add ExistentialPredicate compile fail test

Author: lcnr

src/test/ui/issues/issue-59326-compile-fail.rs

@@ -0,0 +1,28 @@
+trait Service {
+    type S;
+}
+
+trait Framing {
+    type F;
+}
+
+impl Framing for () {
+    type F = ();
+}
+
+impl Framing for u32 {
+    type F = u32;
+}
+
+trait HttpService<F: Framing>: Service<S = F::F> {}
+
+fn build_server<F: FnOnce() -> Box<dyn HttpService<u32, S = ()>>>(_: F) {}
+
+fn make_server<F: Framing>() -> Box<dyn HttpService<F, S = F::F>> {
+    unimplemented!()
+}
+
+fn main() {
+    build_server(|| make_server())
+    //~^ ERROR type mismatch
+}

src/test/ui/issues/issue-59326-compile-fail.stderr

@@ -0,0 +1,9 @@
+error[E0271]: type mismatch resolving `<u32 as Framing>::F == ()`
+  --> $DIR/issue-59326-compile-fail.rs:26:21
+   |
+LL |     build_server(|| make_server())
+   |                     ^^^^^^^^^^^^^ expected `u32`, found `()`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0271`.