Glsl error message improvements

[jakobhellermann]

Before:

After:

[JCapucho]

Besides my personal hate for error reporting in libraries there are some problems especially with the expected case in the InvalidToken error (which should probably be renamed to UnexpectedToken), great work nonetheless :)

Also I think that in the long run we should rename ParseError to Error and add a meta field to it so that all errors are forced to have metadata information, but that's for another PR.

[jakobhellermann]

I personally don't like the library being responsible for error reporting

I'm fine with removing the codespan reporting from this PR and having it just provide more context to the errors, I agree that it isn't really the responsibility of the library.

Currently the wgsl frontend also has emit_to_stderr and emit_to_string functions, do you think they should be moved to bin/naga.rs instead?

[JCapucho]

I personally don't like the library being responsible for error reporting

I'm fine with removing the codespan reporting from this PR and having it just provide more context to the errors, I agree that it isn't really the responsibility of the library.

Currently the wgsl frontend also has emit_to_stderr and emit_to_string functions, do you think they should be moved to bin/naga.rs instead?

No need to remove it, it's just my personal opinion and the other maintainers already showed support for it being included in the library and it's already included in wgsl as you said but I think we should at least make it optional since some end users may only want to compile their already known working shaders and bringing in another dependency would only increase their compile times with no real benefit

[kvark]

Thank you! Changes look reasonable. Let's get @JCapucho having another look.

[JCapucho]

I would like to fix the way the expected tokens are handled in invalid token before merging

[JCapucho]

I'm sorry I didn't express my intent clearly but when I meant a list of tokens I was talking about a literal Vec<Token>

[JCapucho]

Looks good to me, let's just have @kvark take a look, I'm going to squash this afterward unless you want to rebase the broken commits with the ci fixes

[jakobhellermann]

I rebased the commits.

[JCapucho]

I've double checked the PR and found some small things but we can merge it anyways and fix it later

[JCapucho]

Please fix CI and if possible squash the last commit and I'll merge this

[JCapucho]

Thank you for your contribution