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Bug #18990
closed
Pattern matching unexpectedly raises "duplicated key name" error
Status:
Closed
Assignee:
-
Target version:
-
ruby -v:
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x86_64-darwin19]
Description
I've found that sometimes, when matching nested patterns, I get an unexpected "duplicate key name" error but there's no duplicate key in any individual pattern. The "duplicated" key is actually in another pattern that's in scope, which I found was odd. (And the fix is even more odd.)
This seems like unexpected behavior to me. There's an example of this behavior below. The patterns in #all? cause the error, even though they're separate lines.
class User
attr_reader :first_name,
:last_name
def initialize(first_name:, last_name:)
@first_name, @last_name = first_name, last_name
end
def deconstruct_keys(keys)
{ first_name:, last_name: }
end
end
users = [
User.new(first_name: 'Jane', last_name: 'Doe'),
User.new(first_name: 'Jane', last_name: 'Smith'),
]
# Fails
case users
in [{ first_name: 'John', ** }, *]
users.all? { _1 in first_name: 'John' }
in [{ first_name: 'Jane', ** }, *]
users.all? { _1 in first_name: 'Jane' } # => bug.rb:17: duplicated key name
end
Counterintuitively, wrapping the pattern in {} resolves the error.
# Works
case users
in [{ first_name: 'John', ** }, *]
users.all? { _1 in { first_name: 'John' } }
in [{ first_name: 'Jane', ** }, *]
users.all? { _1 in { first_name: 'Jane' } }
end
Seems like a bug?
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