[Feature #18242] and / or と多重代入を組み合わせた場合に意図せずシンタックスエラーになるというバグ報告

[Feature #18242] Parser makes multiple assignment sad in confusing way

• 次のように and / or と多重代入を組み合わせた場合に意図せずシンタックスエラーになるというバグ報告

# これは動作する
1 < 2   and a = 2     # Works
1 < 2   or a = 2      # Works
1 < 2   and (a, b = 2, 1)    # Works
1 < 2   and (a, b = [2, 1])  # Works
2 < 1   or (a, b = 2, 1)     # Works
2 < 1   or (a, b = [2, 1])   # Works

# 以下は動作しない
1 < 2   and a, b = 2, 1      # SyntaxError
1 < 2   and a, b = [2, 1]    # SyntaxError
1 < 2   and (a, b) = 2, 1    # SyntaxError
1 < 2   and (a, b) = [2, 1]  # SyntaxError
(1 < 2) and a, b = 2, 1      # SyntaxError
(1 < 2) and a, b = [2, 1]    # SyntaxError
(1 < 2) and (a, b) = 2, 1    # SyntaxError
(1 < 2) and (a, b) = [2, 1]  # SyntaxError
2 < 1   or a, b = 2, 1       # SyntaxError
2 < 1   or a, b = [2, 1]     # SyntaxError
2 < 1   or (a, b) = 2, 1     # SyntaxError
2 < 1   or (a, b) = [2, 1]   # SyntaxError
(2 < 1) or a, b = 2, 1       # SyntaxError
(2 < 1) or a, b = [2, 1]     # SyntaxError
(2 < 1) or (a, b) = 2, 1     # SyntaxError
(2 < 1) or (a, b) = [2, 1]   # SyntaxError

# 以下のような後置 if / unless は意図する挙動になる
a, b = 2, 1     if 1 < 2     # Works
a, b = [2, 1]   if 1 < 2     # Works
(a, b) = 2, 1   if 1 < 2     # Works
(a, b) = [2, 1] if 1 < 2     # Works
(a, b = [2, 1]) if 1 < 2     # Works
a, b = 2, 1     unless 2 < 1 # Works
a, b = [2, 1]   unless 2 < 1 # Works
(a, b) = 2, 1   unless 2 < 1 # Works
(a, b) = [2, 1] unless 2 < 1 # Works
(a, b = [2, 1]) unless 2 < 1 # Works

• これはバグというか新しい機能追加になるみたいですね？
• すでにパッチはあるみたいですが機能追加なので matz の承認待ちみたい
• 後置 if / unless の変わりに and / or でかけると便利なんですかねー