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 76

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 74

def builder
  @builder
end

Instance Method Details

#env ⇒ Object 



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# File 'lib/rbs/variance_calculator.rb', line 80

def env
  builder.env
end

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



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# File 'lib/rbs/variance_calculator.rb', line 164

def function(type, result:, context:)
  type.each_param do |param|
    type(param.type, result: result, context: negate(context))
  end
  type(type.return_type, result: result, context: context)
end

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



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

def in_inherit(name:, args:, variables:)
  type = if name.class?
           Types::ClassInstance.new(name: name, args: args, location: nil)
         else
           Types::Interface.new(name: name, args: args, location: nil)
         end

  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 84

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

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

  if block = method_type.block
    function(block.type, result: result, context: :contravariant)
  end

  result
end

#in_type_alias(name:) ⇒ Object 



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# File 'lib/rbs/variance_calculator.rb', line 108

def in_type_alias(name:)
  decl = env.alias_decls[name].decl or raise
  variables = decl.type_params.each.map(&:name)
  Result.new(variables: variables).tap do |result|
    type(decl.type, result: result, context: :covariant)
  end
end

#negate(variance) ⇒ Object 



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# File 'lib/rbs/variance_calculator.rb', line 171

def negate(variance)
  case variance
  when :invariant
    :invariant
  when :covariant
    :contravariant
  when :contravariant
    :covariant
  else
    raise
  end
end

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



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# File 'lib/rbs/variance_calculator.rb', line 116

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, Types::Alias
    NoTypeFoundError.check!(type.name,
                            env: env,
                            location: type.location)

    type_params = case type
                  when Types::ClassInstance
                    env.class_decls[type.name].type_params
                  when Types::Interface
                    env.interface_decls[type.name].decl.type_params
                  when Types::Alias
                    env.alias_decls[type.name].decl.type_params
                  end

    type.args.each.with_index do |ty, i|
      if var = type_params[i]
        case var.variance
        when :invariant
          type(ty, result: result, context: :invariant)
        when :covariant
          type(ty, result: result, context: context)
        when :contravariant
          type(ty, result: result, context: negate(context))
        end
      end
    end
  when Types::Proc
    function(type.type, result: result, context: context)
  else
    type.each_type do |ty|
      type(ty, result: result, context: context)
    end
  end
end