bjoernager/rust
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Add regression test and help note

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This commit is contained in:
kadmin 2020-09-06 04:34:20 +00:00
parent cdc8f0606d
commit ee55c1f1d2
3 changed files with 52 additions and 5 deletions
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18
compiler/rustc_typeck/src/impl_wf_check.rs
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@ -187,7 +187,7 @@ fn enforce_impl_params_are_constrained(
}
// (*) This is a horrible concession to reality. I think it'd be
// better to just ban unconstrianed lifetimes outright, but in
// better to just ban unconstrained lifetimes outright, but in
// practice people do non-hygenic macros like:
//
// ```
@ -207,7 +207,7 @@ fn enforce_impl_params_are_constrained(
}
fn report_unused_parameter(tcx: TyCtxt<'_>, span: Span, kind: &str, name: &str) {
struct_span_err!(
let mut err = struct_span_err!(
tcx.sess,
span,
E0207,
@ -215,9 +215,17 @@ fn report_unused_parameter(tcx: TyCtxt<'_>, span: Span, kind: &str, name: &str)
impl trait, self type, or predicates",
kind,
name
)
.span_label(span, format!("unconstrained {} parameter", kind))
.emit();
);
err.span_label(span, format!("unconstrained {} parameter", kind));
if kind == "const" {
err.note(
"expressions using a const parameter must map each value to a distinct output value",
);
err.note(
"proving the result of expressions other than the parameter are unique is not supported",
);
}
err.emit();
}
/// Enforce that we do not have two items in an impl with the same name.