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# frozen_string_literal: true
module RuboCop
module AST
class NodePattern
class Compiler
# Holds the list of bound variable names
class Binding
def initialize
@bound = {}
end
# Yields the first time a given name is bound
#
# @return [String] bound variable name
def bind(name)
var = @bound.fetch(name) do
yield n = @bound[name] = "unify_#{name.gsub('-', '__')}"
n
end
if var == :forbidden_unification
raise Invalid, "Wildcard #{name} was first seen in a subset of a " \
"union and can't be used outside that union"
end
var
end
# Yields for each branch of the given union, forbidding unification of
# bindings which only appear in a subset of the union.
def union_bind(enum) # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
# We need to reset @bound before each branch is processed.
# Moreover we need to keep track of newly encountered wildcards.
# Var `newly_bound_intersection` will hold those that are encountered
# in all branches; these are not a problem.
# Var `partially_bound` will hold those encountered in only a subset
# of the branches; these can't be used outside of the union.
return to_enum __method__, enum unless block_given?
newly_bound_intersection = nil
partially_bound = []
bound_before = @bound.dup
result = enum.each do |e|
@bound = bound_before.dup if newly_bound_intersection
yield e
newly_bound = @bound.keys - bound_before.keys
if newly_bound_intersection.nil?
# First iteration
newly_bound_intersection = newly_bound
else
union = newly_bound_intersection | newly_bound
newly_bound_intersection &= newly_bound
partially_bound |= union - newly_bound_intersection
end
end
# At this point, all members of `newly_bound_intersection` can be used
# for unification outside of the union, but partially_bound may not
forbid(partially_bound)
result
end
private
def forbid(names)
names.each do |name|
@bound[name] = :forbidden_unification
end
end
end
end
end
end
end
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