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Add diagnostics for specific cases for const/type mismatch err #82055

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merged 3 commits into from
Feb 18, 2021
Merged

Add diagnostics for specific cases for const/type mismatch err #82055

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be1ed00
Add additional type info to mismatch err
JulianKnodt Feb 13, 2021
b97951b
Update w/ comments
JulianKnodt Feb 14, 2021
f520295
Remove ordering hint
JulianKnodt Feb 16, 2021
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65 changes: 50 additions & 15 deletions compiler/rustc_typeck/src/astconv/generics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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::{
Expand Down Expand Up @@ -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 { .. },
Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/const-generics/const-param-shadowing.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ error[E0747]: type provided when a constant was expected
LL | fn test<const N: usize>() -> Foo<N> {
| ^
|
help: if this generic argument was intended as a const parameter, try surrounding it with braces:
help: if this generic argument was intended as a const parameter, surround it with braces
|
LL | fn test<const N: usize>() -> Foo<{ N }> {
| ^ ^
Expand Down
18 changes: 18 additions & 0 deletions src/test/ui/const-generics/diagnostics.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
#![crate_type="lib"]
#![feature(min_const_generics)]
#![allow(incomplete_features)]

struct A<const N: u8>;
trait Foo {}
impl Foo for A<N> {}
//~^ ERROR cannot find type
//~| unresolved item provided when a constant

struct B<const N: u8>;
impl<N> Foo for B<N> {}
//~^ ERROR type provided when a constant

struct C<const C: u8, const N: u8>;
impl<const N: u8> Foo for C<N, T> {}
//~^ ERROR cannot find type
//~| unresolved item provided when a constant
52 changes: 52 additions & 0 deletions src/test/ui/const-generics/diagnostics.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,52 @@
error[E0412]: cannot find type `N` in this scope
--> $DIR/diagnostics.rs:7:16
|
LL | struct A<const N: u8>;
| ---------------------- similarly named struct `A` defined here
LL | trait Foo {}
LL | impl Foo for A<N> {}
| ^ help: a struct with a similar name exists: `A`
Comment on lines +7 to +8
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Ideally this would suggest "you meant to add a const N here and write this as A<{ N }>".

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I think it's hard to tell if a Res::Err is this case or the other case where the path was not given enough generic args


error[E0412]: cannot find type `T` in this scope
--> $DIR/diagnostics.rs:16:32
|
LL | struct A<const N: u8>;
| ---------------------- similarly named struct `A` defined here
...
LL | impl<const N: u8> Foo for C<N, T> {}
| ^ help: a struct with a similar name exists: `A`

error[E0747]: unresolved item provided when a constant was expected
--> $DIR/diagnostics.rs:7:16
|
LL | impl Foo for A<N> {}
| ^
|
help: if this generic argument was intended as a const parameter, surround it with braces
|
LL | impl Foo for A<{ N }> {}
| ^ ^

error[E0747]: type provided when a constant was expected
--> $DIR/diagnostics.rs:12:19
|
LL | impl<N> Foo for B<N> {}
| - ^
| |
| help: consider changing this type paramater to a `const`-generic: `const N: u8`

error[E0747]: unresolved item provided when a constant was expected
--> $DIR/diagnostics.rs:16:32
|
LL | impl<const N: u8> Foo for C<N, T> {}
| ^
|
help: if this generic argument was intended as a const parameter, surround it with braces
|
LL | impl<const N: u8> Foo for C<N, { T }> {}
| ^ ^

error: aborting due to 5 previous errors

Some errors have detailed explanations: E0412, E0747.
For more information about an error, try `rustc --explain E0412`.
12 changes: 6 additions & 6 deletions src/test/ui/const-generics/invalid-enum.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,14 +3,14 @@

#[derive(PartialEq, Eq)]
enum CompileFlag {
A,
B,
A,
B,
}

pub fn test_1<const CF: CompileFlag>() {}
pub fn test_2<T, const CF: CompileFlag>(x: T) {}
pub struct Example<const CF: CompileFlag, T=u32>{
x: T,
x: T,
}

impl<const CF: CompileFlag, T> Example<CF, T> {
Expand All @@ -20,15 +20,15 @@ impl<const CF: CompileFlag, T> Example<CF, T> {
pub fn main() {
test_1::<CompileFlag::A>();
//~^ ERROR: expected type, found variant
//~| ERROR: type provided when a constant was expected
//~| ERROR: unresolved item provided when a constant was expected

test_2::<_, CompileFlag::A>(0);
//~^ ERROR: expected type, found variant
//~| ERROR: type provided when a constant was expected
//~| ERROR: unresolved item provided when a constant was expected

let _: Example<CompileFlag::A, _> = Example { x: 0 };
//~^ ERROR: expected type, found variant
//~| ERROR: type provided when a constant was expected
//~| ERROR: unresolved item provided when a constant was expected

let _: Example<Example::ASSOC_FLAG, _> = Example { x: 0 };
//~^ ERROR: type provided when a constant was expected
Expand Down
14 changes: 7 additions & 7 deletions src/test/ui/const-generics/invalid-enum.stderr
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Expand Up @@ -25,13 +25,13 @@ LL | let _: Example<CompileFlag::A, _> = Example { x: 0 };
| not a type
| help: try using the variant's enum: `CompileFlag`

error[E0747]: type provided when a constant was expected
error[E0747]: unresolved item provided when a constant was expected
--> $DIR/invalid-enum.rs:29:18
|
LL | let _: Example<CompileFlag::A, _> = Example { x: 0 };
| ^^^^^^^^^^^^^^
|
help: if this generic argument was intended as a const parameter, try surrounding it with braces:
help: if this generic argument was intended as a const parameter, surround it with braces
|
LL | let _: Example<{ CompileFlag::A }, _> = Example { x: 0 };
| ^ ^
Expand All @@ -42,29 +42,29 @@ error[E0747]: type provided when a constant was expected
LL | let _: Example<Example::ASSOC_FLAG, _> = Example { x: 0 };
| ^^^^^^^^^^^^^^^^^^^
|
help: if this generic argument was intended as a const parameter, try surrounding it with braces:
help: if this generic argument was intended as a const parameter, surround it with braces
|
LL | let _: Example<{ Example::ASSOC_FLAG }, _> = Example { x: 0 };
| ^ ^

error[E0747]: type provided when a constant was expected
error[E0747]: unresolved item provided when a constant was expected
--> $DIR/invalid-enum.rs:21:12
|
LL | test_1::<CompileFlag::A>();
| ^^^^^^^^^^^^^^
|
help: if this generic argument was intended as a const parameter, try surrounding it with braces:
help: if this generic argument was intended as a const parameter, surround it with braces
|
LL | test_1::<{ CompileFlag::A }>();
| ^ ^

error[E0747]: type provided when a constant was expected
error[E0747]: unresolved item provided when a constant was expected
--> $DIR/invalid-enum.rs:25:15
|
LL | test_2::<_, CompileFlag::A>(0);
| ^^^^^^^^^^^^^^
|
help: if this generic argument was intended as a const parameter, try surrounding it with braces:
help: if this generic argument was intended as a const parameter, surround it with braces
|
LL | test_2::<_, { CompileFlag::A }>(0);
| ^ ^
Expand Down