diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index a32a5137bad..7bf50f675aa 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -1,4 +1,4 @@
-/// <reference path="sys.ts"/>
+/// <reference path="sys.ts"/>
 /// <reference path="types.ts"/>
 /// <reference path="core.ts"/>
 /// <reference path="diagnosticInformationMap.generated.ts"/>
@@ -543,7 +543,7 @@ namespace ts {
 
     /* @internal */
     export function createCompilerDiagnosticForInvalidCustomType(opt: CommandLineOptionOfCustomType): Diagnostic {
-        const namesOfType = keysOfMap(opt.type).map(key => `'${key}'`).join(", ");
+        const namesOfType = arrayFrom(opt.type.keys()).map(key => `'${key}'`).join(", ");
         return createCompilerDiagnostic(Diagnostics.Argument_for_0_option_must_be_Colon_1, `--${opt.name}`, namesOfType);
     }
 
@@ -1255,8 +1255,8 @@ namespace ts {
             }
         }
 
-        const literalFiles = valuesOfMap(literalFileMap);
-        const wildcardFiles = valuesOfMap(wildcardFileMap);
+        const literalFiles = arrayFrom(literalFileMap.values());
+        const wildcardFiles = arrayFrom(wildcardFileMap.values());
         wildcardFiles.sort(host.useCaseSensitiveFileNames ? compareStrings : compareStringsCaseInsensitive);
         return {
             fileNames: literalFiles.concat(wildcardFiles),
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index e9dbdb8786a..9f8f1ba3f55 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -156,7 +156,7 @@ namespace ts {
         }
 
         function getKeys() {
-            return keysOfMap(files) as Path[];
+            return arrayFrom(files.keys()) as Path[];
         }
 
         // path should already be well-formed so it does not need to be normalized
@@ -867,7 +867,8 @@ namespace ts {
         return keys;
     }
 
-    function arrayFrom<T>(iterator: Iterator<T>): T[] {
+    /** Shims `Array.from`. */
+    export function arrayFrom<T>(iterator: Iterator<T>): T[] {
         const result: T[] = [];
         for (let { value, done } = iterator.next(); !done; { value, done } = iterator.next()) {
             result.push(value);
@@ -875,19 +876,6 @@ namespace ts {
         return result;
     }
 
-    /**
-     * Array of every key in a map.
-     * May not actually return string[] if numbers were put into the map.
-     */
-    export function keysOfMap(map: Map<{}>): string[] {
-        return arrayFrom(map.keys());
-    }
-
-    /** Array of every value in a map. */
-    export function valuesOfMap<T>(map: Map<T>): T[] {
-        return arrayFrom(map.values());
-    }
-
     /**
      * Calls `callback` for each entry in the map, returning the first defined result.
      * Use `map.forEach` instead for normal iteration.
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index ba5a0d8faea..a0e7d5ba323 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -680,7 +680,7 @@ namespace ts {
                 description = getDiagnosticText(option.description);
                 const element = (<CommandLineOptionOfListType>option).element;
                 const typeMap = <Map<number | string>>element.type;
-                optionsDescriptionMap.set(description, keysOfMap(typeMap).map(key => `'${key}'`));
+                optionsDescriptionMap.set(description, arrayFrom(typeMap.keys()).map(key => `'${key}'`));
             }
             else {
                 description = getDiagnosticText(option.description);
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 4ae2dc7a389..caa51cd5566 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -246,7 +246,7 @@ namespace ts.projectSystem {
     export function checkMapKeys(caption: string, map: Map<any>, expectedKeys: string[]) {
         assert.equal(map.size, expectedKeys.length, `${caption}: incorrect size of map`);
         for (const name of expectedKeys) {
-            assert.isTrue(map.has(name), `${caption} is expected to contain ${name}, actual keys: ${keysOfMap(map)}`);
+            assert.isTrue(map.has(name), `${caption} is expected to contain ${name}, actual keys: ${arrayFrom(map.keys())}`);
         }
     }
 
diff --git a/src/server/project.ts b/src/server/project.ts
index 505eb2f63fb..054b484392e 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -1,4 +1,4 @@
-/// <reference path="..\services\services.ts" />
+/// <reference path="..\services\services.ts" />
 /// <reference path="utilities.ts"/>
 /// <reference path="scriptInfo.ts"/>
 /// <reference path="lsHost.ts"/>
@@ -617,7 +617,7 @@ namespace ts.server {
 
                 const added: string[] = [];
                 const removed: string[] = [];
-                const updated: string[] = keysOfMap(updatedFileNames);
+                const updated: string[] = arrayFrom(updatedFileNames.keys());
 
                 forEachKeyInMap(currentFiles, id => {
                     if (!lastReportedFileNames.has(id)) {
@@ -691,7 +691,7 @@ namespace ts.server {
                 })
             }
 
-            const allFileNames = keysOfMap(referencedFiles) as Path[];
+            const allFileNames = arrayFrom(referencedFiles.keys()) as Path[];
             return filter(allFileNames, file => this.projectService.host.fileExists(file));
         }
 
diff --git a/src/services/documentRegistry.ts b/src/services/documentRegistry.ts
index 4291abf6c1f..80b0133ccfe 100644
--- a/src/services/documentRegistry.ts
+++ b/src/services/documentRegistry.ts
@@ -1,4 +1,4 @@
-namespace ts {
+namespace ts {
     /**
       * The document registry represents a store of SourceFile objects that can be shared between
       * multiple LanguageService instances. A LanguageService instance holds on the SourceFile (AST)
@@ -121,7 +121,7 @@ namespace ts {
         }
 
         function reportStats() {
-            const bucketInfoArray = keysOfMap(buckets).filter(name => name && name.charAt(0) === "_").map(name => {
+            const bucketInfoArray = arrayFrom(buckets.keys()).filter(name => name && name.charAt(0) === "_").map(name => {
                 const entries = buckets.get(name);
                 const sourceFiles: { name: string; refCount: number; references: string[]; }[] = [];
                 entries.forEachValue((key, entry) => {