Generate enum variant assist

This also disables "generate function" when what we clearly want is to
generate an enum variant.

Co-authored-by: Maarten Flippo <maartenflippo@outlook.com>

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

@@ -71,6 +71,10 @@ fn gen_fn(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
                 get_fn_target(ctx, &target_module, call.clone())?
             }
             Some(hir::PathResolution::Def(hir::ModuleDef::Adt(adt))) => {
+                if let hir::Adt::Enum(_) = adt {
+                    return None;
+                }
+
                 let current_module = ctx.sema.scope(call.syntax())?.module();
                 let module = adt.module(ctx.sema.db);
                 target_module = if current_module == module { None } else { Some(module) };
@@ -1738,4 +1742,17 @@ fn foo(value: usize) ${0:-> _} {
 ",
         )
     }
+
+    #[test]
+    fn not_applicable_for_enum_variant() {
+        check_assist_not_applicable(
+            generate_function,
+            r"
+enum Foo {}
+fn main() {
+    Foo::Bar$0(true)
+}
+",
+        );
+    }
 }