Index: src/libcfa/concurrency/threads
===================================================================
--- src/libcfa/concurrency/threads	(revision e15df4c2fcf95d96cb620db7060d7c9e78f55d63)
+++ src/libcfa/concurrency/threads	(revision 6dc78deeb7aa8ae26d290940106fb79598146d3b)
@@ -27,12 +27,12 @@
 // Anything that implements this trait can be resumed.
 // Anything that is resumed is a coroutine.
-trait is_thread(dtype T | sized(T)) {
+trait is_thread(dtype T) {
       void main(T* this);
       thread* get_thread(T* this);
 };
 
-#define DECL_THREAD(X) static inline thread* get_thread(X* this) { return &this->t; } void main(X* this);
+#define DECL_THREAD(X) thread* get_thread(X* this) { return &this->t; } void main(X* this);
 
-forall( dtype T | sized(T) | is_thread(T) )
+forall( dtype T | is_thread(T) )
 static inline coroutine* get_coroutine(T* this) {
 	return &get_thread(this)->c;