`typescript.d.ts` uses ES2015+ globals (`Map`, `ReadonlyMap`) without `/// <reference lib>` directive

[baraknaveh]

TypeScript's own typescript.d.ts uses Map and ReadonlyMap without a /// <reference lib="es2015" /> directive. This causes type errors when the file is checked outside of a tsconfig scope that includes ES2015+ lib types.

Examples in typescript@5.9.3 (lib/typescript.d.ts):

// line 2589
abstract readonly typesRegistry: Map<string, MapLike<string>>;

// line 6592-6596
type ReadonlyUnderscoreEscapedMap<T> = ReadonlyMap<__String, T>;
type UnderscoreEscapedMap<T> = Map<__String, T>;
type SymbolTable = Map<__String, Symbol>;

Suggested fix: Add /// <reference lib="es2015" /> at the top of lib/typescript.d.ts.

[jakebailey]

Isn't this extremely typical? Effectually no published library code on npm includes references to make sure that something like Map is available. In fact, we don't even preserve reference directives from user code in emit unless explicitly annotated with preserve="true".

I don't think there's anything to fix here. If this happens, the compiler error very clearly says what to do.

(And who is really checking against ES5? The default in 6.0 is ES2025!)