Merge branch 'master' into dynamicNames

src/compiler/checker.ts

@@ -7393,7 +7393,7 @@ namespace ts {
                 accessExpression && checkThatExpressionIsProperSymbolReference(accessExpression.argumentExpression, indexType, /*reportError*/ false) ?
                     getPropertyNameForKnownSymbolName((<Identifier>(<PropertyAccessExpression>accessExpression.argumentExpression).name).text) :
                     undefined;
-            if (propName) {
+            if (propName !== undefined) {
                 const prop = getPropertyOfType(objectType, propName);
                 if (prop) {
                     if (accessExpression) {
@@ -9364,25 +9364,39 @@ namespace ts {
                 let result = Ternary.True;
                 const saveErrorInfo = errorInfo;
 
-                outer: for (const t of targetSignatures) {
-                    // Only elaborate errors from the first failure
-                    let shouldElaborateErrors = reportErrors;
-                    for (const s of sourceSignatures) {
-                        const related = signatureRelatedTo(s, t, shouldElaborateErrors);
-                        if (related) {
-                            result &= related;
-                            errorInfo = saveErrorInfo;
-                            continue outer;
+                if (getObjectFlags(source) & ObjectFlags.Instantiated && getObjectFlags(target) & ObjectFlags.Instantiated && source.symbol === target.symbol) {
+                    // We instantiations of the same anonymous type (which typically will be the type of a method).
+                    // Simply do a pairwise comparison of the signatures in the two signature lists instead of the
+                    // much more expensive N * M comparison matrix we explore below.
+                    for (let i = 0; i < targetSignatures.length; i++) {
+                        const related = signatureRelatedTo(sourceSignatures[i], targetSignatures[i], reportErrors);
+                        if (!related) {
+                            return Ternary.False;
                         }
-                        shouldElaborateErrors = false;
+                        result &= related;
                     }
+                }
+                else {
+                    outer: for (const t of targetSignatures) {
+                        // Only elaborate errors from the first failure
+                        let shouldElaborateErrors = reportErrors;
+                        for (const s of sourceSignatures) {
+                            const related = signatureRelatedTo(s, t, shouldElaborateErrors);
+                            if (related) {
+                                result &= related;
+                                errorInfo = saveErrorInfo;
+                                continue outer;
+                            }
+                            shouldElaborateErrors = false;
+                        }
 
-                    if (shouldElaborateErrors) {
-                        reportError(Diagnostics.Type_0_provides_no_match_for_the_signature_1,
-                            typeToString(source),
-                            signatureToString(t, /*enclosingDeclaration*/ undefined, /*flags*/ undefined, kind));
+                        if (shouldElaborateErrors) {
+                            reportError(Diagnostics.Type_0_provides_no_match_for_the_signature_1,
+                                typeToString(source),
+                                signatureToString(t, /*enclosingDeclaration*/ undefined, /*flags*/ undefined, kind));
+                        }
+                        return Ternary.False;
                     }
-                    return Ternary.False;
                 }
                 return result;
             }

src/compiler/core.ts

@@ -251,6 +251,15 @@ namespace ts {
         }
     }
 
+    export function zipToMap<T>(keys: string[], values: T[]): Map<T> {
+        Debug.assert(keys.length === values.length);
+        const map = createMap<T>();
+        for (let i = 0; i < keys.length; ++i) {
+            map.set(keys[i], values[i]);
+        }
+        return map;
+    }
+
     /**
      * Iterates through `array` by index and performs the callback on each element of array until the callback
      * returns a falsey value, then returns false.

src/compiler/diagnosticMessages.json

@@ -3207,9 +3207,16 @@
     },
     "Scoped package detected, looking in '{0}'": {
         "category": "Message",
-        "code": "6182"
+        "code": 6182
+    },
+    "Reusing resolution of module '{0}' to file '{1}' from old program.": {
+        "category": "Message",
+        "code": 6183
+    },
+    "Reusing module resolutions originating in '{0}' since resolutions are unchanged from old program.": {
+        "category": "Message",
+        "code": 6184
     },
-
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005

src/compiler/factory.ts

@@ -1440,6 +1440,44 @@ namespace ts {
             : node;
     }
 
+    export function createInterfaceDeclaration(decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined, name: string | Identifier, typeParameters: TypeParameterDeclaration[] | undefined, heritageClauses: HeritageClause[] | undefined, members: TypeElement[]) {
+        const node = <InterfaceDeclaration>createSynthesizedNode(SyntaxKind.InterfaceDeclaration);
+        node.decorators = asNodeArray(decorators);
+        node.modifiers = asNodeArray(modifiers);
+        node.name = asName(name);
+        node.typeParameters = asNodeArray(typeParameters);
+        node.heritageClauses = asNodeArray(heritageClauses);
+        node.members = createNodeArray(members);
+        return node;
+    }
+
+    export function updateInterfaceDeclaration(node: InterfaceDeclaration, decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined, name: Identifier, typeParameters: TypeParameterDeclaration[] | undefined, heritageClauses: HeritageClause[] | undefined, members: TypeElement[]) {
+        return node.decorators !== decorators
+            || node.modifiers !== modifiers
+            || node.name !== name
+            || node.typeParameters !== typeParameters
+            || node.heritageClauses !== heritageClauses
+            || node.members !== members
+            ? updateNode(createInterfaceDeclaration(decorators, modifiers, name, typeParameters, heritageClauses, members), node)
+            : node;
+    }
+
+    export function createTypeAliasDeclaration(name: string | Identifier, typeParameters: TypeParameterDeclaration[] | undefined, type: TypeNode) {
+        const node = <TypeAliasDeclaration>createSynthesizedNode(SyntaxKind.TypeAliasDeclaration);
+        node.name = asName(name);
+        node.typeParameters = asNodeArray(typeParameters);
+        node.type = type;
+        return node;
+    }
+
+    export function updateTypeAliasDeclaration(node: TypeAliasDeclaration, name: Identifier, typeParameters: TypeParameterDeclaration[] | undefined, type: TypeNode) {
+        return node.name !== name
+            || node.typeParameters !== typeParameters
+            || node.type !== type
+            ? updateNode(createTypeAliasDeclaration(name, typeParameters, type), node)
+            : node;
+    }
+
     export function createEnumDeclaration(decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined, name: string | Identifier, members: EnumMember[]) {
         const node = <EnumDeclaration>createSynthesizedNode(SyntaxKind.EnumDeclaration);
         node.decorators = asNodeArray(decorators);

src/compiler/program.ts

@@ -298,6 +298,7 @@ namespace ts {
         let diagnosticsProducingTypeChecker: TypeChecker;
         let noDiagnosticsTypeChecker: TypeChecker;
         let classifiableNames: Map<string>;
+        let modifiedFilePaths: Path[] | undefined;
 
         const cachedSemanticDiagnosticsForFile: DiagnosticCache = {};
         const cachedDeclarationDiagnosticsForFile: DiagnosticCache = {};
@@ -367,7 +368,8 @@ namespace ts {
         // used to track cases when two file names differ only in casing
         const filesByNameIgnoreCase = host.useCaseSensitiveFileNames() ? createFileMap<SourceFile>(fileName => fileName.toLowerCase()) : undefined;
 
-        if (!tryReuseStructureFromOldProgram()) {
+        const structuralIsReused = tryReuseStructureFromOldProgram();
+        if (structuralIsReused !== StructureIsReused.Completely) {
             forEach(rootNames, name => processRootFile(name, /*isDefaultLib*/ false));
 
             // load type declarations specified via 'types' argument or implicitly from types/ and node_modules/@types folders
@@ -476,89 +478,114 @@ namespace ts {
         }
 
         interface OldProgramState {
-            program: Program;
+            program: Program | undefined;
             file: SourceFile;
+            /** The collection of paths modified *since* the old program. */
             modifiedFilePaths: Path[];
         }
 
-        function resolveModuleNamesReusingOldState(moduleNames: string[], containingFile: string, file: SourceFile, oldProgramState?: OldProgramState) {
-            if (!oldProgramState && !file.ambientModuleNames.length) {
-                // if old program state is not supplied and file does not contain locally defined ambient modules
-                // then the best we can do is fallback to the default logic
+        function resolveModuleNamesReusingOldState(moduleNames: string[], containingFile: string, file: SourceFile, oldProgramState: OldProgramState) {
+            if (structuralIsReused === StructureIsReused.Not && !file.ambientModuleNames.length) {
+                // If the old program state does not permit reusing resolutions and `file` does not contain locally defined ambient modules,
+                // the best we can do is fallback to the default logic.
                 return resolveModuleNamesWorker(moduleNames, containingFile);
             }
 
-            // at this point we know that either
+            const oldSourceFile = oldProgramState.program && oldProgramState.program.getSourceFile(containingFile);
+            if (oldSourceFile !== file && file.resolvedModules) {
+                // `file` was created for the new program.
+                //
+                // We only set `file.resolvedModules` via work from the current function,
+                // so it is defined iff we already called the current function on `file`.
+                // That call happened no later than the creation of the `file` object,
+                // which per above occured during the current program creation.
+                // Since we assume the filesystem does not change during program creation,
+                // it is safe to reuse resolutions from the earlier call.
+                const result: ResolvedModuleFull[] = [];
+                for (const moduleName of moduleNames) {
+                    const resolvedModule = file.resolvedModules.get(moduleName);
+                    result.push(resolvedModule);
+                }
+                return result;
+            }
+            // At this point, we know at least one of the following hold:
             // - file has local declarations for ambient modules
-            // OR
             // - old program state is available
-            // OR
-            // - both of items above
-            // With this it is possible that we can tell how some module names from the initial list will be resolved
-            // without doing actual resolution (in particular if some name was resolved to ambient module).
-            // Such names should be excluded from the list of module names that will be provided to `resolveModuleNamesWorker`
-            // since we don't want to resolve them again.
+            // With this information, we can infer some module resolutions without performing resolution.
 
-            // this is a list of modules for which we cannot predict resolution so they should be actually resolved
+            /** An ordered list of module names for which we cannot recover the resolution. */
             let unknownModuleNames: string[];
-            // this is a list of combined results assembles from predicted and resolved results.
-            // Order in this list matches the order in the original list of module names `moduleNames` which is important
-            // so later we can split results to resolutions of modules and resolutions of module augmentations.
+            /**
+             * The indexing of elements in this list matches that of `moduleNames`.
+             *
+             * Before combining results, result[i] is in one of the following states:
+             * * undefined: needs to be recomputed,
+             * * predictedToResolveToAmbientModuleMarker: known to be an ambient module.
+             * Needs to be reset to undefined before returning,
+             * * ResolvedModuleFull instance: can be reused.
+             */
             let result: ResolvedModuleFull[];
-            // a transient placeholder that is used to mark predicted resolution in the result list
+            /** A transient placeholder used to mark predicted resolution in the result list. */
             const predictedToResolveToAmbientModuleMarker: ResolvedModuleFull = <any>{};
 
+
             for (let i = 0; i < moduleNames.length; i++) {
                 const moduleName = moduleNames[i];
-                // module name is known to be resolved to ambient module if
-                // - module name is contained in the list of ambient modules that are locally declared in the file
-                // - in the old program module name was resolved to ambient module whose declaration is in non-modified file
+                // If we want to reuse resolutions more aggressively, we can refine this to check for whether the
+                // text of the corresponding modulenames has changed.
+                if (file === oldSourceFile) {
+                    const oldResolvedModule = oldSourceFile && oldSourceFile.resolvedModules.get(moduleName);
+                    if (oldResolvedModule) {
+                        if (isTraceEnabled(options, host)) {
+                            trace(host, Diagnostics.Reusing_resolution_of_module_0_to_file_1_from_old_program, moduleName, containingFile);
+                        }
+                        (result || (result = new Array(moduleNames.length)))[i] = oldResolvedModule;
+                        continue;
+                    }
+                }
+                // We know moduleName resolves to an ambient module provided that moduleName:
+                // - is in the list of ambient modules locally declared in the current source file.
+                // - resolved to an ambient module in the old program whose declaration is in an unmodified file
                 //   (so the same module declaration will land in the new program)
-                let isKnownToResolveToAmbientModule = false;
+                let resolvesToAmbientModuleInNonModifiedFile = false;
                 if (contains(file.ambientModuleNames, moduleName)) {
-                    isKnownToResolveToAmbientModule = true;
+                    resolvesToAmbientModuleInNonModifiedFile = true;
                     if (isTraceEnabled(options, host)) {
                         trace(host, Diagnostics.Module_0_was_resolved_as_locally_declared_ambient_module_in_file_1, moduleName, containingFile);
                     }
                 }
                 else {
-                    isKnownToResolveToAmbientModule = checkModuleNameResolvedToAmbientModuleInNonModifiedFile(moduleName, oldProgramState);
+                    resolvesToAmbientModuleInNonModifiedFile = moduleNameResolvesToAmbientModuleInNonModifiedFile(moduleName, oldProgramState);
                 }
 
-                if (isKnownToResolveToAmbientModule) {
-                    if (!unknownModuleNames) {
-                        // found a first module name for which result can be prediced
-                        // this means that this module name should not be passed to `resolveModuleNamesWorker`.
-                        // We'll use a separate list for module names that are definitely unknown.
-                        result = new Array(moduleNames.length);
-                        // copy all module names that appear before the current one in the list
-                        // since they are known to be unknown
-                        unknownModuleNames = moduleNames.slice(0, i);
-                    }
-                    // mark prediced resolution in the result list
-                    result[i] = predictedToResolveToAmbientModuleMarker;
+                if (resolvesToAmbientModuleInNonModifiedFile) {
+                    (result || (result = new Array(moduleNames.length)))[i] = predictedToResolveToAmbientModuleMarker;
                 }
-                else if (unknownModuleNames) {
-                    // found unknown module name and we are already using separate list for those - add it to the list
-                    unknownModuleNames.push(moduleName);
+                else {
+                    // Resolution failed in the old program, or resolved to an ambient module for which we can't reuse the result.
+                    (unknownModuleNames || (unknownModuleNames = [])).push(moduleName);
                 }
             }
 
-            if (!unknownModuleNames) {
-                // we've looked throught the list but have not seen any predicted resolution
-                // use default logic
-                return resolveModuleNamesWorker(moduleNames, containingFile);
-            }
-
-            const resolutions = unknownModuleNames.length
+            const resolutions = unknownModuleNames && unknownModuleNames.length
                 ? resolveModuleNamesWorker(unknownModuleNames, containingFile)
                 : emptyArray;
 
-            // combine results of resolutions and predicted results
+            // Combine results of resolutions and predicted results
+            if (!result) {
+                // There were no unresolved/ambient resolutions.
+                Debug.assert(resolutions.length === moduleNames.length);
+                return <ResolvedModuleFull[]>resolutions;
+            }
+
             let j = 0;
             for (let i = 0; i < result.length; i++) {
-                if (result[i] === predictedToResolveToAmbientModuleMarker) {
-                    result[i] = undefined;
+                if (result[i]) {
+                    // `result[i]` is either a `ResolvedModuleFull` or a marker.
+                    // If it is the former, we can leave it as is.
+                    if (result[i] === predictedToResolveToAmbientModuleMarker) {
+                        result[i] = undefined;
+                    }
                 }
                 else {
                     result[i] = resolutions[j];
@@ -566,18 +593,18 @@ namespace ts {
                 }
             }
             Debug.assert(j === resolutions.length);
+
             return result;
 
-            function checkModuleNameResolvedToAmbientModuleInNonModifiedFile(moduleName: string, oldProgramState?: OldProgramState): boolean {
-                if (!oldProgramState) {
-                    return false;
-                }
+            // If we change our policy of rechecking failed lookups on each program create,
+            // we should adjust the value returned here.
+            function moduleNameResolvesToAmbientModuleInNonModifiedFile(moduleName: string, oldProgramState: OldProgramState): boolean {
                 const resolutionToFile = getResolvedModule(oldProgramState.file, moduleName);
                 if (resolutionToFile) {
                     // module used to be resolved to file - ignore it
                     return false;
                 }
-                const ambientModule = oldProgram.getTypeChecker().tryFindAmbientModuleWithoutAugmentations(moduleName);
+                const ambientModule = oldProgramState.program && oldProgramState.program.getTypeChecker().tryFindAmbientModuleWithoutAugmentations(moduleName);
                 if (!(ambientModule && ambientModule.declarations)) {
                     return false;
                 }
@@ -599,99 +626,107 @@ namespace ts {
             }
         }
 
-        function tryReuseStructureFromOldProgram(): boolean {
+        function tryReuseStructureFromOldProgram(): StructureIsReused {
             if (!oldProgram) {
-                return false;
+                return StructureIsReused.Not;
             }
 
             // check properties that can affect structure of the program or module resolution strategy
             // if any of these properties has changed - structure cannot be reused
             const oldOptions = oldProgram.getCompilerOptions();
             if (changesAffectModuleResolution(oldOptions, options)) {
-                return false;
+                return oldProgram.structureIsReused = StructureIsReused.Not;
             }
 
-            Debug.assert(!oldProgram.structureIsReused);
+            Debug.assert(!(oldProgram.structureIsReused & (StructureIsReused.Completely | StructureIsReused.SafeModules)));
 
             // there is an old program, check if we can reuse its structure
             const oldRootNames = oldProgram.getRootFileNames();
             if (!arrayIsEqualTo(oldRootNames, rootNames)) {
-                return false;
+                return oldProgram.structureIsReused = StructureIsReused.Not;
             }
 
             if (!arrayIsEqualTo(options.types, oldOptions.types)) {
-                return false;
+                return oldProgram.structureIsReused = StructureIsReused.Not;
             }
 
             // check if program source files has changed in the way that can affect structure of the program
             const newSourceFiles: SourceFile[] = [];
             const filePaths: Path[] = [];
             const modifiedSourceFiles: { oldFile: SourceFile, newFile: SourceFile }[] = [];
+            oldProgram.structureIsReused = StructureIsReused.Completely;
 
             for (const oldSourceFile of oldProgram.getSourceFiles()) {
-                let newSourceFile = host.getSourceFileByPath
+                const newSourceFile = host.getSourceFileByPath
                     ? host.getSourceFileByPath(oldSourceFile.fileName, oldSourceFile.path, options.target)
                     : host.getSourceFile(oldSourceFile.fileName, options.target);
 
                 if (!newSourceFile) {
-                    return false;
+                    return oldProgram.structureIsReused = StructureIsReused.Not;
                 }
 
                 newSourceFile.path = oldSourceFile.path;
                 filePaths.push(newSourceFile.path);
 
                 if (oldSourceFile !== newSourceFile) {
+                    // The `newSourceFile` object was created for the new program.
+
                     if (oldSourceFile.hasNoDefaultLib !== newSourceFile.hasNoDefaultLib) {
                         // value of no-default-lib has changed
                         // this will affect if default library is injected into the list of files
-                        return false;
+                        oldProgram.structureIsReused = StructureIsReused.SafeModules;
                     }
 
                     // check tripleslash references
                     if (!arrayIsEqualTo(oldSourceFile.referencedFiles, newSourceFile.referencedFiles, fileReferenceIsEqualTo)) {
                         // tripleslash references has changed
-                        return false;
+                        oldProgram.structureIsReused = StructureIsReused.SafeModules;
                     }
 
                     // check imports and module augmentations
                     collectExternalModuleReferences(newSourceFile);
                     if (!arrayIsEqualTo(oldSourceFile.imports, newSourceFile.imports, moduleNameIsEqualTo)) {
                         // imports has changed
-                        return false;
+                        oldProgram.structureIsReused = StructureIsReused.SafeModules;
                     }
                     if (!arrayIsEqualTo(oldSourceFile.moduleAugmentations, newSourceFile.moduleAugmentations, moduleNameIsEqualTo)) {
                         // moduleAugmentations has changed
-                        return false;
+                        oldProgram.structureIsReused = StructureIsReused.SafeModules;
                     }
 
                     if (!arrayIsEqualTo(oldSourceFile.typeReferenceDirectives, newSourceFile.typeReferenceDirectives, fileReferenceIsEqualTo)) {
                         // 'types' references has changed
-                        return false;
+                        oldProgram.structureIsReused = StructureIsReused.SafeModules;
                     }
 
                     // tentatively approve the file
                     modifiedSourceFiles.push({ oldFile: oldSourceFile, newFile: newSourceFile });
                 }
-                else {
-                    // file has no changes - use it as is
-                    newSourceFile = oldSourceFile;
-                }
 
                 // if file has passed all checks it should be safe to reuse it
                 newSourceFiles.push(newSourceFile);
             }
 
-            const modifiedFilePaths = modifiedSourceFiles.map(f => f.newFile.path);
+            if (oldProgram.structureIsReused !== StructureIsReused.Completely) {
+                return oldProgram.structureIsReused;
+            }
+
+            modifiedFilePaths = modifiedSourceFiles.map(f => f.newFile.path);
             // try to verify results of module resolution
             for (const { oldFile: oldSourceFile, newFile: newSourceFile } of modifiedSourceFiles) {
                 const newSourceFilePath = getNormalizedAbsolutePath(newSourceFile.fileName, currentDirectory);
                 if (resolveModuleNamesWorker) {
                     const moduleNames = map(concatenate(newSourceFile.imports, newSourceFile.moduleAugmentations), getTextOfLiteral);
-                    const resolutions = resolveModuleNamesReusingOldState(moduleNames, newSourceFilePath, newSourceFile, { file: oldSourceFile, program: oldProgram, modifiedFilePaths });
+                    const oldProgramState = { program: oldProgram, file: oldSourceFile, modifiedFilePaths };
+                    const resolutions = resolveModuleNamesReusingOldState(moduleNames, newSourceFilePath, newSourceFile, oldProgramState);
                     // ensure that module resolution results are still correct
                     const resolutionsChanged = hasChangesInResolutions(moduleNames, resolutions, oldSourceFile.resolvedModules, moduleResolutionIsEqualTo);
                     if (resolutionsChanged) {
-                        return false;
+                        oldProgram.structureIsReused = StructureIsReused.SafeModules;
+                        newSourceFile.resolvedModules = zipToMap(moduleNames, resolutions);
+                    }
+                    else {
+                        newSourceFile.resolvedModules = oldSourceFile.resolvedModules;
                     }
                 }
                 if (resolveTypeReferenceDirectiveNamesWorker) {
@@ -700,12 +735,17 @@ namespace ts {
                     // ensure that types resolutions are still correct
                     const resolutionsChanged = hasChangesInResolutions(typesReferenceDirectives, resolutions, oldSourceFile.resolvedTypeReferenceDirectiveNames, typeDirectiveIsEqualTo);
                     if (resolutionsChanged) {
-                        return false;
+                        oldProgram.structureIsReused = StructureIsReused.SafeModules;
+                        newSourceFile.resolvedTypeReferenceDirectiveNames = zipToMap(typesReferenceDirectives, resolutions);
+                    }
+                    else {
+                        newSourceFile.resolvedTypeReferenceDirectiveNames = oldSourceFile.resolvedTypeReferenceDirectiveNames;
                     }
                 }
-                // pass the cache of module/types resolutions from the old source file
-                newSourceFile.resolvedModules = oldSourceFile.resolvedModules;
-                newSourceFile.resolvedTypeReferenceDirectiveNames = oldSourceFile.resolvedTypeReferenceDirectiveNames;
+            }
+
+            if (oldProgram.structureIsReused !== StructureIsReused.Completely) {
+                return oldProgram.structureIsReused;
             }
 
             // update fileName -> file mapping
@@ -720,9 +760,8 @@ namespace ts {
                 fileProcessingDiagnostics.reattachFileDiagnostics(modifiedFile.newFile);
             }
             resolvedTypeReferenceDirectives = oldProgram.getResolvedTypeReferenceDirectives();
-            oldProgram.structureIsReused = true;
 
-            return true;
+            return oldProgram.structureIsReused = StructureIsReused.Completely;
         }
 
         function getEmitHost(writeFileCallback?: WriteFileCallback): EmitHost {
@@ -1528,11 +1567,11 @@ namespace ts {
         function processImportedModules(file: SourceFile) {
             collectExternalModuleReferences(file);
             if (file.imports.length || file.moduleAugmentations.length) {
-                file.resolvedModules = createMap<ResolvedModuleFull>();
                 // Because global augmentation doesn't have string literal name, we can check for global augmentation as such.
                 const nonGlobalAugmentation = filter(file.moduleAugmentations, (moduleAugmentation) => moduleAugmentation.kind === SyntaxKind.StringLiteral);
                 const moduleNames = map(concatenate(file.imports, nonGlobalAugmentation), getTextOfLiteral);
-                const resolutions = resolveModuleNamesReusingOldState(moduleNames, getNormalizedAbsolutePath(file.fileName, currentDirectory), file);
+                const oldProgramState = { program: oldProgram, file, modifiedFilePaths };
+                const resolutions = resolveModuleNamesReusingOldState(moduleNames, getNormalizedAbsolutePath(file.fileName, currentDirectory), file, oldProgramState);
                 Debug.assert(resolutions.length === moduleNames.length);
                 for (let i = 0; i < moduleNames.length; i++) {
                     const resolution = resolutions[i];

src/compiler/types.ts

@@ -2408,7 +2408,14 @@ namespace ts {
         /* @internal */ getResolvedTypeReferenceDirectives(): Map<ResolvedTypeReferenceDirective>;
         /* @internal */ isSourceFileFromExternalLibrary(file: SourceFile): boolean;
         // For testing purposes only.
-        /* @internal */ structureIsReused?: boolean;
+        /* @internal */ structureIsReused?: StructureIsReused;
+    }
+
+    /* @internal */
+    export const enum StructureIsReused {
+        Not         = 0,
+        SafeModules = 1 << 0,
+        Completely  = 1 << 1,
     }
 
     export interface CustomTransformers {

src/compiler/utilities.ts

@@ -122,9 +122,8 @@ namespace ts {
 
     /* @internal */
     export function hasChangesInResolutions<T>(names: string[], newResolutions: T[], oldResolutions: Map<T>, comparer: (oldResolution: T, newResolution: T) => boolean): boolean {
-        if (names.length !== newResolutions.length) {
-            return false;
-        }
+        Debug.assert(names.length === newResolutions.length);
+
         for (let i = 0; i < names.length; i++) {
             const newResolution = newResolutions[i];
             const oldResolution = oldResolutions && oldResolutions.get(names[i]);

src/harness/unittests/cachingInServerLSHost.ts

@@ -201,14 +201,13 @@ namespace ts {
             assert.isTrue(diags.length === 1, "one diagnostic expected");
             assert.isTrue(typeof diags[0].messageText === "string" && ((<string>diags[0].messageText).indexOf("Cannot find module") === 0), "should be 'cannot find module' message");
 
-            // assert that import will success once file appear on disk
             fileMap.set(imported.name, imported);
             fileExistsCalledForBar = false;
             rootScriptInfo.editContent(0, root.content.length, `import {y} from "bar"`);
 
             diags = project.getLanguageService().getSemanticDiagnostics(root.name);
-            assert.isTrue(fileExistsCalledForBar, "'fileExists' should be called");
-            assert.isTrue(diags.length === 0);
+            assert.isTrue(fileExistsCalledForBar, "'fileExists' should be called.");
+            assert.isTrue(diags.length === 0, "The import should succeed once the imported file appears on disk.");
         });
     });
 }

src/harness/unittests/moduleResolution.ts

@@ -1042,7 +1042,7 @@ import b = require("./moduleB");
             assert.equal(diagnostics1.length, 1, "expected one diagnostic");
 
             createProgram(names, {}, compilerHost, program1);
-            assert.isTrue(program1.structureIsReused);
+            assert.isTrue(program1.structureIsReused === StructureIsReused.Completely);
             const diagnostics2 = program1.getFileProcessingDiagnostics().getDiagnostics();
             assert.equal(diagnostics2.length, 1, "expected one diagnostic");
             assert.equal(diagnostics1[0].messageText, diagnostics2[0].messageText, "expected one diagnostic");

src/harness/unittests/reuseProgramStructure.ts

@@ -159,12 +159,14 @@ namespace ts {
         return program;
     }
 
-    function updateProgram(oldProgram: ProgramWithSourceTexts, rootNames: string[], options: CompilerOptions, updater: (files: NamedSourceText[]) => void) {
-        const texts: NamedSourceText[] = (<ProgramWithSourceTexts>oldProgram).sourceTexts.slice(0);
-        updater(texts);
-        const host = createTestCompilerHost(texts, options.target, oldProgram);
+    function updateProgram(oldProgram: ProgramWithSourceTexts, rootNames: string[], options: CompilerOptions, updater: (files: NamedSourceText[]) => void, newTexts?: NamedSourceText[]) {
+        if (!newTexts) {
+            newTexts = (<ProgramWithSourceTexts>oldProgram).sourceTexts.slice(0);
+        }
+        updater(newTexts);
+        const host = createTestCompilerHost(newTexts, options.target, oldProgram);
         const program = <ProgramWithSourceTexts>createProgram(rootNames, options, host, oldProgram);
-        program.sourceTexts = texts;
+        program.sourceTexts = newTexts;
         program.host = host;
         return program;
     }
@@ -217,13 +219,15 @@ namespace ts {
 
     describe("Reuse program structure", () => {
         const target = ScriptTarget.Latest;
-        const files = [
-            { name: "a.ts", text: SourceText.New(
-                `
+        const files: NamedSourceText[] = [
+            {
+                name: "a.ts", text: SourceText.New(
+                    `
 /// <reference path='b.ts'/>
 /// <reference path='non-existing-file.ts'/>
 /// <reference types="typerefs" />
-`, "", `var x = 1`) },
+`, "", `var x = 1`)
+            },
             { name: "b.ts", text: SourceText.New(`/// <reference path='c.ts'/>`, "", `var y = 2`) },
             { name: "c.ts", text: SourceText.New("", "", `var z = 1;`) },
             { name: "types/typerefs/index.d.ts", text: SourceText.New("", "", `declare let z: number;`) },
@@ -234,7 +238,7 @@ namespace ts {
             const program_2 = updateProgram(program_1, ["a.ts"], { target }, files => {
                 files[0].text = files[0].text.updateProgram("var x = 100");
             });
-            assert.isTrue(program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Completely);
             const program1Diagnostics = program_1.getSemanticDiagnostics(program_1.getSourceFile("a.ts"));
             const program2Diagnostics = program_2.getSemanticDiagnostics(program_1.getSourceFile("a.ts"));
             assert.equal(program1Diagnostics.length, program2Diagnostics.length);
@@ -245,7 +249,7 @@ namespace ts {
             const program_2 = updateProgram(program_1, ["a.ts"], { target }, files => {
                 files[0].text = files[0].text.updateProgram("var x = 100");
             });
-            assert.isTrue(program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Completely);
             const program1Diagnostics = program_1.getSemanticDiagnostics(program_1.getSourceFile("a.ts"));
             const program2Diagnostics = program_2.getSemanticDiagnostics(program_1.getSourceFile("a.ts"));
             assert.equal(program1Diagnostics.length, program2Diagnostics.length);
@@ -259,19 +263,19 @@ namespace ts {
                 `;
                 files[0].text = files[0].text.updateReferences(newReferences);
             });
-            assert.isTrue(!program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.SafeModules);
         });
 
         it("fails if change affects type references", () => {
             const program_1 = newProgram(files, ["a.ts"], { types: ["a"] });
             updateProgram(program_1, ["a.ts"], { types: ["b"] }, noop);
-            assert.isTrue(!program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Not);
         });
 
         it("succeeds if change doesn't affect type references", () => {
             const program_1 = newProgram(files, ["a.ts"], { types: ["a"] });
             updateProgram(program_1, ["a.ts"], { types: ["a"] }, noop);
-            assert.isTrue(program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Completely);
         });
 
         it("fails if change affects imports", () => {
@@ -279,7 +283,7 @@ namespace ts {
             updateProgram(program_1, ["a.ts"], { target }, files => {
                 files[2].text = files[2].text.updateImportsAndExports("import x from 'b'");
             });
-            assert.isTrue(!program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.SafeModules);
         });
 
         it("fails if change affects type directives", () => {
@@ -291,25 +295,25 @@ namespace ts {
 /// <reference types="typerefs1" />`;
                 files[0].text = files[0].text.updateReferences(newReferences);
             });
-            assert.isTrue(!program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.SafeModules);
         });
 
         it("fails if module kind changes", () => {
             const program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS });
             updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.AMD }, noop);
-            assert.isTrue(!program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Not);
         });
 
         it("fails if rootdir changes", () => {
             const program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS, rootDir: "/a/b" });
             updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, rootDir: "/a/c" }, noop);
-            assert.isTrue(!program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Not);
         });
 
         it("fails if config path changes", () => {
             const program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS, configFilePath: "/a/b/tsconfig.json" });
             updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, configFilePath: "/a/c/tsconfig.json" }, noop);
-            assert.isTrue(!program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Not);
         });
 
         it("resolution cache follows imports", () => {
@@ -328,7 +332,7 @@ namespace ts {
             const program_2 = updateProgram(program_1, ["a.ts"], options, files => {
                 files[0].text = files[0].text.updateProgram("var x = 2");
             });
-            assert.isTrue(program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Completely);
 
             // content of resolution cache should not change
             checkResolvedModulesCache(program_1, "a.ts", createMapFromTemplate({ "b": createResolvedModule("b.ts") }));
@@ -338,7 +342,7 @@ namespace ts {
             const program_3 = updateProgram(program_2, ["a.ts"], options, files => {
                 files[0].text = files[0].text.updateImportsAndExports("");
             });
-            assert.isTrue(!program_2.structureIsReused);
+            assert.isTrue(program_2.structureIsReused === StructureIsReused.SafeModules);
             checkResolvedModulesCache(program_3, "a.ts", /*expectedContent*/ undefined);
 
             const program_4 = updateProgram(program_3, ["a.ts"], options, files => {
@@ -347,7 +351,7 @@ namespace ts {
                 `;
                 files[0].text = files[0].text.updateImportsAndExports(newImports);
             });
-            assert.isTrue(!program_3.structureIsReused);
+            assert.isTrue(program_3.structureIsReused === StructureIsReused.SafeModules);
             checkResolvedModulesCache(program_4, "a.ts", createMapFromTemplate({ "b": createResolvedModule("b.ts"), "c": undefined }));
         });
 
@@ -365,7 +369,7 @@ namespace ts {
             const program_2 = updateProgram(program_1, ["/a.ts"], options, files => {
                 files[0].text = files[0].text.updateProgram("var x = 2");
             });
-            assert.isTrue(program_1.structureIsReused);
+            assert.isTrue(program_1.structureIsReused === StructureIsReused.Completely);
 
             // content of resolution cache should not change
             checkResolvedTypeDirectivesCache(program_1, "/a.ts", createMapFromTemplate({ "typedefs": { resolvedFileName: "/types/typedefs/index.d.ts", primary: true } }));
@@ -376,7 +380,7 @@ namespace ts {
                 files[0].text = files[0].text.updateReferences("");
             });
 
-            assert.isTrue(!program_2.structureIsReused);
+            assert.isTrue(program_2.structureIsReused === StructureIsReused.SafeModules);
             checkResolvedTypeDirectivesCache(program_3, "/a.ts", /*expectedContent*/ undefined);
 
             updateProgram(program_3, ["/a.ts"], options, files => {
@@ -385,10 +389,74 @@ namespace ts {
                 `;
                 files[0].text = files[0].text.updateReferences(newReferences);
             });
-            assert.isTrue(!program_3.structureIsReused);
+            assert.isTrue(program_3.structureIsReused === StructureIsReused.SafeModules);
             checkResolvedTypeDirectivesCache(program_1, "/a.ts", createMapFromTemplate({ "typedefs": { resolvedFileName: "/types/typedefs/index.d.ts", primary: true } }));
         });
 
+        it("fetches imports after npm install", () => {
+            const file1Ts = { name: "file1.ts", text: SourceText.New("", `import * as a from "a";`, "const myX: number = a.x;") };
+            const file2Ts = { name: "file2.ts", text: SourceText.New("", "", "") };
+            const indexDTS = { name: "node_modules/a/index.d.ts", text: SourceText.New("", "export declare let x: number;", "") };
+            const options: CompilerOptions = { target: ScriptTarget.ES2015, traceResolution: true, moduleResolution: ModuleResolutionKind.NodeJs };
+            const rootFiles = [file1Ts, file2Ts];
+            const filesAfterNpmInstall = [file1Ts, file2Ts, indexDTS];
+
+            const initialProgram = newProgram(rootFiles, rootFiles.map(f => f.name), options);
+            {
+                assert.deepEqual(initialProgram.host.getTrace(),
+                    [
+                        "======== Resolving module 'a' from 'file1.ts'. ========",
+                        "Explicitly specified module resolution kind: 'NodeJs'.",
+                        "Loading module 'a' from 'node_modules' folder, target file type 'TypeScript'.",
+                        "File 'node_modules/a.ts' does not exist.",
+                        "File 'node_modules/a.tsx' does not exist.",
+                        "File 'node_modules/a.d.ts' does not exist.",
+                        "File 'node_modules/a/package.json' does not exist.",
+                        "File 'node_modules/a/index.ts' does not exist.",
+                        "File 'node_modules/a/index.tsx' does not exist.",
+                        "File 'node_modules/a/index.d.ts' does not exist.",
+                        "File 'node_modules/@types/a.d.ts' does not exist.",
+                        "File 'node_modules/@types/a/package.json' does not exist.",
+                        "File 'node_modules/@types/a/index.d.ts' does not exist.",
+                        "Loading module 'a' from 'node_modules' folder, target file type 'JavaScript'.",
+                        "File 'node_modules/a.js' does not exist.",
+                        "File 'node_modules/a.jsx' does not exist.",
+                        "File 'node_modules/a/package.json' does not exist.",
+                        "File 'node_modules/a/index.js' does not exist.",
+                        "File 'node_modules/a/index.jsx' does not exist.",
+                        "======== Module name 'a' was not resolved. ========"
+                    ],
+                    "initialProgram: execute module resolution normally.");
+
+                const initialProgramDiagnostics = initialProgram.getSemanticDiagnostics(initialProgram.getSourceFile("file1.ts"));
+                assert(initialProgramDiagnostics.length === 1, `initialProgram: import should fail.`);
+            }
+
+            const afterNpmInstallProgram = updateProgram(initialProgram, rootFiles.map(f => f.name), options, f => {
+                f[1].text = f[1].text.updateReferences(`/// <reference no-default-lib="true"/>`);
+            }, filesAfterNpmInstall);
+            {
+                assert.deepEqual(afterNpmInstallProgram.host.getTrace(),
+                    [
+                        "======== Resolving module 'a' from 'file1.ts'. ========",
+                        "Explicitly specified module resolution kind: 'NodeJs'.",
+                        "Loading module 'a' from 'node_modules' folder, target file type 'TypeScript'.",
+                        "File 'node_modules/a.ts' does not exist.",
+                        "File 'node_modules/a.tsx' does not exist.",
+                        "File 'node_modules/a.d.ts' does not exist.",
+                        "File 'node_modules/a/package.json' does not exist.",
+                        "File 'node_modules/a/index.ts' does not exist.",
+                        "File 'node_modules/a/index.tsx' does not exist.",
+                        "File 'node_modules/a/index.d.ts' exist - use it as a name resolution result.",
+                        "======== Module name 'a' was successfully resolved to 'node_modules/a/index.d.ts'. ========"
+                    ],
+                    "afterNpmInstallProgram: execute module resolution normally.");
+
+                const afterNpmInstallProgramDiagnostics = afterNpmInstallProgram.getSemanticDiagnostics(afterNpmInstallProgram.getSourceFile("file1.ts"));
+                assert(afterNpmInstallProgramDiagnostics.length === 0, `afterNpmInstallProgram: program is well-formed with import.`);
+            }
+        });
+
         it("can reuse ambient module declarations from non-modified files", () => {
             const files = [
                 { name: "/a/b/app.ts", text: SourceText.New("", "import * as fs from 'fs'", "") },
@@ -468,7 +536,206 @@ namespace ts {
                     "File '/fs.jsx' does not exist.",
                     "======== Module name 'fs' was not resolved. ========",
                 ], "should look for 'fs' again since node.d.ts was changed");
+        });
 
+        it("can reuse module resolutions from non-modified files", () => {
+            const files = [
+                { name: "a1.ts", text: SourceText.New("", "", "let x = 1;") },
+                { name: "a2.ts", text: SourceText.New("", "", "let x = 1;") },
+                { name: "b1.ts", text: SourceText.New("", "export class B { x: number; }", "") },
+                { name: "b2.ts", text: SourceText.New("", "export class B { x: number; }", "") },
+                { name: "node_modules/@types/typerefs1/index.d.ts", text: SourceText.New("", "", "declare let z: string;") },
+                { name: "node_modules/@types/typerefs2/index.d.ts", text: SourceText.New("", "", "declare let z: string;") },
+                {
+                    name: "f1.ts",
+                    text:
+                    SourceText.New(
+                        `/// <reference path="a1.ts"/>${newLine}/// <reference types="typerefs1"/>${newLine}/// <reference no-default-lib="true"/>`,
+                        `import { B } from './b1';${newLine}export let BB = B;`,
+                        "declare module './b1' { interface B { y: string; } }")
+                },
+                {
+                    name: "f2.ts",
+                    text: SourceText.New(
+                        `/// <reference path="a2.ts"/>${newLine}/// <reference types="typerefs2"/>`,
+                        `import { B } from './b2';${newLine}import { BB } from './f1';`,
+                        "(new BB).x; (new BB).y;")
+                },
+            ];
+
+            const options: CompilerOptions = { target: ScriptTarget.ES2015, traceResolution: true, moduleResolution: ModuleResolutionKind.Classic };
+            const program_1 = newProgram(files, files.map(f => f.name), options);
+            let expectedErrors = 0;
+            {
+                assert.deepEqual(program_1.host.getTrace(),
+                    [
+                        "======== Resolving type reference directive 'typerefs1', containing file 'f1.ts', root directory 'node_modules/@types'. ========",
+                        "Resolving with primary search path 'node_modules/@types'.",
+                        "File 'node_modules/@types/typerefs1/package.json' does not exist.",
+                        "File 'node_modules/@types/typerefs1/index.d.ts' exist - use it as a name resolution result.",
+                        "======== Type reference directive 'typerefs1' was successfully resolved to 'node_modules/@types/typerefs1/index.d.ts', primary: true. ========",
+                        "======== Resolving module './b1' from 'f1.ts'. ========",
+                        "Explicitly specified module resolution kind: 'Classic'.",
+                        "File 'b1.ts' exist - use it as a name resolution result.",
+                        "======== Module name './b1' was successfully resolved to 'b1.ts'. ========",
+                        "======== Resolving type reference directive 'typerefs2', containing file 'f2.ts', root directory 'node_modules/@types'. ========",
+                        "Resolving with primary search path 'node_modules/@types'.",
+                        "File 'node_modules/@types/typerefs2/package.json' does not exist.",
+                        "File 'node_modules/@types/typerefs2/index.d.ts' exist - use it as a name resolution result.",
+                        "======== Type reference directive 'typerefs2' was successfully resolved to 'node_modules/@types/typerefs2/index.d.ts', primary: true. ========",
+                        "======== Resolving module './b2' from 'f2.ts'. ========",
+                        "Explicitly specified module resolution kind: 'Classic'.",
+                        "File 'b2.ts' exist - use it as a name resolution result.",
+                        "======== Module name './b2' was successfully resolved to 'b2.ts'. ========",
+                        "======== Resolving module './f1' from 'f2.ts'. ========",
+                        "Explicitly specified module resolution kind: 'Classic'.",
+                        "File 'f1.ts' exist - use it as a name resolution result.",
+                        "======== Module name './f1' was successfully resolved to 'f1.ts'. ========"
+                    ],
+                    "program_1: execute module reoslution normally.");
+
+                const program_1Diagnostics = program_1.getSemanticDiagnostics(program_1.getSourceFile("f2.ts"));
+                assert(program_1Diagnostics.length === expectedErrors, `initial program should be well-formed`);
+            }
+            const indexOfF1 = 6;
+            const program_2 = updateProgram(program_1, program_1.getRootFileNames(), options, f => {
+                const newSourceText = f[indexOfF1].text.updateReferences(`/// <reference path="a1.ts"/>${newLine}/// <reference types="typerefs1"/>`);
+                f[indexOfF1] = { name: "f1.ts", text: newSourceText };
+            });
+
+            {
+                const program_2Diagnostics = program_2.getSemanticDiagnostics(program_2.getSourceFile("f2.ts"));
+                assert(program_2Diagnostics.length === expectedErrors, `removing no-default-lib shouldn't affect any types used.`);
+
+                assert.deepEqual(program_2.host.getTrace(), [
+                    "======== Resolving type reference directive 'typerefs1', containing file 'f1.ts', root directory 'node_modules/@types'. ========",
+                    "Resolving with primary search path 'node_modules/@types'.",
+                    "File 'node_modules/@types/typerefs1/package.json' does not exist.",
+                    "File 'node_modules/@types/typerefs1/index.d.ts' exist - use it as a name resolution result.",
+                    "======== Type reference directive 'typerefs1' was successfully resolved to 'node_modules/@types/typerefs1/index.d.ts', primary: true. ========",
+                    "======== Resolving module './b1' from 'f1.ts'. ========",
+                    "Explicitly specified module resolution kind: 'Classic'.",
+                    "File 'b1.ts' exist - use it as a name resolution result.",
+                    "======== Module name './b1' was successfully resolved to 'b1.ts'. ========",
+                    "======== Resolving type reference directive 'typerefs2', containing file 'f2.ts', root directory 'node_modules/@types'. ========",
+                    "Resolving with primary search path 'node_modules/@types'.",
+                    "File 'node_modules/@types/typerefs2/package.json' does not exist.",
+                    "File 'node_modules/@types/typerefs2/index.d.ts' exist - use it as a name resolution result.",
+                    "======== Type reference directive 'typerefs2' was successfully resolved to 'node_modules/@types/typerefs2/index.d.ts', primary: true. ========",
+                    "Reusing resolution of module './b2' to file 'f2.ts' from old program.",
+                    "Reusing resolution of module './f1' to file 'f2.ts' from old program."
+                ], "program_2: reuse module resolutions in f2 since it is unchanged");
+            }
+
+            const program_3 = updateProgram(program_2, program_2.getRootFileNames(), options, f => {
+                const newSourceText = f[indexOfF1].text.updateReferences(`/// <reference path="a1.ts"/>`);
+                f[indexOfF1] = { name: "f1.ts", text: newSourceText };
+            });
+
+            {
+                const program_3Diagnostics = program_3.getSemanticDiagnostics(program_3.getSourceFile("f2.ts"));
+                assert(program_3Diagnostics.length === expectedErrors, `typerefs2 was unused, so diagnostics should be unaffected.`);
+
+                assert.deepEqual(program_3.host.getTrace(), [
+                    "======== Resolving module './b1' from 'f1.ts'. ========",
+                    "Explicitly specified module resolution kind: 'Classic'.",
+                    "File 'b1.ts' exist - use it as a name resolution result.",
+                    "======== Module name './b1' was successfully resolved to 'b1.ts'. ========",
+                    "======== Resolving type reference directive 'typerefs2', containing file 'f2.ts', root directory 'node_modules/@types'. ========",
+                    "Resolving with primary search path 'node_modules/@types'.",
+                    "File 'node_modules/@types/typerefs2/package.json' does not exist.",
+                    "File 'node_modules/@types/typerefs2/index.d.ts' exist - use it as a name resolution result.",
+                    "======== Type reference directive 'typerefs2' was successfully resolved to 'node_modules/@types/typerefs2/index.d.ts', primary: true. ========",
+                    "Reusing resolution of module './b2' to file 'f2.ts' from old program.",
+                    "Reusing resolution of module './f1' to file 'f2.ts' from old program."
+                ], "program_3: reuse module resolutions in f2 since it is unchanged");
+            }
+
+
+            const program_4 = updateProgram(program_3, program_3.getRootFileNames(), options, f => {
+                const newSourceText = f[indexOfF1].text.updateReferences("");
+                f[indexOfF1] = { name: "f1.ts", text: newSourceText };
+            });
+
+            {
+                const program_4Diagnostics = program_4.getSemanticDiagnostics(program_4.getSourceFile("f2.ts"));
+                assert(program_4Diagnostics.length === expectedErrors, `a1.ts was unused, so diagnostics should be unaffected.`);
+
+                assert.deepEqual(program_4.host.getTrace(), [
+                    "======== Resolving module './b1' from 'f1.ts'. ========",
+                    "Explicitly specified module resolution kind: 'Classic'.",
+                    "File 'b1.ts' exist - use it as a name resolution result.",
+                    "======== Module name './b1' was successfully resolved to 'b1.ts'. ========",
+                    "======== Resolving type reference directive 'typerefs2', containing file 'f2.ts', root directory 'node_modules/@types'. ========",
+                    "Resolving with primary search path 'node_modules/@types'.",
+                    "File 'node_modules/@types/typerefs2/package.json' does not exist.",
+                    "File 'node_modules/@types/typerefs2/index.d.ts' exist - use it as a name resolution result.",
+                    "======== Type reference directive 'typerefs2' was successfully resolved to 'node_modules/@types/typerefs2/index.d.ts', primary: true. ========",
+                    "Reusing resolution of module './b2' to file 'f2.ts' from old program.",
+                    "Reusing resolution of module './f1' to file 'f2.ts' from old program."
+                ], "program_4: reuse module resolutions in f2 since it is unchanged");
+            }
+
+            const program_5 = updateProgram(program_4, program_4.getRootFileNames(), options, f => {
+                const newSourceText = f[indexOfF1].text.updateImportsAndExports(`import { B } from './b1';`);
+                f[indexOfF1] = { name: "f1.ts", text: newSourceText };
+            });
+
+            {
+                const program_5Diagnostics = program_5.getSemanticDiagnostics(program_5.getSourceFile("f2.ts"));
+                assert(program_5Diagnostics.length === ++expectedErrors, `import of BB in f1 fails. BB is of type any. Add one error`);
+
+                assert.deepEqual(program_5.host.getTrace(), [
+                    "======== Resolving module './b1' from 'f1.ts'. ========",
+                    "Explicitly specified module resolution kind: 'Classic'.",
+                    "File 'b1.ts' exist - use it as a name resolution result.",
+                    "======== Module name './b1' was successfully resolved to 'b1.ts'. ========"
+                ], "program_5: exports do not affect program structure, so f2's resolutions are silently reused.");
+            }
+
+            const program_6 = updateProgram(program_5, program_5.getRootFileNames(), options, f => {
+                const newSourceText = f[indexOfF1].text.updateProgram("");
+                f[indexOfF1] = { name: "f1.ts", text: newSourceText };
+            });
+
+            {
+                const program_6Diagnostics = program_6.getSemanticDiagnostics(program_6.getSourceFile("f2.ts"));
+                assert(program_6Diagnostics.length === expectedErrors, `import of BB in f1 fails.`);
+
+                assert.deepEqual(program_6.host.getTrace(), [
+                    "======== Resolving module './b1' from 'f1.ts'. ========",
+                    "Explicitly specified module resolution kind: 'Classic'.",
+                    "File 'b1.ts' exist - use it as a name resolution result.",
+                    "======== Module name './b1' was successfully resolved to 'b1.ts'. ========",
+                    "======== Resolving type reference directive 'typerefs2', containing file 'f2.ts', root directory 'node_modules/@types'. ========",
+                    "Resolving with primary search path 'node_modules/@types'.",
+                    "File 'node_modules/@types/typerefs2/package.json' does not exist.",
+                    "File 'node_modules/@types/typerefs2/index.d.ts' exist - use it as a name resolution result.",
+                    "======== Type reference directive 'typerefs2' was successfully resolved to 'node_modules/@types/typerefs2/index.d.ts', primary: true. ========",
+                    "Reusing resolution of module './b2' to file 'f2.ts' from old program.",
+                    "Reusing resolution of module './f1' to file 'f2.ts' from old program."
+                ], "program_6: reuse module resolutions in f2 since it is unchanged");
+            }
+
+            const program_7 = updateProgram(program_6, program_6.getRootFileNames(), options, f => {
+                const newSourceText = f[indexOfF1].text.updateImportsAndExports("");
+                f[indexOfF1] = { name: "f1.ts", text: newSourceText };
+            });
+
+            {
+                const program_7Diagnostics = program_7.getSemanticDiagnostics(program_7.getSourceFile("f2.ts"));
+                assert(program_7Diagnostics.length === expectedErrors, `removing import is noop with respect to program, so no change in diagnostics.`);
+
+                assert.deepEqual(program_7.host.getTrace(), [
+                    "======== Resolving type reference directive 'typerefs2', containing file 'f2.ts', root directory 'node_modules/@types'. ========",
+                    "Resolving with primary search path 'node_modules/@types'.",
+                    "File 'node_modules/@types/typerefs2/package.json' does not exist.",
+                    "File 'node_modules/@types/typerefs2/index.d.ts' exist - use it as a name resolution result.",
+                    "======== Type reference directive 'typerefs2' was successfully resolved to 'node_modules/@types/typerefs2/index.d.ts', primary: true. ========",
+                    "Reusing resolution of module './b2' to file 'f2.ts' from old program.",
+                    "Reusing resolution of module './f1' to file 'f2.ts' from old program."
+                ], "program_7 should reuse module resolutions in f2 since it is unchanged");
+            }
         });
     });
 

src/harness/unittests/transform.ts

@@ -70,7 +70,7 @@ namespace ts {
                     after: [replaceIdentifiersNamedOldNameWithNewName]
                 },
                 compilerOptions: {
-                    newLine: ts.NewLineKind.CarriageReturnLineFeed
+                    newLine: NewLineKind.CarriageReturnLineFeed
                 }
             }).outputText;
         });

src/server/project.ts

@@ -552,7 +552,7 @@ namespace ts.server {
             // bump up the version if
             // - oldProgram is not set - this is a first time updateGraph is called
             // - newProgram is different from the old program and structure of the old program was not reused.
-            if (!oldProgram || (this.program !== oldProgram && !oldProgram.structureIsReused)) {
+            if (!oldProgram || (this.program !== oldProgram && !(oldProgram.structureIsReused & StructureIsReused.Completely))) {
                 hasChanges = true;
                 if (oldProgram) {
                     for (const f of oldProgram.getSourceFiles()) {

src/services/codefixes/unusedIdentifierFixes.ts

@@ -18,142 +18,150 @@ namespace ts.codefix {
 
             switch (token.kind) {
                 case ts.SyntaxKind.Identifier:
-                    switch (token.parent.kind) {
-                        case ts.SyntaxKind.VariableDeclaration:
-                            switch (token.parent.parent.parent.kind) {
-                                case SyntaxKind.ForStatement:
-                                    const forStatement = <ForStatement>token.parent.parent.parent;
-                                    const forInitializer = <VariableDeclarationList>forStatement.initializer;
-                                    if (forInitializer.declarations.length === 1) {
-                                        return deleteNode(forInitializer);
-                                    }
-                                    else {
-                                        return deleteNodeInList(token.parent);
-                                    }
-
-                                case SyntaxKind.ForOfStatement:
-                                    const forOfStatement = <ForOfStatement>token.parent.parent.parent;
-                                    if (forOfStatement.initializer.kind === SyntaxKind.VariableDeclarationList) {
-                                        const forOfInitializer = <VariableDeclarationList>forOfStatement.initializer;
-                                        return replaceNode(forOfInitializer.declarations[0], createObjectLiteral());
-                                    }
-                                    break;
-
-                                case SyntaxKind.ForInStatement:
-                                    // There is no valid fix in the case of:
-                                    //  for .. in
-                                    return undefined;
-
-                                case SyntaxKind.CatchClause:
-                                    const catchClause = <CatchClause>token.parent.parent;
-                                    const parameter = catchClause.variableDeclaration.getChildren()[0];
-                                    return deleteNode(parameter);
-
-                                default:
-                                    const variableStatement = <VariableStatement>token.parent.parent.parent;
-                                    if (variableStatement.declarationList.declarations.length === 1) {
-                                        return deleteNode(variableStatement);
-                                    }
-                                    else {
-                                        return deleteNodeInList(token.parent);
-                                    }
-                            }
-                            // TODO: #14885
-                            // falls through
-
-                        case SyntaxKind.TypeParameter:
-                            const typeParameters = (<DeclarationWithTypeParameters>token.parent.parent).typeParameters;
-                            if (typeParameters.length === 1) {
-                                const previousToken = getTokenAtPosition(sourceFile, typeParameters.pos - 1);
-                                if (!previousToken || previousToken.kind !== SyntaxKind.LessThanToken) {
-                                    return deleteRange(typeParameters);
-                                }
-                                const nextToken = getTokenAtPosition(sourceFile, typeParameters.end);
-                                if (!nextToken || nextToken.kind !== SyntaxKind.GreaterThanToken) {
-                                    return deleteRange(typeParameters);
-                                }
-                                return deleteNodeRange(previousToken, nextToken);
-                            }
-                            else {
-                                return deleteNodeInList(token.parent);
-                            }
-
-                        case ts.SyntaxKind.Parameter:
-                            const functionDeclaration = <FunctionDeclaration>token.parent.parent;
-                            if (functionDeclaration.parameters.length === 1) {
-                                return deleteNode(token.parent);
-                            }
-                            else {
-                                return deleteNodeInList(token.parent);
-                            }
-
-                        // handle case where 'import a = A;'
-                        case SyntaxKind.ImportEqualsDeclaration:
-                            const importEquals = getAncestor(token, SyntaxKind.ImportEqualsDeclaration);
-                            return deleteNode(importEquals);
-
-                        case SyntaxKind.ImportSpecifier:
-                            const namedImports = <NamedImports>token.parent.parent;
-                            if (namedImports.elements.length === 1) {
-                                // Only 1 import and it is unused. So the entire declaration should be removed.
-                                const importSpec = getAncestor(token, SyntaxKind.ImportDeclaration);
-                                return deleteNode(importSpec);
-                            }
-                            else {
-                                // delete import specifier
-                                return deleteNodeInList(token.parent);
-                            }
-
-                        // handle case where "import d, * as ns from './file'"
-                        // or "'import {a, b as ns} from './file'"
-                        case SyntaxKind.ImportClause: // this covers both 'import |d|' and 'import |d,| *'
-                            const importClause = <ImportClause>token.parent;
-                            if (!importClause.namedBindings) { // |import d from './file'| or |import * as ns from './file'|
-                                const importDecl = getAncestor(importClause, SyntaxKind.ImportDeclaration);
-                                return deleteNode(importDecl);
-                            }
-                            else {
-                                // import |d,| * as ns from './file'
-                                const start = importClause.name.getStart(sourceFile);
-                                const nextToken = getTokenAtPosition(sourceFile, importClause.name.end);
-                                if (nextToken && nextToken.kind === SyntaxKind.CommaToken) {
-                                    // shift first non-whitespace position after comma to the start position of the node
-                                    return deleteRange({ pos: start, end: skipTrivia(sourceFile.text, nextToken.end, /*stopAfterLineBreaks*/ false, /*stopAtComments*/ true) });
-                                }
-                                else {
-                                    return deleteNode(importClause.name);
-                                }
-                            }
-
-                        case SyntaxKind.NamespaceImport:
-                            const namespaceImport = <NamespaceImport>token.parent;
-                            if (namespaceImport.name === token && !(<ImportClause>namespaceImport.parent).name) {
-                                const importDecl = getAncestor(namespaceImport, SyntaxKind.ImportDeclaration);
-                                return deleteNode(importDecl);
-                            }
-                            else {
-                                const previousToken = getTokenAtPosition(sourceFile, namespaceImport.pos - 1);
-                                if (previousToken && previousToken.kind === SyntaxKind.CommaToken) {
-                                    const startPosition = textChanges.getAdjustedStartPosition(sourceFile, previousToken, {}, textChanges.Position.FullStart);
-                                    return deleteRange({ pos: startPosition, end: namespaceImport.end });
-                                }
-                                return deleteRange(namespaceImport);
-                            }
-                    }
-                    break;
+                    return deleteIdentifier();
 
                 case SyntaxKind.PropertyDeclaration:
                 case SyntaxKind.NamespaceImport:
                     return deleteNode(token.parent);
+
+                default:
+                    return deleteDefault();
             }
-            if (isDeclarationName(token)) {
-                return deleteNode(token.parent);
+
+            function deleteDefault() {
+                if (isDeclarationName(token)) {
+                    return deleteNode(token.parent);
+                }
+                else if (isLiteralComputedPropertyDeclarationName(token)) {
+                    return deleteNode(token.parent.parent);
+                }
+                else {
+                    return undefined;
+                }
             }
-            else if (isLiteralComputedPropertyDeclarationName(token)) {
-                return deleteNode(token.parent.parent);
+
+            function deleteIdentifier(): CodeAction[] | undefined {
+                switch (token.parent.kind) {
+                    case ts.SyntaxKind.VariableDeclaration:
+                        return deleteVariableDeclaration(<ts.VariableDeclaration>token.parent);
+
+                    case SyntaxKind.TypeParameter:
+                        const typeParameters = (<DeclarationWithTypeParameters>token.parent.parent).typeParameters;
+                        if (typeParameters.length === 1) {
+                            const previousToken = getTokenAtPosition(sourceFile, typeParameters.pos - 1);
+                            if (!previousToken || previousToken.kind !== SyntaxKind.LessThanToken) {
+                                return deleteRange(typeParameters);
+                            }
+                            const nextToken = getTokenAtPosition(sourceFile, typeParameters.end);
+                            if (!nextToken || nextToken.kind !== SyntaxKind.GreaterThanToken) {
+                                return deleteRange(typeParameters);
+                            }
+                            return deleteNodeRange(previousToken, nextToken);
+                        }
+                        else {
+                            return deleteNodeInList(token.parent);
+                        }
+
+                    case ts.SyntaxKind.Parameter:
+                        const functionDeclaration = <FunctionDeclaration>token.parent.parent;
+                        if (functionDeclaration.parameters.length === 1) {
+                            return deleteNode(token.parent);
+                        }
+                        else {
+                            return deleteNodeInList(token.parent);
+                        }
+
+                    // handle case where 'import a = A;'
+                    case SyntaxKind.ImportEqualsDeclaration:
+                        const importEquals = getAncestor(token, SyntaxKind.ImportEqualsDeclaration);
+                        return deleteNode(importEquals);
+
+                    case SyntaxKind.ImportSpecifier:
+                        const namedImports = <NamedImports>token.parent.parent;
+                        if (namedImports.elements.length === 1) {
+                            // Only 1 import and it is unused. So the entire declaration should be removed.
+                            const importSpec = getAncestor(token, SyntaxKind.ImportDeclaration);
+                            return deleteNode(importSpec);
+                        }
+                        else {
+                            // delete import specifier
+                            return deleteNodeInList(token.parent);
+                        }
+
+                    // handle case where "import d, * as ns from './file'"
+                    // or "'import {a, b as ns} from './file'"
+                    case SyntaxKind.ImportClause: // this covers both 'import |d|' and 'import |d,| *'
+                        const importClause = <ImportClause>token.parent;
+                        if (!importClause.namedBindings) { // |import d from './file'| or |import * as ns from './file'|
+                            const importDecl = getAncestor(importClause, SyntaxKind.ImportDeclaration);
+                            return deleteNode(importDecl);
+                        }
+                        else {
+                            // import |d,| * as ns from './file'
+                            const start = importClause.name.getStart(sourceFile);
+                            const nextToken = getTokenAtPosition(sourceFile, importClause.name.end);
+                            if (nextToken && nextToken.kind === SyntaxKind.CommaToken) {
+                                // shift first non-whitespace position after comma to the start position of the node
+                                return deleteRange({ pos: start, end: skipTrivia(sourceFile.text, nextToken.end, /*stopAfterLineBreaks*/ false, /*stopAtComments*/ true) });
+                            }
+                            else {
+                                return deleteNode(importClause.name);
+                            }
+                        }
+
+                    case SyntaxKind.NamespaceImport:
+                        const namespaceImport = <NamespaceImport>token.parent;
+                        if (namespaceImport.name === token && !(<ImportClause>namespaceImport.parent).name) {
+                            const importDecl = getAncestor(namespaceImport, SyntaxKind.ImportDeclaration);
+                            return deleteNode(importDecl);
+                        }
+                        else {
+                            const previousToken = getTokenAtPosition(sourceFile, namespaceImport.pos - 1);
+                            if (previousToken && previousToken.kind === SyntaxKind.CommaToken) {
+                                const startPosition = textChanges.getAdjustedStartPosition(sourceFile, previousToken, {}, textChanges.Position.FullStart);
+                                return deleteRange({ pos: startPosition, end: namespaceImport.end });
+                            }
+                            return deleteRange(namespaceImport);
+                        }
+
+                    default:
+                        return deleteDefault();
+                }
             }
-            else {
-                return undefined;
+
+            // token.parent is a variableDeclaration
+            function deleteVariableDeclaration(varDecl: ts.VariableDeclaration): CodeAction[] | undefined {
+                switch (varDecl.parent.parent.kind) {
+                    case SyntaxKind.ForStatement:
+                        const forStatement = <ForStatement>varDecl.parent.parent;
+                        const forInitializer = <VariableDeclarationList>forStatement.initializer;
+                        if (forInitializer.declarations.length === 1) {
+                            return deleteNode(forInitializer);
+                        }
+                        else {
+                            return deleteNodeInList(varDecl);
+                        }
+
+                    case SyntaxKind.ForOfStatement:
+                        const forOfStatement = <ForOfStatement>varDecl.parent.parent;
+                        Debug.assert(forOfStatement.initializer.kind === SyntaxKind.VariableDeclarationList);
+                        const forOfInitializer = <VariableDeclarationList>forOfStatement.initializer;
+                        return replaceNode(forOfInitializer.declarations[0], createObjectLiteral());
+
+                    case SyntaxKind.ForInStatement:
+                        // There is no valid fix in the case of:
+                        //  for .. in
+                        return undefined;
+
+                    default:
+                        const variableStatement = <VariableStatement>varDecl.parent.parent;
+                        if (variableStatement.declarationList.declarations.length === 1) {
+                            return deleteNode(variableStatement);
+                        }
+                        else {
+                            return deleteNodeInList(varDecl);
+                        }
+                }
             }
 
             function deleteNode(n: Node) {

src/services/formatting/rules.ts

@@ -84,6 +84,7 @@ namespace ts.formatting {
         public NoSpaceBeforeComma: Rule;
 
         public SpaceAfterCertainKeywords: Rule;
+        public NoSpaceAfterNewKeywordOnConstructorSignature: Rule;
         public SpaceAfterLetConstInVariableDeclaration: Rule;
         public NoSpaceBeforeOpenParenInFuncCall: Rule;
         public SpaceAfterFunctionInFuncDecl: Rule;
@@ -334,6 +335,7 @@ namespace ts.formatting {
             this.NoSpaceBeforeComma = new Rule(RuleDescriptor.create2(Shared.TokenRange.Any, SyntaxKind.CommaToken), RuleOperation.create2(new RuleOperationContext(Rules.IsNonJsxSameLineTokenContext), RuleAction.Delete));
 
             this.SpaceAfterCertainKeywords = new Rule(RuleDescriptor.create4(Shared.TokenRange.FromTokens([SyntaxKind.VarKeyword, SyntaxKind.ThrowKeyword, SyntaxKind.NewKeyword, SyntaxKind.DeleteKeyword, SyntaxKind.ReturnKeyword, SyntaxKind.TypeOfKeyword, SyntaxKind.AwaitKeyword]), Shared.TokenRange.Any), RuleOperation.create2(new RuleOperationContext(Rules.IsNonJsxSameLineTokenContext), RuleAction.Space));
+            this.NoSpaceAfterNewKeywordOnConstructorSignature = new Rule(RuleDescriptor.create1(SyntaxKind.NewKeyword, SyntaxKind.OpenParenToken), RuleOperation.create2(new RuleOperationContext(Rules.IsNonJsxSameLineTokenContext, Rules.IsConstructorSignatureContext), RuleAction.Delete));
             this.SpaceAfterLetConstInVariableDeclaration = new Rule(RuleDescriptor.create4(Shared.TokenRange.FromTokens([SyntaxKind.LetKeyword, SyntaxKind.ConstKeyword]), Shared.TokenRange.Any), RuleOperation.create2(new RuleOperationContext(Rules.IsNonJsxSameLineTokenContext, Rules.IsStartOfVariableDeclarationList), RuleAction.Space));
             this.NoSpaceBeforeOpenParenInFuncCall = new Rule(RuleDescriptor.create2(Shared.TokenRange.Any, SyntaxKind.OpenParenToken), RuleOperation.create2(new RuleOperationContext(Rules.IsNonJsxSameLineTokenContext, Rules.IsFunctionCallOrNewContext, Rules.IsPreviousTokenNotComma), RuleAction.Delete));
             this.SpaceAfterFunctionInFuncDecl = new Rule(RuleDescriptor.create3(SyntaxKind.FunctionKeyword, Shared.TokenRange.Any), RuleOperation.create2(new RuleOperationContext(Rules.IsFunctionDeclContext), RuleAction.Space));
@@ -530,7 +532,8 @@ namespace ts.formatting {
                 this.SpaceBeforeAt,
                 this.NoSpaceAfterAt,
                 this.SpaceAfterDecorator,
-                this.NoSpaceBeforeNonNullAssertionOperator
+                this.NoSpaceBeforeNonNullAssertionOperator,
+                this.NoSpaceAfterNewKeywordOnConstructorSignature
             ];
 
             // These rules are applied after high priority rules.
@@ -881,6 +884,10 @@ namespace ts.formatting {
             return context.contextNode.kind === SyntaxKind.TypeLiteral; // && context.contextNode.parent.kind !== SyntaxKind.InterfaceDeclaration;
         }
 
+        static IsConstructorSignatureContext(context: FormattingContext): boolean {
+            return context.contextNode.kind === SyntaxKind.ConstructSignature;
+        }
+
         static IsTypeArgumentOrParameterOrAssertion(token: TextRangeWithKind, parent: Node): boolean {
             if (token.kind !== SyntaxKind.LessThanToken && token.kind !== SyntaxKind.GreaterThanToken) {
                 return false;

src/services/importTracker.ts

@@ -212,6 +212,10 @@ namespace ts.FindAllReferences {
                 return;
             }
 
+            if (!decl.importClause) {
+                return;
+            }
+
             const { importClause } = decl;
 
             const { namedBindings } = importClause;

tests/baselines/reference/noImplicitAnyStringIndexerOnObject.errors.txt

@@ -4,4 +4,5 @@ tests/cases/compiler/noImplicitAnyStringIndexerOnObject.ts(1,9): error TS7017: E
 ==== tests/cases/compiler/noImplicitAnyStringIndexerOnObject.ts (1 errors) ====
     var x = {}["hello"];
             ~~~~~~~~~~~
-!!! error TS7017: Element implicitly has an 'any' type because type '{}' has no index signature.
+!!! error TS7017: Element implicitly has an 'any' type because type '{}' has no index signature.
+    var y: string = { '': 'foo' }[''];

tests/baselines/reference/noImplicitAnyStringIndexerOnObject.js

@@ -1,5 +1,7 @@
 //// [noImplicitAnyStringIndexerOnObject.ts]
-var x = {}["hello"];
+var x = {}["hello"];
+var y: string = { '': 'foo' }[''];
 
 //// [noImplicitAnyStringIndexerOnObject.js]
 var x = {}["hello"];
+var y = { '': 'foo' }[''];

tests/cases/compiler/noImplicitAnyStringIndexerOnObject.ts

@@ -1,3 +1,4 @@
 // @noimplicitany: true
 
-var x = {}["hello"];
+var x = {}["hello"];
+var y: string = { '': 'foo' }[''];

tests/cases/fourslash/findAllRefsNoImportClause.ts

@@ -0,0 +1,11 @@
+/// <reference path="fourslash.ts" />
+
+// https://github.com/Microsoft/TypeScript/issues/15452
+
+// @Filename: /a.ts
+////export const [|{| "isWriteAccess": true, "isDefinition": true |}x|] = 0;
+
+// @Filename: /b.ts
+////import "./a";
+
+verify.singleReferenceGroup("const x: 0");

tests/cases/fourslash/formattingOnConstructorSignature.ts

@@ -0,0 +1,9 @@
+/// <reference path='fourslash.ts' />
+
+/////*1*/interface Gourai { new   () {} }
+/////*2*/type Stylet = { new   () {} }
+format.document();
+goTo.marker("1");
+verify.currentLineContentIs("interface Gourai { new() {} }");
+goTo.marker("2");
+verify.currentLineContentIs("type Stylet = { new() {} }");