Bug Report

An d.ts file containing an undeclared typename is generated when a generic typename bound to a function container is rebound to a nested function definition which is used as part of the outer function's return type.

🔎 Search Terms

declaration emit bound shadow undeclared typename

🕗 Version & Regression Information

4.3.5 does not exhibit, but 4.4.4+ does (as per the playground)
as of $now it is also present in nightly on the playground

• This changed between versions 4.3.5 and 4.4.4

⏯ Playground Link

Playground link with relevant code

💻 Code

function foo<T>(v:T) {
    function x<T>(v: T) { return v; }
    function y() : T { return v; }
    return {
        x, // decl emit: <T_1>(v:T_1) => T_1
        y  // decl emit: () => T_2 // can't find name 'T_2'
    };
}

🙁 Actual behavior

error in declaration file

🙂 Expected behavior

no error in declaration file
(or error at compile time if you want to not allow shadowing like this.