Merge pull request #3068 from ruby/claude/fix-type-param-rename-substitution

Fix TypeParam.rename to substitute variables in bounds and default types

Author: soutaro

lib/rbs/ast/type_param.rb

@@ -114,7 +114,7 @@ def self.subst_var(vars, type)
       def self.rename(params, new_names:)
         raise unless params.size == new_names.size
 
-        subst = Substitution.build(new_names, Types::Variable.build(new_names))
+        subst = Substitution.build(params.map(&:name), Types::Variable.build(new_names))
 
         params.map.with_index do |param, index|
           new_name = new_names[index]

test/rbs/ast/type_param_test.rb

@@ -66,4 +66,28 @@ def test_normalize_args
       assert_equal ["::Integer", "::Array[::Integer]", "::Array[::Array[::Integer]]"], args.map(&:to_s)
     end
   end
+
+  def test_rename
+    params = [
+      TypeParam.new(name: :A, variance: :covariant, upper_bound: nil, lower_bound: nil, location: nil),
+      TypeParam.new(
+        name: :B,
+        variance: :invariant,
+        upper_bound: parse_type("::Array[A]"),
+        lower_bound: nil,
+        default_type: parse_type("::Hash[A, B]"),
+        location: nil
+      ).unchecked!
+    ]
+
+    TypeParam.rename(params, new_names: [:X, :Y]).tap do |renamed|
+      assert_equal [:X, :Y], renamed.map(&:name)
+      assert_equal :covariant, renamed[0].variance
+      assert_equal :invariant, renamed[1].variance
+      assert_predicate renamed[1], :unchecked?
+
+      assert_equal parse_type("::Array[X]", variables: [:X]), renamed[1].upper_bound_type
+      assert_equal parse_type("::Hash[X, Y]", variables: [:X, :Y]), renamed[1].default_type
+    end
+  end
 end