From 9ffdc83474daef704f5aa5bb953b324daaeab588 Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@ruby-lang.org>
Date: Tue, 24 Feb 2026 12:16:49 +0000
Subject: [PATCH] Fix TypeError for rest_positionals/rest_keywords in method
 signature display

rest_positionals and rest_keywords are single Symbols, not Arrays,
so use << instead of concat.
---
 lib/typeprof/core/graph/box.rb               |  4 ++--
 test/cli_test.rb                             | 12 ++++++++++++
 test/fixtures/rest_params/rest_params.rb     | 10 ++++++++++
 test/fixtures/rest_params/typeprof.conf.json |  7 +++++++
 4 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 test/fixtures/rest_params/rest_params.rb
 create mode 100644 test/fixtures/rest_params/typeprof.conf.json

diff --git a/lib/typeprof/core/graph/box.rb b/lib/typeprof/core/graph/box.rb
index e06600e33..15a1c67e5 100644
--- a/lib/typeprof/core/graph/box.rb
+++ b/lib/typeprof/core/graph/box.rb
@@ -662,11 +662,11 @@ def show(output_parameter_names)
         names = []
         names.concat(@node.req_positionals)
         names.concat(@node.opt_positionals)
-        names.concat(@node.rest_positionals) if @node.rest_positionals
+        names << @node.rest_positionals if @node.rest_positionals
         names.concat(@node.post_positionals)
         names.concat(@node.req_keywords)
         names.concat(@node.opt_keywords)
-        names.concat(@node.rest_keywords) if @node.rest_keywords
+        names << @node.rest_keywords if @node.rest_keywords
         args = args.zip(names).map do |arg, name|
           name ? "#{ arg } #{ name }" : arg
         end
diff --git a/test/cli_test.rb b/test/cli_test.rb
index 3d14a476a..0bf240a08 100644
--- a/test/cli_test.rb
+++ b/test/cli_test.rb
@@ -76,6 +76,18 @@ def foo: (String n) -> String
       END
     end
 
+    def test_e2e_output_param_names_rest
+      assert_equal(<<~END, test_run("rest_params", ["--show-parameter-names", "."]))
+        # TypeProf #{ TypeProf::VERSION }
+
+        # ./rest_params.rb
+        class Object
+          def foo: (*Integer args) -> Array[Integer]
+          def bar: (**String kwargs) -> { x: String }
+        end
+      END
+    end
+
     def test_e2e_output_source_location
       assert_equal(<<~END, test_run("basic", ["--show-source-location", "."]))
         # TypeProf #{ TypeProf::VERSION }
diff --git a/test/fixtures/rest_params/rest_params.rb b/test/fixtures/rest_params/rest_params.rb
new file mode 100644
index 000000000..682635b26
--- /dev/null
+++ b/test/fixtures/rest_params/rest_params.rb
@@ -0,0 +1,10 @@
+def foo(*args)
+  args
+end
+
+def bar(**kwargs)
+  kwargs
+end
+
+foo(1)
+bar(x: "str")
diff --git a/test/fixtures/rest_params/typeprof.conf.json b/test/fixtures/rest_params/typeprof.conf.json
new file mode 100644
index 000000000..eec7817ee
--- /dev/null
+++ b/test/fixtures/rest_params/typeprof.conf.json
@@ -0,0 +1,7 @@
+{
+    "typeprof_version": "experimental",
+    "rbs_dir": "sig/",
+    "analysis_unit_dirs": [
+        "."
+    ]
+}