[Literals][Indexes][Type assertion] Is that a bug? #14093
Description
Literal types related topics & conversations
Related to this issue PR that regulates literal type inference and its behavior in self-type changing can be found here: #10676
TypeScript Version: 2.1.6
Code
interface T {[key: string]: 'literal'} let FOO: (obj: T) => T; let DOOMED = { prop:'literal' } // DOOMED.prop === 'string' but not the literal FOO(DOOMED) // fails as expected FOO(<T>DOOMED) // fails FOO(DOOMED as T) // fails! let SAVED: T = { prop:'literal' } FOO(SAVED) // okExpected behavior:
Type assertion is expected to work in both cases <> and as but doesn't
Actual behavior:
Fails
Error:
FOO(<T>DOOMED) // fails ~~~~~~~~~ error TS2352: Type '{ prop: string; }' cannot be converted to type 'T'. Property 'prop' is incompatible with index signature. Type 'string' is not comparable to type '"literal"'. FOO(DOOMED as T) // fails! ~~~~~~~~~~~ error TS2352: Type '{ prop: string; }' cannot be converted to type 'T'.