rust/compiler/rustc_infer/src/errors/mod.rs

use rustc_macros::Diagnostic;
use rustc_span::Span;

#[derive(Diagnostic)]
#[diag(infer_opaque_hidden_type)]
pub struct OpaqueHiddenTypeDiag {
    #[primary_span]
    #[label]
    pub span: Span,
    #[note(infer_opaque_type)]
    pub opaque_type: Span,
    #[note(infer_hidden_type)]
    pub hidden_type: Span,
}