Fix pylint-dev#3675: safe_infer now finds ambiguity when number of …

…arguments differ

ChangeLog

@@ -22,6 +22,11 @@ Release date: TBA
 ..
   Put bug fixes that should not wait for a new minor version here
 
+* ``safe_infer`` no longer makes an inference given two function
+  definitions with differing numbers of arguments.
+
+  Closes #3675
+
 ..
   Insert your changelog randomly, it will reduce merge conflicts
   (Ie. not necessarily at the end)

pylint/checkers/utils.py

@@ -1251,6 +1251,19 @@ def safe_infer(node: nodes.NodeNG, context=None) -> Optional[nodes.NodeNG]:
             inferred_type = _get_python_type_of_node(inferred)
             if inferred_type not in inferred_types:
                 return None  # If there is ambiguity on the inferred node.
+            if isinstance(inferred, astroid.FunctionDef):
+                # Special case due to unexpected inference ambiguity
+                if (
+                    inferred.name == "TemporaryFile"
+                    and value.name == "NamedTemporaryFile"
+                ):
+                    continue
+                if (
+                    inferred.args.args is not None
+                    and value.args.args is not None
+                    and len(inferred.args.args) != len(value.args.args)
+                ):
+                    return None  # Different number of arguments indicates ambiguity
     except astroid.InferenceError:
         return None  # There is some kind of ambiguity
     except StopIteration:

tests/functional/t/too/too_many_function_args.py

@@ -0,0 +1,19 @@
+"""https://github.com/PyCQA/pylint/issues/3675"""
+
+
+def noop(x):  # pylint: disable=invalid-name
+    """Return value unchanged"""
+    return x
+
+
+def add(x, y):  # pylint: disable=invalid-name
+    """Add two values"""
+    return x + y
+
+
+def main(param):
+    """Should not emit too-many-function-args"""
+    tmp = noop  # matched first
+    if param == 0:
+        tmp = add
+    return tmp(1, 1.01)