Auto merge of #109356 - jackh726:issue-108544, r=lcnr

Only check outlives goals on impl compared to trait

Fixes #108544

r? `@compiler-errors`

2 files changed, 38 insertions, 0 deletions

diff --git a/tests/ui/implied-bounds/implied_bounds_entailment_skip_non_outlives.rs b/tests/ui/implied-bounds/implied_bounds_entailment_skip_non_outlives.rs
new file mode 100644
index 00000000000..8dcc35a281a
--- /dev/null
+++ b/tests/ui/implied-bounds/implied_bounds_entailment_skip_non_outlives.rs
@@ -0,0 +1,23 @@
+// check-pass
+// See issue #109356. We don't want a false positive to the `implied_bounds_entailment` lint.
+
+use std::borrow::Cow;
+
+pub trait Trait {
+    fn method(self) -> Option<Cow<'static, str>>
+    where
+        Self: Sized;
+}
+
+impl<'a> Trait for Cow<'a, str> {
+    // If we're not careful here, we'll check `WF(return-type)` using the trait
+    // and impl where clauses, requiring that `Cow<'a, str>: Sized`. This is
+    // obviously true, but if we pick the `Self: Sized` clause from the trait
+    // over the "inherent impl", we will require `'a == 'static`, which triggers
+    // the `implied_bounds_entailment` lint.
+    fn method(self) -> Option<Cow<'static, str>> {
+        None
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/implied-bounds/trait-where-clause-implied.rs b/tests/ui/implied-bounds/trait-where-clause-implied.rs
new file mode 100644
index 00000000000..5f9ab66d3c8
--- /dev/null
+++ b/tests/ui/implied-bounds/trait-where-clause-implied.rs
@@ -0,0 +1,15 @@
+// check-pass
+
+pub trait Trait<'a, 'b> {
+    fn method(self, _: &'static &'static ())
+    where
+        'a: 'b;
+}
+
+impl<'a> Trait<'a, 'static> for () {
+    // On first glance, this seems like we have the extra implied bound that
+    // `'a: 'static`, but we know this from the trait method where clause.
+    fn method(self, _: &'static &'a ()) {}
+}
+
+fn main() {}