Rollup merge of #55800 - estebank:abolish-ice-for-lifetime, r=oli-obk

Fix ICE in `return_type_impl_trait`

Fix #55796.

src/test/ui/issues/issue-55796.rs

@@ -0,0 +1,22 @@
+pub trait EdgeTrait<N> {
+    fn target(&self) -> N;
+}
+
+pub trait Graph<'a> {
+    type Node;
+    type Edge: EdgeTrait<Self::Node>;
+    type NodesIter: Iterator<Item = Self::Node> + 'a;
+    type EdgesIter: Iterator<Item = Self::Edge> + 'a;
+
+    fn nodes(&'a self) -> Self::NodesIter;
+    fn out_edges(&'a self, u: &Self::Node) -> Self::EdgesIter;
+    fn in_edges(&'a self, u: &Self::Node) -> Self::EdgesIter;
+
+    fn out_neighbors(&'a self, u: &Self::Node) -> Box<Iterator<Item = Self::Node>> {
+        Box::new(self.out_edges(u).map(|e| e.target()))
+    }
+
+    fn in_neighbors(&'a self, u: &Self::Node) -> Box<Iterator<Item = Self::Node>> {
+        Box::new(self.in_edges(u).map(|e| e.target()))
+    }
+}

src/test/ui/issues/issue-55796.stderr

@@ -0,0 +1,50 @@
+error[E0601]: `main` function not found in crate `issue_55796`
+   |
+   = note: consider adding a `main` function to `$DIR/issue-55796.rs`
+
+error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
+  --> $DIR/issue-55796.rs:16:9
+   |
+LL |         Box::new(self.out_edges(u).map(|e| e.target()))
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: first, the lifetime cannot outlive the lifetime 'a as defined on the trait at 5:17...
+  --> $DIR/issue-55796.rs:5:17
+   |
+LL | pub trait Graph<'a> {
+   |                 ^^
+note: ...so that the type `std::iter::Map<<Self as Graph<'a>>::EdgesIter, [closure@$DIR/issue-55796.rs:16:40: 16:54]>` will meet its required lifetime bounds
+  --> $DIR/issue-55796.rs:16:9
+   |
+LL |         Box::new(self.out_edges(u).map(|e| e.target()))
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: but, the lifetime must be valid for the static lifetime...
+   = note: ...so that the expression is assignable:
+           expected std::boxed::Box<(dyn std::iter::Iterator<Item=<Self as Graph<'a>>::Node> + 'static)>
+              found std::boxed::Box<dyn std::iter::Iterator<Item=<Self as Graph<'a>>::Node>>
+
+error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
+  --> $DIR/issue-55796.rs:20:9
+   |
+LL |         Box::new(self.in_edges(u).map(|e| e.target()))
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: first, the lifetime cannot outlive the lifetime 'a as defined on the trait at 5:17...
+  --> $DIR/issue-55796.rs:5:17
+   |
+LL | pub trait Graph<'a> {
+   |                 ^^
+note: ...so that the type `std::iter::Map<<Self as Graph<'a>>::EdgesIter, [closure@$DIR/issue-55796.rs:20:39: 20:53]>` will meet its required lifetime bounds
+  --> $DIR/issue-55796.rs:20:9
+   |
+LL |         Box::new(self.in_edges(u).map(|e| e.target()))
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: but, the lifetime must be valid for the static lifetime...
+   = note: ...so that the expression is assignable:
+           expected std::boxed::Box<(dyn std::iter::Iterator<Item=<Self as Graph<'a>>::Node> + 'static)>
+              found std::boxed::Box<dyn std::iter::Iterator<Item=<Self as Graph<'a>>::Node>>
+
+error: aborting due to 3 previous errors
+
+Some errors occurred: E0495, E0601.
+For more information about an error, try `rustc --explain E0495`.