Try adding originalKeywordKind to the prototype as an experiment.

Author: DanielRosenwasser

src/compiler/types.ts

@@ -1685,6 +1685,9 @@ export interface Identifier extends PrimaryExpression, Declaration, JSDocContain
     isInJSDocNamespace?: boolean;                             // if the node is a member in a JSDoc namespace
     /** @internal */ typeArguments?: NodeArray<TypeNode | TypeParameterDeclaration>; // Only defined on synthesized nodes. Though not syntactically valid, used in emitting diagnostics, quickinfo, and signature help.
     /** @internal */ jsdocDotPos?: number;                       // Identifier occurs in JSDoc-style generic: Id.<T>
+    /**
+     * @deprecated `originalKeywordKind` will be removed in the future.
+     */ readonly originalKeywordKind?: SyntaxKind;
     /**@internal*/ hasExtendedUnicodeEscape?: boolean;
 }
 

src/compiler/utilities.ts

@@ -7317,6 +7317,12 @@ function Identifier(this: Mutable<Node>, kind: SyntaxKind, pos: number, end: num
     (this as Identifier).flowNode = undefined;
 }
 
+Object.defineProperty(Identifier.prototype, "originalKeywordKind" satisfies keyof Identifier, {
+    get(this: Identifier) {
+        return stringToToken(this.escapedText as string);
+    }
+});
+
 function SourceMapSource(this: SourceMapSource, fileName: string, text: string, skipTrivia?: (pos: number) => number) {
     this.fileName = fileName;
     this.text = text;