diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index bf69228152e..be867db68fb 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -135,36 +135,34 @@ namespace ts {
         return configFile.options.rootDir || getDirectoryPath(Debug.assertDefined(configFile.options.configFilePath));
     }
 
+    function getOutputPathWithoutChangingExt(inputFileName: string, configFile: ParsedCommandLine, ignoreCase: boolean, outputDir: string | undefined) {
+        return outputDir ?
+            resolvePath(
+                outputDir,
+                getRelativePathFromDirectory(rootDirOfOptions(configFile), inputFileName, ignoreCase)
+            ) :
+            inputFileName;
+    }
+
     /* @internal */
     export function getOutputDeclarationFileName(inputFileName: string, configFile: ParsedCommandLine, ignoreCase: boolean) {
         Debug.assert(!fileExtensionIs(inputFileName, Extension.Dts) && hasTSFileExtension(inputFileName));
-        let outputPath: string;
-        const declarationDir = configFile.options.declarationDir || configFile.options.outDir;
-        if (declarationDir) {
-            const relativePath = getRelativePathFromDirectory(rootDirOfOptions(configFile), inputFileName, ignoreCase);
-            outputPath = resolvePath(declarationDir, relativePath);
-        }
-        else {
-            outputPath = inputFileName;
-        }
-        return changeExtension(outputPath, Extension.Dts);
+        return changeExtension(
+            getOutputPathWithoutChangingExt(inputFileName, configFile, ignoreCase, configFile.options.declarationDir || configFile.options.outDir),
+            Extension.Dts
+        );
     }
 
     function getOutputJSFileName(inputFileName: string, configFile: ParsedCommandLine, ignoreCase: boolean) {
-        let outputPath: string;
-        if (configFile.options.outDir) {
-            const relativePath = getRelativePathFromDirectory(rootDirOfOptions(configFile), inputFileName, ignoreCase);
-            outputPath = resolvePath(configFile.options.outDir, relativePath);
-        }
-        else {
-            outputPath = inputFileName;
-        }
         const isJsonFile = fileExtensionIs(inputFileName, Extension.Json);
-        const outputFileName = changeExtension(outputPath, isJsonFile ?
-            Extension.Json :
-            fileExtensionIs(inputFileName, Extension.Tsx) && configFile.options.jsx === JsxEmit.Preserve ?
-                Extension.Jsx :
-                Extension.Js);
+        const outputFileName = changeExtension(
+            getOutputPathWithoutChangingExt(inputFileName, configFile, ignoreCase, configFile.options.outDir),
+            isJsonFile ?
+                Extension.Json :
+                fileExtensionIs(inputFileName, Extension.Tsx) && configFile.options.jsx === JsxEmit.Preserve ?
+                    Extension.Jsx :
+                    Extension.Js
+        );
         return !isJsonFile || comparePaths(inputFileName, outputFileName, Debug.assertDefined(configFile.options.configFilePath), ignoreCase) !== Comparison.EqualTo ?
             outputFileName :
             undefined;
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 757fd69b3f9..979423cdfaa 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -2741,7 +2741,7 @@ namespace ts {
 
             // List of collected files is complete; validate exhautiveness if this is a project with a file list
             if (options.composite) {
-                const rootPaths = rootNames.map(r => toPath(r));
+                const rootPaths = rootNames.map(toPath);
                 for (const file of files) {
                     // Ignore declaration files
                     if (file.isDeclarationFile) continue;
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index f489aceae2d..73e32241f81 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -3437,7 +3437,12 @@ namespace ts {
     }
 
     /** Don't call this for `--outFile`, just for `--outDir` or plain emit. `--outFile` needs additional checks. */
-    export function sourceFileMayBeEmitted(sourceFile: SourceFile, options: CompilerOptions, isSourceFileFromExternalLibrary: (file: SourceFile) => boolean, getResolvedProjectReferenceToRedirect: (fileName: string) => ResolvedProjectReference | undefined) {
+    export function sourceFileMayBeEmitted(
+        sourceFile: SourceFile,
+        options: CompilerOptions,
+        isSourceFileFromExternalLibrary: (file: SourceFile) => boolean,
+        getResolvedProjectReferenceToRedirect: (fileName: string) => ResolvedProjectReference | undefined
+    ) {
         return !(options.noEmitForJsFiles && isSourceFileJS(sourceFile)) &&
             !sourceFile.isDeclarationFile &&
             !isSourceFileFromExternalLibrary(sourceFile) &&