Don't ice on bad transmute in typeck in new solver

compiler/rustc_hir_typeck/src/intrinsicck.rs

@@ -40,13 +40,25 @@ fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
 }
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+    /// FIXME: Move this check out of typeck, since it'll easily cycle when revealing opaques,
+    /// and we shouldn't need to check anything here if the typeck results are tainted.
     pub(crate) fn check_transmute(&self, from: Ty<'tcx>, to: Ty<'tcx>, hir_id: HirId) {
         let tcx = self.tcx;
         let dl = &tcx.data_layout;
         let span = tcx.hir().span(hir_id);
         let normalize = |ty| {
             let ty = self.resolve_vars_if_possible(ty);
-            self.tcx.normalize_erasing_regions(self.typing_env(self.param_env), ty)
+            if let Ok(ty) =
+                self.tcx.try_normalize_erasing_regions(self.typing_env(self.param_env), ty)
+            {
+                ty
+            } else {
+                Ty::new_error_with_message(
+                    tcx,
+                    span,
+                    "tried to normalize non-wf type in check_transmute",
+                )
+            }
         };
         let from = normalize(from);
         let to = normalize(to);

tests/ui/traits/next-solver/dont-ice-on-bad-transmute-in-typeck.rs

@@ -0,0 +1,17 @@
+//@ compile-flags: -Znext-solver
+
+trait Trait<'a> {
+    type Assoc;
+}
+
+fn foo(x: for<'a> fn(<() as Trait<'a>>::Assoc)) {
+    //~^ ERROR the trait bound `for<'a> (): Trait<'a>` is not satisfied
+    //~| ERROR the trait bound `for<'a> (): Trait<'a>` is not satisfied
+    //~| ERROR the trait bound `for<'a> (): Trait<'a>` is not satisfied
+    unsafe { std::mem::transmute::<_, ()>(x); }
+    //~^ ERROR the trait bound `for<'a> (): Trait<'a>` is not satisfied
+    //~| ERROR the trait bound `for<'a> (): Trait<'a>` is not satisfied
+    //~| ERROR the trait bound `for<'a> (): Trait<'a>` is not satisfied
+}
+
+fn main() {}

tests/ui/traits/next-solver/dont-ice-on-bad-transmute-in-typeck.stderr

@@ -0,0 +1,75 @@
+error[E0277]: the trait bound `for<'a> (): Trait<'a>` is not satisfied
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:7:11
+   |
+LL | fn foo(x: for<'a> fn(<() as Trait<'a>>::Assoc)) {
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> Trait<'a>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:3:1
+   |
+LL | trait Trait<'a> {
+   | ^^^^^^^^^^^^^^^
+
+error[E0277]: the trait bound `for<'a> (): Trait<'a>` is not satisfied
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:7:8
+   |
+LL | fn foo(x: for<'a> fn(<() as Trait<'a>>::Assoc)) {
+   |        ^ the trait `for<'a> Trait<'a>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:3:1
+   |
+LL | trait Trait<'a> {
+   | ^^^^^^^^^^^^^^^
+
+error[E0277]: the trait bound `for<'a> (): Trait<'a>` is not satisfied
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:11:14
+   |
+LL |     unsafe { std::mem::transmute::<_, ()>(x); }
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> Trait<'a>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:3:1
+   |
+LL | trait Trait<'a> {
+   | ^^^^^^^^^^^^^^^
+
+error[E0277]: the trait bound `for<'a> (): Trait<'a>` is not satisfied
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:11:36
+   |
+LL |     unsafe { std::mem::transmute::<_, ()>(x); }
+   |                                    ^ the trait `for<'a> Trait<'a>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:3:1
+   |
+LL | trait Trait<'a> {
+   | ^^^^^^^^^^^^^^^
+
+error[E0277]: the trait bound `for<'a> (): Trait<'a>` is not satisfied
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:11:43
+   |
+LL |     unsafe { std::mem::transmute::<_, ()>(x); }
+   |                                           ^ the trait `for<'a> Trait<'a>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:3:1
+   |
+LL | trait Trait<'a> {
+   | ^^^^^^^^^^^^^^^
+
+error[E0277]: the trait bound `for<'a> (): Trait<'a>` is not satisfied
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:7:1
+   |
+LL | fn foo(x: for<'a> fn(<() as Trait<'a>>::Assoc)) {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> Trait<'a>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-ice-on-bad-transmute-in-typeck.rs:3:1
+   |
+LL | trait Trait<'a> {
+   | ^^^^^^^^^^^^^^^
+
+error: aborting due to 6 previous errors
+
+For more information about this error, try `rustc --explain E0277`.