B018: Find more constants w/o assign (#201)

This check now also finds:
* numbers (ints, float, complex)
* lists
* sets
* dicts
* binary strings
* joined strings (f-strings)
* name constants (True, False, None)

bugbear.py

@@ -579,7 +579,19 @@ def check_for_b903(self, node):
 
     def check_for_b018(self, node):
         for subnode in node.body[1:]:
-            if isinstance(subnode, ast.Expr) and isinstance(subnode.value, ast.Str):
+            if isinstance(subnode, ast.Expr) and isinstance(
+                subnode.value,
+                (
+                    ast.Str,
+                    ast.Num,
+                    ast.Bytes,
+                    ast.NameConstant,
+                    ast.JoinedStr,
+                    ast.List,
+                    ast.Set,
+                    ast.Dict,
+                ),
+            ):
                 self.errors.append(B018(subnode.lineno, subnode.col_offset))
 
 

tests/b018_classes.py

@@ -0,0 +1,31 @@
+"""
+Should emit:
+B018 - on lines 15-26, 31
+"""
+
+
+class Foo1:
+    """abc"""
+
+
+class Foo2:
+    """abc"""
+
+    a = 2
+    "str"  # Str
+    1j  # Number (complex)
+    1  # Number (int)
+    1.0  # Number (float)
+    b"foo"  # Binary
+    f"{int}"  # JoinedStr
+    True  # NameConstant (True)
+    False  # NameConstant (False)
+    None  # NameConstant (None)
+    [1, 2]  # list
+    {1, 2}  # set
+    {"foo": "bar"}  # dict
+
+
+class Foo3:
+    a = 2
+    "str"

tests/b018_functions.py

@@ -0,0 +1,30 @@
+"""
+Should emit:
+B018 - on lines 14-25, 30
+"""
+
+
+def foo1():
+    """my docstring"""
+
+
+def foo2():
+    """my docstring"""
+    a = 2
+    "str"  # Str
+    1j  # Number (complex)
+    1  # Number (int)
+    1.0  # Number (float)
+    b"foo"  # Binary
+    f"{int}"  # JoinedStr
+    True  # NameConstant (True)
+    False  # NameConstant (False)
+    None  # NameConstant (None)
+    [1, 2]  # list
+    {1, 2}  # set
+    {"foo": "bar"}  # dict
+
+
+def foo3():
+    a = 2
+    "str"

tests/test_bugbear.py

@@ -212,13 +212,23 @@ def test_b017(self):
         expected = self.errors(B017(22, 8))
         self.assertEqual(errors, expected)
 
-    def test_b018(self):
-        filename = Path(__file__).absolute().parent / "b018.py"
+    def test_b018_functions(self):
+        filename = Path(__file__).absolute().parent / "b018_functions.py"
         bbc = BugBearChecker(filename=str(filename))
         errors = list(bbc.run())
-        self.assertEqual(
-            errors, self.errors(B018(14, 4), B018(19, 4), B018(30, 4), B018(35, 4))
-        )
+
+        expected = [B018(line, 4) for line in range(14, 26)]
+        expected.append(B018(30, 4))
+        self.assertEqual(errors, self.errors(*expected))
+
+    def test_b018_classes(self):
+        filename = Path(__file__).absolute().parent / "b018_classes.py"
+        bbc = BugBearChecker(filename=str(filename))
+        errors = list(bbc.run())
+
+        expected = [B018(line, 4) for line in range(15, 27)]
+        expected.append(B018(31, 4))
+        self.assertEqual(errors, self.errors(*expected))
 
     def test_b901(self):
         filename = Path(__file__).absolute().parent / "b901.py"