Bug #16343: Inconsistent behavior of 'circular argument reference' error

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.7.0dev (2019-11-04T16:32:26Z trunk a087e027bf) [x86_64-darwin19]
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN

[ibylich (Ilya Bylich)]

The following code gives a syntax error:

m { |foo = proc { || foo }|  }
# => SyntaxError (-e:14: circular argument reference - foo)

But this code is valid:

m { |foo = proc { |bar| foo }|  }

Is it intentional? foo becomes a proc that returns itself, so there must be a circular dependency

[jeremyevans0 (Jeremy Evans)]

On Ruby 2.2-2.6, there is a warning instead of an error in the first case, but I think that is invalid. The reason for the warning/error is to complain about this code:

def a(b=b)
  b
end

Here, a would return nil, because of how the default argument values are handled. The reason the warning was added is because in Ruby 2.1 and below, calling a with no arguments would call the b method to get the value for the b argument.

m { |foo = proc { || foo }| } is not a case I think we should warn about, since it doesn't have the same issue. m { |foo = proc { || foo }.call| } could have the same issue, but it seems unlikely to occur in real world code.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset git|ed90ec3e0d8ff7789569b40ba36d3b3ce0e706e6.

---

Clear current argument name at empty block argument [Bug #16343]

[byroot (Jean Boussier)]

• Related to Bug #20478: Circular parameter syntax error rules added