Wrong macro expansion #20480
Description
I wrote a macro that compiles flawlessly. Then I tested it with the new r-a trait solver, and was surprised to see it failing.
After some investigation, I found out that the macro expansion seems to cut off early.
rust-analyzer version: rust-analyzer version: 0.4.2579-standalone (b2a58b8 2025-08-12) [c:\Users\Stefnotch.vscode\extensions\rust-lang.rust-analyzer-0.4.2579-win32-x64\server\rust-analyzer.exe]
rustc version: rustc 1.91.0-nightly (2e2642e 2025-08-16)
editor or extension: VSCode, current nightly version of r-a
relevant settings:
"rust-analyzer.diagnostics.experimental.enable": true,
code snippet to reproduce:
The following code compiles. However, r-a complains expected Box<dyn DemoTrait, Global>, found Box<ThisDoesNot, Global>rust-analyzer E0308
pub trait DemoTrait {}
pub struct ThisWorks;
pub struct ThisDoesNot;
macro_rules! mod_items {
( $( Foobar $( $ast:ty)? ),+ ) => {
$(
$(impl DemoTrait for $ast {})+
)?
};
}
fn testo() {
let a: Box<dyn DemoTrait> = Box::new(ThisWorks);
let a: Box<dyn DemoTrait> = Box::new(ThisDoesNot);
}
mod_items! {
Foobar ThisWorks,
Foobar ThisDoesNot
}When looking at the macro expansion (F1 expand macro recursively), one only gets
// Recursive expansion of mod_items! macro
// ========================================
impl DemoTrait for ThisWorks {}
what expansion was expected
// Recursive expansion of mod_items! macro
// ========================================
impl DemoTrait for ThisWorks {}
impl DemoTrait for ThisDoesNot {}