Missing type layout information in nightly for stdlib generic types

[mischnic]

rust-analyzer version: rust-analyzer version: 1.96.0-nightly (3102493c 2026-03-12) [/Users/niklas/.rustup/toolchains/nightly-2026-03-13-aarch64-apple-darwin/bin/rust-analyzer]

rustc version: nightly-2026-03-13

editor or extension: vscode with 0.3.2819

relevant settings:

[toolchain]
channel = "nightly-2026-03-13"
components = ["rustfmt", "clippy", "rust-analyzer"]
profile = "minimal"

repository link: https://github.com/mischnic/rust-analyzer-generic-size-nightly

code snippet to reproduce:

use std::num::NonZero;

pub struct Test<K, T = u8> {
    pub k: K,
    pub t: T,
}

// "needs Drop"
pub struct X {
    pub a: Vec<u32>,     // "needs Drop"
    pub b: NonZero<i32>, // "no Drop"
    pub c: u32,          // "size = 4, align = 0x4, no Drop"
    pub d: Test<i32>,    // "size = 8, align = 0x4, no Drop"
}

fn main() {
    // "size = 8, align = 0x4, no Drop"
    let _x = Test { k: 42, t: 255 };

    // "no Drop"
    let _y = std::num::NonZero::new(1i32).unwrap();
    println!("Hello, world!");
}

When using a recent nightly version, the hover menu doesn't compute the size/alignment/layout information for generic types from the standard library. Locally-declared generic types work fine though.

With channel = "1.94.0", all these types are correctly computed.
1.95.0-beta.3 is broken as well

[mischnic]

Looks like nightly versions using pattern types for NonZero<T> broke it: rust-lang/rust#148537

So this is the problem:

rust-analyzer/crates/hir-ty/src/layout.rs

Lines 356 to 359 in 6254616

	TyKind::Pat(_, _) | TyKind::UnsafeBinder(_) => {
	return Err(LayoutError::NotImplemented);
	}

[mischnic]

Here'a currently failing test for crates/ide/src/hover/tests.rs

#[test]
fn hover_pattern_types() {
    check(
        r#"
struct NonZeroU8Pattern(u8 is 1..);

fn main() {
    let zz$0 = NonZeroU8Pattern(1);
}"#,
        expect![[r#"
            *zz*

            ```rust
            let zz: NonZeroU8Pattern
            ```

            ---

            size = 1, align = 0x1, no Drop
        "#]],
    );
}

[ChayimFriedman2]

Right, we need to implement pattern types layout.

[Veykril]

Ugh that got split out of the original PR so I missed this happening, we probably need to backport a change as well (if we manage to fix this by the time 1.95 releases). Then again, this just prevents layout compute, not giving false layouts so its not that bad i guess

[mischnic]

Yeah, it's not critical.
I noticed this because in my codebase, almost all types transitively contain a NonZero<u32>, so I basically never get layouts displayed anymore now.

[Veykril]

We should be able to implement this nowadays, back then it was blocked on a rewrite (that has now happened)