Fix ICE caused by associated_item_def_ids on wrong type in resolve diag

compiler/rustc_resolve/src/lib.rs

@@ -2332,30 +2332,44 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     fn field_idents(&self, def_id: DefId) -> Option<Vec<Ident>> {
         match def_id.as_local() {
             Some(def_id) => self.field_names.get(&def_id).cloned(),
-            None => Some(
-                self.tcx
-                    .associated_item_def_ids(def_id)
-                    .iter()
-                    .map(|&def_id| {
-                        Ident::new(self.tcx.item_name(def_id), self.tcx.def_span(def_id))
-                    })
-                    .collect(),
-            ),
+            None if matches!(
+                self.tcx.def_kind(def_id),
+                DefKind::Struct | DefKind::Union | DefKind::Variant
+            ) =>
+            {
+                Some(
+                    self.tcx
+                        .associated_item_def_ids(def_id)
+                        .iter()
+                        .map(|&def_id| {
+                            Ident::new(self.tcx.item_name(def_id), self.tcx.def_span(def_id))
+                        })
+                        .collect(),
+                )
+            }
+            _ => None,
         }
     }
 
     fn field_defaults(&self, def_id: DefId) -> Option<Vec<Symbol>> {
         match def_id.as_local() {
             Some(def_id) => self.field_defaults.get(&def_id).cloned(),
-            None => Some(
-                self.tcx
-                    .associated_item_def_ids(def_id)
-                    .iter()
-                    .filter_map(|&def_id| {
-                        self.tcx.default_field(def_id).map(|_| self.tcx.item_name(def_id))
-                    })
-                    .collect(),
-            ),
+            None if matches!(
+                self.tcx.def_kind(def_id),
+                DefKind::Struct | DefKind::Union | DefKind::Variant
+            ) =>
+            {
+                Some(
+                    self.tcx
+                        .associated_item_def_ids(def_id)
+                        .iter()
+                        .filter_map(|&def_id| {
+                            self.tcx.default_field(def_id).map(|_| self.tcx.item_name(def_id))
+                        })
+                        .collect(),
+                )
+            }
+            _ => None,
         }
     }
 

tests/ui/structs/default-field-values/struct-fields-ice-147325.rs

@@ -0,0 +1,11 @@
+// ICE #147325: When the user mistakenly uses struct syntax to construct an enum,
+// the field_idents and field_defaults functions will trigger an error
+
+mod m {
+    struct Priv1;
+}
+
+fn main() {
+    Option { field1: m::Priv1 } //~ ERROR expected struct, variant or union type, found enum
+    //~^ ERROR unit struct `Priv1` is private
+}

tests/ui/structs/default-field-values/struct-fields-ice-147325.stderr

@@ -0,0 +1,22 @@
+error[E0574]: expected struct, variant or union type, found enum `Option`
+  --> $DIR/struct-fields-ice-147325.rs:9:5
+   |
+LL |     Option { field1: m::Priv1 }
+   |     ^^^^^^ not a struct, variant or union type
+
+error[E0603]: unit struct `Priv1` is private
+  --> $DIR/struct-fields-ice-147325.rs:9:25
+   |
+LL |     Option { field1: m::Priv1 }
+   |                         ^^^^^ private unit struct
+   |
+note: the unit struct `Priv1` is defined here
+  --> $DIR/struct-fields-ice-147325.rs:5:5
+   |
+LL |     struct Priv1;
+   |     ^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0574, E0603.
+For more information about an error, try `rustc --explain E0574`.