test/spec/tuples.wast - external/github.com/WebAssembly/binaryen - Git at Google

 (assert_invalid
   (module
     (func $foo
       (local $temp ((ref func) i32))
     )
   )
   "var must be defaultable"
 )
	(assert_invalid
	(module
	(func $foo
	(local $temp ((ref func) i32))
	)
	)
	"var must be defaultable"
	)