Error linting project using wasm-bindgen on nighlty

[alexlapa]

cargo clippy --all -- -D clippy::pedantic -D warnings is ok

running cargo +nightly clippy --all -- -D clippy::pedantic -D warnings produces:

error: integer type suffix should be separated by an underscore
  --> jason/src/api/connection.rs:28:1
   |
28 | #[wasm_bindgen]
   | ^^^^^^^^^^^^^^^ help: add an underscore: `#[wasm_bindg_u32`
   |
   = note: `-D clippy::unseparated-literal-suffix` implied by `-D clippy::pedantic`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unseparated_literal_suffix

cargo clippy -V 
clippy 0.0.212 (e3cb40e 2019-06-25)

cargo +nightly clippy -V
clippy 0.0.212 (aeadf15 2019-09-03)

Reproduction.

[flip1995]

cc #4421 @lzutao

It seems that

if let Some(firstch) = src.chars().next();
if char::to_digit(firstch, 10).is_some();

was necessary. I think, we should add this back in, instead of the

rust-clippy/clippy_lints/src/misc_early.rs

Lines 434 to 439 in c3d4294

	let lit_snip = match snippet_opt(cx, lit.span) {
	Some(snip) => {
	// The snip could be empty in case of expand from procedure macro
	if snip.is_empty() || snip.contains('!') {
	return;
	}

hack. But this time we should document, why this exists.

[tesuji]

I added it back in #4510. But unfortunately, proc-macro is out of my league.
It would be nice if someone could add a regression test for this.

[flip1995]

@alexlapa Can you provide a minimal reproducible example or share the code this lint triggered on?

[alexlapa]

@flip1995 ,

Sure. https://github.com/alexlapa/rust-clippy-4507-reproduction

[flip1995]

Thanks! Extract from expanded code:

        // ...
        unsafe fn __wbg_foo_new(_: u32) -> u32 {
            {
                ::std::rt::begin_panic("cannot convert to JsValue outside of the wasm target",
                                       &("src/lib.rs", 3u32, 1u32))
            }
        }
        // ...

It seems, we only have to write a proc macro which produces code with 0u32 (or similar) in it. This should be easily done by extending

rust-clippy/mini-macro/src/lib.rs

Lines 7 to 8 in 9672a04

	#[proc_macro_derive(ClippyMiniMacroTest)]
	pub fn mini_macro(_: TokenStream) -> TokenStream {

@lzutao do you want to take a shot at this? Otherwise I can add a test case to the PR this weekend.

[tesuji]

Fixed in #4510.