Typescript: Emit with name-colliding helper functions is incorrect when target >=ES2015

TypeScript Version: 3.6.3

Search Terms: helper rename

Code

// @target: es2015

declare function __awaiter(): void;
class C {
    async func() {
    }
}

Expected behavior:
Some sort of error is emitted (when the target requires the helper) notifying the user that the generated code will not work OR maybe the helper is emitted with an alternative name.

Actual behavior:
The emit declares an __awaiter function, but attempts to call __awaiter_1.

Playground Link: here

Related Issues: