fix: Do not ICE when missing match arm with ill-formed subty is met

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -191,7 +191,18 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
         variant.fields.iter().map(move |field| {
             let ty = field.ty(self.tcx, args);
             // `field.ty()` doesn't normalize after instantiating.
-            let ty = self.tcx.normalize_erasing_regions(self.typing_env, ty);
+            let ty =
+                self.tcx.try_normalize_erasing_regions(self.typing_env, ty).unwrap_or_else(|e| {
+                    self.tcx.dcx().span_delayed_bug(
+                        self.scrut_span,
+                        format!(
+                            "Failed to normalize {:?} in typing_env={:?} while getting variant sub tys for {ty:?}",
+                            e.get_type_for_failure(),
+                            self.typing_env,
+                        ),
+                    );
+                    ty
+                });
             let ty = self.reveal_opaque_ty(ty);
             (field, ty)
         })

tests/ui/pattern/missing-ctor-with-ill-formed-inner-ty-issue-148192.rs

@@ -0,0 +1,20 @@
+trait WhereTrait {
+    type Type;
+}
+
+fn foo(e: Enum) {
+    if let Enum::Map(_) = e {}
+
+    match e {
+        //~^ ERROR: non-exhaustive patterns: `Enum::Map2(_)` not covered
+        Enum::Map(_) => (),
+    }
+}
+
+enum Enum {
+    Map(()),
+    Map2(<() as WhereTrait>::Type),
+    //~^ ERROR: the trait bound `(): WhereTrait` is not satisfied
+}
+
+fn main() {}

tests/ui/pattern/missing-ctor-with-ill-formed-inner-ty-issue-148192.stderr

@@ -0,0 +1,37 @@
+error[E0277]: the trait bound `(): WhereTrait` is not satisfied
+  --> $DIR/missing-ctor-with-ill-formed-inner-ty-issue-148192.rs:16:10
+   |
+LL |     Map2(<() as WhereTrait>::Type),
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `WhereTrait` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/missing-ctor-with-ill-formed-inner-ty-issue-148192.rs:1:1
+   |
+LL | trait WhereTrait {
+   | ^^^^^^^^^^^^^^^^
+
+error[E0004]: non-exhaustive patterns: `Enum::Map2(_)` not covered
+  --> $DIR/missing-ctor-with-ill-formed-inner-ty-issue-148192.rs:8:11
+   |
+LL |     match e {
+   |           ^ pattern `Enum::Map2(_)` not covered
+   |
+note: `Enum` defined here
+  --> $DIR/missing-ctor-with-ill-formed-inner-ty-issue-148192.rs:14:6
+   |
+LL | enum Enum {
+   |      ^^^^
+LL |     Map(()),
+LL |     Map2(<() as WhereTrait>::Type),
+   |     ---- not covered
+   = note: the matched value is of type `Enum`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
+   |
+LL ~         Enum::Map(_) => (),
+LL ~         Enum::Map2(_) => todo!(),
+   |
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0004, E0277.
+For more information about an error, try `rustc --explain E0004`.