Several named capture warnings in date/format #3865
Description
Environment
JRuby 9k versions through 9.1.
Expected Behavior
Ideally none of the standard library sources should produce warnings in verbose mode.
Actual Behavior
Our date/format.rb, created by @eregon, produces the following errors when loaded in verbose mode:
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - year
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - mon
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - mday
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - yday
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - cwyear
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - cweek
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - cwday
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - hour
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - min
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - sec
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - sec_fraction
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:960: warning: named capture conflicts a local variable - zone
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:1005: warning: named capture conflicts a local variable - hour
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:1005: warning: named capture conflicts a local variable - min
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:1005: warning: named capture conflicts a local variable - sec
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:1005: warning: named capture conflicts a local variable - sec_fraction
/Users/headius/projects/jruby/lib/ruby/stdlib/date/format.rb:1005: warning: named capture conflicts a local variable - zone
These errors are Ruby's attempt to warn us that we're using the same local variable name as a named capture. I do not believe this warning is useful, and I have filed https://bugs.ruby-lang.org/issues/12359 to have it removed from Ruby. If that bug is not accepted, we'll need to change this code to eliminate the warnings.