Bump walrus to v0.20

[daxpedda]

Just checking what CI says for now.

Fixes #2389.

[daxpedda]

Thank you @Liamolucko for solving the discovered issue in rustwasm/walrus#245.

[daxpedda]

So I did try the new DWARF debugging support, but it fails pretty fast for me:

fn main() {
    panic!("test");
}

cargo build --target wasm32-unknown-unknown
wasm-bindgen target/wasm32-unknown-unknown/debug/test.wasm --target web --keep-debug

thread 'main' panicked at 'assertion failed: self.row.address_offset >= self.prev_row.address_offset', /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/gimli-0.26.2/src/write/line.rs:469:9
stack backtrace:
   0: rust_begin_unwind
             at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/std/src/panicking.rs:578:5
   1: core::panicking::panic_fmt
             at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panicking.rs:67:14
   2: core::panicking::panic
             at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/panicking.rs:117:5
   3: gimli::write::line::LineProgram::op_advance
             at /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/gimli-0.26.2/src/write/line.rs:469:9
   4: gimli::write::line::LineProgram::end_sequence
             at /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/gimli-0.26.2/src/write/line.rs:338:26
   5: walrus::module::debug::dwarf::ConvertContext<R>::convert_line_program
             at /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/walrus-0.20.1/src/module/debug/dwarf.rs:210:33
   6: walrus::module::debug::dwarf::ConvertContext<R>::convert_attributes
             at /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/walrus-0.20.1/src/module/debug/dwarf.rs:47:36
   7: <walrus::module::debug::ModuleDebugData as walrus::emit::Emit>::emit
             at /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/walrus-0.20.1/src/module/debug/mod.rs:217:17
   8: walrus::module::Module::emit_wasm
             at /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/walrus-0.20.1/src/module/mod.rs:368:13
   9: wasm_bindgen_cli_support::Output::_emit
             at /home/user/rust/wasm-bindgen/crates/cli-support/src/lib.rs:655:26
  10: wasm_bindgen_cli_support::Output::emit
             at /home/user/rust/wasm-bindgen/crates/cli-support/src/lib.rs:648:9
  11: wasm_bindgen_cli_support::Bindgen::generate
             at /home/user/rust/wasm-bindgen/crates/cli-support/src/lib.rs:306:9
  12: wasm_bindgen::rmain
             at /home/user/rust/wasm-bindgen/crates/cli/src/bin/wasm-bindgen.rs:155:5
  13: wasm_bindgen::main
             at /home/user/rust/wasm-bindgen/crates/cli/src/bin/wasm-bindgen.rs:87:21
  14: core::ops::function::FnOnce::call_once
             at /rustc/90c541806f23a127002de5b4038be731ba1458ca/library/core/src/ops/function.rs:250:5

[daxpedda]

Took me some time to figure out how exactly Wasm DWARF debugging in the browser works in general, but got it to work.
The bug described before can just be skipped by running in release mode, because it's just a debug_assert!.

[daxpedda]

I did some more research on this today and I think this generally works out.
Chrome doesn't require source maps but Firefox does, which was part of the initial confusion I had at first.

I'm concerned about the debug_assert! we are hitting above, but I don't know much about the details here.
@guybedford would you mind taking a look at that?
Let me know if I can do anything to help.

[daxpedda]

Currently stuck on rustwasm/walrus#247.

[d3lm]

Any updates on this? CC @guybedford

[guybedford]

Walrus 0.20.2 has just been released thanks to @nokotan which looks like it should now resolve this issue.

[daxpedda]

Thanks @guybedford for the ping!
Thanks @nokotan for fixing this!

[d3lm]

Thank you all! This is awesome 🔥

[d3lm]

Is there a chance to get a new version published with this?

[daxpedda]

Currently waiting for an outcome on #3709, then I'm happy to push for a new release.