Improve interface type compaisons (#308)

When compared against a module, `_Interface` will inspect the instance
methods defined on that module.

Author: joeldrapper

lib/literal/types/interface_type.rb

@@ -2,18 +2,14 @@
 
 # @api private
 class Literal::Types::InterfaceType
-	# TODO: We can generate this and make it much more extensive.
-	METHOD_TYPE_MAPPINGS = {
-		:call => Set[Proc, Method],
-		:to_proc => Set[Proc, Method, Symbol],
-		:to_s => Set[String],
-	}.freeze
-
 	include Literal::Type
 
+	# List of `===` method owners where the comparison will only match for objects with the same class
+	OwnClassTypeMethodOwners = Set[String, Integer, Kernel, Float, NilClass, TrueClass, FalseClass].freeze
+
 	def initialize(*methods)
 		raise Literal::ArgumentError.new("_Interface type must have at least one method.") if methods.size < 1
-		@methods = methods
+		@methods = methods.to_set.freeze
 		freeze
 	end
 
@@ -24,21 +20,30 @@ def inspect
 	end
 
 	def ===(value)
-		@methods.all? { |m| value.respond_to?(m) }
+		@methods.each do |method|
+			return false unless value.respond_to?(method)
+		end
+
+		true
 	end
 
 	def >=(other)
 		case other
 		when Literal::Types::InterfaceType
-			@methods.all? { |m| other.methods.include?(m) }
+			@methods.subset?(other.methods)
 		when Module
-			@methods.map { |m| METHOD_TYPE_MAPPINGS[m] }.all? { |types| types&.include?(other) }
+			public_methods = other.public_instance_methods.to_set
+			@methods.subset?(public_methods)
 		when Literal::Types::IntersectionType
 			other.types.any? { |type| Literal.subtype?(type, self) }
 		when Literal::Types::ConstraintType
 			other.object_constraints.any? { |type| Literal.subtype?(type, self) }
 		else
-			false
+			if OwnClassTypeMethodOwners.include?(other.method(:===).owner)
+				self === other
+			else
+				false
+			end
 		end
 	end
 

test/types/_interface.test.rb

@@ -23,6 +23,14 @@
 	refute_subtype _Interface(:b), _Interface(:a)
 	refute_subtype _Interface(:a), _Interface(:a, :b)
 	refute_subtype Proc, _Interface(:to_proc, :random_method)
+
+	assert_subtype "Hello", _Interface(:to_s)
+	assert_subtype 1, _Interface(:+, :-)
+	assert_subtype Object.new, _Interface(:inspect)
+	assert_subtype 1.234, _Interface(:to_i)
+	assert_subtype nil, _Interface(:nil?)
+	assert_subtype true, _Interface(:to_s)
+	assert_subtype false, _Interface(:to_s)
 end
 
 test "error message" do