expose escapeLeadingUnderscores

Fixes: microsoft#25343

Author: ajafff

src/compiler/utilities.ts

@@ -563,11 +563,6 @@ namespace ts {
         return isString(value) ? '"' + escapeNonAsciiString(value) + '"' : "" + value;
     }
 
-    // Add an extra underscore to identifiers that start with two underscores to avoid issues with magic names like '__proto__'
-    export function escapeLeadingUnderscores(identifier: string): __String {
-        return (identifier.length >= 2 && identifier.charCodeAt(0) === CharacterCodes._ && identifier.charCodeAt(1) === CharacterCodes._ ? "_" + identifier : identifier) as __String;
-    }
-
     // Make an identifier from an external module name by extracting the string after the last "/" and replacing
     // all non-alphanumeric characters with underscores
     export function makeIdentifierFromModuleName(moduleName: string): string {
@@ -4792,6 +4787,11 @@ namespace ts {
         return undefined;
     }
 
+    /** Add an extra underscore to identifiers that start with two underscores to avoid issues with magic names like '__proto__' */
+    export function escapeLeadingUnderscores(identifier: string): __String {
+        return (identifier.length >= 2 && identifier.charCodeAt(0) === CharacterCodes._ && identifier.charCodeAt(1) === CharacterCodes._ ? "_" + identifier : identifier) as __String;
+    }
+
     /**
      * Remove extra underscore from escaped identifier text content.
      *

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -3184,6 +3184,8 @@ declare namespace ts {
      * @returns The original parse tree node if found; otherwise, undefined.
      */
     function getParseTreeNode<T extends Node>(node: Node | undefined, nodeTest?: (node: Node) => node is T): T | undefined;
+    /** Add an extra underscore to identifiers that start with two underscores to avoid issues with magic names like '__proto__' */
+    function escapeLeadingUnderscores(identifier: string): __String;
     /**
      * Remove extra underscore from escaped identifier text content.
      *

tests/baselines/reference/api/typescript.d.ts

@@ -3184,6 +3184,8 @@ declare namespace ts {
      * @returns The original parse tree node if found; otherwise, undefined.
      */
     function getParseTreeNode<T extends Node>(node: Node | undefined, nodeTest?: (node: Node) => node is T): T | undefined;
+    /** Add an extra underscore to identifiers that start with two underscores to avoid issues with magic names like '__proto__' */
+    function escapeLeadingUnderscores(identifier: string): __String;
     /**
      * Remove extra underscore from escaped identifier text content.
      *