Issue #8953 has been reported by gfx (Goro Fuji).

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Bug #8953: `str =~ /pattern/` does not call =~ method if (1) str is a String, (2) /pattern/ is a Regexp literal
https://bugs.ruby-lang.org/issues/8953

Author: gfx (Goro Fuji)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.4.0]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


The expression `a =~ b` does not call the =~ method in some cases.
I think it is a bug that results from optimizations.

See the following code for details:

Code that does not work as expected (shows nothing):

$ ruby -e 's = "foo"; class << s; def =~ (rhs); raise "a"; end; end;  s =~ /foo/' # does nothing

Code that works as expected (raises errors):

$ ruby -e 's = "foo"; class << s; def =~ (rhs); raise "a"; end; end;  s.=~ /foo/' # call =~ as a method
$ ruby -e 's = "foo"; class << s; def =~ (rhs); raise "a"; end; end;  s =~ -> { /foo/ }.call' # RHS is not a Regexp literal but a Regexp object
$ ruby -e 's = Objec.new; class << s; def =~ (rhs); raise "a"; end; end;  s =~ /foo/' # LHS is not a String



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