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.



61
62
63
 
# 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.



59
60
61
 
# File 'lib/rbs/variance_calculator.rb', line 59

def builder
  @builder
end

Instance Method Details

#env ⇒ Object 



65
66
67
 
# File 'lib/rbs/variance_calculator.rb', line 65

def env
  builder.env
end

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



88
89
90
91
92
93
94
 
# 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 



69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
 
# 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 



96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
 
# 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
    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
                  end

    type.args.each.with_index do |ty, i|
      var = 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