check_expr_struct_fields: taint context with errors if struct definit…

…ion is malformed

compiler/rustc_hir_typeck/src/expr.rs

@@ -1671,6 +1671,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let mut error_happened = false;
 
+        if variant.fields.len() != remaining_fields.len() {
+            // Some field is defined more than once. Make sure we don't try to
+            // instantiate this struct in static/const context.
+            let guar =
+                self.dcx().span_delayed_bug(expr.span, "struct fields have non-unique names");
+            self.set_tainted_by_errors(guar);
+            error_happened = true;
+        }
+
         // Type-check each field.
         for (idx, field) in hir_fields.iter().enumerate() {
             let ident = tcx.adjust_ident(field.ident, variant.def_id);

tests/crashes/124464.rs → tests/ui/static/duplicated-fields-issue-124464.rs

@@ -1,12 +1,16 @@
-//@ known-bug: rust-lang/rust #124464
+// Don't const eval fields with ambiguous layout.
+// See issues #125842 and #124464.
+
 enum TestOption<T> {
     TestSome(T),
     TestSome(T),
+//~^ ERROR the name `TestSome` is defined multiple times
 }
 
 pub struct Request {
     bar: TestOption<u64>,
     bar: u8,
+//~^ ERROR field `bar` is already declared
 }
 
 fn default_instance() -> &'static Request {

tests/ui/static/duplicated-fields-issue-124464.stderr

@@ -0,0 +1,22 @@
+error[E0428]: the name `TestSome` is defined multiple times
+  --> $DIR/duplicated-fields-issue-124464.rs:6:5
+   |
+LL |     TestSome(T),
+   |     ----------- previous definition of the type `TestSome` here
+LL |     TestSome(T),
+   |     ^^^^^^^^^^^ `TestSome` redefined here
+   |
+   = note: `TestSome` must be defined only once in the type namespace of this enum
+
+error[E0124]: field `bar` is already declared
+  --> $DIR/duplicated-fields-issue-124464.rs:12:5
+   |
+LL |     bar: TestOption<u64>,
+   |     -------------------- `bar` first declared here
+LL |     bar: u8,
+   |     ^^^^^^^ field already declared
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0124, E0428.
+For more information about an error, try `rustc --explain E0124`.

tests/ui/static/duplicated-fields-issue-125842.rs

@@ -0,0 +1,21 @@
+// Do not try to evaluate static initalizers that reference
+// ill-defined types. This used to be an ICE.
+// See issues #125842 and #124464.
+struct Struct {
+    field: Option<u8>,
+    field: u8,
+//~^ ERROR field `field` is already declared
+}
+
+static STATIC_A: Struct = Struct {
+    field: 1
+};
+
+static STATIC_B: Struct = {
+    let field = 1;
+    Struct {
+        field,
+    }
+};
+
+fn main() {}

tests/ui/static/duplicated-fields-issue-125842.stderr

@@ -0,0 +1,11 @@
+error[E0124]: field `field` is already declared
+  --> $DIR/duplicated-fields-issue-125842.rs:6:5
+   |
+LL |     field: Option<u8>,
+   |     ----------------- `field` first declared here
+LL |     field: u8,
+   |     ^^^^^^^^^ field already declared
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0124`.