Function argument names are lost in .d.ts files

[Vlad-Shcherbina]

To reproduce:

1. Check out the recent version:

   git clone [email protected]:rustwasm/wasm-bindgen.git
   cd wasm-bindgen
   git checkout eaaf3461
   

2. Run without-a-bundler example:

   cd .\examples\without-a-bundler\
   cargo build --target wasm32-unknown-unknown --release
   mkdir pkg
   cargo run --manifest-path ../../crates/cli/Cargo.toml --bin wasm-bindgen -- ../../target/wasm32-unknown-unknown/release/without_a_bundler.wasm --out-dir pkg --browser
   

These commands are from build.sh, except I was running them on Windows.

4. Examine pkg/*.d.ts files.

Expected

These files to contain meaningful function signatures like function add(a: number, b: number): number.

Actual

The file pkg/without_a_bundler_bg.d.ts is as expected.
The file pkg/without_a_bundler.d.ts, however, contains the following:

/* tslint:disable */
/**
* @returns {void} 
*/
export function main(): void;
/**
* @param {number} arg0 
* @param {number} arg1 
* @returns {number} 
*/
export function add(arg0: number, arg1: number): number;

Argument names are lost and replaced with arg0, arg1.

---

It is important for the latter file to contain useful function signatures, because that's the definition file that will be used by TypeScript when importing the wrapper module without_a_bundler.js.

[alexcrichton]

Thanks for the report! I think this is a duplicate of #1129 so I'm going to close this in favor of that