Unescape identifiers used in code completion

src/harness/fourslash.ts

@@ -717,6 +717,8 @@ namespace FourSlash {
         public verifyCompletionEntryDetails(entryName: string, expectedText: string, expectedDocumentation?: string, kind?: string) {
             const details = this.getCompletionEntryDetails(entryName);
 
+            assert(details, "no completion entry available");
+
             assert.equal(ts.displayPartsToString(details.displayParts), expectedText, this.assertionMessageAtLastKnownMarker("completion entry details text"));
 
             if (expectedDocumentation !== undefined) {

src/services/services.ts

@@ -3234,7 +3234,7 @@ namespace ts {
                 }
             }
 
-            return name;
+            return unescapeIdentifier(name);
         }
 
         function getCompletionData(fileName: string, position: number) {

tests/cases/fourslash/codeCompletionEscaping.ts

@@ -0,0 +1,8 @@
+/// <reference path="fourslash.ts" />
+
+// @Filename: a.js
+// @allowJs: true
+////__foo;/**/
+
+goTo.marker();
+verify.completionListContains("__foo", undefined, undefined, "warning");