add Range::new_from_bounds

[robtfm]

when working with naga IR i've found i need to be able to construct Ranges (specifically for Statement::Emit which can't be constructed otherwise). it is possible currently, but only via serde hacking.

i added a Range::new_from_bounds method to allow construction.

first PR, apologies if i missed any standard process.

[teoxoy]

i need to be able to construct Ranges (specifically for Statement::Emit which can't be constructed otherwise).

What about using Arena.range_from? That's what we use in our front-ends.

[robtfm]

thanks, i could work with that if i had to, but it's a bit awkward as i'm not building statements and expressions in tandem.

my context is i am removing parts of naga modules, so i iterate through determining my filter for the various parts, then rebuild expressions and blocks (etc) separately afterwards. i guess i could rework it if you're opposed to adding this.

[teoxoy]

I see, so you are using this serde_range "hack" to do this.