Rollup merge of rust-lang#127409 - gurry:127332-ice-with-expr-not-struct, r=oli-obk

Emit a wrap expr span_bug only if context is not tainted

Fixes rust-lang#127332

The ICE occurs because of this `span_bug`: https://github.com/rust-lang/rust/blob/51917e2e69702e5752bce6a4f3bfd285d0f4ae39/compiler/rustc_hir_typeck/src/expr_use_visitor.rs#L732-L738
which is triggered by the fact that we're trying to use an `enum` in a `with` expression instead of a `struct`.

The issue originates in commit rust-lang@814bfe9   from PR rust-lang#127202. As per the title of that commit the ICEing code should not be reachable any more, but looks like it still is.

This PR changes the code so that the `span_bug` will be emitted only if the context is not tainted by a previous error.

Author: matthiaskrgr

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -734,7 +734,9 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                 // 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

@@ -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.rs

@@ -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`.