3 ms·

> by explicitly annotating `promisedString` you are widening the type from the inferred `number` to `any` That's something I don't understand. Isn't that incor

• WorldMaker 9y ago
  TS is trying to unify RHS and LHS. TS follows a somewhat complicated widening process to unify unannotated generics, somewhat leaning towards ease of use over strictness. Adding additional strictness checks like noImplicitAny can help catch these situation. (In this case, it doesn't help, because the resolve argument is inferred `resolve: (value: any) => void` rather than `resolve: any` which would give a clear implicit any error. Inferred any in generic callbacks sound like a good strictness test to add...) In this case in Typescript it is generally more strict to add a type annotation to the generic than the LHS: let promise = new Promise<string>((resolve) => resolve(42)) // This won't work This is as much because the inference here that matters isn't between LHS and RHS but between generic arguments and function return inference.