The rust compiler is permissive of f32 and f64 suffix

[philberty]

During development of gccrs it was found in PR Rust-GCC/gccrs#126 that the rust compiler is permissive of the float suffix on literals but the spec does not show this.

[ehuss]

Thanks for the PR! I think this is already covered in the floating point grammar:

DEC_LITERAL (. DEC_LITERAL)? FLOAT_EXPONENT? FLOAT_SUFFIX

Is there any particular reason to mention this as part of the integer grammar?

[Havvy]

The floating point grammar, as quoted by ehuss, is defined at https://doc.rust-lang.org/stable/reference/tokens.html#floating-point-literals

The changes in this PR are factually incorrect, but there is at least one change that can be made: Adding 5f32 (or any other whole number...) as an example in the examples list. If you want to do that, go for it.

[philberty]

Apologies if this is not the correct place to add this. When testing gccrs vs rust it was noticed that f32 and f64 suffix was allowed on integers abut the integer token spec didn't mention thus our lexer enforced that f32 and f64 was an invalid suffix for this integer token.

Maybe just adding f32 and f64 is enough to the list of accepted suffix types is enough for this change.

[ehuss]

f32 and f64 suffixes are already listed in the FLOAT_LITERAL production. f32 and f64 suffixed DEC_LITERAL values aren't integers. The grammar needs to be considered as a whole to understand what kind of lookahead is necessary to parse the text to differentiate between different rules.

[Havvy]

Since this PR is factually incorrect due to a misunderstanding of how to read the grammar, I am closing it.

Nonetheless, thanks for the attempt to help.