Type inference fails with braces in const generics

[araraloren]

rust-analyzer version: (eg. output of "rust-analyzer: Show RA Version" command, accessible in VSCode via Ctrl/⌘+Shift+P)

0.3.2719-standalone (87cf6631c6 2025-12-14)

rustc version: (eg. output of rustc -V)

rustc 1.92.0 (ded5c06cf 2025-12-08)

editor or extension: (eg. VSCode, Vim, Emacs, etc. For VSCode users, specify your extension version; for users of other editors, provide the distribution if applicable)

VScode

relevant settings: (eg. client settings, or environment variables like CARGO, RUSTC, RUSTUP_HOME or CARGO_HOME)

repository link (if public, optional): (eg. rust-analyzer)

https://github.com/araraloren/example

code snippet to reproduce:

https://github.com/araraloren/example/blob/main/src/main.rs

// add your code here
// trait definition 
    fn at_least<const M: usize>(self) -> Between<M, { usize::MAX }, C, Self> {
        self.between::<M, { usize::MAX }>()
    }

    fn at_most<const N: usize>(self) -> Between<0, N, C, Self> {
        self.between::<0, N>()
    }
// code
    let num = '9'.at_least::<1>();
    let ver = num.sep_once(".", num); // type inference failure

    let mut ctx = CharsCtx::new("");

    ctx.ctor(&ver)?;

    let num = '9'.at_most::<1>();
    let ver = num.sep_once(".", num); // okay

[ChayimFriedman2]

This is the same issue as #21315: somehow, the presence of the unevalutated const prevents method resolution from picking the method.

However I will close that one as a duplicate of this, and not the opposite, because this one has a nicer MRE (thank you for that!)

[dfireBird]

Can I take a stab at this if you're not working on this? (I want to go over the const lowering as well)

[ChayimFriedman2]

I'm not working on this currently, so feel free.

[ChayimFriedman2]

@dfireBird Also note that there are two separate things: making us to be able to infer & compute this constant, which is part of the larger work of unifying TyLoweringContext and InferenceContext, and figuring out why when the constant is not inferred we can't resolve the method.