use deduplicate

Author: Arthur Ozga

src/harness/fourslash.ts

@@ -2150,32 +2150,23 @@ namespace FourSlash {
          * @param fileName Path to file where error should be retrieved from.
          */
         private getCodeFixActions(fileName: string, errorCode?: number): ts.CodeAction[] {
-            const diagnostics: ts.Diagnostic[] = this.getDiagnostics(fileName);
+            const diagnosticsForCodeFix = this.getDiagnostics(fileName).map(diagnostic => {
+                return {
+                    start: diagnostic.start,
+                    length: diagnostic.length,
+                    code: diagnostic.code
+                }
+            });
+            const dedupedDiagnositcs = ts.deduplicate(diagnosticsForCodeFix, ts.equalOwnProperties);
 
             let actions: ts.CodeAction[] = undefined;
 
-            const checkedDiagnostics = ts.createMap<boolean>();
-
-            for (const diagnostic of diagnostics) {
+            for (const diagnostic of dedupedDiagnositcs) {
 
                 if (errorCode && errorCode !== diagnostic.code) {
                     continue;
                 }
 
-                const summary = JSON.stringify({
-                    start: diagnostic.start,
-                    length: diagnostic.length,
-                    code: diagnostic.code
-                });
-
-                if (checkedDiagnostics.has(summary)) {
-                    // Don't want to ask for code fixes in an identical position for the same error code twice.
-                    continue;
-                }
-                else {
-                    checkedDiagnostics.set(summary, true);
-                }
-
                 const newActions = this.languageService.getCodeFixesAtPosition(fileName, diagnostic.start, diagnostic.length, [diagnostic.code]);
                 if (newActions && newActions.length) {
                     actions = actions ? actions.concat(newActions) : newActions;

src/services/services.ts

@@ -1688,13 +1688,7 @@ namespace ts {
 
             let allFixes: CodeAction[] = [];
 
-            // De-duplicate error codes.
-            const errorCodeSet: number[] = [];
-            for (const code of errorCodes) {
-                errorCodeSet[code] = code;
-            }
-
-            forEach(errorCodeSet, error => {
+            forEach(deduplicate(errorCodes), error => {
                 cancellationToken.throwIfCancellationRequested();
 
                 const context = {