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Rollup merge of #82055 - JulianKnodt:ty_where_const, r=estebank

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Add diagnostics for specific cases for const/type mismatch err

For now, this adds at least more information so better diagnostics can be emitted for const mismatch errors.

I'm not sure what exactly we want to emit, so I've left notes there temporarily, also to see if this is the right approach

r? ```@lcnr```
cc: ```@estebank```
This commit is contained in:
Yuki Okushi 2021-02-18 15:57:26 +09:00 • committed by GitHub
commit 0c25d154bd
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6 changed files with 134 additions and 29 deletions
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65
compiler/rustc_typeck/src/astconv/generics.rs
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@ -6,8 +6,9 @@ use crate::astconv::{
use crate::errors::AssocTypeBindingNotAllowed;
use crate::structured_errors::{StructuredDiagnostic, WrongNumberOfGenericArgs};
use rustc_ast::ast::ParamKindOrd;
use rustc_errors::{struct_span_err, Applicability, ErrorReported};
use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorReported};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::DefId;
use rustc_hir::GenericArg;
use rustc_middle::ty::{
@ -43,23 +44,57 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
}
let add_braces_suggestion = |arg: &GenericArg<'_>, err: &mut DiagnosticBuilder<'_>| {
let suggestions = vec![
(arg.span().shrink_to_lo(), String::from("{ ")),
(arg.span().shrink_to_hi(), String::from(" }")),
];
err.multipart_suggestion(
"if this generic argument was intended as a const parameter, \
surround it with braces",
suggestions,
Applicability::MaybeIncorrect,
);
};
// Specific suggestion set for diagnostics
match (arg, &param.kind) {
(
GenericArg::Type(hir::Ty { kind: hir::TyKind::Path { .. }, .. }),
GenericParamDefKind::Const { .. },
) => {
let suggestions = vec![
(arg.span().shrink_to_lo(), String::from("{ ")),
(arg.span().shrink_to_hi(), String::from(" }")),
];
err.multipart_suggestion(
"if this generic argument was intended as a const parameter, \
try surrounding it with braces:",
suggestions,
Applicability::MaybeIncorrect,
);
}
GenericArg::Type(hir::Ty {
kind: hir::TyKind::Path(rustc_hir::QPath::Resolved(_, path)),
..
}),
GenericParamDefKind::Const,
) => match path.res {
Res::Err => {
add_braces_suggestion(arg, &mut err);
err.set_primary_message(
"unresolved item provided when a constant was expected",
)
.emit();
return;
}
Res::Def(DefKind::TyParam, src_def_id) => {
if let Some(param_local_id) = param.def_id.as_local() {
let param_hir_id = tcx.hir().local_def_id_to_hir_id(param_local_id);
let param_name = tcx.hir().ty_param_name(param_hir_id);
let param_type = tcx.type_of(param.def_id);
if param_type.is_suggestable() {
err.span_suggestion(
tcx.def_span(src_def_id),
"consider changing this type paramater to a `const`-generic",
format!("const {}: {}", param_name, param_type),
Applicability::MaybeIncorrect,
);
};
}
}
_ => add_braces_suggestion(arg, &mut err),
},
(
GenericArg::Type(hir::Ty { kind: hir::TyKind::Path(_), .. }),
GenericParamDefKind::Const,
) => add_braces_suggestion(arg, &mut err),
(
GenericArg::Type(hir::Ty { kind: hir::TyKind::Array(_, len), .. }),
GenericParamDefKind::Const { .. },