From 29f05c17cb8d9c581b4465569982ce7d66b94987 Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@ruby-lang.org>
Date: Fri, 3 Apr 2026 15:27:01 +0900
Subject: [PATCH] Add attr_writer support

Implement AttrWriterMetaNode to handle attr_writer declarations,
generating setter methods that write to instance variables. Previously
attr_writer was silently ignored.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 lib/typeprof/core/ast.rb      |  2 ++
 lib/typeprof/core/ast/meta.rb | 56 +++++++++++++++++++++++++++++++++++
 scenario/misc/attr_writer.rb  | 17 +++++++++++
 3 files changed, 75 insertions(+)
 create mode 100644 scenario/misc/attr_writer.rb

diff --git a/lib/typeprof/core/ast.rb b/lib/typeprof/core/ast.rb
index d1ec4ef8c..f4ec8f526 100644
--- a/lib/typeprof/core/ast.rb
+++ b/lib/typeprof/core/ast.rb
@@ -278,6 +278,8 @@ def self.create_node(raw_node, lenv, use_result = true, allow_meta = false)
             return IncludeMetaNode.new(raw_node, lenv)
           when :attr_reader
             return AttrReaderMetaNode.new(raw_node, lenv)
+          when :attr_writer
+            return AttrWriterMetaNode.new(raw_node, lenv)
           when :attr_accessor
             return AttrAccessorMetaNode.new(raw_node, lenv)
           end
diff --git a/lib/typeprof/core/ast/meta.rb b/lib/typeprof/core/ast/meta.rb
index 2da05462f..c4aa0b641 100644
--- a/lib/typeprof/core/ast/meta.rb
+++ b/lib/typeprof/core/ast/meta.rb
@@ -86,6 +86,62 @@ def install0(genv)
       end
     end
 
+    class AttrWriterMetaNode < Node
+      def initialize(raw_node, lenv)
+        super(raw_node, lenv)
+        @args = []
+        raw_node.arguments.arguments.each do |raw_arg|
+          @args << raw_arg.value.to_sym if raw_arg.type == :symbol_node
+        end
+      end
+
+      attr_reader :args
+
+      def attrs = { args: }
+
+      def mname_code_range(name)
+        idx = @args.index(name.to_sym)
+        node = @raw_node.arguments.arguments[idx].location
+        @lenv.code_range_from_node(node)
+      end
+
+      def define0(genv)
+        @args.map do |arg|
+          mod = genv.resolve_ivar(lenv.cref.cpath, false, :"@#{ arg }")
+          mod.add_def(self)
+          mod
+        end
+      end
+
+      def define_copy(genv)
+        @args.map do |arg|
+          mod = genv.resolve_ivar(lenv.cref.cpath, false, :"@#{ arg }")
+          mod.add_def(self)
+          mod.remove_def(@prev_node)
+          mod
+        end
+        super(genv)
+      end
+
+      def undefine0(genv)
+        @args.each do |arg|
+          mod = genv.resolve_ivar(lenv.cref.cpath, false, :"@#{ arg }")
+          mod.remove_def(self)
+        end
+      end
+
+      def install0(genv)
+        @args.zip(@static_ret) do |arg, ive|
+          vtx = Vertex.new(self)
+          @changes.add_edge(genv, vtx, ive.vtx)
+          ret_box = @changes.add_escape_box(genv, vtx)
+          f_args = FormalArguments.new([vtx], [], nil, [], [], [], nil, nil)
+          @changes.add_method_def_box(genv, @lenv.cref.cpath, false, :"#{ arg }=", f_args, [ret_box])
+        end
+        Source.new
+      end
+    end
+
     class AttrAccessorMetaNode < Node
       def initialize(raw_node, lenv)
         super(raw_node, lenv)
diff --git a/scenario/misc/attr_writer.rb b/scenario/misc/attr_writer.rb
new file mode 100644
index 000000000..8a39fc9cd
--- /dev/null
+++ b/scenario/misc/attr_writer.rb
@@ -0,0 +1,17 @@
+## update
+class Foo
+  attr_writer :x
+
+  def get_x
+    @x
+  end
+end
+
+Foo.new.x = 1
+Foo.new.get_x
+
+## assert
+class Foo
+  def x=: (Integer) -> Integer
+  def get_x: -> Integer
+end