Compilation error non-primitive cast: '(f64, f64)' as '(f32, f32)' in function returning struct

[JakubKoralewski]

Found this error while using SDrawer from Surrealism UI.

Error

cargo run
   Compiling slint-non-primitive-cast-f64-f64-f32-f32-repro v0.1.0 (D:\...\slint-non-primitive-cast-f64-f64-f32-f32-repro)
error[E0605]: non-primitive cast: `(f64, f64)` as `(f32, f32)`
   --> D:\...\slint-non-primitive-cast-f64-f64-f32-f32-repro\target\debug\build\slint-non-primitive-cast-f64-f64-f32-f32-repro-1d21787b4cb0939a\out\appwindow.rs:466:14
    |
466 | /              ({
467 | |                  (0f64 , 100f64 ,) }
468 | |             ) as _ }
    | |__________________^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object

For more information about this error, try `rustc --explain E0605`.
error: could not compile `slint-non-primitive-cast-f64-f64-f32-f32-repro` (bin "slint-non-primitive-cast-f64-f64-f32-f32-repro") due to 1 previous error

Code

import { VerticalBox } from "std-widgets.slint";

export component AppWindow inherits Window {
    function default-height-width()->{height:percent,width:percent} {
        {height: 0%, width: 100%}
    }
    VerticalBox {
        height: default-height-width().height;
        width: default-height-width().width;
    }
}

Versions

$ rustup toolchain list  
nightly-x86_64-pc-windows-msvc (default)
$ cargo --version
cargo 1.82.0-nightly (2f738d617 2024-08-13)
$ rustc --version
rustc 1.82.0-nightly (506052d49 2024-08-16)
> ver
Microsoft Windows [Version 10.0.19045.4780]

Same on stable

> rustup toolchain list
stable-x86_64-pc-windows-msvc (default)
> rustc --version
rustc 1.80.1 (3f5fd8dd4 2024-08-06)
> cargo --version
cargo 1.80.1 (376290515 2024-07-16)

Same on WSL

$ rustup toolchain list
stable-x86_64-unknown-linux-gnu (default)
$ rustc --version
rustc 1.80.1 (3f5fd8dd4 2024-08-06)
$ cargo --version
cargo 1.80.1 (376290515 2024-07-16)
$ uname -a
Linux DESKTOP-NI12FI7 5.15.133.1-microsoft-standard-WSL2 #1 SMP Thu Oct 5 21:02:42 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

Repo

repro repo https://github.com/JakubKoralewski/slint-non-primitive-cast-f64-f64-f32-f32-repro

Notes

Seems to work on slintpad. Same error with return keyword.

Fixed when using named struct:

struct Size {
    width: percent,
    height: percent
}

export component AppWindow inherits Window {
    function default-height-width()->Size {
        return {height: 0%, width: 100%};
    }
    VerticalBox {
        height: default-height-width().height;
        width: default-height-width().width;
    }
}

[ogoffart]

Thanks for the bug report.
I can reproduce, and the fix is in #5889