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Add note about wrapping in braces

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Previously it was not clear why this errored or if it was even supported, as there was no
diagnostic that suggested wrapping it in braces.

Thus, add a simple diagnostic that suggests wrapping enum variants in braces.
This commit is contained in:
kadmin 2022-12-30 05:09:09 +00:00
parent 2c7536eaae
commit 077fae94a1
3 changed files with 70 additions and 10 deletions
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29
compiler/rustc_hir_analysis/src/astconv/mod.rs
View File

@ -1199,17 +1199,26 @@ fn add_predicates_for_ast_type_binding(
(_, _) => {
let got = if let Some(_) = term.ty() { "type" } else { "constant" };
let expected = def_kind.descr(assoc_item_def_id);
let reported = tcx
.sess
.struct_span_err(
let mut err = tcx.sess.struct_span_err(
binding.span,
&format!("expected {expected} bound, found {got}"),
);
err.span_note(
tcx.def_span(assoc_item_def_id),
&format!("{expected} defined here"),
);
if let hir::def::DefKind::AssocConst = def_kind
&& let Some(t) = term.ty() && (t.is_enum() || t.references_error())
&& tcx.features().associated_const_equality {
err.span_suggestion(
binding.span,
&format!("expected {expected} bound, found {got}"),
)
.span_note(
tcx.def_span(assoc_item_def_id),
&format!("{expected} defined here"),
)
.emit();
"if equating a const, try wrapping with braces",
format!("{} = {{ const }}", binding.item_name),
Applicability::HasPlaceholders,
);
}
let reported = err.emit();
term = match def_kind {
hir::def::DefKind::AssocTy => {
tcx.ty_error_with_guaranteed(reported).into()

18
src/test/ui/const-generics/assoc_const_eq_diagnostic.rs Normal file
View File

@ -0,0 +1,18 @@
#![feature(associated_const_equality)]
pub enum Mode {
Cool,
}
pub trait Parse {
const MODE: Mode;
}
pub trait CoolStuff: Parse<MODE = Mode::Cool> {}
//~^ ERROR expected associated constant bound
//~| ERROR expected type
fn no_help() -> Mode::Cool {}
//~^ ERROR expected type, found variant
fn main() {}

33
src/test/ui/const-generics/assoc_const_eq_diagnostic.stderr Normal file
View File

@ -0,0 +1,33 @@
error[E0573]: expected type, found variant `Mode::Cool`
--> $DIR/assoc_const_eq_diagnostic.rs:11:35
|
LL | pub trait CoolStuff: Parse<MODE = Mode::Cool> {}
| ^^^^^^^^^^
| |
| not a type
| help: try using the variant's enum: `Mode`
error[E0573]: expected type, found variant `Mode::Cool`
--> $DIR/assoc_const_eq_diagnostic.rs:15:17
|
LL | fn no_help() -> Mode::Cool {}
| ^^^^^^^^^^
| |
| not a type
| help: try using the variant's enum: `Mode`
error: expected associated constant bound, found type
--> $DIR/assoc_const_eq_diagnostic.rs:11:28
|
LL | pub trait CoolStuff: Parse<MODE = Mode::Cool> {}
| ^^^^^^^^^^^^^^^^^ help: if equating a const, try wrapping with braces: `MODE = { const }`
|
note: associated constant defined here
--> $DIR/assoc_const_eq_diagnostic.rs:8:5
|
LL | const MODE: Mode;
| ^^^^^^^^^^^^^^^^
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0573`.