Merge pull request #3394 from Snowapril/fix-ga-param-chaining

DimitrisJim · web-flow · commit 612e943c6c17 · 2021-11-02T23:37:38.000+02:00
Fix `GenericAlias` parameter chaining
diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
@@ -173,8 +173,6 @@ def test_exposed_type(self):
         self.assertEqual(a.__args__, (int,))
         self.assertEqual(a.__parameters__, ())
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_parameters(self):
         from typing import List, Dict, Callable
         D0 = dict[str, int]
@@ -214,8 +212,6 @@ def test_parameters(self):
         self.assertEqual(L5.__args__, (Callable[[K, V], K],))
         self.assertEqual(L5.__parameters__, (K, V))
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_parameter_chaining(self):
         from typing import List, Dict, Union, Callable
         self.assertEqual(list[T][int], list[int])
diff --git a/extra_tests/snippets/test_typing.py b/extra_tests/snippets/test_typing.py
diff --git a/vm/src/builtins/genericalias.rs b/vm/src/builtins/genericalias.rs
@@ -175,20 +175,25 @@ fn is_typevar(obj: &PyObjectRef) -> bool {
 }
 
 fn make_parameters(args: &PyTupleRef, vm: &VirtualMachine) -> PyTupleRef {
-    let mut parameters: Vec<PyObjectRef> = vec![];
+    let mut parameters: Vec<PyObjectRef> = Vec::with_capacity(args.len());
     for arg in args.as_slice() {
         if is_typevar(arg) {
-            parameters.push(arg.clone());
-        } else if let Ok(tuple) = arg
+            if !parameters.iter().any(|param| param.is(arg)) {
+                parameters.push(arg.clone());
+            }
+        } else if let Ok(subparams) = arg
             .clone()
             .get_attr("__parameters__", vm)
             .and_then(|obj| PyTupleRef::try_from_object(vm, obj))
         {
-            for subparam in tuple.as_slice() {
-                parameters.push(subparam.clone());
+            for subparam in subparams.as_slice() {
+                if !parameters.iter().any(|param| param.is(subparam)) {
+                    parameters.push(subparam.clone());
+                }
             }
         }
     }
+    parameters.shrink_to_fit();
 
     PyTuple::new_ref(parameters, &vm.ctx)
 }
@@ -204,27 +209,33 @@ fn subs_tvars(
     argitems: &[PyObjectRef],
     vm: &VirtualMachine,
 ) -> PyResult {
-    obj.clone_class()
-        .get_attr("__parameters__")
+    obj.clone()
+        .get_attr("__parameters__", vm)
+        .ok()
         .and_then(|sub_params| {
             PyTupleRef::try_from_object(vm, sub_params)
                 .ok()
                 .map(|sub_params| {
-                    let sub_args = sub_params
-                        .as_slice()
-                        .iter()
-                        .map(|arg| {
-                            if let Some(idx) = tuple_index(params, arg) {
-                                argitems[idx].clone()
-                            } else {
-                                arg.clone()
-                            }
-                        })
-                        .collect::<Vec<_>>();
-                    let sub_args: PyObjectRef = PyTuple::new_ref(sub_args, &vm.ctx).into();
-                    obj.get_item(sub_args, vm)
+                    if sub_params.len() > 0 {
+                        let sub_args = sub_params
+                            .as_slice()
+                            .iter()
+                            .map(|arg| {
+                                if let Some(idx) = tuple_index(params, arg) {
+                                    argitems[idx].clone()
+                                } else {
+                                    arg.clone()
+                                }
+                            })
+                            .collect::<Vec<_>>();
+                        let sub_args: PyObjectRef = PyTuple::new_ref(sub_args, &vm.ctx).into();
+                        Some(obj.get_item(sub_args, vm))
+                    } else {
+                        None
+                    }
                 })
         })
+        .flatten()
         .unwrap_or(Ok(obj))
 }
 
