Implementes the block ABI.2010.3.16 natively via the objc_block intrinsic and the Objc_Block builtin type.

See: https://clang.llvm.org/docs/Block-ABI-Apple.html

base/runtime/core_builtin.odin

@@ -5,6 +5,11 @@ import "base:intrinsics"
 @builtin
 Maybe :: union($T: typeid) {T}
 
+/*
+Represents an Objective-C block with a given procedure signature T
+*/
+@builtin
+Objc_Block :: struct($T: typeid) where intrinsics.type_is_proc(T) { using _: intrinsics.objc_object }
 
 /*
 Recovers the containing/parent struct from a pointer to one of its fields.

base/runtime/procs_darwin.odin

@@ -1,9 +1,12 @@
 #+private
 package runtime
 
-@(priority_index=-1e6)
+@(priority_index=-1e5)
 foreign import ObjC "system:objc"
 
+@(priority_index=-1e6)
+foreign import libSystem "system:System"
+
 import "base:intrinsics"
 
 objc_id    :: ^intrinsics.objc_object
@@ -34,3 +37,10 @@ foreign ObjC {
 	object_getClass           :: proc "c" (obj: objc_id) -> objc_Class ---
 }
 
+foreign libSystem {
+	_NSConcreteGlobalBlock: intrinsics.objc_class
+	_NSConcreteStackBlock:  intrinsics.objc_class
+
+	_Block_object_assign  :: proc "c" (rawptr, rawptr, i32) ---
+	_Block_object_dispose :: proc "c" (rawptr, i32) ---
+}