.opAssign disabled without @disable

[denizzzka via Digitalmars-d-learn]

Hi!

DMD and LDC2 complain about disabled opAssign, but I am not used 
@disable and depend package "gfm" also isn't uses @disable.

Steps to reproduce:

git clone https://github.com/denizzzka/r-tree.git
cd r-tree
git checkout 803eed22
dub test

Fetching gfm 6.0.0 (getting selected version)...
Placing gfm 6.0.0 to /home/denizzz/.dub/packages/...
Generating test runner configuration '__test__library__' for 
'library' (sourceLibrary).
Performing "unittest" build using dmd for x86_64.
gfm:math 6.0.0: building configuration "library"...
r-tree ~master: building configuration "__test__library__"...
source/package.d(109,31): Error: function 
rtree.RAMNode!(Box!(int, 2), ubyte).RAMNode.opAssign is not 
callable because it is annotated with @disable
source/package.d(110,26): Error: function 
rtree.RAMNode!(Box!(int, 2), ubyte).RAMNode.opAssign is not 
callable because it is annotated with @disable
source/package.d(330,25): Error: template instance 
rtree.RTree!(RAMNode!(Box!(int, 2), ubyte), true) error 
instantiating
dmd failed with exit code 1.

If I am try to add opAssign to struct RAMNode manually it is 
compiles. (But there is enough postblit constructor.)