FIX #3: get local names from desctructive assignments

Makefile

@@ -1,5 +1,8 @@
 check:
-	make -j2 types style
+	make -j3 test types style
+
+test:
+	python -m pytest
 
 types:
 	mypy --strict --implicit-optional .

mr_proper/utils/ast.py

@@ -62,7 +62,8 @@ def is_imported_from_stdlib(name: str, file_ast_tree: ast.Module) -> Optional[bo
 def get_local_var_names_from_funcdef(funcdef_node: AnyFuncdef) -> List[str]:
     local_vars_names: List[str] = []
     for assign_node in get_nodes_from_funcdef_body(funcdef_node, [ast.Assign]):
-        local_vars_names += [t.id for t in assign_node.targets if isinstance(t, ast.Name)]
+        for target in assign_node.targets:
+            local_vars_names += [n.id for n in ast.walk(target) if isinstance(n, ast.Name)]
     for annassign_node in get_nodes_from_funcdef_body(funcdef_node, [ast.AnnAssign]):
         if isinstance(annassign_node.target, ast.Name):
             local_vars_names.append(annassign_node.target.id)
@@ -74,7 +75,7 @@ def get_local_var_names_from_funcdef(funcdef_node: AnyFuncdef) -> List[str]:
         for n in ast.walk(funcdef_node)
         if isinstance(n, ast.ExceptHandler) and n.name
     }
-    return local_vars_names
+    return list(set(local_vars_names))
 
 
 def get_local_var_names_from_loop(loop_node: Union[ast.comprehension, ast.For]) -> List[str]:

tests/test_pure_checker.py

@@ -0,0 +1,12 @@
+import ast
+
+from mr_proper.public_api import is_function_pure
+
+
+def test_ok_for_destructive_assignment():
+    funcdef = ast.parse("""
+        def foo(a):
+            b, c = a
+            return b * c
+    """.strip()).body[0]
+    assert is_function_pure(funcdef)