[ruby/prism] Implement case equality on nodes

https://github.com/ruby/prism/commit/dc121e4fdf

prism/templates/lib/prism/node.rb.erb

@@ -219,10 +219,10 @@ module Prism
     def deconstruct_keys(keys)
       { <%= (node.fields.map { |field| "#{field.name}: #{field.name}" } + ["location: location"]).join(", ") %> }
     end
-
     <%- node.fields.each do |field| -%>
+
     <%- if field.comment.nil? -%>
-    # <%= "private " if field.is_a?(Prism::Template::FlagsField) %>attr_reader <%= field.name %>: <%= field.rbs_class %>
+    # <%= "protected " if field.is_a?(Prism::Template::FlagsField) %>attr_reader <%= field.name %>: <%= field.rbs_class %>
     <%- else -%>
     <%- field.each_comment_line do |line| -%>
     #<%= line %>
@@ -248,9 +248,8 @@ module Prism
       end
     end
     <%- else -%>
-    attr_reader :<%= field.name -%><%= "\n    private :#{field.name}" if field.is_a?(Prism::Template::FlagsField) %>
+    attr_reader :<%= field.name -%><%= "\n    protected :#{field.name}" if field.is_a?(Prism::Template::FlagsField) %>
     <%- end -%>
-
     <%- end -%>
     <%- node.fields.each do |field| -%>
     <%- case field -%>
@@ -349,6 +348,22 @@ module Prism
     def self.type
       :<%= node.human %>
     end
+
+    # Implements case-equality for the node. This is effectively == but without
+    # comparing the value of locations. Locations are checked only for presence.
+    def ===(other)
+      other.is_a?(<%= node.name %>)<%= " &&" if node.fields.any? %>
+        <%- node.fields.each_with_index do |field, index| -%>
+        <%- if field.is_a?(Prism::Template::LocationField) || field.is_a?(Prism::Template::OptionalLocationField) -%>
+        (<%= field.name %>.nil? == other.<%= field.name %>.nil?)<%= " &&" if index != node.fields.length - 1 %>
+        <%- elsif field.is_a?(Prism::Template::NodeListField) || field.is_a?(Prism::Template::ConstantListField) -%>
+        (<%= field.name %>.length == other.<%= field.name %>.length) &&
+        <%= field.name %>.zip(other.<%= field.name %>).all? { |left, right| left === right }<%= " &&" if index != node.fields.length - 1 %>
+        <%- else -%>
+        (<%= field.name %> === other.<%= field.name %>)<%= " &&" if index != node.fields.length - 1 %>
+        <%- end -%>
+        <%- end -%>
+    end
   end
   <%- end -%>
   <%- flags.each_with_index do |flag, flag_index| -%>

test/prism/ruby_api_test.rb

@@ -244,6 +244,21 @@ module Prism
       assert_equal 16, base[parse_expression("0x1")]
     end
 
+    def test_node_equality
+      assert_operator parse_expression("1"), :===, parse_expression("1")
+      assert_operator Prism.parse("1").value, :===, Prism.parse("1").value
+
+      complex_source = "class Something; @var = something.else { _1 }; end"
+      assert_operator parse_expression(complex_source), :===, parse_expression(complex_source)
+
+      refute_operator parse_expression("1"), :===, parse_expression("2")
+      refute_operator parse_expression("1"), :===, parse_expression("0x1")
+
+      complex_source_1 = "class Something; @var = something.else { _1 }; end"
+      complex_source_2 = "class Something; @var = something.else { _2 }; end"
+      refute_operator parse_expression(complex_source_1), :===, parse_expression(complex_source_2)
+    end
+
     private
 
     def parse_expression(source)