compiler now ignores constant statements

The compile ignores constant statements and emit a SyntaxWarning warning.

Don't emit the warning for string statement because triple quoted string is a
common syntax for multiline comments.

Don't emit the warning on ellipis neither: 'def f(): ...' is a legit syntax for
abstract functions.

Changes:

* test_ast: ignore SyntaxWarning when compiling test statements. Modify
  test_load_const() to use assignment expressions rather than constant
  expression.
* test_code: add more kinds of constant statements, ignore SyntaxWarning when
  testing that the compiler removes constant statements.
* test_grammar: ignore SyntaxWarning on the statement "1"

1 files changed, 5 insertions, 1 deletions

diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index 8f8d71c..2d6f5ed 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -7,6 +7,7 @@ import unittest
 import sys
 # testing import *
 from sys import *
+from test import support
 
 
 class TokenTests(unittest.TestCase):
@@ -424,8 +425,11 @@ class GrammarTests(unittest.TestCase):
     # Tested below
 
     def test_expr_stmt(self):
+        msg = 'ignore constant statement'
+        with support.check_warnings((msg, SyntaxWarning)):
+            exec("1")
+
         # (exprlist '=')* exprlist
-        1
         1, 2, 3
         x = 1
         x = 1, 2, 3