[mypyc] Implement list.clear() primitive

mypyc/lib-rt/CPy.h

@@ -667,6 +667,7 @@ PyObject *CPySequence_Multiply(PyObject *seq, CPyTagged t_size);
 PyObject *CPySequence_RMultiply(CPyTagged t_size, PyObject *seq);
 PyObject *CPySequence_InPlaceMultiply(PyObject *seq, CPyTagged t_size);
 PyObject *CPyList_GetSlice(PyObject *obj, CPyTagged start, CPyTagged end);
+char CPyList_Clear(PyObject *list);
 PyObject *CPyList_Copy(PyObject *list);
 int CPySequence_Check(PyObject *obj);
 

mypyc/lib-rt/list_ops.c

@@ -29,6 +29,23 @@ PyObject *CPyList_Build(Py_ssize_t len, ...) {
     return res;
 }
 
+char CPyList_Clear(PyObject *list) {
+    if (PyList_CheckExact(list)) {
+        PyList_Clear(list);
+    } else {
+        _Py_IDENTIFIER(clear);
+        PyObject *name = _PyUnicode_FromId(&PyId_clear);
+        if (name == NULL) {
+            return 0;
+        }
+        PyObject *res = PyObject_CallMethodNoArgs(list, name);
+        if (res == NULL) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
 PyObject *CPyList_Copy(PyObject *list) {
     if(PyList_CheckExact(list)) {
         return PyList_GetSlice(list, 0, PyList_GET_SIZE(list));

mypyc/primitives/list_ops.py

@@ -271,6 +271,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# list.clear()
+method_op(
+    name="clear",
+    arg_types=[list_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="CPyList_Clear",
+    error_kind=ERR_FALSE,
+)
+
 # list.copy()
 method_op(
     name="copy",

mypyc/test-data/fixtures/ir.py

@@ -245,6 +245,7 @@ def sort(self) -> None: pass
     def reverse(self) -> None: pass
     def remove(self, o: _T) -> None: pass
     def index(self, o: _T) -> int: pass
+    def clear(self) -> None: pass
     def copy(self) -> List[_T]: pass
 
 class dict(Mapping[_K, _V]):

mypyc/test-data/irbuild-lists.test

@@ -220,6 +220,18 @@ L0:
     r1 = r0 << 1
     return r1
 
+[case testListClear]
+from typing import List
+def f(l: List[int]) -> None:
+    return l.clear()
+[out]
+def f(l):
+    l :: list
+    r0 :: bit
+L0:
+    r0 = CPyList_Clear(l)
+    return 1
+
 [case testListCopy]
 from typing import List
 from typing import Any

mypyc/test-data/run-lists.test

@@ -51,6 +51,32 @@ print(2, a)
 1 [-1, 5]
 2 [340282366920938463463374607431768211461, -170141183460469231731687303715884105736]
 
+[case testListClear]
+from typing import List, Any
+from copysubclass import subc
+
+def test_list_clear() -> None:
+    l1 = [1, 2, 3, -4, 5]
+    l1.clear()
+    assert l1 == []
+    l1.clear()
+    assert l1 == []
+    l2: List[Any] = []
+    l2.clear()
+    assert l2 == []
+    l3 = [1, 2, 3, "abcdef"]
+    l3.clear()
+    assert l3 == []
+    # subclass testing
+    l4: subc = subc([1, 2, 3])
+    l4.clear()
+    assert l4 == []
+
+[file copysubclass.py]
+from typing import Any
+class subc(list[Any]):
+    pass
+
 [case testListCopy]
 from typing import List
 from copysubclass import subc