On type mismatch involving associated type, suggest constraint

When an associated type is found when a specific type was expected, if
possible provide a structured suggestion constraining the associated
type in a bound.

```
error[E0271]: type mismatch resolving `<T as Foo>::Y == i32`
  --> $DIR/associated-types-multiple-types-one-trait.rs:13:5
   |
LL |     want_y(t);
   |     ^^^^^^ expected `i32`, found associated type
...
LL | fn want_y<T:Foo<Y=i32>>(t: &T) { }
   |                 ----- required by this bound in `want_y`
   |
   = note:         expected type `i32`
           found associated type `<T as Foo>::Y`
help: consider constraining the associated type `<T as Foo>::Y` to `i32`
   |
LL | fn have_x_want_y<T:Foo<X=u32, Y = i32>>(t: &T)
   |                             ^^^^^^^^^
```

```
error[E0308]: mismatched types
  --> $DIR/trait-with-missing-associated-type-restriction.rs:12:9
   |
LL |     qux(x.func())
   |         ^^^^^^^^ expected `usize`, found associated type
   |
   = note:         expected type `usize`
           found associated type `<impl Trait as Trait>::A`
help: consider constraining the associated type `<impl Trait as Trait>::A` to `usize`
   |
LL | fn foo(x: impl Trait<A = usize>) {
   |                     ^^^^^^^^^^
```
This commit is contained in:
Esteban Küber 2020-04-13 13:36:35 -07:00
parent f05a524044
commit 3a795fba03
22 changed files with 469 additions and 66 deletions

View File

@ -4,7 +4,7 @@ use rustc_errors::{pluralize, Applicability, DiagnosticBuilder};
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_span::symbol::sym;
use rustc_span::Span;
use rustc_span::{BytePos, Span};
use rustc_target::spec::abi;
use std::borrow::Cow;
@ -401,7 +401,10 @@ 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(p), _) | (_, ty::Param(p)) => {
(ty::Param(p), ty::Dynamic(..))
| (ty::Dynamic(..), ty::Param(p))
| (ty::Param(p), ty::Opaque(..))
| (ty::Opaque(..), 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) {
@ -441,11 +444,18 @@ impl<T> Trait<T> for X {
#traits-as-parameters",
);
}
(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");
}
}
(ty::Projection(_), _) => {
db.note(&format!(
"consider constraining the associated type `{}` to `{}` or calling a \
method that returns `{}`",
values.expected, values.found, values.expected,
method that returns `{0}`",
values.expected, values.found,
));
if self.sess.teach(&db.get_code().unwrap()) {
db.help(
@ -470,15 +480,18 @@ impl Trait for X {
https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
);
}
(_, ty::Projection(_)) => {
db.note(&format!(
(_, ty::Projection(proj_ty)) => {
let msg = format!(
"consider constraining the associated type `{}` to `{}`",
values.found, values.expected,
));
db.note(
"for more information, visit \
https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
);
if !self.suggest_constraint(db, &msg, body_owner_def_id, proj_ty, values) {
db.help(&msg);
db.note(
"for more information, visit \
https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
);
}
}
_ => {}
}
@ -513,4 +526,115 @@ impl Trait for X {
_ => {}
}
}
fn suggest_constraint(
&self,
db: &mut DiagnosticBuilder<'_>,
msg: &str,
body_owner_def_id: DefId,
proj_ty: &ty::ProjectionTy<'tcx>,
values: &ExpectedFound<Ty<'tcx>>,
) -> bool {
let assoc = self.associated_item(proj_ty.item_def_id);
let trait_ref = proj_ty.trait_ref(*self);
if let Some(item) = self.hir().get_if_local(body_owner_def_id) {
if let Some(hir_generics) = item.generics() {
// Get the `DefId` for the type parameter corresponding to `A` in `<A as T>::Foo`.
// This will also work for `impl Trait`.
let def_id = if let ty::Param(param_ty) = proj_ty.self_ty().kind {
let generics = self.generics_of(body_owner_def_id);
generics.type_param(&param_ty, *self).def_id
} else {
return false;
};
// First look in the `where` clause, as this might be
// `fn foo<T>(x: T) where T: Trait`.
for predicate in hir_generics.where_clause.predicates {
if let hir::WherePredicate::BoundPredicate(pred) = predicate {
if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) =
pred.bounded_ty.kind
{
if path.res.opt_def_id() == Some(def_id) {
// This predicate is binding type param `A` in `<A as T>::Foo` to
// something, potentially `T`.
} else {
continue;
}
} else {
continue;
}
if self.constrain_associated_type_structured_suggestion(
db,
&trait_ref,
pred.bounds,
&assoc,
values,
msg,
) {
return true;
}
}
}
for param in hir_generics.params {
if self.hir().opt_local_def_id(param.hir_id).map(|id| id.to_def_id())
== Some(def_id)
{
// This is type param `A` in `<A as T>::Foo`.
return self.constrain_associated_type_structured_suggestion(
db,
&trait_ref,
param.bounds,
&assoc,
values,
msg,
);
}
}
}
}
false
}
fn constrain_associated_type_structured_suggestion(
&self,
db: &mut DiagnosticBuilder<'_>,
trait_ref: &ty::TraitRef<'tcx>,
bounds: hir::GenericBounds<'_>,
assoc: &ty::AssocItem,
values: &ExpectedFound<Ty<'tcx>>,
msg: &str,
) -> bool {
for bound in bounds {
match bound {
hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::None) => {
// Relate the type param against `T` in `<A as T>::Foo`.
if ptr.trait_ref.trait_def_id() == Some(trait_ref.def_id) {
if let Ok(has_params) = self
.sess
.source_map()
.span_to_snippet(ptr.span)
.map(|snippet| snippet.ends_with('>'))
{
let (span, sugg) = if has_params {
let pos = ptr.span.hi() - BytePos(1);
let span = Span::new(pos, pos, ptr.span.ctxt());
(span, format!(", {} = {}", assoc.ident, values.expected))
} else {
(
ptr.span.shrink_to_hi(),
format!("<{} = {}>", assoc.ident, values.expected),
)
};
db.span_suggestion(span, msg, sugg, Applicability::MaybeIncorrect);
return true;
}
}
}
_ => {}
}
}
false
}
}

View File

@ -8,8 +8,10 @@ LL | let _: Bar = x.boo();
|
= note: expected struct `Bar`
found associated type `<I as Foo>::A`
= note: consider constraining the associated type `<I as Foo>::A` to `Bar`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
help: consider constraining the associated type `<I as Foo>::A` to `Bar`
|
LL | fn foo2<I: Foo<A = Bar>>(x: I) {
| ^^^^^^^^^
error[E0271]: type mismatch resolving `<isize as Foo>::A == Bar`
--> $DIR/associated-types-eq-3.rs:38:5

View File

@ -12,8 +12,6 @@ LL | is_iterator_of::<Option<T>, _>(&adapter);
|
= note: expected enum `std::option::Option<T>`
found type `T`
= 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
error: aborting due to previous error

View File

@ -9,8 +9,10 @@ LL | fn want_y<T:Foo<Y=i32>>(t: &T) { }
|
= note: expected type `i32`
found associated type `<T as Foo>::Y`
= note: consider constraining the associated type `<T as Foo>::Y` to `i32`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
help: consider constraining the associated type `<T as Foo>::Y` to `i32`
|
LL | fn have_x_want_y<T:Foo<X=u32, Y = i32>>(t: &T)
| ^^^^^^^^^
error[E0271]: type mismatch resolving `<T as Foo>::X == u32`
--> $DIR/associated-types-multiple-types-one-trait.rs:18:5
@ -23,8 +25,10 @@ LL | fn want_x<T:Foo<X=u32>>(t: &T) { }
|
= note: expected type `u32`
found associated type `<T as Foo>::X`
= note: consider constraining the associated type `<T as Foo>::X` to `u32`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
help: consider constraining the associated type `<T as Foo>::X` to `u32`
|
LL | fn have_y_want_x<T:Foo<Y=i32, X = u32>>(t: &T)
| ^^^^^^^^^
error: aborting due to 2 previous errors

View File

@ -6,7 +6,7 @@ LL | type Item<'a> where T: 'a = <std::slice::Iter<'a, T> as Iterator>::Item
|
= note: expected reference `&T`
found associated type `<std::vec::Vec<T> as Iterable>::Item<'_>`
= note: consider constraining the associated type `<std::vec::Vec<T> as Iterable>::Item<'_>` to `&_`
= help: consider constraining the associated type `<std::vec::Vec<T> as Iterable>::Item<'_>` to `&_`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
error[E0271]: type mismatch resolving `for<'a> <<[T] as Iterable>::Iter<'a> as std::iter::Iterator>::Item == <[T] as Iterable>::Item<'a>`
@ -17,7 +17,7 @@ LL | type Item<'a> where T: 'a = <std::slice::Iter<'a, T> as Iterator>::Item
|
= note: expected reference `&T`
found associated type `<[T] as Iterable>::Item<'_>`
= note: consider constraining the associated type `<[T] as Iterable>::Item<'_>` to `&_`
= help: consider constraining the associated type `<[T] as Iterable>::Item<'_>` to `&_`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
error[E0271]: type mismatch resolving `for<'a> <<std::vec::Vec<T> as Iterable>::Iter<'a> as std::iter::Iterator>::Item == <std::vec::Vec<T> as Iterable>::Item<'a>`

View File

@ -6,7 +6,7 @@ LL | let v = Unit2.m(
|
= note: expected struct `Unit4`
found associated type `<_ as Ty<'_>>::V`
= note: consider constraining the associated type `<_ as Ty<'_>>::V` to `Unit4`
= help: consider constraining the associated type `<_ as Ty<'_>>::V` to `Unit4`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
error[E0271]: type mismatch resolving `<[closure@$DIR/issue-62203-hrtb-ice.rs:42:17: 42:39] as std::ops::FnOnce<((&u8,),)>>::Output == Unit3`

View File

@ -14,9 +14,11 @@ LL | fn foo_fail<T: Trait>() -> impl FooLike<Output=T::Assoc> {
|
= note: expected type `()`
found associated type `<T as impl_trait::Trait>::Assoc`
= note: consider constraining the associated type `<T as impl_trait::Trait>::Assoc` to `()`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
= note: the return type of a function must have a statically known size
help: consider constraining the associated type `<T as impl_trait::Trait>::Assoc` to `()`
|
LL | fn foo_fail<T: Trait<Assoc = ()>>() -> impl FooLike<Output=T::Assoc> {
| ^^^^^^^^^^^^
error: `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
--> $DIR/bound-normalization-fail.rs:43:41
@ -32,9 +34,11 @@ LL | fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output=T::Assoc> {
|
= note: expected type `()`
found associated type `<T as lifetimes::Trait<'static>>::Assoc`
= note: consider constraining the associated type `<T as lifetimes::Trait<'static>>::Assoc` to `()`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
= note: the return type of a function must have a statically known size
help: consider constraining the associated type `<T as lifetimes::Trait<'static>>::Assoc` to `()`
|
LL | fn foo2_fail<'a, T: Trait<'a, Assoc = ()>>() -> impl FooLike<Output=T::Assoc> {
| ^^^^^^^^^^^^
error: aborting due to 3 previous errors; 1 warning emitted

View File

@ -25,7 +25,7 @@ LL | let _: i32 = Leak::leak(hide(0_i32));
|
= note: expected type `i32`
found associated type `<impl Foo as Leak>::T`
= note: consider constraining the associated type `<impl Foo as Leak>::T` to `i32`
= help: consider constraining the associated type `<impl Foo as Leak>::T` to `i32`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
error[E0308]: mismatched types

View File

@ -10,8 +10,6 @@ LL | x
|
= note: expected struct `std::string::String`
found type parameter `impl Debug`
= 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
error: aborting due to previous error

View File

@ -9,8 +9,6 @@ LL | self.iter()
|
= note: expected type parameter `I`
found struct `std::slice::Iter<'_, N>`
= 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
error[E0599]: no method named `iter` found for reference `&G` in the current scope
--> $DIR/issue-13853.rs:27:23

View File

@ -8,8 +8,6 @@ LL | extern "rust-call" fn call(&self, (_,): (T,)) {}
|
= note: expected fn pointer `extern "rust-call" fn(&Foo, (&'a T,))`
found fn pointer `extern "rust-call" fn(&Foo, (T,))`
= 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
error[E0053]: method `call_mut` has an incompatible type for trait
--> $DIR/issue-20225.rs:11:3
@ -21,8 +19,6 @@ LL | extern "rust-call" fn call_mut(&mut self, (_,): (T,)) {}
|
= note: expected fn pointer `extern "rust-call" fn(&mut Foo, (&'a T,))`
found fn pointer `extern "rust-call" fn(&mut Foo, (T,))`
= 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
error[E0053]: method `call_once` has an incompatible type for trait
--> $DIR/issue-20225.rs:18:3
@ -35,8 +31,6 @@ LL | extern "rust-call" fn call_once(self, (_,): (T,)) {}
|
= note: expected fn pointer `extern "rust-call" fn(Foo, (&'a T,))`
found fn pointer `extern "rust-call" fn(Foo, (T,))`
= 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
error: aborting due to 3 previous errors

View File

@ -8,8 +8,6 @@ LL | const C: S0<u8> = Self(0);
|
= note: expected type parameter `T`
found type `{integer}`
= 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
error[E0308]: mismatched types
--> $DIR/issue-69306.rs:5:23
@ -21,8 +19,6 @@ LL | const C: S0<u8> = Self(0);
|
= note: expected struct `S0<u8>`
found struct `S0<T>`
= 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
error[E0308]: mismatched types
--> $DIR/issue-69306.rs:10:14
@ -35,8 +31,6 @@ LL | Self(0);
|
= note: expected type parameter `T`
found type `{integer}`
= 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
error[E0308]: mismatched types
--> $DIR/issue-69306.rs:27:14
@ -49,8 +43,6 @@ LL | Self(0);
|
= note: expected type parameter `T`
found type `{integer}`
= 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
error[E0308]: mismatched types
--> $DIR/issue-69306.rs:33:32
@ -62,8 +54,6 @@ LL | const C: S1<u8, u8> = Self(0, 1);
|
= note: expected type parameter `T`
found type `{integer}`
= 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
error[E0308]: mismatched types
--> $DIR/issue-69306.rs:33:27
@ -75,8 +65,6 @@ LL | const C: S1<u8, u8> = Self(0, 1);
|
= note: expected struct `S1<u8, _>`
found struct `S1<T, _>`
= 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
error[E0308]: mismatched types
--> $DIR/issue-69306.rs:41:14

View File

@ -9,8 +9,6 @@ LL | Some(true)
|
= note: expected type parameter `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
error: aborting due to previous error

View File

@ -25,7 +25,7 @@ LL | generic::<()>()
|
= note: expected unit type `()`
found associated type `<() as Foo>::Assoc`
= note: consider constraining the associated type `<() as Foo>::Assoc` to `()`
= help: consider constraining the associated type `<() as Foo>::Assoc` to `()`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
error: aborting due to 2 previous errors

View File

@ -21,7 +21,7 @@ LL | Example::generate(t)
|
= note: expected struct `std::boxed::Box<T>`
found associated type `<T as Example>::Output`
= note: consider constraining the associated type `<T as Example>::Output` to `std::boxed::Box<T>`
= help: consider constraining the associated type `<T as Example>::Output` to `std::boxed::Box<T>`
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
error: aborting due to 2 previous errors

View File

@ -12,8 +12,6 @@ LL | x
|
= note: expected struct `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>`
found type parameter `F`
= 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
error[E0308]: mismatched types
--> $DIR/expected-boxed-future-isnt-pinned.rs:18:5

View File

@ -0,0 +1,43 @@
// run-rustfix
#![allow(unused)] // for the fixed file
trait Trait<T = Self> {
type A;
fn func(&self) -> Self::A;
}
struct S<T>(T);
impl<K> S<K> {
fn foo<'a, T: Trait + 'a>(&self, _: impl Trait, x: impl Trait<A = usize>, _: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn ban<T>(x: T) where T: Trait<A = usize> {
qux(x.func()) //~ ERROR mismatched types
}
}
fn foo<'a, T: Trait + 'a>(_: impl Trait, x: impl Trait<A = usize>, _: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn bar<T: Trait<A = usize>>(x: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn foo2(x: impl Trait<i32, A = usize>) {
qux(x.func()) //~ ERROR mismatched types
}
fn bar2<T: Trait<i32, A = usize>>(x: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn ban<T>(x: T) where T: Trait<A = usize> {
qux(x.func()) //~ ERROR mismatched types
}
fn qux(_: usize) {}
fn main() {}

View File

@ -0,0 +1,43 @@
// run-rustfix
#![allow(unused)] // for the fixed file
trait Trait<T = Self> {
type A;
fn func(&self) -> Self::A;
}
struct S<T>(T);
impl<K> S<K> {
fn foo<'a, T: Trait + 'a>(&self, _: impl Trait, x: impl Trait, _: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn ban<T>(x: T) where T: Trait {
qux(x.func()) //~ ERROR mismatched types
}
}
fn foo<'a, T: Trait + 'a>(_: impl Trait, x: impl Trait, _: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn bar<T: Trait>(x: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn foo2(x: impl Trait<i32>) {
qux(x.func()) //~ ERROR mismatched types
}
fn bar2<T: Trait<i32>>(x: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn ban<T>(x: T) where T: Trait {
qux(x.func()) //~ ERROR mismatched types
}
fn qux(_: usize) {}
fn main() {}

View File

@ -0,0 +1,94 @@
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction-fixable.rs:13:13
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<impl Trait as Trait>::A`
help: consider constraining the associated type `<impl Trait as Trait>::A` to `usize`
|
LL | fn foo<'a, T: Trait + 'a>(&self, _: impl Trait, x: impl Trait<A = usize>, _: T) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction-fixable.rs:17:13
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<T as Trait>::A`
help: consider constraining the associated type `<T as Trait>::A` to `usize`
|
LL | fn ban<T>(x: T) where T: Trait<A = usize> {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction-fixable.rs:22:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<impl Trait as Trait>::A`
help: consider constraining the associated type `<impl Trait as Trait>::A` to `usize`
|
LL | fn foo<'a, T: Trait + 'a>(_: impl Trait, x: impl Trait<A = usize>, _: T) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction-fixable.rs:26:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<T as Trait>::A`
help: consider constraining the associated type `<T as Trait>::A` to `usize`
|
LL | fn bar<T: Trait<A = usize>>(x: T) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction-fixable.rs:30:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<impl Trait<i32> as Trait<i32>>::A`
help: consider constraining the associated type `<impl Trait<i32> as Trait<i32>>::A` to `usize`
|
LL | fn foo2(x: impl Trait<i32, A = usize>) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction-fixable.rs:34:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<T as Trait<i32>>::A`
help: consider constraining the associated type `<T as Trait<i32>>::A` to `usize`
|
LL | fn bar2<T: Trait<i32, A = usize>>(x: T) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction-fixable.rs:38:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<T as Trait>::A`
help: consider constraining the associated type `<T as Trait>::A` to `usize`
|
LL | fn ban<T>(x: T) where T: Trait<A = usize> {
| ^^^^^^^^^^^
error: aborting due to 7 previous errors
For more information about this error, try `rustc --explain E0308`.

View File

@ -0,0 +1,41 @@
// These are all the possible variations of this error I could think of for.
// `trait-with-missing-associated-type-restriction-fixable.rs` contains the subset of these that
// can be fixed with `rustfix`.
trait Trait<T = Self> {
type A;
fn func(&self) -> Self::A;
}
fn foo(_: impl Trait, x: impl Trait) {
qux(x.func()) //~ ERROR mismatched types
}
fn bar<T: Trait>(x: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn foo2(x: impl Trait<i32>) {
qux(x.func()) //~ ERROR mismatched types
}
fn bar2<T: Trait<i32>>(x: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn baz<D: std::fmt::Debug, T: Trait<A = D>>(x: T) {
qux(x.func()) //~ ERROR mismatched types
}
fn bat(x: &mut dyn Trait<(), A = ()>) {
qux(x) //~ ERROR mismatched types
}
fn ban<T>(x: T) where T: Trait {
qux(x.func()) //~ ERROR mismatched types
}
fn qux(_: usize) {}
fn main() {}

View File

@ -0,0 +1,88 @@
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction.rs:12:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<impl Trait as Trait>::A`
help: consider constraining the associated type `<impl Trait as Trait>::A` to `usize`
|
LL | fn foo(_: impl Trait, x: impl Trait<A = usize>) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction.rs:16:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<T as Trait>::A`
help: consider constraining the associated type `<T as Trait>::A` to `usize`
|
LL | fn bar<T: Trait<A = usize>>(x: T) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction.rs:20:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<impl Trait<i32> as Trait<i32>>::A`
help: consider constraining the associated type `<impl Trait<i32> as Trait<i32>>::A` to `usize`
|
LL | fn foo2(x: impl Trait<i32, A = usize>) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction.rs:24:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<T as Trait<i32>>::A`
help: consider constraining the associated type `<T as Trait<i32>>::A` to `usize`
|
LL | fn bar2<T: Trait<i32, A = usize>>(x: T) {
| ^^^^^^^^^^^
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction.rs:28:9
|
LL | fn baz<D: std::fmt::Debug, T: Trait<A = D>>(x: T) {
| - this type parameter
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found type parameter `D`
|
= note: expected type `usize`
found type parameter `D`
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction.rs:32:9
|
LL | qux(x)
| ^ expected `usize`, found mutable reference
|
= note: expected type `usize`
found mutable reference `&mut dyn Trait<(), A = ()>`
error[E0308]: mismatched types
--> $DIR/trait-with-missing-associated-type-restriction.rs:36:9
|
LL | qux(x.func())
| ^^^^^^^^ expected `usize`, found associated type
|
= note: expected type `usize`
found associated type `<T as Trait>::A`
help: consider constraining the associated type `<T as Trait>::A` to `usize`
|
LL | fn ban<T>(x: T) where T: Trait<A = usize> {
| ^^^^^^^^^^^
error: aborting due to 7 previous errors
For more information about this error, try `rustc --explain E0308`.

View File

@ -9,8 +9,6 @@ LL | Self::TSVariant(());
|
= note: expected type parameter `T`
found unit type `()`
= 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
error[E0109]: type arguments are not allowed for this type
--> $DIR/enum-variant-generic-args.rs:15:27
@ -35,8 +33,6 @@ LL | Self::<()>::TSVariant(());
|
= note: expected type parameter `T`
found unit type `()`
= 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
error[E0109]: type arguments are not allowed for this type
--> $DIR/enum-variant-generic-args.rs:20:16
@ -61,8 +57,6 @@ LL | Self::SVariant { v: () };
|
= note: expected type parameter `T`
found unit type `()`
= 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
error[E0109]: type arguments are not allowed for this type
--> $DIR/enum-variant-generic-args.rs:28:26
@ -81,8 +75,6 @@ LL | Self::SVariant::<()> { v: () };
|
= note: expected type parameter `T`
found unit type `()`
= 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
error[E0109]: type arguments are not allowed for this type
--> $DIR/enum-variant-generic-args.rs:31:16
@ -101,8 +93,6 @@ LL | Self::<()>::SVariant { v: () };
|
= note: expected type parameter `T`
found unit type `()`
= 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
error[E0109]: type arguments are not allowed for this type
--> $DIR/enum-variant-generic-args.rs:34:16
@ -127,8 +117,6 @@ LL | Self::<()>::SVariant::<()> { v: () };
|
= note: expected type parameter `T`
found unit type `()`
= 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
error[E0109]: type arguments are not allowed for this type
--> $DIR/enum-variant-generic-args.rs:41:26