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Inconsistent treatment of non-widening string literal types and += #13865
Description
TypeScript Version: 2.1.5
I'm seeing some inconsistent and confusing behavior regarding non-widening string literal types.
The type checker treats ... += ... differently than ... = ... + ... which looks like a bug to me.
Code:
Example 1:
const empty: "" = "";
let foo = empty;
foo += "bar"; // OKExample 2:
const empty: "" = "";
let foo = empty;
foo = foo + "bar"; // Error: Type 'string' is not assignable to type '""'.Expected behavior: Either both examples type-check correctly or none of them do.
Actual behavior: Example 1 type-checks correctly while Example 2 doesn't.
Activity
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