Respect the f32 and f64 suffix on literals

[philberty]

Rust is permissive for integers being marked as floats so the check in the lexer can be removed here.

[SimplyTheOther]

PR looks great. I had one query about whether integers given a float type hint are actually treated as floats, or whether they are treated as integers with the type hint being ignored (or complained about during type check or whatever).

[SimplyTheOther]

The code below here (the make_int) would be incorrect (assuming that an integer with a type hint of a float type is treated as a float). What should happen instead is that make_float is called if the type hint is 'f32' or 'f64', while 'make_int' should be called otherwise. This is assuming that I have understood the spec properly.

I suppose it depends on whether rust is actually permissive on integers being marked as floats (i.e. allows integers to be given a float type hint) or whether the float type hint means that the integer is treated as a float.

If my interpretation is wrong, feel free to ignore this.

[philberty]

Yeah this was not clear from the spec to me either. From testing the rust compiler i found this is permissive:

fn main() {
    let a: i32 = 5i32;
    let b: f32 = 5f32;
}

Without this change we determine:

float1.rs:3:18: error: invalid type suffix ‘f32’ for integer (decimal) literal
    3 |     let b: f32 = 5f32;
      |   

[philberty]

What if i split this change into two parts one where we support f32 and f64 suffix but remove this integer support for float suffix as a separate PR

[bjorn3]

Yeah this was not clear from the spec to me either.

It may be a good idea to document this kind of things in the reference (https://github.com/rust-lang/reference/), so other alternative implementations don't have to discover it again.

[philberty]

I've created rust-lang/reference#922