Check for non-ast SyntaxErrors

pyflakes/api.py

@@ -53,12 +53,30 @@ def check(codeString, filename, reporter=None):
     except Exception:
         reporter.unexpectedError(filename, 'problem decoding source')
         return 1
+
+    # Some syntax errors are only detected when compiling to bytecode (like
+    # return outside of function), because they aren't encoded in the
+    # grammar. We do this separately because we can still report on other
+    # errors in this case.
+    try:
+        compile(tree, filename, "exec")
+    except SyntaxError:
+        value = sys.exc_info()[1]
+        msg = value.args[0]
+
+        (lineno, offset, text) = value.lineno, value.offset, value.text
+
+        reporter.syntaxError(filename, msg, lineno, offset, text)
+        additional_messages = 1
+    else:
+        additional_messages = 0
+
     # Okay, it's syntactically valid.  Now check it.
     w = checker.Checker(tree, filename)
     w.messages.sort(key=lambda m: m.lineno)
     for warning in w.messages:
         reporter.flake(warning)
-    return len(w.messages)
+    return len(w.messages) + additional_messages
 
 
 def checkPath(filename, reporter=None):

pyflakes/test/test_api.py

@@ -392,6 +392,31 @@ def test_nonKeywordAfterKeywordSyntaxError(self):
 foo(bar=baz, bax)
 %s""" % (sourcePath, column, last_line)])
 
+    def test_nonastSyntaxError(self):
+        """
+        SyntaxError that is not encoded in the ast, and can only be detected
+        by compiling to bytecode, like return outside of function.
+        """
+        source = """\
+return
+"""
+        sourcePath = self.makeTempFile(source)
+        if sys.version_info[0] == 3:
+            self.assertHasErrors(
+                sourcePath,
+                ["""\
+%s:1:0: 'return' outside function
+return
+     ^
+""" % sourcePath])
+        else:
+            self.assertHasErrors(
+                sourcePath,
+                ["""\
+%s:1: 'return' outside function
+return
+""" % sourcePath])
+
     def test_invalidEscape(self):
         """
         The invalid escape syntax raises ValueError in Python 2