diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_typeck/src/impl_wf_check.rs | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/compiler/rustc_typeck/src/impl_wf_check.rs b/compiler/rustc_typeck/src/impl_wf_check.rs index 891e482b431..4901d6041d6 100644 --- a/compiler/rustc_typeck/src/impl_wf_check.rs +++ b/compiler/rustc_typeck/src/impl_wf_check.rs @@ -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. |