also fix map in B023. update comments

Author: jakkdl

bugbear.py

@@ -592,7 +592,7 @@ def check_for_b023(self, loop_node):  # noqa: C901
                 # check for filter&reduce
                 if (
                     isinstance(node.func, ast.Name)
-                    and node.func.id in ("filter", "reduce")
+                    and node.func.id in ("filter", "reduce", "map")
                 ) or (
                     isinstance(node.func, ast.Attribute)
                     and node.func.attr == "reduce"
@@ -610,11 +610,14 @@ def check_for_b023(self, loop_node):  # noqa: C901
                     ):
                         safe_functions.append(keyword.value)
 
+            # mark `return lambda: x` as safe
+            # does not (currently) check inner lambdas in a returned expression
+            # e.g. `return (lambda: x, )
             if isinstance(node, ast.Return):
                 if isinstance(node.value, FUNCTION_NODES):
                     safe_functions.append(node.value)
-                # TODO: ast.walk(node) and mark all child nodes safe?
 
+            # find unsafe functions
             if isinstance(node, FUNCTION_NODES) and node not in safe_functions:
                 argnames = {
                     arg.arg for arg in ast.walk(node.args) if isinstance(arg, ast.arg)

tests/b023.py

@@ -121,6 +121,14 @@ def myfunc(x):
     max(range(3), key=lambda y: x * y)
     sorted(range(3), key=lambda y: x * y)
 
+    any(map(lambda y: x < y, range(3)))
+    all(map(lambda y: x < y, range(3)))
+    set(map(lambda y: x < y, range(3)))
+    list(map(lambda y: x < y, range(3)))
+    tuple(map(lambda y: x < y, range(3)))
+    sorted(map(lambda y: x < y, range(3)))
+    frozenset(map(lambda y: x < y, range(3)))
+
     any(filter(lambda y: x < y, range(3)))
     all(filter(lambda y: x < y, range(3)))
     set(filter(lambda y: x < y, range(3)))
@@ -156,7 +164,7 @@ def iter_f(names):
             return lambda: name if exists(name) else None
 
         if foo(name):
-            return [lambda: name]  # false alarm, should be fixed?
+            return [lambda: name]  # known false alarm
 
         if False:
             return [lambda: i for i in range(3)]  # error

tests/test_bugbear.py

@@ -356,8 +356,8 @@ def test_b023(self):
             B023(115, 36, vars=("x",)),
             B023(116, 37, vars=("x",)),
             B023(117, 36, vars=("x",)),
-            B023(159, 28, vars=("name",)),  # false alarm?
-            B023(162, 28, vars=("i",)),
+            B023(167, 28, vars=("name",)),  # known false alarm
+            B023(170, 28, vars=("i",)),
         )
         self.assertEqual(errors, expected)