Add support for nested multi-target nodes in destructuring assignment (#354)

This commit adds support for nested destructuring assignments like
`a, (b, c) = [1, [2, 3]]`, which previously caused a
"RuntimeError: not supported yet: multi_target_node" error.

Changes:
- Add MultiTargetNode class to handle nested destructuring targets
- Extend create_target_node to support :multi_target_node type
- Add nil guards for `rights` parameter in MAsgnBox and Type::Array#splat_assign
- Add comprehensive test cases for nested destructuring patterns

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: sinsoku

lib/typeprof/core/ast.rb

@@ -270,6 +270,8 @@ def self.create_target_node(raw_node, lenv)
         IndexWriteNode.new(raw_node, dummy_node, lenv)
       when :call_target_node
         CallWriteNode.new(raw_node, dummy_node, lenv)
+      when :multi_target_node
+        MultiTargetNode.new(raw_node, dummy_node, lenv)
       else
         pp raw_node
         raise "not supported yet: #{ raw_node.type }"

lib/typeprof/core/ast/misc.rb

@@ -139,6 +139,63 @@ def retrieve_at(pos, &blk)
       end
     end
 
+    class MultiTargetNode < Node
+      def initialize(raw_node, rhs, lenv)
+        super(raw_node, lenv)
+        @rhs = rhs
+        @lefts = raw_node.lefts.map do |raw_lhs|
+          AST.create_target_node(raw_lhs, lenv)
+        end
+        if raw_node.rest
+          case raw_node.rest.type
+          when :splat_node
+            if raw_node.rest.expression
+              @rest = AST.create_target_node(raw_node.rest.expression, lenv)
+            end
+          when :implicit_rest_node
+            # no assignment target
+          else
+            raise "unexpected rest node in multi_target: #{raw_node.rest.type}"
+          end
+        end
+        @rights = raw_node.rights.map do |raw_rhs|
+          AST.create_target_node(raw_rhs, lenv)
+        end
+      end
+
+      attr_reader :rhs, :lefts, :rest, :rights
+
+      def subnodes = { rhs:, lefts:, rest:, rights: }
+
+      def install0(genv)
+        # The rhs should be installed by the parent MultiWriteNode
+        # Here we set up the multi-assignment box for nested destructuring
+        value = @rhs.install(genv)
+
+        @lefts.each {|lhs| lhs.install(genv) }
+        @lefts.each {|lhs| lhs.rhs.ret || raise(lhs.rhs.inspect) }
+        lefts = @lefts.map {|lhs| lhs.rhs.ret }
+
+        rest_elem = nil
+        if @rest
+          rest_elem = Vertex.new(self)
+          @rest.install(genv)
+          @rest.rhs.ret || raise(@rest.rhs.inspect)
+          @changes.add_edge(genv, Source.new(Type::Instance.new(genv, genv.mod_ary, [rest_elem])), @rest.rhs.ret)
+        end
+
+        rights = nil
+        if @rights && !@rights.empty?
+          @rights.each {|rhs| rhs.install(genv) }
+          @rights.each {|rhs| rhs.rhs.ret || raise(rhs.rhs.inspect) }
+          rights = @rights.map {|rhs| rhs.rhs.ret }
+        end
+
+        box = @changes.add_masgn_box(genv, value, lefts, rest_elem, rights)
+        box.ret
+      end
+    end
+
     class MatchWriteNode < Node
       def initialize(raw_node, lenv)
         super(raw_node, lenv)

lib/typeprof/core/graph/box.rb

@@ -1073,7 +1073,7 @@ def run0(genv, changes)
         else
           if @lefts.size >= 1
             edges << [Source.new(ty), @lefts[0]]
-          elsif @rights.size >= 1
+          elsif @rights && @rights.size >= 1
             edges << [Source.new(ty), @rights[0]]
           else
             edges << [Source.new(ty), @rest_elem]

lib/typeprof/core/type.rb

@@ -112,6 +112,7 @@ def splat_assign(genv, lefts, rest_elem, rights)
         edges = []
         state = :left
         j = nil
+        rights_size = rights ? rights.size : 0
         @elems.each_with_index do |elem, i|
           case state
           when :left
@@ -123,7 +124,7 @@ def splat_assign(genv, lefts, rest_elem, rights)
               redo
             end
           when :rest
-            if @elems.size - i > rights.size
+            if @elems.size - i > rights_size
               edges << [elem, rest_elem]
             else
               state = :right

scenario/variable/masgn_nested.rb

@@ -0,0 +1,34 @@
+## update
+def test_nested_destructuring
+  a, (b, c) = [1, [2, 3]]
+  [a, b, c]
+end
+
+def test_nested_with_strings
+  x, (y, z) = ["foo", ["bar", "baz"]]
+  [x, y, z]
+end
+
+def test_deeper_nesting
+  a, (b, (c, d)) = [1, [2, [3, 4]]]
+  [a, b, c, d]
+end
+
+def test_nested_with_rest
+  a, (b, *rest) = [1, [2, 3, 4]]
+  [a, b, rest]
+end
+
+def test_nested_with_rest_and_rights
+  a, (b, *rest, c) = [1, [2, 3, 4, 5]]
+  [a, b, rest, c]
+end
+
+## assert
+class Object
+  def test_nested_destructuring: -> [Integer, Integer, Integer]
+  def test_nested_with_strings: -> [String, String, String]
+  def test_deeper_nesting: -> [Integer, Integer, Integer, Integer]
+  def test_nested_with_rest: -> [Integer, Integer, Array[Integer]]
+  def test_nested_with_rest_and_rights: -> [Integer, Integer, Array[Integer], Integer]
+end