Class expression async method infers void return, rejecting return <value> (both modes)

[nickna]

A class expression async method whose body returns a value is rejected because its return type is inferred as void. The equivalent class declaration infers the return correctly.

Repro

const C = class { async m() { return 5; } };
(new C().m() as Promise<number>).then(v => console.log(v));

Type Error: Type '5' is not assignable to type 'void'

Contrast — the class declaration form works (prints 5):

class C { async m() { return 5; } }
(new C().m() as Promise<number>).then(v => console.log(v));   // 5 ✓

Notes

• Reproduces in both the interpreter and compiled mode (it is a type-checker inference gap, so it is independent of back end).
• The class-expression method path does not infer a method's return type from its body the way the class-declaration path does — it defaults to void, so any return <value> then fails TS2322.
• Found while scoping Compiled mode: computed symbol-keyed class method follow-ups (#647) #755 (compiled class-expression follow-ups). Independent of that change.