Closed
Description
TypeScript Version: No issue in 3.0.3, broken in both 3.2.2 and 3.3.0-dev.20190112 (using tsconfig from tsc --init)
Search Terms: unrelated, nondeterministic, mapped type, generic
Code
I'm sorry, I couldn't manage to reduce this further since it disappears when the code is too simple (probably some checking depth limitation?)
// when I replace this import by just inlining the corresponding types,
// the error disappears
import { TypeOf, Type } from "io-ts";
type ToB<S extends any> = { [k in keyof S]: TypeOf<S[k]> };
type ToA<S> = { [k in keyof S]: Type<S[k]> };
type NeededInfo<MyNamespaceSchema = {}> = {
ASchema: ToA<MyNamespaceSchema>;
};
export const ASchema = {
initialize: null as any
};
export type MyInfo = NeededInfo<ToB<typeof ASchema>>;
const tmp1: MyInfo = null!;
function tmp2<N extends NeededInfo>(n: N) {}
// tmp2(tmp1); // uncommenting this line removes a type error from a completely unrelated line ??
class Server<X extends NeededInfo> {}
export class MyServer extends Server<MyInfo> {} // not assignable error at `MyInfo`Expected behavior: No type error regardless of whether the line //tmp2(tmp1) is commented or not.
Actual behavior:
When that line is commented out, I get a type error in the export class line, which is completely unrelated:
[ts]
Type 'NeededInfo<ToB<{ initialize: any; }>>' does not satisfy the constraint 'NeededInfo<{}>'.
Types of property 'ASchema' are incompatible.
Type 'ToA<ToB<{ initialize: any; }>>' is not assignable to type 'ToA<{}>'.
Type '{}' is not assignable to type 'ToB<{ initialize: any; }>'. [2344]
Playground Link: Impossible because it stops happening when Type and TypeOf are inlined.
I know the above code looks dumb, but trust me this is causing weird breakage in a large code base.