string-iterator-helpers.ts:3:7 - error SC2020: 'IteratorObject<string, undefined, unknown>' is part of the standard library types but has no scriptc lowering yet

  2 | // refused instead of failing at run time.
  3 | const upper = "abc"[Symbol.iterator]().map((c) => c.toUpperCase());
    |       ^~~~~
  4 | 

  hint: the type checker sees the full standard library, but only the supported surface compiles (https://scriptc.dev/limitations)

string-iterator-helpers.ts:3:15 - error SC2020: 'StringIterator.map' is part of the standard library types but has no scriptc lowering yet

  2 | // refused instead of failing at run time.
  3 | const upper = "abc"[Symbol.iterator]().map((c) => c.toUpperCase());
    |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  4 | 

  hint: iterator helpers lower on chains from arr.values() or arr.entries() that end in a terminal (toArray, forEach, reduce, some, every, find) — spread the string first: [...s].values()