type 'string'.
+tests/cases/conformance/types/rest/objectRest.ts(43,35): error TS2537: Type '{ a: number; b: string; }' has no matching index signature for type 'string'.
 tests/cases/conformance/types/rest/objectRest.ts(43,57): error TS2403: Subsequent variable declarations must have the same type.  Variable 'o' must be of type '{ a: number; b: string; }', but here has type 'Rest<{ a: number; b: string; }, string>'.
 tests/cases/conformance/types/rest/objectRest.ts(44,53): error TS2322: Type 'Rest<{ a: number; b: string; }, string>' is not assignable to type '{ a: number; b: string; }'.
   Property 'a' is missing in type 'Rest<{ a: number; b: string; }, string>'.
 
 
-==== tests/cases/conformance/types/rest/objectRest.ts (2 errors) ====
+==== tests/cases/conformance/types/rest/objectRest.ts (6 errors) ====
     var o = { a: 1, b: 'no' }
     var { ...clone } = o;
     var { a, ...justB } = o;
@@ -11,6 +15,10 @@ tests/cases/conformance/types/rest/objectRest.ts(44,53): error TS2322: Type 'Res
     var { ['b']: renamed, ...justA } = o;
     var { 'b': renamed, ...justA } = o;
     var { b: { '0': n, '1': oooo }, ...justA } = o;
+               ~~~
+!!! error TS2339: Property '0' does not exist on type 'String'.
+                       ~~~
+!!! error TS2339: Property '1' does not exist on type 'String'.
     
     let o2 = { c: 'terrible idea?', d: 'yes' };
     var { d: renamed, ...d } = o2;
@@ -47,6 +55,10 @@ tests/cases/conformance/types/rest/objectRest.ts(44,53): error TS2322: Type 'Res
     let computed = 'b';
     let computed2 = 'a';
     var { [computed]: stillNotGreat, [computed2]: soSo,  ...o } = o;
+           ~~~~~~~~
+!!! error TS2537: Type '{ a: number; b: string; }' has no matching index signature for type 'string'.
+                                      ~~~~~~~~~
+!!! error TS2537: Type '{ a: number; b: string; }' has no matching index signature for type 'string'.
                                                             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'o' must be of type '{ a: number; b: string; }', but here has type 'Rest<{ a: number; b: string; }, string>'.
     ({ [computed]: stillNotGreat, [computed2]: soSo, ...o } = o);
diff --git a/tests/baselines/reference/objectRest.types b/tests/baselines/reference/objectRest.types
index e664c5e64cd..6a5f823e9dd 100644
--- a/tests/baselines/reference/objectRest.types
+++ b/tests/baselines/reference/objectRest.types
@@ -36,8 +36,8 @@ var { 'b': renamed, ...justA } = o;
 
 var { b: { '0': n, '1': oooo }, ...justA } = o;
 >b : any
->n : string
->oooo : string
+>n : any
+>oooo : any
 >justA : Rest<{ a: number; b: string; }, "b">
 >o : { a: number; b: string; }
 
diff --git a/tests/baselines/reference/parameterInitializersForwardReferencing1_es6.errors.txt b/tests/baselines/reference/parameterInitializersForwardReferencing1_es6.errors.txt
index 59280d2006a..c65f327161e 100644
--- a/tests/baselines/reference/parameterInitializersForwardReferencing1_es6.errors.txt
+++ b/tests/baselines/reference/parameterInitializersForwardReferencing1_es6.errors.txt
@@ -1,9 +1,10 @@
 tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(13,20): error TS2373: Initializer of parameter 'bar' cannot reference identifier 'foo' declared after it.
 tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(21,18): error TS2372: Parameter 'a' cannot be referenced in its initializer.
 tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(25,22): error TS2372: Parameter 'async' cannot be referenced in its initializer.
+tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(29,15): error TS2537: Type 'any[]' has no matching index signature for type 'string'.
 
 
-==== tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts (3 errors) ====
+==== tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts (4 errors) ====
     let foo: string = "";
     
     function f1 (bar = foo) { // unexpected compiler error; works at runtime
@@ -39,6 +40,8 @@ tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.t
     }
     
     function f7({[foo]: bar}: any[]) {
+                  ~~~
+!!! error TS2537: Type 'any[]' has no matching index signature for type 'string'.
         let foo: number = 2;
     }
     
diff --git a/tests/baselines/reference/restElementWithBindingPattern2.errors.txt b/tests/baselines/reference/restElementWithBindingPattern2.errors.txt
index 8e744ac54a3..44e2c8f13ed 100644
--- a/tests/baselines/reference/restElementWithBindingPattern2.errors.txt
+++ b/tests/baselines/reference/restElementWithBindingPattern2.errors.txt
@@ -1,7 +1,7 @@
-tests/cases/conformance/es6/destructuring/restElementWithBindingPattern2.ts(1,16): error TS2459: Type 'number[]' has no property 'b' and no string index signature.
+tests/cases/conformance/es6/destructuring/restElementWithBindingPattern2.ts(1,16): error TS2339: Property 'b' does not exist on type 'number[]'.
 
 
 ==== tests/cases/conformance/es6/destructuring/restElementWithBindingPattern2.ts (1 errors) ====
     var [...{0: a, b }] = [0, 1];
                    ~
-!!! error TS2459: Type 'number[]' has no property 'b' and no string index signature.
\ No newline at end of file
+!!! error TS2339: Property 'b' does not exist on type 'number[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/showConfig/Default initialized TSConfig/tsconfig.json b/tests/baselines/reference/showConfig/Default initialized TSConfig/tsconfig.json
new file mode 100644
index 00000000000..cd727e8ccdc
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Default initialized TSConfig/tsconfig.json	
@@ -0,0 +1,3 @@
+{
+    "compilerOptions": {}
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with advanced options/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with advanced options/tsconfig.json
new file mode 100644
index 00000000000..6dbccf64bb9
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with advanced options/tsconfig.json	
@@ -0,0 +1,8 @@
+{
+    "compilerOptions": {
+        "declaration": true,
+        "declarationDir": "./lib",
+        "skipLibCheck": true,
+        "noErrorTruncation": true
+    }
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with boolean value compiler options/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with boolean value compiler options/tsconfig.json
new file mode 100644
index 00000000000..650a347f895
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with boolean value compiler options/tsconfig.json	
@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "noUnusedLocals": true
+    }
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with enum value compiler options/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with enum value compiler options/tsconfig.json
new file mode 100644
index 00000000000..0052b1327f1
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with enum value compiler options/tsconfig.json	
@@ -0,0 +1,6 @@
+{
+    "compilerOptions": {
+        "target": "es5",
+        "jsx": "react"
+    }
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with files options/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with files options/tsconfig.json
new file mode 100644
index 00000000000..cd727e8ccdc
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with files options/tsconfig.json	
@@ -0,0 +1,3 @@
+{
+    "compilerOptions": {}
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with incorrect compiler option value/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with incorrect compiler option value/tsconfig.json
new file mode 100644
index 00000000000..c75e5d4ae1d
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with incorrect compiler option value/tsconfig.json	
@@ -0,0 +1,8 @@
+{
+    "compilerOptions": {
+        "lib": [
+            "es5",
+            "es2015.promise"
+        ]
+    }
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with incorrect compiler option/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with incorrect compiler option/tsconfig.json
new file mode 100644
index 00000000000..cd727e8ccdc
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with incorrect compiler option/tsconfig.json	
@@ -0,0 +1,3 @@
+{
+    "compilerOptions": {}
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with list compiler options with enum value/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with list compiler options with enum value/tsconfig.json
new file mode 100644
index 00000000000..6da42b43907
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with list compiler options with enum value/tsconfig.json	
@@ -0,0 +1,8 @@
+{
+    "compilerOptions": {
+        "lib": [
+            "es5",
+            "es2015.core"
+        ]
+    }
+}
diff --git a/tests/baselines/reference/showConfig/Show TSConfig with list compiler options/tsconfig.json b/tests/baselines/reference/showConfig/Show TSConfig with list compiler options/tsconfig.json
new file mode 100644
index 00000000000..7b5da8e7d3c
--- /dev/null
+++ b/tests/baselines/reference/showConfig/Show TSConfig with list compiler options/tsconfig.json	
@@ -0,0 +1,8 @@
+{
+    "compilerOptions": {
+        "types": [
+            "jquery",
+            "mocha"
+        ]
+    }
+}
diff --git a/tests/cases/compiler/destructuredMaappedTypeIsNotImplicitlyAny.ts b/tests/cases/compiler/destructuredMaappedTypeIsNotImplicitlyAny.ts
new file mode 100644
index 00000000000..4fd88fd5c8e
--- /dev/null
+++ b/tests/cases/compiler/destructuredMaappedTypeIsNotImplicitlyAny.ts
@@ -0,0 +1,8 @@
+// @noImplicitAny: true
+function foo<T extends string>(key: T, obj: { [_ in T]: number }) {
+    const { [key]: bar } = obj; // Element implicitly has an 'any' type because type '{ [_ in T]: number; }' has no index signature.
+    bar; // bar : any
+
+    // Note: this does work:
+    const lorem = obj[key];
+}
\ No newline at end of file
diff --git a/tests/projects/container/compositeExec/tsconfig.json b/tests/projects/container/compositeExec/tsconfig.json
index f28a9e44eee..4f44b8a562d 100644
--- a/tests/projects/container/compositeExec/tsconfig.json
+++ b/tests/projects/container/compositeExec/tsconfig.json
@@ -1,7 +1,8 @@
 {
     "compilerOptions": {
         "outFile": "../built/local/compositeExec.js",
-        "composite": true
+        "composite": true,
+        "declarationMap": true
     },
     "files": [
         "index.ts"