Add test for rust-lang#12372 (generate enum variant in different file)

crates/ide-assists/src/handlers/generate_enum_variant.rs

@@ -136,6 +136,43 @@ enum Foo {
 fn main() {
     Foo::Baz
 }
+",
+        )
+    }
+
+    #[test]
+    fn generate_basic_enum_variant_in_different_file() {
+        check_assist(
+            generate_enum_variant,
+            r"
+//- /main.rs
+mod foo;
+use foo::Foo;
+
+fn main() {
+    Foo::Baz$0
+}
+
+//- /foo.rs
+enum Foo {
+    Bar,
+}
+",
+            r"
+//- /main.rs
+mod foo;
+use foo::Foo;
+
+fn main() {
+    Foo::Baz
+}
+
+//- /foo.rs
+enum Foo {
+    Bar,
+    Baz,
+}
+
 ",
         )
     }