Make same_type_modulo_infer a proper TypeRelation

2 files changed, 67 insertions, 0 deletions

diff --git a/src/test/ui/implied-bounds/issue-100690.rs b/src/test/ui/implied-bounds/issue-100690.rs
new file mode 100644
index 00000000000..5599cd410ba
--- /dev/null
+++ b/src/test/ui/implied-bounds/issue-100690.rs
@@ -0,0 +1,45 @@
+// This code (probably) _should_ compile, but it currently does not because we
+// are not smart enough about implied bounds.
+
+use std::io;
+
+fn real_dispatch<T, F>(f: F) -> Result<(), io::Error>
+//~^ NOTE required by a bound in this
+where
+    F: FnOnce(&mut UIView<T>) -> Result<(), io::Error> + Send + 'static,
+    //~^ NOTE required by this bound in `real_dispatch`
+    //~| NOTE required by a bound in `real_dispatch`
+{
+    todo!()
+}
+
+#[derive(Debug)]
+struct UIView<'a, T: 'a> {
+    _phantom: std::marker::PhantomData<&'a mut T>,
+}
+
+trait Handle<'a, T: 'a, V, R> {
+    fn dispatch<F>(&self, f: F) -> Result<(), io::Error>
+    where
+        F: FnOnce(&mut V) -> R + Send + 'static;
+}
+
+#[derive(Debug, Clone)]
+struct TUIHandle<T> {
+    _phantom: std::marker::PhantomData<T>,
+}
+
+impl<'a, T: 'a> Handle<'a, T, UIView<'a, T>, Result<(), io::Error>> for TUIHandle<T> {
+    fn dispatch<F>(&self, f: F) -> Result<(), io::Error>
+    where
+        F: FnOnce(&mut UIView<'a, T>) -> Result<(), io::Error> + Send + 'static,
+    {
+        real_dispatch(f)
+        //~^ ERROR expected a `FnOnce<(&mut UIView<'_, T>,)>` closure, found `F`
+        //~| NOTE expected an `FnOnce<(&mut UIView<'_, T>,)>` closure, found `F`
+        //~| NOTE expected a closure with arguments
+        //~| NOTE required by a bound introduced by this call
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/implied-bounds/issue-100690.stderr b/src/test/ui/implied-bounds/issue-100690.stderr
new file mode 100644
index 00000000000..3f6af70d8ed
--- /dev/null
+++ b/src/test/ui/implied-bounds/issue-100690.stderr
@@ -0,0 +1,22 @@
+error[E0277]: expected a `FnOnce<(&mut UIView<'_, T>,)>` closure, found `F`
+  --> $DIR/issue-100690.rs:37:23
+   |
+LL |         real_dispatch(f)
+   |         ------------- ^ expected an `FnOnce<(&mut UIView<'_, T>,)>` closure, found `F`
+   |         |
+   |         required by a bound introduced by this call
+   |
+   = note: expected a closure with arguments `(&mut UIView<'a, T>,)`
+              found a closure with arguments `(&mut UIView<'_, T>,)`
+note: required by a bound in `real_dispatch`
+  --> $DIR/issue-100690.rs:9:8
+   |
+LL | fn real_dispatch<T, F>(f: F) -> Result<(), io::Error>
+   |    ------------- required by a bound in this
+...
+LL |     F: FnOnce(&mut UIView<T>) -> Result<(), io::Error> + Send + 'static,
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `real_dispatch`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.