reword

python · benjaminp · Oct 5, 2017 · Feb 13, 2017 · Oct 5, 2017 · Oct 5, 2017
commit 07560411f34dfd464b1d3b0874401288c1a8b60c
diff --git a/Lib/lib2to3/Grammar.txt b/Lib/lib2to3/Grammar.txt
@@ -164,21 +164,21 @@ comp_iter: comp_for | comp_if
 comp_for: [ASYNC] 'for' exprlist 'in' or_test [comp_iter]
 comp_if: 'if' old_test [comp_iter]

-# See note above regarding testlist_safe to see why testlist_safe is
-# necessary. Unfortunately we can't use it indiscriminately in all derivations
-# using comp_for-like pattern because testlist_safe derivation contains
-# comma which clashes with trailing comma in arglist.
+# As noted above, testlist_safe extends the syntax allowed in list
+# comprehensions and generators. We can't use it indiscriminately in all
+# derivations using a comp_for-like pattern because the testlist_safe derivation
+# contains comma which clashes with trailing comma in arglist.
 #
-# The above was an issue because the parser would not follow the correct derivation
+# This was an issue because the parser would not follow the correct derivation
 # when parsing syntactically valid Python code. Since testlist_safe was created
 # specifically to handle list comprehensions and generator expressions enclosed
-# with parentheses it's safe to only use it in those. That avoids the issue
-# mentioned above and we can parse code like set(x for x in [],).
+# with parentheses, it's safe to only use it in those. That avoids the issue; we
+# can parse code like set(x for x in [],).
 #
-# Note that the syntax supported by this set of rules is not a valid Python 3
-# syntax, hence the prefix "old".
+# The syntax supported by this set of rules is not a valid Python 3 syntax,
+# hence the prefix "old".
 #
-# See the bug report: http://bugs.python.org/issue27494
+# See https://bugs.python.org/issue27494
 old_comp_iter: old_comp_for | old_comp_if
 old_comp_for: [ASYNC] 'for' exprlist 'in' testlist_safe [old_comp_iter]
 old_comp_if: 'if' old_test [old_comp_iter]

diff --git a/Misc/NEWS.d/next/Library/2017-09-26-01-43-17.bpo-27494.37QnaT.rst b/Misc/NEWS.d/next/Library/2017-09-26-01-43-17.bpo-27494.37QnaT.rst
@@ -1,2 +1,2 @@
-2to3 doesn't choke on a trailing comma following a generator expression
-anymore.
+Make 2to3 accept a trailing comma in generator expressions. For example, ``set(x
+for x in [],)`` is now allowed.