Preserve parent CallContext when inferring nested functions (#1982)

Author: cdce8p

ChangeLog

@@ -14,9 +14,12 @@ Release date: TBA
 
 * Fix issues with ``typing_extensions.TypeVar``.
 
-
 * Fix ``ClassDef.fromlino`` for PyPy 3.8 (v7.3.11) if class is wrapped by a decorator.
 
+* Preserve parent CallContext when inferring nested functions.
+
+  Closes PyCQA/pylint#8074
+
 
 What's New in astroid 2.13.3?
 =============================

astroid/brain/brain_typing.py

@@ -28,7 +28,6 @@
     Const,
     JoinedStr,
     Name,
-    NodeNG,
     Subscript,
     Tuple,
 )
@@ -380,36 +379,6 @@ def infer_special_alias(
     return iter([class_def])
 
 
-def _looks_like_typing_cast(node: Call) -> bool:
-    return isinstance(node, Call) and (
-        isinstance(node.func, Name)
-        and node.func.name == "cast"
-        or isinstance(node.func, Attribute)
-        and node.func.attrname == "cast"
-    )
-
-
-def infer_typing_cast(
-    node: Call, ctx: context.InferenceContext | None = None
-) -> Iterator[NodeNG]:
-    """Infer call to cast() returning same type as casted-from var."""
-    if not isinstance(node.func, (Name, Attribute)):
-        raise UseInferenceDefault
-
-    try:
-        func = next(node.func.infer(context=ctx))
-    except (InferenceError, StopIteration) as exc:
-        raise UseInferenceDefault from exc
-    if (
-        not isinstance(func, FunctionDef)
-        or func.qname() != "typing.cast"
-        or len(node.args) != 2
-    ):
-        raise UseInferenceDefault
-
-    return node.args[1].infer(context=ctx)
-
-
 AstroidManager().register_transform(
     Call,
     inference_tip(infer_typing_typevar_or_newtype),
@@ -418,9 +387,6 @@ def infer_typing_cast(
 AstroidManager().register_transform(
     Subscript, inference_tip(infer_typing_attr), _looks_like_typing_subscript
 )
-AstroidManager().register_transform(
-    Call, inference_tip(infer_typing_cast), _looks_like_typing_cast
-)
 
 if PY39_PLUS:
     AstroidManager().register_transform(

astroid/context.py

@@ -161,13 +161,14 @@ def __str__(self) -> str:
 class CallContext:
     """Holds information for a call site."""
 
-    __slots__ = ("args", "keywords", "callee")
+    __slots__ = ("args", "keywords", "callee", "parent_call_context")
 
     def __init__(
         self,
         args: list[NodeNG],
         keywords: list[Keyword] | None = None,
         callee: NodeNG | None = None,
+        parent_call_context: CallContext | None = None,
     ):
         self.args = args  # Call positional arguments
         if keywords:
@@ -176,6 +177,9 @@ def __init__(
             arg_value_pairs = []
         self.keywords = arg_value_pairs  # Call keyword arguments
         self.callee = callee  # Function being called
+        self.parent_call_context = (
+            parent_call_context  # Parent CallContext for nested calls
+        )
 
 
 def copy_context(context: InferenceContext | None) -> InferenceContext:

astroid/inference.py

@@ -273,7 +273,10 @@ def infer_call(
         try:
             if hasattr(callee, "infer_call_result"):
                 callcontext.callcontext = CallContext(
-                    args=self.args, keywords=self.keywords, callee=callee
+                    args=self.args,
+                    keywords=self.keywords,
+                    callee=callee,
+                    parent_call_context=callcontext.callcontext,
                 )
                 yield from callee.infer_call_result(caller=self, context=callcontext)
         except InferenceError:

astroid/protocols.py

@@ -470,7 +470,7 @@ def arguments_assigned_stmts(
         # reset call context/name
         callcontext = context.callcontext
         context = copy_context(context)
-        context.callcontext = None
+        context.callcontext = callcontext.parent_call_context
         args = arguments.CallSite(callcontext, context=context)
         return args.infer_argument(self.parent, node_name, context)
     return _arguments_infer_argname(self, node_name, context)

tests/unittest_brain.py

@@ -2132,8 +2132,7 @@ class A:
             pass
 
         b = 42
-        a = cast(A, b)
-        a
+        cast(A, b)
         """
         )
         inferred = next(node.infer())
@@ -2148,14 +2147,33 @@ class A:
             pass
 
         b = 42
-        a = typing.cast(A, b)
-        a
+        typing.cast(A, b)
         """
         )
         inferred = next(node.infer())
         assert isinstance(inferred, nodes.Const)
         assert inferred.value == 42
 
+    def test_typing_cast_multiple_inference_calls(self) -> None:
+        ast_nodes = builder.extract_node(
+            """
+        from typing import TypeVar, cast
+        T = TypeVar("T")
+        def ident(var: T) -> T:
+            return cast(T, var)
+
+        ident(2)  #@
+        ident("Hello")  #@
+        """
+        )
+        i0 = next(ast_nodes[0].infer())
+        assert isinstance(i0, nodes.Const)
+        assert i0.value == 2
+
+        i1 = next(ast_nodes[1].infer())
+        assert isinstance(i1, nodes.Const)
+        assert i1.value == "Hello"
+
 
 @pytest.mark.skipif(
     not HAS_TYPING_EXTENSIONS,

tests/unittest_inference_calls.py

@@ -146,8 +146,6 @@ def g(y):
 def test_inner_call_with_dynamic_argument() -> None:
     """Test function where return value is the result of a separate function call,
     with a dynamic value passed to the inner function.
-
-    Currently, this is Uninferable.
     """
     node = builder.extract_node(
         """
@@ -163,7 +161,8 @@ def g(y):
     assert isinstance(node, nodes.NodeNG)
     inferred = node.inferred()
     assert len(inferred) == 1
-    assert inferred[0] is Uninferable
+    assert isinstance(inferred[0], nodes.Const)
+    assert inferred[0].value == 3
 
 
 def test_method_const_instance_attr() -> None: