Update fix for E731

Thanks to @mypalmike for thinking of the extra cases

Author: sigmavirus24

pep8.py

@@ -108,7 +108,7 @@
 KEYWORD_REGEX = re.compile(r'(\s*)\b(?:%s)\b(\s*)' % r'|'.join(KEYWORDS))
 OPERATOR_REGEX = re.compile(r'(?:[^,\s])(\s*)(?:[-+*/|!<=>%&^]+)(\s*)')
 LAMBDA_REGEX = re.compile(r'\blambda\b')
-FIELD_ASSIGNMENT_REGEX = re.compile('\s*.+\..+\s=')
+IDENTIFIER_REGEX = re.compile('\s*[^.[\]]+\s=')
 HUNK_REGEX = re.compile(r'^@@ -\d+(?:,\d+)? \+(\d+)(?:,(\d+))? @@.*$')
 
 # Work around Python < 2.6 behaviour, which does not generate NL after
@@ -873,7 +873,7 @@ def compound_statements(logical_line):
              before.count('[') <= before.count(']') and   # [1:2] (slice)
              before.count('(') <= before.count(')'))):    # (annotation)
             if LAMBDA_REGEX.search(before):
-                if not FIELD_ASSIGNMENT_REGEX.search(before):
+                if IDENTIFIER_REGEX.match(before):
                     yield 0, ("E731 do not assign a lambda expression, use a"
                               " def")
                 break

testsuite/E73.py

@@ -8,3 +8,11 @@
 #: Okay
 f = object()
 f.method = lambda: 'Method'
+#: Okay
+f = {}
+f['a'] = lambda x: x ** 2
+#: Okay
+f = []
+f.append(lambda x: x ** 2)
+#: Okay
+lambda: 'no-op'