Bug #10456: kwargs and block without comma should probably be a syntax error

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-darwin13.0]
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN

[bobbytables (Robert Ross)]

ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-darwin13.0]

I experienced something very weird, when you define a method like this:

def wat(something: nil &block)
end

It actually doesn't come back as a syntax error

Roberts-MacBook-Pro-2:~ robert$ cat test.rb; echo
def wat(name: "" &block)
end
Roberts-MacBook-Pro-2:~ robert$ ruby -c test.rb
Syntax OK

Within the method, the block is never assigned either actually on method call:

irb(main):007:0> def wat(something: nil &block)
irb(main):008:1> puts "Block: #{block}"
irb(main):009:1> end
=> :wat
irb(main):010:0> wat(something: 'hello') { "My block here" }
NameError: undefined local variable or method `block' for main:Object
  from (irb):8:in `wat'
  from (irb):10
  from /Users/robert/.rbenv/versions/2.1.1/bin/irb:11:in `<main>'

This behavior seems unlikely, it caught me off guard for sure.

def wat(something: nil &block)
end

nil &block is a legal expression (calling the & method on nil with block as the argument).

The expression is evaluated at method call time, not method definition time, so that's where the (correct) error shows up.

In fact, if you run with warnings enabled, you see:

$ ruby -w -e "def wat(something: nil &block); end"
-e:1: warning: `&' after local variable or literal is interpreted as binary operator
-e:1: warning: even though it seems like argument prefix

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Status changed from Open to Rejected