Support RuboCop::AST::ComplexNode

This PR supports `RuboCop::AST::ComplexNode`.

The `complex` type is categorized as a `numeric` type,
so it should be handled transparently alongside `int`, `float`, and `rational`.

```ruby
int: :numeric,
float: :numeric,
rational: :numeric,
complex: :numeric,
```

https://github.com/rubocop/rubocop-ast/blob/v1.44.1/lib/rubocop/ast/node.rb#L106-L109

This eliminates the need for redundant branching, such as in rubocop/rubocop#14146.

Author: koic

changelog/new_support_rubocop_ast_complex_node.md

@@ -0,0 +1 @@
+* [#379](https://github.com/rubocop/rubocop-ast/pull/379): Support `RuboCop::AST::ComplexNode`. ([@koic][])

lib/rubocop/ast.rb

@@ -48,6 +48,7 @@
 require_relative 'ast/node/case_node'
 require_relative 'ast/node/casgn_node'
 require_relative 'ast/node/class_node'
+require_relative 'ast/node/complex_node'
 require_relative 'ast/node/const_node'
 require_relative 'ast/node/def_node'
 require_relative 'ast/node/defined_node'

lib/rubocop/ast/builder.rb

@@ -38,6 +38,7 @@ def self.included(base)
         casgn:               CasgnNode,
         case:                CaseNode,
         class:               ClassNode,
+        complex:             ComplexNode,
         const:               ConstNode,
         def:                 DefNode,
         defined?:            DefinedNode,

lib/rubocop/ast/node/complex_node.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module AST
+    # A node extension for `complex` nodes. This will be used in place of a plain
+    # node when the builder constructs the AST, making its methods available to
+    # all `complex` nodes within RuboCop.
+    class ComplexNode < Node
+      include BasicLiteralNode
+      include NumericNode
+    end
+  end
+end

lib/rubocop/ast/node/mixin/basic_literal_node.rb

@@ -3,7 +3,7 @@
 module RuboCop
   module AST
     # Common functionality for primitive literal nodes: `sym`, `str`,
-    # `int`, `float`, `rational`...
+    # `int`, `float`, `rational`, `complex`...
     module BasicLiteralNode
       # Returns the value of the literal.
       #

lib/rubocop/ast/node/mixin/numeric_node.rb

@@ -2,7 +2,7 @@
 
 module RuboCop
   module AST
-    # Common functionality for primitive numeric nodes: `int`, `float`, `rational`...
+    # Common functionality for primitive numeric nodes: `int`, `float`, `rational`, `complex`...
     module NumericNode
       SIGN_REGEX = /\A[+-]/.freeze
       private_constant :SIGN_REGEX

spec/rubocop/ast/complex_node_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::AST::ComplexNode do
+  subject(:complex_node) { parse_source(source).ast }
+
+  describe '.new' do
+    let(:source) { '+4.2i' }
+
+    it { is_expected.to be_a(described_class) }
+  end
+
+  describe '#sign?' do
+    subject { complex_node.sign? }
+
+    context 'when explicit positive complex' do
+      let(:source) { '+4.2i' }
+
+      it { is_expected.to be(true) }
+    end
+
+    context 'when explicit negative complex' do
+      let(:source) { '-4.2i' }
+
+      it { is_expected.to be(true) }
+    end
+  end
+
+  describe '#value' do
+    let(:source) { '+4.2i' }
+
+    it { expect(complex_node.value).to eq(+4.2i) }
+  end
+end