Bug #19583: Unary minus inconsistency when used with variables and literals

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

[hurricup (Alexandr Evstigneev)]

This feels a bit inconsistent and I could not find an explanation.

This is fine and - has higher precedence than .

-2.upto 0 do |arg|
puts arg
end

But this is not working, won't even compile (requires parens):

var = 2
-var.upto 0 do |arg|
puts arg
end

I presume that in the first example there is no unary minus operation, just negative literal.

Ok, according to this - my assumption is correct. The question is - why?

def some
  puts -2
  a = 42
  puts -a
end

puts RubyVM::InstructionSequence.of(method :some).disasm

[hurricup (Alexandr Evstigneev)]

• Description updated (diff)

[Hanmac (Hans Mackowiak)]

-2 is a literal
- 2 is a function call of -@

and -@ doesn't have preference over function call, see this:

a = 2
v = -a.to_s
p v #=> 2

[byroot (Jean Boussier)]

• Status changed from Open to Closed

Yeah, I don't think this is a bug, and even if we decided another precedence would have been better, changing it would break way too much code.