Rollup merge of #92683 - jackh726:issue-92033, r=estebank

Suggest copying trait associated type bounds on lifetime error

Closes #92033

Kind of the most simple suggestion to make - we don't try to be fancy. Turns out, it's still pretty useful (the couple existing tests that trigger this error end up fixed - for this error - upon applying the fix).

r? ``@estebank``
cc ``@nikomatsakis``

6 files changed, 77 insertions, 25 deletions

diff --git a/src/test/ui/generic-associated-types/impl_bounds.stderr b/src/test/ui/generic-associated-types/impl_bounds.stderr
index 5be431f2933..bd0dea37219 100644
--- a/src/test/ui/generic-associated-types/impl_bounds.stderr
+++ b/src/test/ui/generic-associated-types/impl_bounds.stderr
@@ -19,8 +19,13 @@ LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
 error[E0478]: lifetime bound not satisfied
   --> $DIR/impl_bounds.rs:17:35
    |
+LL |     type B<'a, 'b> where 'a: 'b;
+   |     ---------------------------- definition of `B` from trait
+...
 LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
-   |                                   ^^^^^^^^^^^^^^^
+   |                                -  ^^^^^^^^^^^^^^^
+   |                                |
+   |                                help: try copying this clause from the trait: `, 'a: 'b`
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
   --> $DIR/impl_bounds.rs:17:12
diff --git a/src/test/ui/generic-associated-types/issue-88595.rs b/src/test/ui/generic-associated-types/issue-88595.rs
index e397390783f..c97d17811ba 100644
--- a/src/test/ui/generic-associated-types/issue-88595.rs
+++ b/src/test/ui/generic-associated-types/issue-88595.rs
@@ -8,7 +8,7 @@ trait A<'a> {
     // FIXME(generic_associated_types): Remove one of the below bounds
     // https://github.com/rust-lang/rust/pull/90678#discussion_r744976085
     where
-        'a: 'b, Self: 'a, Self: 'b;
+        Self: 'a, Self: 'b;
 
     fn a(&'a self) -> Self::B<'a>;
 }
@@ -17,8 +17,7 @@ struct C;
 
 impl<'a> A<'a> for C {
     type B<'b> = impl Clone;
-    //~^ ERROR: lifetime bound not satisfied
-    //~| ERROR: could not find defining uses
+    //~^ ERROR: could not find defining uses
 
     fn a(&'a self) -> Self::B<'a> {} //~ ERROR: non-defining opaque type use in defining scope
 }
diff --git a/src/test/ui/generic-associated-types/issue-88595.stderr b/src/test/ui/generic-associated-types/issue-88595.stderr
index cb462871ccd..4e4f86bbac8 100644
--- a/src/test/ui/generic-associated-types/issue-88595.stderr
+++ b/src/test/ui/generic-associated-types/issue-88595.stderr
@@ -1,22 +1,5 @@
-error[E0478]: lifetime bound not satisfied
-  --> $DIR/issue-88595.rs:19:18
-   |
-LL |     type B<'b> = impl Clone;
-   |                  ^^^^^^^^^^
-   |
-note: lifetime parameter instantiated with the lifetime `'a` as defined here
-  --> $DIR/issue-88595.rs:18:6
-   |
-LL | impl<'a> A<'a> for C {
-   |      ^^
-note: but lifetime parameter must outlive the lifetime `'b` as defined here
-  --> $DIR/issue-88595.rs:19:12
-   |
-LL |     type B<'b> = impl Clone;
-   |            ^^
-
 error: non-defining opaque type use in defining scope
-  --> $DIR/issue-88595.rs:23:23
+  --> $DIR/issue-88595.rs:22:23
    |
 LL |     fn a(&'a self) -> Self::B<'a> {}
    |                       ^^^^^^^^^^^
@@ -35,6 +18,5 @@ error: could not find defining uses
 LL |     type B<'b> = impl Clone;
    |                  ^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0478`.
diff --git a/src/test/ui/generic-associated-types/issue-90014.stderr b/src/test/ui/generic-associated-types/issue-90014.stderr
index 23e8d08af34..f8fb71bbddb 100644
--- a/src/test/ui/generic-associated-types/issue-90014.stderr
+++ b/src/test/ui/generic-associated-types/issue-90014.stderr
@@ -1,8 +1,13 @@
 error[E0477]: the type `&mut ()` does not fulfill the required lifetime
   --> $DIR/issue-90014.rs:14:20
    |
+LL |     type Fut<'a> where Self: 'a;
+   |     ---------------------------- definition of `Fut` from trait
+...
 LL |     type Fut<'a> = impl Future<Output = ()>;
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 -  ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 |
+   |                 help: try copying this clause from the trait: `where Self: 'a`
    |
 note: type must outlive the lifetime `'a` as defined here
   --> $DIR/issue-90014.rs:14:14
diff --git a/src/test/ui/generic-associated-types/issue-92033.rs b/src/test/ui/generic-associated-types/issue-92033.rs
new file mode 100644
index 00000000000..1d5f7d5c009
--- /dev/null
+++ b/src/test/ui/generic-associated-types/issue-92033.rs
@@ -0,0 +1,39 @@
+#![feature(generic_associated_types)]
+
+struct Texture;
+
+trait Surface {
+    type TextureIter<'a>: Iterator<Item = &'a Texture>
+    where
+        Self: 'a;
+
+    fn get_texture(&self) -> Self::TextureIter<'_>;
+}
+
+trait Swapchain {
+    type Surface<'a>: Surface
+    where
+        Self: 'a;
+
+    fn get_surface(&self) -> Self::Surface<'_>;
+}
+
+impl<'s> Surface for &'s Texture {
+    type TextureIter<'a> = std::option::IntoIter<&'a Texture>;
+    //~^ ERROR the type
+
+    fn get_texture(&self) -> Self::TextureIter<'_> {
+        let option: Option<&Texture> = Some(self);
+        option.into_iter()
+    }
+}
+
+impl Swapchain for Texture {
+    type Surface<'a> = &'a Texture;
+
+    fn get_surface(&self) -> Self::Surface<'_> {
+        self
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/generic-associated-types/issue-92033.stderr b/src/test/ui/generic-associated-types/issue-92033.stderr
new file mode 100644
index 00000000000..caa6618f398
--- /dev/null
+++ b/src/test/ui/generic-associated-types/issue-92033.stderr
@@ -0,0 +1,22 @@
+error[E0477]: the type `&'s Texture` does not fulfill the required lifetime
+  --> $DIR/issue-92033.rs:22:28
+   |
+LL | /     type TextureIter<'a>: Iterator<Item = &'a Texture>
+LL | |     where
+LL | |         Self: 'a;
+   | |_________________- definition of `TextureIter` from trait
+...
+LL |       type TextureIter<'a> = std::option::IntoIter<&'a Texture>;
+   |                           -  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                           |
+   |                           help: try copying this clause from the trait: `where Self: 'a`
+   |
+note: type must outlive the lifetime `'a` as defined here
+  --> $DIR/issue-92033.rs:22:22
+   |
+LL |     type TextureIter<'a> = std::option::IntoIter<&'a Texture>;
+   |                      ^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0477`.