Class: RBS::VarianceCalculator

Inherits:
Object
  • Object
show all
Defined in:
lib/rbs/variance_calculator.rb

Defined Under Namespace

Classes: Result

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(builder:) ⇒ VarianceCalculator

Returns a new instance of VarianceCalculator.



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# File 'lib/rbs/variance_calculator.rb', line 61

def initialize(builder:)
  @builder = builder
end

Instance Attribute Details

#builder ⇒ Object (readonly)

Returns the value of attribute builder.



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# File 'lib/rbs/variance_calculator.rb', line 59

def builder
  @builder
end

Instance Method Details

#env ⇒ Object 



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# File 'lib/rbs/variance_calculator.rb', line 65

def env
  builder.env
end

#in_inherit(name:, args:, variables:) ⇒ Object 



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# File 'lib/rbs/variance_calculator.rb', line 88

def in_inherit(name:, args:, variables:)
  type = Types::ClassInstance.new(name: name, args: args, location: nil)

  Result.new(variables: variables).tap do |result|
    type(type, result: result, context: :covariant)
  end
end

#in_method_type(method_type:, variables:) ⇒ Object 



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# File 'lib/rbs/variance_calculator.rb', line 69

def in_method_type(method_type:, variables:)
  result = Result.new(variables: variables)

  method_type.type.each_param do |param|
    type(param.type, result: result, context: :contravariant)
  end

  if method_type.block
    method_type.block.type.each_param do |param|
      type(param.type, result: result, context: :covariant)
    end
    type(method_type.block.type.return_type, result: result, context: :contravariant)
  end

  type(method_type.type.return_type, result: result, context: :covariant)

  result
end

#type(type, result:, context:) ⇒ Object 



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# File 'lib/rbs/variance_calculator.rb', line 96

def type(type, result:, context:)
  case type
  when Types::Variable
    if result.include?(type.name)
      case context
      when :covariant
        result.covariant(type.name)
      when :contravariant
        result.contravariant(type.name)
      when :invariant
        result.invariant(type.name)
      end
    end
  when Types::ClassInstance, Types::Interface
    decl = env.find_class(type.name)
    type.args.each.with_index do |ty, i|
      var = decl.type_params.params[i]
      case var.variance
      when :invariant
        type(ty, result: result, context: :invariant)
      when :covariant
        type(ty, result: result, context: context)
      when :contravariant
        con = case context
              when :invariant
                :invariant
              when :covariant
                :contravariant
              when :contravariant
                :covariant
              end
        type(ty, result: result, context: con)
      end
    end
  when Types::Tuple, Types::Record, Types::Union, Types::Intersection
    # Covariant types
    type.each_type do |ty|
      type(ty, result: result, context: context)
    end
  end
end