Issue #21026 has been updated by zverok (Victor Shepelev).
It already doesn't seem to actually do anything
This is a bunch of technicalities... But I don’t think it doesn’t do anyting :) As far as I understand, every `__FILE__` invocation in the source code produces a _new_ instance of a string with the contents of the current file name: ```ruby p __FILE__.object_id #=> 16 p __FILE__.object_id #=> 24 p __FILE__.frozen? #=> false ``` So, this code: ```ruby def __FILE__.a puts "works!" end ``` can be treated as this: ```ruby o = __FILE__ def o.a puts "works!" end o.a # prints "works!" ``` (The subsequent calls of `__FILE__` doesn’t have `a` method because they all return different objects.) So, the code “works” (even if it is not of much utility). But the example with parentheses is interesting: it is not about __FILE__, any attempt to define a method on literal works this way: ```ruby def ("file").a end ``` results in... ``` test.rb:1: syntax error found (SyntaxError)
1 | def ("file").a | ^~~~~~ cannot define singleton method for literals 2 | puts "works!" 3 | end
...so I guess `__FILE__ ` is mostly treated as literal... Except when it does not :)
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Bug #21026: `def __FILE__.a; end` should be a syntax error
https://bugs.ruby-lang.org/issues/21026#change-111442
* Author: Earlopain (Earlopain _)
* Status: Open
* ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
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Constants like `__FILE__`, `__LINE__` and `__ENCODING__` are literals and as such you shouldn't be able to defined singleton methods on them.
It already doesn't seem to actually do anything:
```rb
def __FILE__.a
end
__FILE__.a #=> undefined method 'a' for an instance of String (NoMethodError)
Wrapping it in brackets correctly reports a syntax error: ```rb code.rb:1: syntax error found (SyntaxError)
1 | def (__FILE__).a | ^~~~~~~~ cannot define singleton method for literals 2 | end
The behavior is consistent between prism and parse.y
`__ENCODING__` is frozen and so will result in a runtime error. Same for `__LINE__`, and also `__FILE__` with frozen string literals.
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https://bugs.ruby-lang.org/