Only use localeCompare in CompareStrings

src/compiler/core.ts

@@ -23,6 +23,10 @@ namespace ts {
     // More efficient to create a collator once and use its `compare` than to call `a.localeCompare(b)` many times.
     export const collator: { compare(a: string, b: string): number } = typeof Intl === "object" && typeof Intl.Collator === "function" ? new Intl.Collator() : undefined;
 
+    // This means "compare in a case insensitive manner but consider accentsor other diacritic marks"
+    // (e.g. a ≠ b, a ≠ á, a = A)
+    const accentSensitivity: Intl.CollatorOptions = { usage: "sort", sensitivity: "accent" };
+
     /**
      * Use this function instead of calling "String.prototype.localeCompre". This function will preform appropriate check to make sure that
      *  "typeof Intl" is correct as there are reported issues #11110  nad #11339.
@@ -1029,13 +1033,13 @@ namespace ts {
         return a < b ? Comparison.LessThan : Comparison.GreaterThan;
     }
 
-    export function compareStrings(a: string, b: string, ignoreCase?: boolean): Comparison {
+    export function compareStrings(a: string, b: string, locales?: string | string[], options?: Intl.CollatorOptions): Comparison {
         if (a === b) return Comparison.EqualTo;
         if (a === undefined) return Comparison.LessThan;
         if (b === undefined) return Comparison.GreaterThan;
-        if (ignoreCase) {
-            const result = localeCompare(a, b, /*locales*/ undefined, /*options*/  { usage: "sort", sensitivity: "accent" });
-            if (result) {
+        if (options) {
+            if (collator && String.prototype.localeCompare) {
+                const result =  a.localeCompare(b, locales, options);
                 return result < 0 ? Comparison.LessThan : result > 0 ? Comparison.GreaterThan : Comparison.EqualTo;
             }
 
@@ -1048,7 +1052,7 @@ namespace ts {
     }
 
     export function compareStringsCaseInsensitive(a: string, b: string) {
-        return compareStrings(a, b, /*ignoreCase*/ true);
+        return compareStrings(a, b, /*locales*/ undefined, accentSensitivity);
     }
 
     function getDiagnosticFileName(diagnostic: Diagnostic): string {
@@ -1418,7 +1422,8 @@ namespace ts {
         const bComponents = getNormalizedPathComponents(b, currentDirectory);
         const sharedLength = Math.min(aComponents.length, bComponents.length);
         for (let i = 0; i < sharedLength; i++) {
-            const result = compareStrings(aComponents[i], bComponents[i], ignoreCase);
+            const result = compareStrings(aComponents[i], bComponents[i],
+                /*locales*/ undefined, /*options*/ ignoreCase ? accentSensitivity : undefined);
             if (result !== Comparison.EqualTo) {
                 return result;
             }
@@ -1440,7 +1445,8 @@ namespace ts {
         }
 
         for (let i = 0; i < parentComponents.length; i++) {
-            const result = compareStrings(parentComponents[i], childComponents[i], ignoreCase);
+            const result = compareStrings(parentComponents[i], childComponents[i],
+                /*locales*/ undefined, /*options*/ ignoreCase ? accentSensitivity : undefined);
             if (result !== Comparison.EqualTo) {
                 return false;
             }

src/harness/harness.ts

@@ -1634,7 +1634,7 @@ namespace Harness {
 
         export function collateOutputs(outputFiles: Harness.Compiler.GeneratedFile[]): string {
             // Collect, test, and sort the fileNames
-            outputFiles.sort((a, b) => ts.localeCompare(cleanName(a.fileName), cleanName(b.fileName)));
+            outputFiles.sort((a, b) => ts.compareStrings(cleanName(a.fileName), cleanName(b.fileName)));
 
             // Emit them
             let result = "";

src/server/session.ts

@@ -959,7 +959,7 @@ namespace ts.server {
                         result.push({ name, kind, kindModifiers, sortText, replacementSpan: convertedSpan });
                     }
                     return result;
-                }, []).sort((a, b) => localeCompare(a.name, b.name));
+                }, []).sort((a, b) => ts.compareStrings(a.name, b.name));
             }
             else {
                 return completions;

src/services/navigateTo.ts

@@ -188,8 +188,8 @@ namespace ts.NavigateTo {
             // We first sort case insensitively.  So "Aaa" will come before "bar".
             // Then we sort case sensitively, so "aaa" will come before "Aaa".
             return i1.matchKind - i2.matchKind ||
-                ts.localeCompare(i1.name, i2.name, /*locales*/ undefined, /*options*/ baseSensitivity) ||
-                ts.localeCompare(i1.name, i2.name);
+                ts.compareStrings(i1.name, i2.name, /*locales*/ undefined, /*options*/ baseSensitivity) ||
+                ts.compareStrings(i1.name, i2.name);
         }
 
         function createNavigateToItem(rawItem: RawNavigateToItem): NavigateToItem {

src/services/navigationBar.ts

@@ -335,7 +335,7 @@ namespace ts.NavigationBar {
             if (chA === "'" && chB === "\"") {
                 return -1;
             }
-            const cmp = ts.localeCompare(chA.toLocaleLowerCase(), chB.toLocaleLowerCase());
+            const cmp = ts.compareStrings(chA.toLocaleLowerCase(), chB.toLocaleLowerCase());
             if (cmp !== 0) {
                 return cmp;
             }