[GR-18163] Fix Struct setters to raise FrozenError when a struct is frozen

CHANGELOG.md

@@ -23,6 +23,7 @@ Compatibility:
 * Fix `Kernel#raise` and don't override `cause` at exception re-raising (#3831, @andrykonchin).
 * Return a pointer with `#type_size` of 1 for `Pointer#read_pointer` (@eregon).
 * Fix `rb_str_locktmp()` and `rb_str_unlocktmp()` to raise `FrozenError` when string argument is frozen (#3752, @andrykonchin).
+* Fix Struct setters to raise `FrozenError` when a struct is frozen (#3850, @andrykonchin).
 
 Performance:
 

spec/ruby/core/struct/element_set_spec.rb

@@ -26,4 +26,11 @@
     -> { car[-4] = true         }.should raise_error(IndexError)
     -> { car[Object.new] = true }.should raise_error(TypeError)
   end
+
+  it "raises a FrozenError on a frozen struct" do
+    car = StructClasses::Car.new('Ford', 'Ranger')
+    car.freeze
+
+    -> { car[:model] = 'Escape' }.should raise_error(FrozenError)
+  end
 end

spec/ruby/core/struct/struct_spec.rb

@@ -33,6 +33,13 @@
     car['model'].should == 'F150'
     car[1].should == 'F150'
   end
+
+  it "writer methods raise a FrozenError on a frozen struct" do
+    car = StructClasses::Car.new('Ford', 'Ranger')
+    car.freeze
+
+    -> { car.model = 'Escape' }.should raise_error(FrozenError)
+  end
 end
 
 describe "Struct subclasses" do

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

@@ -58,7 +58,10 @@ def self.new(*attrs, keyword_init: nil, &block)
 
       attrs.each do |a|
         define_method(a) { Primitive.object_hidden_var_get(self, a) }
-        define_method(:"#{a}=") { |value| Primitive.object_hidden_var_set(self, a, value) }
+        define_method(:"#{a}=") do |value|
+          Primitive.check_frozen self
+          Primitive.object_hidden_var_set(self, a, value)
+        end
       end
 
       def self.new(...)