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Improve error messages for bad type constraints

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Co-authored-by: Esteban Kuber <esteban@kuber.com.ar>
This commit is contained in:
Michael Howell 2021-09-28 12:48:58 -07:00
parent 8a7c1306b4
commit befdfb5c71
5 changed files with 34 additions and 30 deletions
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31
compiler/rustc_parse/src/parser/path.rs
View File

@ -495,25 +495,28 @@ impl<'a> Parser<'a> {
None => {
let after_eq = eq.shrink_to_hi();
let before_next = self.token.span.shrink_to_lo();
let the_type_placeholder = if matches!(self.token.kind, token::Comma | token::Gt) {
" TheType"
} else {
" TheType "
};
self.struct_span_err(after_eq.to(before_next), "missing type to the right of `=`")
.span_suggestion(
let mut err = self
.struct_span_err(after_eq.to(before_next), "missing type to the right of `=`");
if matches!(self.token.kind, token::Comma | token::Gt) {
err.span_suggestion(
self.sess.source_map().next_point(eq).to(before_next),
"to constrain the associated type, add a type after `=`",
the_type_placeholder.to_string(),
" TheType".to_string(),
Applicability::HasPlaceholders,
)
.span_suggestion(
);
err.span_suggestion(
eq.to(before_next),
&format!("remove the `=` if `{}` is a type", ident),
String::new(),
Applicability::MaybeIncorrect,
)
.emit();
} else {
err.span_label(
self.token.span,
&format!("expected type, found {}", super::token_descr(&self.token)),
)
};
return Err(err);
}
}
Ok(self.mk_ty(span, ast::TyKind::Err))
@ -584,6 +587,12 @@ impl<'a> Parser<'a> {
"expected lifetime, type, or constant, found keyword `const`",
);
if self.check_const_arg() {
err.span_suggestion_verbose(
start.until(self.token.span),
"the `const` keyword is only needed in the definition of the type",
String::new(),
Applicability::MaybeIncorrect,
);
err.emit();
GenericArg::Const(self.parse_const_arg()?)
} else {

6
src/test/ui/const-generics/parser-error-recovery/issue-89013-no-assoc.stderr
View File

@ -3,6 +3,12 @@ error: expected lifetime, type, or constant, found keyword `const`
|
LL | impl Foo<const 3> for Bar {
| ^^^^^
|
help: the `const` keyword is only needed in the definition of the type
|
LL - impl Foo<const 3> for Bar {
LL + impl Foo<3> for Bar {
|
error: aborting due to previous error

1
src/test/ui/const-generics/parser-error-recovery/issue-89013-type.rs
View File

@ -8,7 +8,6 @@ const T: usize = 42;
impl Foo<N = type 3> for Bar {
//~^ERROR missing type to the right of `=`
//~^^ERROR found keyword `type`
fn do_x(&self) -> [u8; 3] {
[0u8; 3]
}

20
src/test/ui/const-generics/parser-error-recovery/issue-89013-type.stderr
View File

@ -2,23 +2,7 @@ error: missing type to the right of `=`
--> $DIR/issue-89013-type.rs:9:13
|
LL | impl Foo<N = type 3> for Bar {
| ^
|
help: to constrain the associated type, add a type after `=`
|
LL | impl Foo<N = TheType type 3> for Bar {
| +++++++
help: remove the `=` if `N` is a type
|
LL - impl Foo<N = type 3> for Bar {
LL + impl Foo<N type 3> for Bar {
|
| ^---- expected type, found keyword `type`
error: expected one of `,`, `>`, a const expression, lifetime, or type, found keyword `type`
--> $DIR/issue-89013-type.rs:9:14
|
LL | impl Foo<N = type 3> for Bar {
| ^^^^ expected one of `,`, `>`, a const expression, lifetime, or type
error: aborting due to 2 previous errors
error: aborting due to previous error

6
src/test/ui/const-generics/parser-error-recovery/issue-89013.stderr
View File

@ -3,6 +3,12 @@ error: expected lifetime, type, or constant, found keyword `const`
|
LL | impl Foo<N = const 3> for Bar {
| ^^^^^
|
help: the `const` keyword is only needed in the definition of the type
|
LL - impl Foo<N = const 3> for Bar {
LL + impl Foo<N = 3> for Bar {
|
error: cannot constrain an associated constant to a value
--> $DIR/issue-89013.rs:9:10