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Bug #15880

Wrong precedence of the if modifier in pattern matching

Added by ibylich (Ilya Bylich) 10 months ago. Updated 10 months ago.

Status:
Rejected
Priority:
Normal
Assignee:
-
Target version:
-
ruby -v:
ruby 2.7.0dev (2019-05-20 trunk ab0f2deab1) [x86_64-darwin18]
[ruby-core:92863]

Description

When "If" is used as an "If modifier" it runs before the expression that it wraps:

=> puts 1 if (puts 2; true)
2
1

However, when it's used in the pattern matching destructuring runs first:

class A
  def deconstruct
    puts 'deconstruct called'
    [1]
  end
end

p case A.new
in A[1] if (puts 'if check'; true)
  'yes'
else
  'no'
end

# prints
# deconstruct called
# if check
# "yes"

I personally think that it's very confusing as it doesn't reflect the code. I assumed it to not run destructuring if the check returns false (especially because destructuring is allowed to have side-effects)

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