Modify Struct#{inspect,to_s} to match MRI when the struct is nested inside of an anonymous class or module.

Co-authored-by: Stan Lo <[email protected]>

Author: nirvdrum

CHANGELOG.md

@@ -76,6 +76,7 @@ Compatibility:
 * Fix `Enumerable` methods `each_cons` and `each_slice` to return receiver (#2733, @horakivo)
 * `Module` methods `#private`, `#public`, `#protected`, `#module_function` now returns their arguments like in CRuby 3.1 (#2733, @horakivo)
 * `Kernel#exit!`, killing Fibers and internal errors do not run code in `ensure` clauses anymore, the same as CRuby (@eregon).
+* Modify `Struct#{inspect,to_s}` to match MRI when the struct is nested inside of an anonymous class or module (@st0012, @nirvdrum).
 
 Performance:
 

spec/ruby/core/struct/shared/inspect.rb

@@ -2,4 +2,22 @@
   it "returns a string representation without the class name for anonymous structs" do
     Struct.new(:a).new("").send(@method).should == '#<struct a="">'
   end
+
+  it "returns a string representation without the class name for structs nested in anonymous classes" do
+    obj = Object.new
+    obj.singleton_class.class_eval <<~DOC
+      class Foo < Struct.new(:a); end
+    DOC
+
+    obj.singleton_class::Foo.new("").send(@method).should == '#<struct a="">'
+  end
+
+  it "returns a string representation without the class name for structs nested in anonymous modules" do
+    m = Module.new
+    m.module_eval <<~DOC
+      class Foo < Struct.new(:a); end
+    DOC
+
+    m::Foo.new("").send(@method).should == '#<struct a="">'
+  end
 end

src/main/ruby/truffleruby/core/struct.rb

@@ -147,7 +147,7 @@ def to_s
 
       name = self.class.name
 
-      if Primitive.nil?(name) || name.empty?
+      if Primitive.nil?(name) || name.empty? || name[0] == '#'
         return "#<struct #{values.join(', ')}>"
       else
         return "#<struct #{self.class.name} #{values.join(', ')}>"