Support &method(:name) call for block_pass

lib/steep/type_construction.rb

@@ -2401,7 +2401,17 @@ def synthesize(node, hint: nil, condition: false)
             if value_node
               type, constr = synthesize(value_node, hint: hint)
 
-              if hint.is_a?(AST::Types::Proc) && value_node.type == :sym
+              if hint.is_a?(AST::Types::Proc) && value_node.type == :send && value_node.children[1] == :method && type.is_a?(AST::Types::Name::Instance) && type.name.to_s == '::Method'
+                method_name = value_node.children[2].children[0]
+                if method = calculate_interface(AST::Types::Self.instance, private: true)&.methods&.[](method_name)
+                  # TODO: select appropriate method type from `method.method_types`.
+                  type = AST::Types::Proc.new(
+                    type: method.method_types.first&.type || raise,
+                    block: nil,
+                    self_type: nil
+                  )
+                end
+              elsif hint.is_a?(AST::Types::Proc) && value_node.type == :sym
                 if hint.one_arg?
                   if hint.type.params
                     # Assumes Symbol#to_proc implementation

test/type_construction_test.rb

@@ -6950,6 +6950,62 @@ def m: [T] () { (untyped) -> T } -> T
     end
   end
 
+  def test_block_pass_and_method__valid
+    with_checker(<<-RBS) do |checker|
+class Object
+  def method: (Symbol) -> Method
+  def my_to_s: (Integer) -> String
+end
+
+class Method
+end
+    RBS
+      source = parse_ruby(<<-EOF)
+x = [1, 2, 3]
+r = x.map(&method(:my_to_s))
+      EOF
+
+      with_standard_construction(checker, source) do |construction, typing|
+        pair = construction.synthesize(source.node)
+
+        assert_no_error typing
+
+        assert_equal parse_type("::Array[::String]"), pair.context.type_env[:r]
+      end
+    end
+  end
+
+  def test_block_pass_and_method__invalid
+    with_checker(<<-RBS) do |checker|
+class Object
+  def method: (Symbol) -> Method
+  def my_to_s: (String) -> String
+end
+
+class Method
+end
+    RBS
+      source = parse_ruby(<<-EOF)
+x = [1, 2, 3]
+r = x.map(&method(:my_to_s))
+      EOF
+
+      with_standard_construction(checker, source) do |construction, typing|
+        pair = construction.synthesize(source.node)
+
+        assert_typing_error typing, size: 1 do |errors|
+          assert_any!(errors) do |error|
+            assert_instance_of Diagnostic::Ruby::BlockTypeMismatch, error
+            assert /^\^\(::Integer\) -> X\(\d+\)$/ =~ error.expected.to_s
+            assert_equal parse_type("^(::String) -> ::String"), error.actual
+          end
+        end
+
+        assert_equal parse_type("::Array[untyped]"), pair.context.type_env[:r]
+      end
+    end
+  end
+
   def test_send_unsatisfiable_constraint
     with_checker(<<RBS) do |checker|
 class SendTest