Class: Steep::Subtyping::Constraints

Inherits:
Object
  • Object
show all
Defined in:
lib/steep/subtyping/constraints.rb

Defined Under Namespace

Classes: UnsatisfiableConstraint, UnsatisfiedInvariantError

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(unknowns:) ⇒ Constraints

Returns a new instance of Constraints.



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# File 'lib/steep/subtyping/constraints.rb', line 78

def initialize(unknowns:)
  @dictionary = {}
  @vars = Set.new

  unknowns.each do |var|
    dictionary[var] = [Set.new, Set.new]
  end
end

Instance Attribute Details

#dictionary ⇒ Object (readonly)

Returns the value of attribute dictionary.



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# File 'lib/steep/subtyping/constraints.rb', line 75

def dictionary
  @dictionary
end

#vars ⇒ Object (readonly)

Returns the value of attribute vars.



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# File 'lib/steep/subtyping/constraints.rb', line 76

def vars
  @vars
end

Class Method Details

.empty ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 87

def self.empty
  new(unknowns: [])
end

Instance Method Details

#add(var, sub_type: nil, super_type: nil) ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 104

def add(var, sub_type: nil, super_type: nil)
  subs, supers = dictionary[var]

  if super_type && !super_type.is_a?(AST::Types::Top)
    supers << eliminate_variable(super_type, to: AST::Types::Top.new)
  end

  if sub_type && !sub_type.is_a?(AST::Types::Bot)
    subs << eliminate_variable(sub_type, to: AST::Types::Bot.new)
  end

  super_fvs = supers.each.with_object(Set.new) do |type, fvs|
    fvs.merge(type.free_variables)
  end
  sub_fvs = subs.each.with_object(Set.new) do |type, fvs|
    fvs.merge(type.free_variables)
  end

  unless super_fvs.disjoint?(unknowns) || sub_fvs.disjoint?(unknowns)
    raise UnsatisfiedInvariantError.new(
      reason: UnsatisfiedInvariantError::UnknownsFreeVariableNotDisjoint.new(
        var: var,
        lower_bound: sub_type,
        upper_bound: super_type
      ),
      constraints: self
    )
  end
end

#add_var(*vars) ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 91

def add_var(*vars)
  vars.each do |var|
    self.vars << var
  end

  unless Set.new(vars).disjoint?(unknowns)
    raise UnsatisfiedInvariantError.new(
      reason: UnsatisfiedInvariantError::VariablesUnknownsNotDisjoint.new(vars: vars),
      constraints: constraints
    )
  end
end

#each ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 256

def each
  if block_given?
    dictionary.each_key do |var|
      yield var, lower_bound(var), upper_bound(var)
    end
  else
    enum_for :each
  end
end

#eliminate_variable(type, to:) ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 134

def eliminate_variable(type, to:)
  case type
  when AST::Types::Name
    type.args.map do |ty|
      eliminate_variable(ty, to: AST::Types::Any.new)
    end.yield_self do |args|
      AST::Types::Name.new(
        name: type.name,
        args: args
      )
    end
  when AST::Types::Union
    type.types.map do |ty|
      eliminate_variable(ty, to: AST::Types::Any.new)
    end.yield_self do |types|
      AST::Types::Union.build(types: types)
    end
  when AST::Types::Intersection
    type.types.map do |ty|
      eliminate_variable(ty, to: AST::Types::Any.new)
    end.yield_self do |types|
      AST::Types::Intersection.build(types: types)
    end
  when AST::Types::Var
    if vars.member?(type.name)
      to
    else
      type
    end
  else
    type
  end
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/steep/subtyping/constraints.rb', line 176

def empty?
  dictionary.keys.empty?
end

#has_constraint?(var) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/steep/subtyping/constraints.rb', line 251

def has_constraint?(var)
  lower, upper = dictionary[var]
  !lower.empty? || !upper.empty?
end

#lower_bound(var) ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 192

def lower_bound(var)
  lower_bound, _ = dictionary[var]

  case lower_bound.size
  when 0
    AST::Types::Bot.new
  when 1
    lower_bound.first
  else
    AST::Types::Intersection.build(types: lower_bound.to_a)
  end
end

#solution(checker, variance:, variables:) ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 205

def solution(checker, variance:, variables:)
  vars = []
  types = []

  dictionary.each_key do |var|
    if variables.include?(var)
      if has_constraint?(var)
        upper_bound = upper_bound(var)
        lower_bound = lower_bound(var)
        relation = Relation.new(sub_type: lower_bound, super_type: upper_bound)

        checker.check(relation, constraints: self.class.empty).yield_self do |result|
          if result.success?
            vars << var

            type = case
                   when variance.contravariant?(var)
                     upper_bound
                   when variance.covariant?(var)
                     lower_bound
                   else
                     if lower_bound.level.join > upper_bound.level.join
                       upper_bound
                     else
                       lower_bound
                     end
                   end

            types << type
          else
            raise UnsatisfiableConstraint.new(var: var,
                                              sub_type: lower_bound,
                                              super_type: upper_bound,
                                              result: result)
          end
        end
      else
        vars << var
        types << AST::Types::Any.new
      end
    end
  end

  Interface::Substitution.build(vars, types)
end

#to_s ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 266

def to_s
  strings = each.map do |var, lower_bound, upper_bound|
    "#{lower_bound} <: #{var} <: #{upper_bound}"
  end

  "#{unknowns.to_a.join(",")}/#{vars.to_a.join(",")} |- { #{strings.join(", ")} }"
end

#unknown?(var) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/steep/subtyping/constraints.rb', line 168

def unknown?(var)
  dictionary.key?(var)
end

#unknowns ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 172

def unknowns
  Set.new(dictionary.keys)
end

#upper_bound(var) ⇒ Object 



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# File 'lib/steep/subtyping/constraints.rb', line 180

def upper_bound(var)
  _, upper_bound = dictionary[var]
  case upper_bound.size
  when 0
    AST::Types::Top.new
  when 1
    upper_bound.first
  else
    AST::Types::Union.build(types: upper_bound.to_a)
  end
end