Compiler: add primitive to get a class' instance type id

Useful when overriding allocate to correctly set the type id

src/compiler/crystal/codegen/primitives.cr

@@ -47,6 +47,8 @@ class Crystal::CodeGenVisitor
               codegen_primitive_object_id node, target_def, call_args
             when "object_crystal_type_id"
               codegen_primitive_object_crystal_type_id node, target_def, call_args
+            when "class_crystal_instance_type_id"
+              codegen_primitive_class_crystal_instance_type_id node, target_def, call_args
             when "symbol_to_s"
               codegen_primitive_symbol_to_s node, target_def, call_args
             when "class"
@@ -566,6 +568,10 @@ class Crystal::CodeGenVisitor
     end
   end
 
+  def codegen_primitive_class_crystal_instance_type_id(node, target_def, call_args)
+    type_id(context.type.instance_type)
+  end
+
   def codegen_primitive_symbol_to_s(node, target_def, call_args)
     load(gep @llvm_mod.globals[SYMBOL_TABLE_NAME], int(0), call_args[0])
   end

src/compiler/crystal/semantic/main_visitor.cr

@@ -2175,6 +2175,8 @@ module Crystal
         node.type = program.uint64
       when "object_crystal_type_id"
         node.type = program.int32
+      when "class_crystal_instance_type_id"
+        node.type = program.int32
       when "symbol_to_s"
         node.type = program.string
       when "class"

src/object.cr

@@ -1144,4 +1144,9 @@ class Object
       \{% end %}
     end
   end
+
+  protected def self.set_crystal_type_id(ptr)
+    ptr.as(LibC::SizeT*).value = LibC::SizeT.new(crystal_instance_type_id)
+    ptr
+  end
 end

src/primitives.cr

@@ -51,6 +51,12 @@ class Reference
   end
 end
 
+class Class
+  @[Primitive(:class_crystal_instance_type_id)]
+  def crystal_instance_type_id
+  end
+end
+
 struct Bool
   # Returns true if *self* is equal to *other*.
   @[Primitive(:binary)]

src/weak_ref.cr

@@ -9,7 +9,10 @@ class WeakRef(T)
   end
 
   def self.allocate
-    GC.malloc_atomic(sizeof(self)).as(self)
+    ptr = GC.malloc_atomic(sizeof(self)).as(self)
+    # TODO: uncomment after 0.20.1
+    # set_crystal_type_id(ptr)
+    ptr
   end
 
   # Returns the referenced object or `Nil` if it has been garbage-collected.