Preserve argument names

[c410-f3r]

Part of #1129.

• Closures aren't supported.
• Still not sure about

  wasm-bindgen/crates/backend/src/codegen.rs

  Line 426 in e075d04

  let ident = Ident::new(&format!("arg{}", i), Span::call_site());

  and

  wasm-bindgen/crates/cli-support/src/js/rust2js.rs

  Line 95 in e075d04

  fn shim_argument(&mut self) -> String {

  .

[alexcrichton]

This is looking pretty good to me, thanks for this! Can you also manually confirm that the names of the arguments for TypeScript are coming through as well?

I think it's reasonable to avoid naming arguments for closures since in general they don't have names, and shim_argument can be safely ignored because it's largely just used for auxiliary internal purposes rather than public-facing-API purposes

[alexcrichton]

If possible it'd be great to use &'a str here to allow the encoder/decoder to be pretty lean and avoid the extra String allocations

[c410-f3r]

I wish! syn's Ident doesn't expose &str and only implements ToString.

[c410-f3r]

Can you also manually confirm that the names of the arguments for TypeScript are coming through as well?

[alexcrichton]

Ok thanks for checking and clarifying about String, thanks again for the PR!