Misc #11372: Confusing a+b=9 ... unintented behavior, valid statement

• Status: Rejected
• Assignee: -

[kozel (Dug Dough)]

Hello, I found that when = is written instead of ==, it can cause unintended effects and it is hard to notice this typo, because it is valid statement. For example valid statement a+b=7 ,due to the everything is a expression, is treated as a+(b=11) and not interpreted as syntax error, like in other languages.

Should't be this behavior changed?
My suggestion is to make the assignment operator unable to be used as expresion (syntactically). It would prevent that mistakes.
Optionally (for 'backward compatibility', or 'override'), assignment enclosed in parentheses would still be treated as expression , that would make a+(b=9) valid. The meaning of extra parentheses would mean "This is not mistake, i want to use the value of variable b as expression".

[kozel (Dug Dough)]

Just small error: Number 11 is wrong, 7 is right. :)

[matz (Yukihiro Matsumoto)]

• Status changed from Open to Rejected

Hi,

Although I can understand how you feel, the change will break millions of Ruby programs.
There could be milder option, like warning for certain usege of equal sign in expressions.

Matz.