70 lines
1.8 KiB
Ruby
70 lines
1.8 KiB
Ruby
# typed: strict
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# frozen_string_literal: true
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# Most objects are cloneable, but not all. For example you can't dup methods:
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#
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# ```ruby
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# method(:puts).dup # => TypeError: allocator undefined for Method
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# ```
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#
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# Classes may signal their instances are not duplicable removing +dup+/+clone+
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# or raising exceptions from them. So, to dup an arbitrary object you normally
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# use an optimistic approach and are ready to catch an exception, say:
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#
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# ```ruby
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# arbitrary_object.dup rescue object
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# ```
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#
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# Rails dups objects in a few critical spots where they are not that arbitrary.
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# That `rescue` is very expensive (like 40 times slower than a predicate) and it
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# is often triggered.
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#
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# That's why we hardcode the following cases and check duplicable? instead of
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# using that rescue idiom.
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# rubocop:disable Layout/EmptyLines
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# rubocop:enable Layout/EmptyLines
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class Object
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# Can you safely dup this object?
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#
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# False for method objects;
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# true otherwise.
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sig { returns(T::Boolean) }
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def duplicable? = true
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end
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class Method
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# Methods are not duplicable:
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#
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# ```ruby
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# method(:puts).duplicable? # => false
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# method(:puts).dup # => TypeError: allocator undefined for Method
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# ```
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sig { returns(FalseClass) }
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def duplicable? = false
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end
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class UnboundMethod
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# Unbound methods are not duplicable:
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#
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# ```ruby
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# method(:puts).unbind.duplicable? # => false
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# method(:puts).unbind.dup # => TypeError: allocator undefined for UnboundMethod
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# ```
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sig { returns(FalseClass) }
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def duplicable? = false
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end
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require "singleton"
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module Singleton
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# Singleton instances are not duplicable:
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#
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# ```ruby
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# Class.new.include(Singleton).instance.dup # TypeError (can't dup instance of singleton
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# ```
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sig { returns(FalseClass) }
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def duplicable? = false
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end
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