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Show type parameter name and definition in type mismatch error messages #66014

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Nov 6, 2019
Merged

Show type parameter name and definition in type mismatch error messages #66014

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6a30ce6
Add type parameter name to type mismatch error messages
dkadashev Oct 31, 2019
036f182
Show type param definitions in type mismatch errors
dkadashev Oct 31, 2019
4e10b75
Update tests
dkadashev Nov 1, 2019
774e60b
Prettify mismatched types error message in a special case
dkadashev Nov 2, 2019
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10 changes: 9 additions & 1 deletion src/librustc/infer/error_reporting/mod.rs
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Expand Up @@ -1190,8 +1190,16 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
}

// In some (most?) cases cause.body_id points to actual body, but in some cases
// it's a actual definition. According to the comments (e.g. in
// librustc_typeck/check/compare_method.rs:compare_predicate_entailment) the latter
// is relied upon by some other code. This might (or might not) need cleanup.
let body_owner_def_id = self.tcx.hir().opt_local_def_id(cause.body_id)
.unwrap_or_else(|| {
self.tcx.hir().body_owner_def_id(hir::BodyId { hir_id: cause.body_id })
});
self.check_and_note_conflicting_crates(diag, terr, span);
self.tcx.note_and_explain_type_err(diag, terr, span);
self.tcx.note_and_explain_type_err(diag, terr, span, body_owner_def_id);

// It reads better to have the error origin as the final
// thing.
Expand Down
21 changes: 18 additions & 3 deletions src/librustc/ty/error.rs
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Expand Up @@ -241,7 +241,7 @@ impl<'tcx> ty::TyS<'tcx> {
ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
ty::Projection(_) => "associated type".into(),
ty::UnnormalizedProjection(_) => "non-normalized associated type".into(),
ty::Param(_) => "type parameter".into(),
ty::Param(p) => format!("type parameter `{}`", p).into(),
ty::Opaque(..) => "opaque type".into(),
ty::Error => "type error".into(),
}
Expand All @@ -254,6 +254,7 @@ impl<'tcx> TyCtxt<'tcx> {
db: &mut DiagnosticBuilder<'_>,
err: &TypeError<'tcx>,
sp: Span,
body_owner_def_id: DefId,
) {
use self::TypeError::*;

Expand Down Expand Up @@ -288,7 +289,16 @@ impl<'tcx> TyCtxt<'tcx> {
);
}
},
(ty::Param(_), ty::Param(_)) => {
(ty::Param(expected), ty::Param(found)) => {
let generics = self.generics_of(body_owner_def_id);
let e_span = self.def_span(generics.type_param(expected, self).def_id);
if !sp.contains(e_span) {
db.span_label(e_span, "expected type parameter");
}
let f_span = self.def_span(generics.type_param(found, self).def_id);
if !sp.contains(f_span) {
db.span_label(f_span, "found type parameter");
}
db.note("a type parameter was expected, but a different one was found; \
you might be missing a type parameter or trait bound");
db.note("for more information, visit \
Expand All @@ -301,7 +311,12 @@ impl<'tcx> TyCtxt<'tcx> {
(ty::Param(_), ty::Projection(_)) | (ty::Projection(_), ty::Param(_)) => {
db.note("you might be missing a type parameter or trait bound");
}
(ty::Param(_), _) | (_, ty::Param(_)) => {
(ty::Param(p), _) | (_, ty::Param(p)) => {
let generics = self.generics_of(body_owner_def_id);
let p_span = self.def_span(generics.type_param(p, self).def_id);
if !sp.contains(p_span) {
db.span_label(p_span, "this type parameter");
}
db.help("type parameters must be constrained to match other types");
if self.sess.teach(&db.get_code().unwrap()) {
db.help("given a type parameter `T` and a method `foo`:
Expand Down
5 changes: 4 additions & 1 deletion src/test/ui/associated-types/associated-types-issue-20346.stderr
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Expand Up @@ -4,8 +4,11 @@ error[E0271]: type mismatch resolving `<Adapter<I> as Iterator>::Item == std::op
LL | fn is_iterator_of<A, I: Iterator<Item=A>>(_: &I) {}
| -------------- ------ required by this bound in `is_iterator_of`
...
LL | fn test_adapter<T, I: Iterator<Item=Option<T>>>(it: I) {
| - this type parameter
...
LL | is_iterator_of::<Option<T>, _>(&adapter);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected enum `std::option::Option`, found type parameter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected enum `std::option::Option`, found type parameter `T`
|
= note: expected type `std::option::Option<T>`
found type `T`
Expand Down
5 changes: 4 additions & 1 deletion src/test/ui/compare-method/reordered-type-param.stderr
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Expand Up @@ -5,7 +5,10 @@ LL | fn b<C:Clone,D>(&self, x: C) -> C;
| - type in trait
...
LL | fn b<F:Clone,G>(&self, _x: G) -> G { panic!() }
| ^ expected type parameter, found a different type parameter
| - - ^ expected type parameter `F`, found type parameter `G`
| | |
| | found type parameter
| expected type parameter
|
= note: expected type `fn(&E, F) -> F`
found type `fn(&E, G) -> G`
Expand Down
4 changes: 3 additions & 1 deletion src/test/ui/impl-trait/impl-generic-mismatch-ab.stderr
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Expand Up @@ -5,7 +5,9 @@ LL | fn foo<A: Debug>(&self, a: &A, b: &impl Debug);
| -- type in trait
...
LL | fn foo<B: Debug>(&self, a: &impl Debug, b: &B) { }
| ^^^^^^^^^^^ expected type parameter, found a different type parameter
| - ^^^^^^^^^^^ expected type parameter `B`, found type parameter `impl Debug`
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Calling this "type parameter impl Debug" is a little confusing. What about "opaque type impl Debug", or something similar instead?

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That would be reasonable. This output is just a consequence of opaque types being represented as type parameters and having to proactively account for them. Personally I would love to split them into two to avoid a lot of special casing we end up doing, like the one we would have to do here.

| |
| expected type parameter
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|
= note: expected type `fn(&(), &B, &impl Debug)`
found type `fn(&(), &impl Debug, &B)`
Expand Down
6 changes: 4 additions & 2 deletions src/test/ui/impl-trait/universal-mismatched-type.stderr
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Expand Up @@ -2,9 +2,11 @@ error[E0308]: mismatched types
--> $DIR/universal-mismatched-type.rs:4:5
|
LL | fn foo(x: impl Debug) -> String {
| ------ expected `std::string::String` because of return type
| ---------- ------ expected `std::string::String` because of return type
| |
| this type parameter
LL | x
| ^ expected struct `std::string::String`, found type parameter
| ^ expected struct `std::string::String`, found type parameter `impl Debug`
|
= note: expected type `std::string::String`
found type `impl Debug`
Expand Down
11 changes: 8 additions & 3 deletions src/test/ui/impl-trait/universal-two-impl-traits.stderr
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@@ -1,11 +1,16 @@
error[E0308]: mismatched types
--> $DIR/universal-two-impl-traits.rs:5:9
|
LL | fn foo(x: impl Debug, y: impl Debug) -> String {
| ---------- ---------- found type parameter
| |
| expected type parameter
LL | let mut a = x;
LL | a = y;
| ^ expected type parameter, found a different type parameter
| ^ expected type parameter `impl Debug`, found a different type parameter `impl Debug`
|
= note: expected type `impl Debug` (type parameter)
found type `impl Debug` (type parameter)
= note: expected type `impl Debug` (type parameter `impl Debug`)
found type `impl Debug` (type parameter `impl Debug`)
= note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
= note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters

Expand Down
4 changes: 2 additions & 2 deletions src/test/ui/issues/issue-13853.stderr
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Expand Up @@ -2,10 +2,10 @@ error[E0308]: mismatched types
--> $DIR/issue-13853.rs:14:9
|
LL | fn nodes<'a, I: Iterator<Item=&'a N>>(&self) -> I
| - expected `I` because of return type
| - this type parameter - expected `I` because of return type
...
LL | self.iter()
| ^^^^^^^^^^^ expected type parameter, found struct `std::slice::Iter`
| ^^^^^^^^^^^ expected type parameter `I`, found struct `std::slice::Iter`
|
= note: expected type `I`
found type `std::slice::Iter<'_, N>`
Expand Down
13 changes: 10 additions & 3 deletions src/test/ui/issues/issue-20225.stderr
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@@ -1,8 +1,10 @@
error[E0053]: method `call` has an incompatible type for trait
--> $DIR/issue-20225.rs:6:3
|
LL | impl<'a, T> Fn<(&'a T,)> for Foo {
| - this type parameter
LL | extern "rust-call" fn call(&self, (_,): (T,)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected reference, found type parameter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected reference, found type parameter `T`
|
= note: expected type `extern "rust-call" fn(&Foo, (&'a T,))`
found type `extern "rust-call" fn(&Foo, (T,))`
Expand All @@ -12,8 +14,10 @@ LL | extern "rust-call" fn call(&self, (_,): (T,)) {}
error[E0053]: method `call_mut` has an incompatible type for trait
--> $DIR/issue-20225.rs:12:3
|
LL | impl<'a, T> FnMut<(&'a T,)> for Foo {
| - this type parameter
LL | extern "rust-call" fn call_mut(&mut self, (_,): (T,)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected reference, found type parameter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected reference, found type parameter `T`
|
= note: expected type `extern "rust-call" fn(&mut Foo, (&'a T,))`
found type `extern "rust-call" fn(&mut Foo, (T,))`
Expand All @@ -23,8 +27,11 @@ LL | extern "rust-call" fn call_mut(&mut self, (_,): (T,)) {}
error[E0053]: method `call_once` has an incompatible type for trait
--> $DIR/issue-20225.rs:20:3
|
LL | impl<'a, T> FnOnce<(&'a T,)> for Foo {
| - this type parameter
...
LL | extern "rust-call" fn call_once(self, (_,): (T,)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected reference, found type parameter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected reference, found type parameter `T`
|
= note: expected type `extern "rust-call" fn(Foo, (&'a T,))`
found type `extern "rust-call" fn(Foo, (T,))`
Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/issues/issue-24204.stderr
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Expand Up @@ -5,7 +5,7 @@ LL | trait Trait: Sized {
| ------------------ required by `Trait`
...
LL | fn test<T: Trait<B=i32>>(b: i32) -> T where T::A: MultiDispatch<i32> { T::new(b) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected type parameter, found associated type
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected type parameter `T`, found associated type
|
= note: expected type `T`
found type `<<T as Trait>::A as MultiDispatch<i32>>::O`
Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/issues/issue-2951.rs
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Expand Up @@ -4,7 +4,7 @@ fn foo<T, U>(x: T, y: U) {
//~^ ERROR mismatched types
//~| expected type `T`
//~| found type `U`
//~| expected type parameter, found a different type parameter
//~| expected type parameter `T`, found type parameter `U`
}

fn main() {
Expand Down
7 changes: 6 additions & 1 deletion src/test/ui/issues/issue-2951.stderr
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@@ -1,8 +1,13 @@
error[E0308]: mismatched types
--> $DIR/issue-2951.rs:3:10
|
LL | fn foo<T, U>(x: T, y: U) {
| - - found type parameter
| |
| expected type parameter
LL | let mut xx = x;
LL | xx = y;
| ^ expected type parameter, found a different type parameter
| ^ expected type parameter `T`, found type parameter `U`
|
= note: expected type `T`
found type `U`
Expand Down
7 changes: 5 additions & 2 deletions src/test/ui/mismatched_types/issue-35030.stderr
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@@ -1,10 +1,13 @@
error[E0308]: mismatched types
--> $DIR/issue-35030.rs:9:14
|
LL | impl<bool> Parser<bool> for bool {
| ---- this type parameter
LL | fn parse(text: &str) -> Option<bool> {
LL | Some(true)
| ^^^^ expected type parameter, found bool
| ^^^^ expected type parameter `bool`, found bool
|
= note: expected type `bool` (type parameter)
= note: expected type `bool` (type parameter `bool`)
found type `bool` (bool)
= help: type parameters must be constrained to match other types
= note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
Expand Down
15 changes: 12 additions & 3 deletions src/test/ui/structs/struct-path-self-type-mismatch.stderr
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Expand Up @@ -7,8 +7,13 @@ LL | Self { inner: 1.5f32 };
error[E0308]: mismatched types
--> $DIR/struct-path-self-type-mismatch.rs:15:20
|
LL | impl<T> Foo<T> {
| - expected type parameter
LL | fn new<U>(u: U) -> Foo<U> {
| - found type parameter
...
LL | inner: u
| ^ expected type parameter, found a different type parameter
| ^ expected type parameter `T`, found type parameter `U`
|
= note: expected type `T`
found type `U`
Expand All @@ -18,14 +23,18 @@ LL | inner: u
error[E0308]: mismatched types
--> $DIR/struct-path-self-type-mismatch.rs:13:9
|
LL | impl<T> Foo<T> {
| - found type parameter
LL | fn new<U>(u: U) -> Foo<U> {
| ------ expected `Foo<U>` because of return type
| - ------ expected `Foo<U>` because of return type
| |
| expected type parameter
LL | / Self {
LL | |
LL | | inner: u
LL | |
LL | | }
| |_________^ expected type parameter, found a different type parameter
| |_________^ expected type parameter `U`, found type parameter `T`
|
= note: expected type `Foo<U>`
found type `Foo<T>`
Expand Down
6 changes: 3 additions & 3 deletions src/test/ui/structs/struct-path-self.stderr
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@@ -1,4 +1,4 @@
error[E0071]: expected struct, variant or union type, found type parameter
error[E0071]: expected struct, variant or union type, found type parameter `Self`
--> $DIR/struct-path-self.rs:5:17
|
LL | let s = Self {};
Expand All @@ -10,13 +10,13 @@ error[E0109]: type arguments are not allowed for this type
LL | let z = Self::<u8> {};
| ^^ type argument not allowed

error[E0071]: expected struct, variant or union type, found type parameter
error[E0071]: expected struct, variant or union type, found type parameter `Self`
--> $DIR/struct-path-self.rs:7:17
|
LL | let z = Self::<u8> {};
| ^^^^^^^^^^ not a struct

error[E0071]: expected struct, variant or union type, found type parameter
error[E0071]: expected struct, variant or union type, found type parameter `Self`
--> $DIR/struct-path-self.rs:11:13
|
LL | Self { .. } => {}
Expand Down
30 changes: 24 additions & 6 deletions src/test/ui/type-alias-enum-variants/enum-variant-generic-args.stderr
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@@ -1,8 +1,11 @@
error[E0308]: mismatched types
--> $DIR/enum-variant-generic-args.rs:13:25
|
LL | impl<T> Enum<T> {
| - this type parameter
LL | fn ts_variant() {
LL | Self::TSVariant(());
| ^^ expected type parameter, found ()
| ^^ expected type parameter `T`, found ()
|
= note: expected type `T`
found type `()`
Expand All @@ -24,8 +27,11 @@ LL | Self::<()>::TSVariant(());
error[E0308]: mismatched types
--> $DIR/enum-variant-generic-args.rs:17:31
|
LL | impl<T> Enum<T> {
| - this type parameter
...
LL | Self::<()>::TSVariant(());
| ^^ expected type parameter, found ()
| ^^ expected type parameter `T`, found ()
|
= note: expected type `T`
found type `()`
Expand All @@ -47,8 +53,11 @@ LL | Self::<()>::TSVariant::<()>(());
error[E0308]: mismatched types
--> $DIR/enum-variant-generic-args.rs:26:29
|
LL | impl<T> Enum<T> {
| - this type parameter
...
LL | Self::SVariant { v: () };
| ^^ expected type parameter, found ()
| ^^ expected type parameter `T`, found ()
|
= note: expected type `T`
found type `()`
Expand All @@ -64,8 +73,11 @@ LL | Self::SVariant::<()> { v: () };
error[E0308]: mismatched types
--> $DIR/enum-variant-generic-args.rs:28:35
|
LL | impl<T> Enum<T> {
| - this type parameter
...
LL | Self::SVariant::<()> { v: () };
| ^^ expected type parameter, found ()
| ^^ expected type parameter `T`, found ()
|
= note: expected type `T`
found type `()`
Expand All @@ -81,8 +93,11 @@ LL | Self::<()>::SVariant { v: () };
error[E0308]: mismatched types
--> $DIR/enum-variant-generic-args.rs:31:35
|
LL | impl<T> Enum<T> {
| - this type parameter
...
LL | Self::<()>::SVariant { v: () };
| ^^ expected type parameter, found ()
| ^^ expected type parameter `T`, found ()
|
= note: expected type `T`
found type `()`
Expand All @@ -104,8 +119,11 @@ LL | Self::<()>::SVariant::<()> { v: () };
error[E0308]: mismatched types
--> $DIR/enum-variant-generic-args.rs:34:41
|
LL | impl<T> Enum<T> {
| - this type parameter
...
LL | Self::<()>::SVariant::<()> { v: () };
| ^^ expected type parameter, found ()
| ^^ expected type parameter `T`, found ()
|
= note: expected type `T`
found type `()`
Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/type/type-parameter-names.rs
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Expand Up @@ -6,7 +6,7 @@ fn foo<Foo, Bar>(x: Foo) -> Bar {
//~^ ERROR mismatched types
//~| expected type `Bar`
//~| found type `Foo`
//~| expected type parameter, found a different type parameter
//~| expected type parameter `Bar`, found type parameter `Foo`
}

fn main() {}
7 changes: 5 additions & 2 deletions src/test/ui/type/type-parameter-names.stderr
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Expand Up @@ -2,9 +2,12 @@ error[E0308]: mismatched types
--> $DIR/type-parameter-names.rs:5:5
|
LL | fn foo<Foo, Bar>(x: Foo) -> Bar {
| --- expected `Bar` because of return type
| --- --- --- expected `Bar` because of return type
| | |
| | expected type parameter
| found type parameter
LL | x
| ^ expected type parameter, found a different type parameter
| ^ expected type parameter `Bar`, found type parameter `Foo`
|
= note: expected type `Bar`
found type `Foo`
Expand Down
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