Bug #16389: Unexpected tINTEGER in conditional expression

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.6.4p104 (2019-08-28 revision 67798) [x86_64-darwin18]
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN

[codinganarchy (Matthew Tanous)]

I'm not sure that this is a bug, or simply an unexpected result of operator precedence, but I am seeing a result that appears to me to be an issue.

When putting a conditional expression after a command call using unless, I am seeing a syntax error when I believe the syntax should be valid. In particular:

def foo
    puts "This method just has to exist"
end

foo unless (@bar&.nil? && @baz&.> 15)

This producessyntax error, unexpected tINTEGER, expecting ')' following the &.> safe navigation. I would not expect a syntax error here.

This seems a strange result to me, as foo unless (@bar&.nil? and @baz&.> 15) appears to work as expected, producing no syntax error.

Please let me know if I am missing something in either my expectation or the issue report. Thanks!

[mame (Yusuke Endoh)]

• Status changed from Open to Closed

You need to parenthesize the argument 15.

foo unless (@bar&.nil? && @baz&.>(15))

I don't think that your expectation is wrong, but due to parser limitation, we cannot place a non-parenthesized method call as an argument of &&. It is a good practice to write parentheses for method calls, except some trivial cases (e.g., no-argument method calls and p arg).

[mame (Yusuke Endoh)]

• Status changed from Closed to Rejected

[codinganarchy (Matthew Tanous)]

mame (Yusuke Endoh) wrote:

I don't think that your expectation is wrong, but due to parser limitation, we cannot place a non-parenthesized method call as an argument of &&. It is a good practice to write parentheses for method calls, except some trivial cases (e.g., no-argument method calls and p arg).

Just to clarify, if you don't mind, is this also due to the difference between .> (a method) and > (an operator)? I ask as foo unless (@bar&.nil? && @baz > 15) does not result in a syntax error, though using && @baz.> 15 will.

[nobu (Nobuyoshi Nakada)]

codinganarchy (Matthew Tanous) wrote:

Just to clarify, if you don't mind, is this also due to the difference between .> (a method) and > (an operator)? I ask as foo unless (@bar&.nil? && @baz > 15) does not result in a syntax error, though using && @baz.> 15 will.

Yes, this is an issue of syntax precedence.
As comparison operators have higher precedence than logical operators, nil && bar > 15 is interpreted as nil && (bar > 15).
OTOH, a method call without parentheses has lower precedence, because its arguments may contain such logical expressions, so the combination of them, e.g, nil && p a && b, is ambiguous/confusing.