Don't construct preds w escaping bound vars in diagnostic_hir_wf_check

compiler/rustc_hir_analysis/src/hir_wf_check.rs

@@ -4,7 +4,7 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{ObligationCause, WellFormedLoc};
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, TyCtxt, TypingMode, fold_regions};
+use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt, TypingMode, fold_regions};
 use rustc_span::def_id::LocalDefId;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 use tracing::debug;
@@ -77,6 +77,15 @@ fn diagnostic_hir_wf_check<'tcx>(
             let tcx_ty = fold_regions(self.tcx, tcx_ty, |r, _| {
                 if r.is_bound() { self.tcx.lifetimes.re_erased } else { r }
             });
+
+            // We may be checking the WFness of a type in an opaque with a non-lifetime bound.
+            // Perhaps we could rebind all the escaping bound vars, but they're coming from
+            // arbitrary debruijn indices and aren't particularly important anyways, since they
+            // are only coming from `feature(non_lifetime_binders)` anyways.
+            if tcx_ty.has_escaping_bound_vars() {
+                return;
+            }
+
             let cause = traits::ObligationCause::new(
                 ty.span,
                 self.def_id,

tests/ui/traits/non_lifetime_binders/diagnostic-hir-wf-check.rs

@@ -0,0 +1,18 @@
+// Make sure not to construct predicates with escaping bound vars in `diagnostic_hir_wf_check`.
+// Regression test for <https://github.com/rust-lang/rust/issues/139330>.
+
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+trait A<T: ?Sized> {}
+impl<T: ?Sized> A<T> for () {}
+
+trait B {}
+struct W<T: B>(T);
+
+fn b() -> (W<()>, impl for<C> A<C>) { (W(()), ()) }
+//~^ ERROR the trait bound `(): B` is not satisfied
+//~| ERROR the trait bound `(): B` is not satisfied
+//~| ERROR the trait bound `(): B` is not satisfied
+
+fn main() {}

tests/ui/traits/non_lifetime_binders/diagnostic-hir-wf-check.stderr

@@ -0,0 +1,65 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/diagnostic-hir-wf-check.rs:4:12
+   |
+LL | #![feature(non_lifetime_binders)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0277]: the trait bound `(): B` is not satisfied
+  --> $DIR/diagnostic-hir-wf-check.rs:13:12
+   |
+LL | fn b() -> (W<()>, impl for<C> A<C>) { (W(()), ()) }
+   |            ^^^^^ the trait `B` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/diagnostic-hir-wf-check.rs:10:1
+   |
+LL | trait B {}
+   | ^^^^^^^
+note: required by a bound in `W`
+  --> $DIR/diagnostic-hir-wf-check.rs:11:13
+   |
+LL | struct W<T: B>(T);
+   |             ^ required by this bound in `W`
+
+error[E0277]: the trait bound `(): B` is not satisfied
+  --> $DIR/diagnostic-hir-wf-check.rs:13:42
+   |
+LL | fn b() -> (W<()>, impl for<C> A<C>) { (W(()), ()) }
+   |                                        - ^^ the trait `B` is not implemented for `()`
+   |                                        |
+   |                                        required by a bound introduced by this call
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/diagnostic-hir-wf-check.rs:10:1
+   |
+LL | trait B {}
+   | ^^^^^^^
+note: required by a bound in `W`
+  --> $DIR/diagnostic-hir-wf-check.rs:11:13
+   |
+LL | struct W<T: B>(T);
+   |             ^ required by this bound in `W`
+
+error[E0277]: the trait bound `(): B` is not satisfied
+  --> $DIR/diagnostic-hir-wf-check.rs:13:40
+   |
+LL | fn b() -> (W<()>, impl for<C> A<C>) { (W(()), ()) }
+   |                                        ^^^^^ the trait `B` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/diagnostic-hir-wf-check.rs:10:1
+   |
+LL | trait B {}
+   | ^^^^^^^
+note: required by a bound in `W`
+  --> $DIR/diagnostic-hir-wf-check.rs:11:13
+   |
+LL | struct W<T: B>(T);
+   |             ^ required by this bound in `W`
+
+error: aborting due to 3 previous errors; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0277`.