name of non-Rpitit assoc item error
#140259
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C-bug
Category: This is a bug.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
S-has-mcve
Status: A Minimal Complete and Verifiable Example has been found for this issue
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
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veigaribo
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reduction: trait ServerFn {
type Output;
fn run_body() -> impl Sized;
}
struct MyServerFn {}
macro_rules! f {
() => {
impl ServerFn for MyServerFn {
type Output = ();
fn run_body() -> impl Sized {}
}
};
}
f! {}
fn problem<T: ServerFn<Output = i64>>(_: T) {}
fn main() {
problem(MyServerFn {});
}@rustbot label S-has-mcve |
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matthiaskrgr
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Apr 25, 2025
…son, r=nnethercote Don't use item name to look up associated item from trait item This fix should be self-justifying b/c the fact that we were using identifiers here was kinda sus anyways, esp b/c we have a failproof way of doing the comparison :) I'll leave some info about why this repro needs a macro. Fixes rust-lang#140259 r? `@nnethercote`
rust-timer
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Apr 25, 2025
Rollup merge of rust-lang#140278 - compiler-errors:name-based-comparison, r=nnethercote Don't use item name to look up associated item from trait item This fix should be self-justifying b/c the fact that we were using identifiers here was kinda sus anyways, esp b/c we have a failproof way of doing the comparison :) I'll leave some info about why this repro needs a macro. Fixes rust-lang#140259 r? `@nnethercote`
jieyouxu
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I've encountered a compiler error in the latest rustc nightly (2025-04-23) and made a somewhat small reproduction example. It is, however, far from minimal, unfortunately. If I substitute the code, which contains macros, for the version with the macros expanded, and naively sidestep some issues I don't quite understand, the error seems to stop happening. It is possible this bug is related to something else, but, since it is on the latest nightly, I would assume it hasn't been addressed yet.
Code
I've got a Cargo project at https://github.com/veigaribo/rust-rpitit-error/.
Analyzing
src/main.rs, the definition ofMyServerFnError(up to line 24) is mostly noise so that I can create a server function in line 26/27. That server function expands to a function with the same name, but also to a struct with pascal case naming (MyServerFnin this case) that implements theServerFntrait, defined here: https://github.com/leptos-rs/leptos/blob/2b50ddc0db85e12c7667a938ad5ce8c563da3f1b/server_fn/src/lib.rs#L216.The error happens when I create a function (
problemin this case) with a parameter bounded onServerFnwith an specific associated type (Outputin this case) set to some type, and then I invoke that function with aServerFntype that does not satisfy that associated type (line 34).ServerFnseems to carry some significance.ServerFnmanually, and, as previously stated, I also could not reproduce the problem with the macros expanded. So theservermacro may carry some significance too. It is defined at https://github.com/leptos-rs/leptos/blob/2b50ddc0db85e12c7667a938ad5ce8c563da3f1b/leptos_macro/src/lib.rs#L925.Meta
rustc --version --verbose:Error output
Output of
cargo runBacktrace
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