Do not ICE in privacy when type inference fails.

compiler/rustc_privacy/src/lib.rs

@@ -973,8 +973,12 @@ impl<'tcx> NamePrivacyVisitor<'tcx> {
 
 impl<'tcx> Visitor<'tcx> for NamePrivacyVisitor<'tcx> {
     fn visit_nested_body(&mut self, body_id: hir::BodyId) {
-        let old_maybe_typeck_results =
-            self.maybe_typeck_results.replace(self.tcx.typeck_body(body_id));
+        let new_typeck_results = self.tcx.typeck_body(body_id);
+        // Do not try reporting privacy violations if we failed to infer types.
+        if new_typeck_results.tainted_by_errors.is_some() {
+            return;
+        }
+        let old_maybe_typeck_results = self.maybe_typeck_results.replace(new_typeck_results);
         self.visit_body(self.tcx.hir().body(body_id));
         self.maybe_typeck_results = old_maybe_typeck_results;
     }

tests/crashes/122736.rs → tests/ui/privacy/no-ice-on-inference-failure.rs

@@ -1,9 +1,9 @@
-//@ known-bug: #122736
 fn main_ref() {
     let array = [(); {
         let mut x = &0;
         let mut n = 0;
         while n < 5 {
+            //~^ ERROR constant evaluation is taking a long time
             x = &0;
         }
         0

tests/ui/privacy/no-ice-on-inference-failure.stderr

@@ -0,0 +1,27 @@
+error: constant evaluation is taking a long time
+  --> $DIR/no-ice-on-inference-failure.rs:5:9
+   |
+LL | /         while n < 5 {
+LL | |
+LL | |             x = &0;
+LL | |         }
+   | |_________^
+   |
+   = note: this lint makes sure the compiler doesn't get stuck due to infinite loops in const eval.
+           If your compilation actually takes a long time, you can safely allow the lint.
+help: the constant being evaluated
+  --> $DIR/no-ice-on-inference-failure.rs:2:22
+   |
+LL |       let array = [(); {
+   |  ______________________^
+LL | |         let mut x = &0;
+LL | |         let mut n = 0;
+LL | |         while n < 5 {
+...  |
+LL | |         0
+LL | |     }];
+   | |_____^
+   = note: `#[deny(long_running_const_eval)]` on by default
+
+error: aborting due to 1 previous error
+