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Bug #20637
closedSyntaxError class definition in method body can be bypassed
Status:
Closed
Assignee:
-
Target version:
-
ruby -v:
ruby 3.4.0dev (2024-07-11T06:59:45Z master a1f7432550) [x86_64-linux]
Description
Class definition in method body is prohibited in Ruby
def f
class ::A; end # class definition in method body (SyntaxError)
module B; end # module definition in method body (SyntaxError)
end
But it can be bypassed by using class <<
def f
class << Object.new
class ::A; end # Syntax OK
module B; end # Syntax OK
end
end
Updated by zverok (Victor Shepelev) 4 months ago
As far as I understand, that’s legitimate code that works and might be useful for some metaprogramming:
def f(o)
class << o
class ::A; end # Syntax OK
module B; end # Syntax OK
end
end
o = Object.new
f(o)
o.singleton_class::B #=> #<Class:0x00007efd52a7bba0>::B
A #=> A
Updated by tompng (tomoya ishida) 4 months ago
dynamic constant assignment (SyntaxError) can be also bypassed
def f
class << Object.new
::A = 1
end
end
Updated by matz (Yukihiro Matsumoto) 3 months ago
Hmm, I think I'd let them unchanged. I don't think it's worth prohibiting constant definition in singleton class definitions.
Matz.
Updated by matz (Yukihiro Matsumoto) 3 months ago
- Status changed from Open to Closed
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