add support of cfg attributes on enum variants #4279

Signed-off-by: Benjamin Coenen <5719034+bnjjj@users.noreply.github.com>

crates/ra_hir_def/src/adt.rs

@@ -117,7 +117,13 @@ fn lower_enum(
     ast: &InFile<ast::EnumDef>,
     module_id: ModuleId,
 ) {
-    for var in ast.value.variant_list().into_iter().flat_map(|it| it.variants()) {
+    let expander = CfgExpander::new(db, ast.file_id, module_id.krate);
+    let variants =
+        ast.value.variant_list().into_iter().flat_map(|it| it.variants()).filter(|var| {
+            let attrs = expander.parse_attrs(var);
+            expander.is_cfg_enabled(&attrs)
+        });
+    for var in variants {
         trace.alloc(
             || var.clone(),
             || EnumVariantData {

crates/ra_hir_ty/src/tests.rs

@@ -360,6 +360,33 @@ fn no_such_field_with_feature_flag_diagnostics() {
     assert_snapshot!(diagnostics, @r###""###);
 }
 
+#[test]
+fn no_such_field_enum_with_feature_flag_diagnostics() {
+    let diagnostics = TestDB::with_files(
+        r#"
+        //- /lib.rs crate:foo cfg:feature=foo
+        enum Foo {
+            #[cfg(not(feature = "foo"))]
+            Buz,
+            #[cfg(feature = "foo")]
+            Bar,
+            Baz
+        }
+
+        fn test_fn(f: Foo) {
+            match f {
+                Foo::Bar => {},
+                Foo::Baz => {},
+            }
+        }
+        "#,
+    )
+    .diagnostics()
+    .0;
+
+    assert_snapshot!(diagnostics, @r###""###);
+}
+
 #[test]
 fn no_such_field_with_feature_flag_diagnostics_on_struct_lit() {
     let diagnostics = TestDB::with_files(