From 71de020cbf092ff92be5dcd29ea38b0c9d49edae Mon Sep 17 00:00:00 2001
From: Soutaro Matsumoto <matsumoto@soutaro.com>
Date: Sat, 30 Apr 2022 21:46:14 +0900
Subject: [PATCH] Remove `to_a` error message

The error message is printed because `Factory#interface` is called with unsupported types. This commit adds a guard.
---
 lib/steep/type_construction.rb |  5 +++++
 test/type_construction_test.rb | 26 ++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/lib/steep/type_construction.rb b/lib/steep/type_construction.rb
index 7d5765c65..2c221d4c0 100644
--- a/lib/steep/type_construction.rb
+++ b/lib/steep/type_construction.rb
@@ -3981,6 +3981,11 @@ def try_tuple_type(node, hint)
     end
 
     def try_convert(type, method)
+      case type
+      when AST::Types::Any, AST::Types::Bot, AST::Types::Top, AST::Types::Var
+        return
+      end
+
       interface = checker.factory.interface(type, private: false)
       if entry = interface.methods[method]
         method_type = entry.method_types.find do |method_type|
diff --git a/test/type_construction_test.rb b/test/type_construction_test.rb
index a8bdc5f5c..36b2c9cd1 100644
--- a/test/type_construction_test.rb
+++ b/test/type_construction_test.rb
@@ -8673,6 +8673,32 @@ def to_a: () -> Array[T]
     end
   end
 
+  def test_to_a_untyped
+    with_checker(<<-RBS) do |checker|
+    RBS
+
+      source = parse_ruby(<<-'RUBY')
+# @type var a: untyped
+a = _ = nil
+[*a]
+
+# @type var b: top
+b = _ = nil
+[*b]
+
+# @type var c: bot
+c = _ = nil 
+[*c]
+      RUBY
+
+      with_standard_construction(checker, source) do |construction, typing|
+        _, constr = construction.synthesize(source.node)
+
+        assert_no_error typing
+      end
+    end
+  end
+
   def test_case_const_unexpected_error
     with_checker(<<-RBS) do |checker|
 class UnexpectedErrorTest