Move a span_bug under a condition that cx is tainted

Fixes an ICE caused when a with expression is not a struct

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -734,7 +734,9 @@ fn walk_struct_expr<'hir>(
                 // struct; however, when EUV is run during typeck, it
                 // may not. This will generate an error earlier in typeck,
                 // so we can just ignore it.
-                span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
+                if self.cx.tainted_by_errors().is_ok() {
+                    span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
+                }
             }
         }
 

tests/crashes/127332.rs

@@ -1,9 +0,0 @@
-//@ known-bug: rust-lang/rust #127332
-
-async fn fun() {
-    enum Foo {
-        A { x: u32 },
-    }
-    let orig = Foo::A { x: 5 };
-    Foo::A { x: 6, ..orig };
-}

tests/ui/typeck/ice-with-expr-not-struct-127332.rs

@@ -0,0 +1,15 @@
+// Regression test for ICE #127332
+
+// Tests that we do not ICE when a with expr is
+// not a struct but something else like an enum
+
+fn main() {
+    let x = || {
+        enum Foo {
+            A { x: u32 },
+        }
+        let orig = Foo::A { x: 5 };
+        Foo::A { x: 6, ..orig };
+        //~^ ERROR functional record update syntax requires a struct
+    };
+}

tests/ui/typeck/ice-with-expr-not-struct-127332.stderr

@@ -0,0 +1,9 @@
+error[E0436]: functional record update syntax requires a struct
+  --> $DIR/ice-with-expr-not-struct-127332.rs:12:26
+   |
+LL |         Foo::A { x: 6, ..orig };
+   |                          ^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0436`.