bjoernager/rust
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Add help message for unused type param

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This commit is contained in:
kadmin 2021-05-01 04:39:50 +00:00
parent b52769b804
commit 50c86db4fa
22 changed files with 49 additions and 3 deletions
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15
compiler/rustc_typeck/src/check/wfcheck.rs
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@ -1298,12 +1298,14 @@ fn check_variances_for_type_defn<'tcx>(
match param.name {
hir::ParamName::Error => {}
_ => report_bivariance(tcx, param.span, param.name.ident().name),
_ => report_bivariance(tcx, param),
}
}
}
fn report_bivariance(tcx: TyCtxt<'_>, span: Span, param_name: Symbol) {
fn report_bivariance(tcx: TyCtxt<'_>, param: &rustc_hir::GenericParam<'_>) {
let span = param.span;
let param_name = param.name.ident().name;
let mut err = error_392(tcx, span, param_name);
let suggested_marker_id = tcx.lang_items().phantom_data();
@ -1318,7 +1320,14 @@ fn report_bivariance(tcx: TyCtxt<'_>, span: Span, param_name: Symbol) {
format!("consider removing `{}` or referring to it in a field", param_name)
};
err.help(&msg);
err.emit();
if matches!(param.kind, rustc_hir::GenericParamKind::Type { .. }) {
err.help(&format!(
"if you intended `{0}` to be a const parameter, use `const {0}: usize` instead",
param_name
));
}
err.emit()
}
/// Feature gates RFC 2056 -- trivial bounds, checking for global bounds that