Bug report: Quartus will not load correct library in VHDL

> Why not just make your life easier and call them :

Because

(1) it is a minimum-sample.

In my real project, they will be called such as "local_xxx" or "sub_xxx",

that will be conflicts someday and hand-mangling makes hard to read/write codes, and

(2) for the polymorphism. To implements and evaluate new ideas, algorithms and/or logics for the FPGA,

to change the sub-module implemented on logic X to logic Y's,

it is one of a simple way to change the library.

To achieve (2) will easy; Select the architecture or use macros to replace, but (1) -- hiding modules is a best way to avoid conflicts -- is difficult.