Rollup merge of #82066 - matthewjasper:trait-ref-fix, r=jackh726

Ensure valid TraitRefs are created for GATs

This fixes `ProjectionTy::trait_ref` to use the correct substs. Places that need all of the substs have been updated to not use `trait_ref`.

r? ````@jackh726````

14 files changed, 300 insertions, 76 deletions

diff --git a/src/test/pretty/gat-bounds.rs b/src/test/pretty/gat-bounds.rs
index 789e4bc80ac..8877c6cc992 100644
--- a/src/test/pretty/gat-bounds.rs
+++ b/src/test/pretty/gat-bounds.rs
@@ -13,4 +13,6 @@ impl X for () {
     type Y<T> where Self: Sized = u32;
 }
 
+fn f<T: X<Y<()> = i32>>() {}
+
 fn main() { }
diff --git a/src/test/ui/generic-associated-types/constraint-assoc-type-suggestion.rs b/src/test/ui/generic-associated-types/constraint-assoc-type-suggestion.rs
new file mode 100644
index 00000000000..36db3d1bb9e
--- /dev/null
+++ b/src/test/ui/generic-associated-types/constraint-assoc-type-suggestion.rs
@@ -0,0 +1,17 @@
+// Test that correct syntax is used in suggestion to constrain associated type
+
+#![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
+
+trait X {
+    type Y<T>;
+}
+
+fn f<T: X>(a: T::Y<i32>) {
+    //~^ HELP consider constraining the associated type `<T as X>::Y<i32>` to `Vec<i32>`
+    //~| SUGGESTION Y<i32> = Vec<i32>>
+    let b: Vec<i32> = a;
+    //~^ ERROR mismatched types
+}
+
+fn main() {}
diff --git a/src/test/ui/generic-associated-types/constraint-assoc-type-suggestion.stderr b/src/test/ui/generic-associated-types/constraint-assoc-type-suggestion.stderr
new file mode 100644
index 00000000000..ecf559d9e94
--- /dev/null
+++ b/src/test/ui/generic-associated-types/constraint-assoc-type-suggestion.stderr
@@ -0,0 +1,27 @@
+warning: the feature `generic_associated_types` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/constraint-assoc-type-suggestion.rs:3:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information
+
+error[E0308]: mismatched types
+  --> $DIR/constraint-assoc-type-suggestion.rs:13:23
+   |
+LL |     let b: Vec<i32> = a;
+   |            --------   ^ expected struct `Vec`, found associated type
+   |            |
+   |            expected due to this
+   |
+   = note:       expected struct `Vec<i32>`
+           found associated type `<T as X>::Y<i32>`
+help: consider constraining the associated type `<T as X>::Y<i32>` to `Vec<i32>`
+   |
+LL | fn f<T: X<Y<i32> = Vec<i32>>>(a: T::Y<i32>) {
+   |          ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/generic-associated-types/generic-associated-type-bounds.rs b/src/test/ui/generic-associated-types/generic-associated-type-bounds.rs
new file mode 100644
index 00000000000..8094450e5e1
--- /dev/null
+++ b/src/test/ui/generic-associated-types/generic-associated-type-bounds.rs
@@ -0,0 +1,35 @@
+// run-pass
+
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+
+pub trait X {
+    type Y<'a>;
+    fn m(&self) -> Self::Y<'_>;
+}
+
+impl X for () {
+    type Y<'a> = &'a ();
+
+    fn m(&self) -> Self::Y<'_> {
+        self
+    }
+}
+
+fn f(x: &impl for<'a> X<Y<'a> = &'a ()>) -> &() {
+    x.m()
+}
+
+fn g<T: for<'a> X<Y<'a> = &'a ()>>(x: &T) -> &() {
+    x.m()
+}
+
+fn h(x: &()) -> &() {
+    x.m()
+}
+
+fn main() {
+    f(&());
+    g(&());
+    h(&());
+}
diff --git a/src/test/ui/generic-associated-types/issue-76535.rs b/src/test/ui/generic-associated-types/issue-76535.rs
index 2b4757d8d15..5e73a882986 100644
--- a/src/test/ui/generic-associated-types/issue-76535.rs
+++ b/src/test/ui/generic-associated-types/issue-76535.rs
@@ -1,11 +1,11 @@
 #![feature(generic_associated_types)]
- //~^ WARNING the feature
+//~^ WARNING the feature
 
 pub trait SubTrait {}
 
 pub trait SuperTrait {
     type SubType<'a>: SubTrait;
-      //~^ ERROR missing generics for associated
+    //~^ ERROR missing generics for associated
 
     fn get_sub<'a>(&'a mut self) -> Self::SubType<'a>;
 }
@@ -36,6 +36,4 @@ impl SuperTrait for SuperStruct {
 
 fn main() {
     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
-      //~^ ERROR the trait
-      //~| ERROR the trait
 }
diff --git a/src/test/ui/generic-associated-types/issue-76535.stderr b/src/test/ui/generic-associated-types/issue-76535.stderr
index ce4875af9c0..17661e0d90a 100644
--- a/src/test/ui/generic-associated-types/issue-76535.stderr
+++ b/src/test/ui/generic-associated-types/issue-76535.stderr
@@ -23,41 +23,6 @@ help: use angle brackets to add missing lifetime argument
 LL |     type SubType<'a><'a>: SubTrait;
    |                 ^^^^
 
-error[E0038]: the trait `SuperTrait` cannot be made into an object
-  --> $DIR/issue-76535.rs:38:14
-   |
-LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
-   |
-   = help: consider moving `get_sub` to another trait
-note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
-  --> $DIR/issue-76535.rs:10:37
-   |
-LL | pub trait SuperTrait {
-   |           ---------- this trait cannot be made into an object...
-...
-LL |     fn get_sub<'a>(&'a mut self) -> Self::SubType<'a>;
-   |                                     ^^^^^^^^^^^^^^^^^ ...because method `get_sub` references the `Self` type in its return type
-
-error[E0038]: the trait `SuperTrait` cannot be made into an object
-  --> $DIR/issue-76535.rs:38:57
-   |
-LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
-   |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
-   |
-   = help: consider moving `get_sub` to another trait
-note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
-  --> $DIR/issue-76535.rs:10:37
-   |
-LL | pub trait SuperTrait {
-   |           ---------- this trait cannot be made into an object...
-...
-LL |     fn get_sub<'a>(&'a mut self) -> Self::SubType<'a>;
-   |                                     ^^^^^^^^^^^^^^^^^ ...because method `get_sub` references the `Self` type in its return type
-   = note: required because of the requirements on the impl of `CoerceUnsized<Box<dyn SuperTrait<SubType = SubStruct<'_>>>>` for `Box<SuperStruct>`
-   = note: required by cast to type `Box<dyn SuperTrait<SubType = SubStruct<'_>>>`
-
-error: aborting due to 3 previous errors; 1 warning emitted
+error: aborting due to previous error; 1 warning emitted
 
-Some errors have detailed explanations: E0038, E0107.
-For more information about an error, try `rustc --explain E0038`.
+For more information about this error, try `rustc --explain E0107`.
diff --git a/src/test/ui/generic-associated-types/issue-79422.rs b/src/test/ui/generic-associated-types/issue-79422.rs
index 26b38430dd9..aeb33ca5464 100644
--- a/src/test/ui/generic-associated-types/issue-79422.rs
+++ b/src/test/ui/generic-associated-types/issue-79422.rs
@@ -19,7 +19,7 @@ impl<'a, T> RefCont<'a, T> for Box<T> {
 
 trait MapLike<K, V> {
     type VRefCont<'a>: RefCont<'a, V>;
-      //~^ ERROR missing generics
+    //~^ ERROR missing generics
     fn get<'a>(&'a self, key: &K) -> Option<Self::VRefCont<'a>>;
 }
 
@@ -42,6 +42,5 @@ impl<K, V: Default> MapLike<K, V> for Source {
 fn main() {
     let m = Box::new(std::collections::BTreeMap::<u8, u8>::new())
         as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
-      //~^ ERROR the trait
-      //~^^^ ERROR the trait
+    //~^^ ERROR type mismatch resolving
 }
diff --git a/src/test/ui/generic-associated-types/issue-79422.stderr b/src/test/ui/generic-associated-types/issue-79422.stderr
index d2e12962715..a119bff03e2 100644
--- a/src/test/ui/generic-associated-types/issue-79422.stderr
+++ b/src/test/ui/generic-associated-types/issue-79422.stderr
@@ -14,41 +14,17 @@ help: use angle brackets to add missing lifetime argument
 LL |     type VRefCont<'a><'a>: RefCont<'a, V>;
    |                  ^^^^
 
-error[E0038]: the trait `MapLike` cannot be made into an object
-  --> $DIR/issue-79422.rs:44:12
-   |
-LL |         as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
-   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
-   |
-   = help: consider moving `get` to another trait
-note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
-  --> $DIR/issue-79422.rs:23:38
-   |
-LL | trait MapLike<K, V> {
-   |       ------- this trait cannot be made into an object...
-...
-LL |     fn get<'a>(&'a self, key: &K) -> Option<Self::VRefCont<'a>>;
-   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^ ...because method `get` references the `Self` type in its return type
-
-error[E0038]: the trait `MapLike` cannot be made into an object
+error[E0271]: type mismatch resolving `<BTreeMap<u8, u8> as MapLike<u8, u8>>::VRefCont<'static> == (dyn RefCont<'_, u8> + 'static)`
   --> $DIR/issue-79422.rs:43:13
    |
 LL |     let m = Box::new(std::collections::BTreeMap::<u8, u8>::new())
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
-   |
-   = help: consider moving `get` to another trait
-note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
-  --> $DIR/issue-79422.rs:23:38
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected trait object `dyn RefCont`, found reference
    |
-LL | trait MapLike<K, V> {
-   |       ------- this trait cannot be made into an object...
-...
-LL |     fn get<'a>(&'a self, key: &K) -> Option<Self::VRefCont<'a>>;
-   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^ ...because method `get` references the `Self` type in its return type
-   = note: required because of the requirements on the impl of `CoerceUnsized<Box<dyn MapLike<u8, u8, VRefCont = (dyn RefCont<'_, u8> + 'static)>>>` for `Box<BTreeMap<u8, u8>>`
-   = note: required by cast to type `Box<dyn MapLike<u8, u8, VRefCont = (dyn RefCont<'_, u8> + 'static)>>`
+   = note: expected trait object `(dyn RefCont<'_, u8> + 'static)`
+                 found reference `&'static u8`
+   = note: required for the cast to the object type `dyn MapLike<u8, u8, VRefCont = (dyn RefCont<'_, u8> + 'static)>`
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0038, E0107.
-For more information about an error, try `rustc --explain E0038`.
+Some errors have detailed explanations: E0107, E0271.
+For more information about an error, try `rustc --explain E0107`.
diff --git a/src/test/ui/generic-associated-types/method-unsatified-assoc-type-predicate.rs b/src/test/ui/generic-associated-types/method-unsatified-assoc-type-predicate.rs
new file mode 100644
index 00000000000..2de4c7b8492
--- /dev/null
+++ b/src/test/ui/generic-associated-types/method-unsatified-assoc-type-predicate.rs
@@ -0,0 +1,35 @@
+// Test that the predicate printed in an unresolved method error prints the
+// generics for a generic associated type.
+
+#![feature(generic_associated_types)]
+//~^ WARNING the feature `generic_associated_types` is incomplete
+//~| NOTE `#[warn(incomplete_features)]` on by default
+//~| NOTE see issue #44265
+
+trait X {
+    type Y<T>;
+}
+
+trait M {
+    fn f(&self) {}
+}
+
+impl<T: X<Y<i32> = i32>> M for T {}
+
+struct S;
+//~^ NOTE method `f` not found for this
+//~| NOTE doesn't satisfy `<S as X>::Y<i32> = i32`
+//~| NOTE doesn't satisfy `S: M`
+
+impl X for S {
+    type Y<T> = bool;
+}
+
+fn f(a: S) {
+    a.f();
+    //~^ ERROR the method `f` exists for struct `S`, but its trait bounds were not satisfied
+    //~| NOTE method cannot be called on `S` due to unsatisfied trait bounds
+    //~| NOTE the following trait bounds were not satisfied:
+}
+
+fn main() {}
diff --git a/src/test/ui/generic-associated-types/method-unsatified-assoc-type-predicate.stderr b/src/test/ui/generic-associated-types/method-unsatified-assoc-type-predicate.stderr
new file mode 100644
index 00000000000..c94155d13c3
--- /dev/null
+++ b/src/test/ui/generic-associated-types/method-unsatified-assoc-type-predicate.stderr
@@ -0,0 +1,29 @@
+warning: the feature `generic_associated_types` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/method-unsatified-assoc-type-predicate.rs:4:12
+   |
+LL | #![feature(generic_associated_types)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information
+
+error[E0599]: the method `f` exists for struct `S`, but its trait bounds were not satisfied
+  --> $DIR/method-unsatified-assoc-type-predicate.rs:29:7
+   |
+LL | struct S;
+   | ---------
+   | |
+   | method `f` not found for this
+   | doesn't satisfy `<S as X>::Y<i32> = i32`
+   | doesn't satisfy `S: M`
+...
+LL |     a.f();
+   |       ^ method cannot be called on `S` due to unsatisfied trait bounds
+   |
+   = note: the following trait bounds were not satisfied:
+           `<S as X>::Y<i32> = i32`
+           which is required by `S: M`
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0599`.
diff --git a/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.rs b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.rs
new file mode 100644
index 00000000000..0024e127a98
--- /dev/null
+++ b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.rs
@@ -0,0 +1,36 @@
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+
+pub trait X {
+    type Y<'a>;
+    fn m(&self) -> Self::Y<'_>;
+}
+
+impl X for () {
+    type Y<'a> = &'a ();
+
+    fn m(&self) -> Self::Y<'_> {
+        self
+    }
+}
+
+fn f(x: &impl for<'a> X<Y<'a> = &'a ()>) -> &'static () {
+    x.m()
+    //~^ ERROR explicit lifetime required
+}
+
+fn g<T: for<'a> X<Y<'a> = &'a ()>>(x: &T) -> &'static () {
+    x.m()
+    //~^ ERROR explicit lifetime required
+}
+
+fn h(x: &()) -> &'static () {
+    x.m()
+    //~^ ERROR explicit lifetime required
+}
+
+fn main() {
+    f(&());
+    g(&());
+    h(&());
+}
diff --git a/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr
new file mode 100644
index 00000000000..13b765dfa57
--- /dev/null
+++ b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr
@@ -0,0 +1,27 @@
+error[E0621]: explicit lifetime required in the type of `x`
+  --> $DIR/projection-type-lifetime-mismatch.rs:18:5
+   |
+LL | fn f(x: &impl for<'a> X<Y<'a> = &'a ()>) -> &'static () {
+   |         ------------------------------- help: add explicit lifetime `'static` to the type of `x`: `&'static impl for<'a> X<Y<'a> = &'a ()>`
+LL |     x.m()
+   |     ^^^^^ lifetime `'static` required
+
+error[E0621]: explicit lifetime required in the type of `x`
+  --> $DIR/projection-type-lifetime-mismatch.rs:23:5
+   |
+LL | fn g<T: for<'a> X<Y<'a> = &'a ()>>(x: &T) -> &'static () {
+   |                                       -- help: add explicit lifetime `'static` to the type of `x`: `&'static T`
+LL |     x.m()
+   |     ^^^^^ lifetime `'static` required
+
+error[E0621]: explicit lifetime required in the type of `x`
+  --> $DIR/projection-type-lifetime-mismatch.rs:28:5
+   |
+LL | fn h(x: &()) -> &'static () {
+   |         --- help: add explicit lifetime `'static` to the type of `x`: `&'static ()`
+LL |     x.m()
+   |     ^^^^^ lifetime `'static` required
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0621`.
diff --git a/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.rs b/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.rs
new file mode 100644
index 00000000000..7bcc7ba752a
--- /dev/null
+++ b/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.rs
@@ -0,0 +1,28 @@
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+
+pub trait X {
+    type Y<'a: 'static>;
+    //~^ WARNING unnecessary lifetime parameter
+}
+
+impl X for () {
+    type Y<'a> = &'a ();
+}
+
+struct B<'a, T: for<'r> X<Y<'r> = &'r ()>> {
+    f: <T as X>::Y<'a>,
+    //~^ ERROR lifetime bound not satisfied
+}
+
+struct C<'a, T: X> {
+    f: <T as X>::Y<'a>,
+    //~^ ERROR lifetime bound not satisfied
+}
+
+struct D<'a> {
+    f: <() as X>::Y<'a>,
+    //~^ ERROR lifetime bound not satisfied
+}
+
+fn main() {}
diff --git a/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr b/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr
new file mode 100644
index 00000000000..1c81d33ccfe
--- /dev/null
+++ b/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr
@@ -0,0 +1,50 @@
+warning: unnecessary lifetime parameter `'a`
+  --> $DIR/unsatified-item-lifetime-bound.rs:5:12
+   |
+LL |     type Y<'a: 'static>;
+   |            ^^^^^^^^^^^
+   |
+   = help: you can use the `'static` lifetime directly, in place of `'a`
+
+error[E0478]: lifetime bound not satisfied
+  --> $DIR/unsatified-item-lifetime-bound.rs:14:8
+   |
+LL |     f: <T as X>::Y<'a>,
+   |        ^^^^^^^^^^^^^^^
+   |
+note: lifetime parameter instantiated with the lifetime `'a` as defined on the struct at 13:10
+  --> $DIR/unsatified-item-lifetime-bound.rs:13:10
+   |
+LL | struct B<'a, T: for<'r> X<Y<'r> = &'r ()>> {
+   |          ^^
+   = note: but lifetime parameter must outlive the static lifetime
+
+error[E0478]: lifetime bound not satisfied
+  --> $DIR/unsatified-item-lifetime-bound.rs:19:8
+   |
+LL |     f: <T as X>::Y<'a>,
+   |        ^^^^^^^^^^^^^^^
+   |
+note: lifetime parameter instantiated with the lifetime `'a` as defined on the struct at 18:10
+  --> $DIR/unsatified-item-lifetime-bound.rs:18:10
+   |
+LL | struct C<'a, T: X> {
+   |          ^^
+   = note: but lifetime parameter must outlive the static lifetime
+
+error[E0478]: lifetime bound not satisfied
+  --> $DIR/unsatified-item-lifetime-bound.rs:24:8
+   |
+LL |     f: <() as X>::Y<'a>,
+   |        ^^^^^^^^^^^^^^^^
+   |
+note: lifetime parameter instantiated with the lifetime `'a` as defined on the struct at 23:10
+  --> $DIR/unsatified-item-lifetime-bound.rs:23:10
+   |
+LL | struct D<'a> {
+   |          ^^
+   = note: but lifetime parameter must outlive the static lifetime
+
+error: aborting due to 3 previous errors; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0478`.