Issue #14990: tokenize: correctly fail with SyntaxError on invalid encoding declaration.

Lib/test/test_tokenize.py

@@ -674,6 +674,10 @@ class TestTokenizerAdheresToPep0263(TestCase):
         f = 'tokenize_tests-utf8-coding-cookie-and-utf8-bom-sig.txt'
         self.assertTrue(self._testFile(f))
 
+    def test_bad_coding_cookie(self):
+        self.assertRaises(SyntaxError, self._testFile, 'bad_coding.py')
+        self.assertRaises(SyntaxError, self._testFile, 'bad_coding2.py')
+
 
 class Test_Tokenize(TestCase):
 

Lib/tokenize.py

@@ -310,7 +310,7 @@ def detect_encoding(readline):
             raise SyntaxError("unknown encoding: " + encoding)
 
         if bom_found:
-            if codec.name != 'utf-8':
+            if encoding != 'utf-8':
                 # This behaviour mimics the Python interpreter
                 raise SyntaxError('encoding problem: utf-8')
             encoding += '-sig'

Misc/NEWS

@@ -87,6 +87,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #14990: Correctly fail with SyntaxError on invalid encoding
+  declaration.
+
 - Issue #15247: FileIO now raises an error when given a file descriptor
   pointing to a directory.