Rollup merge of #154804 - cijiugechu:fix/host-effect-hrtb-ice, r=adwinwhite

Fix ICE when reporting host-effect errors for const Fn HRTBs in next trait solver

Avoid leaking bound vars into the diagnostic selection path for HRTB host-effect predicates.

Closes #151894 .

Author: JonathanBrouwer

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -874,7 +874,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         }
 
         if let Ok(Some(ImplSource::UserDefined(impl_data))) =
-            SelectionContext::new(self).select(&obligation.with(self.tcx, trait_ref.skip_binder()))
+            self.enter_forall(trait_ref, |trait_ref_for_select| {
+                SelectionContext::new(self).select(&obligation.with(self.tcx, trait_ref_for_select))
+            })
         {
             let impl_did = impl_data.impl_def_id;
             let trait_did = trait_ref.def_id();

tests/ui/traits/next-solver/diagnostics/const-host-effect-hrtb-no-ice.rs

@@ -0,0 +1,12 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/151894
+//@ compile-flags: -Znext-solver=globally
+
+#![feature(const_trait_impl)]
+
+const fn with_positive<F: for<'a> [const] Fn(&'a ())>() {}
+
+const _: () = {
+    with_positive::<()>(); //~ ERROR expected a `Fn(&'a ())` closure, found `()`
+};
+
+fn main() {}

tests/ui/traits/next-solver/diagnostics/const-host-effect-hrtb-no-ice.stderr

@@ -0,0 +1,16 @@
+error[E0277]: expected a `Fn(&'a ())` closure, found `()`
+  --> $DIR/const-host-effect-hrtb-no-ice.rs:9:21
+   |
+LL |     with_positive::<()>();
+   |                     ^^ expected an `Fn(&'a ())` closure, found `()`
+   |
+   = help: the trait `for<'a> Fn(&'a ())` is not implemented for `()`
+note: required by a bound in `with_positive`
+  --> $DIR/const-host-effect-hrtb-no-ice.rs:6:27
+   |
+LL | const fn with_positive<F: for<'a> [const] Fn(&'a ())>() {}
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `with_positive`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.