added a test case for reporting mismatched traits

src/test/ui/error-codes/E0308-2.rs

@@ -0,0 +1,12 @@
+trait DynEq {}
+
+impl<'a> PartialEq for &'a (dyn DynEq + 'static) {
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
+impl Eq for &dyn DynEq {} //~ ERROR E0308
+
+fn main() {
+}

src/test/ui/error-codes/E0308-2.stderr

@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+  --> $DIR/E0308-2.rs:9:6
+   |
+LL | impl Eq for &dyn DynEq {}
+   |      ^^ lifetime mismatch
+   |
+   = note: expected trait `std::cmp::PartialEq`
+              found trait `std::cmp::PartialEq`
+note: the lifetime `'_` as defined on the impl at 9:13...
+  --> $DIR/E0308-2.rs:9:13
+   |
+LL | impl Eq for &dyn DynEq {}
+   |             ^
+   = note: ...does not necessarily outlive the static lifetime
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.