Implement Reference.pre_initialize in the interpreter (#14968)

spec/primitives/reference_spec.cr

@@ -37,8 +37,7 @@ describe "Primitives: reference" do
     end
   end
 
-  # TODO: implement in the interpreter
-  pending_interpreted describe: ".pre_initialize" do
+  describe ".pre_initialize" do
     it "doesn't fail on complex ivar initializer if value is discarded (#14325)" do
       bar_buffer = GC.malloc(instance_sizeof(Outer))
       Outer.pre_initialize(bar_buffer)
@@ -55,7 +54,12 @@ describe "Primitives: reference" do
     it "sets type ID" do
       foo_buffer = GC.malloc(instance_sizeof(Foo))
       base = Foo.pre_initialize(foo_buffer).as(Base)
-      base.crystal_type_id.should eq(Foo.crystal_instance_type_id)
+      base.should be_a(Foo)
+      base.as(typeof(Foo.crystal_instance_type_id)*).value.should eq(Foo.crystal_instance_type_id)
+      {% unless flag?(:interpreted) %}
+        # FIXME: `Object#crystal_type_id` is incorrect for virtual types in the interpreter (#14967)
+        base.crystal_type_id.should eq(Foo.crystal_instance_type_id)
+      {% end %}
     end
 
     it "runs inline instance initializers" do
@@ -89,7 +93,7 @@ describe "Primitives: reference" do
     end
   end
 
-  pending_interpreted describe: ".unsafe_construct" do
+  describe ".unsafe_construct" do
     it "constructs an object in-place" do
       foo_buffer = GC.malloc(instance_sizeof(Foo))
       foo = Foo.unsafe_construct(foo_buffer, 123_i64)

src/compiler/crystal/interpreter/instructions.cr

@@ -1276,6 +1276,16 @@ require "./repl"
           ptr
         end,
       },
+      reset_class: {
+        operands:   [size : Int32, type_id : Int32],
+        pop_values: [pointer : Pointer(UInt8)],
+        push:       true,
+        code:       begin
+          pointer.clear(size)
+          pointer.as(Int32*).value = type_id
+          pointer
+        end,
+      },
       put_metaclass: {
         operands:   [size : Int32, union_type : Bool],
         push:       true,

src/compiler/crystal/interpreter/primitives.cr

@@ -178,6 +178,30 @@ class Crystal::Repl::Compiler
           pop(sizeof(Pointer(Void)), node: nil)
         end
       end
+    when "pre_initialize"
+      type =
+        if obj
+          discard_value(obj)
+          obj.type.instance_type
+        else
+          scope.instance_type
+        end
+
+      accept_call_members(node)
+
+      dup sizeof(Pointer(Void)), node: nil
+      reset_class(aligned_instance_sizeof_type(type), type_id(type), node: node)
+
+      initializer_compiled_defs = @context.type_instance_var_initializers(type)
+      unless initializer_compiled_defs.empty?
+        initializer_compiled_defs.size.times do
+          dup sizeof(Pointer(Void)), node: nil
+        end
+
+        initializer_compiled_defs.each do |compiled_def|
+          call compiled_def, node: nil
+        end
+      end
     when "tuple_indexer_known_index"
       unless @wants_value
         accept_call_members(node)