Bug report: Quartus will not load correct library in VHDL

Synthesis directives are not part of VHDL, they are just attributes that altera specify to affect the behaviour of their synthesisor. It is not extension to VHDL - anyone can define their own attributes in VHDL.

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> VHDL has no ability to "hide" modules behind namespaces.

it will be incorrect partially.

In at least Altera-implemented-version, VHDL has ability to port modules into namespaces (libraries),

that hides sub-modules (if does not write "use xxx.all;"), that I just had wanted function.

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Like I said, unless you specify the libraries in the libraries settings or in the .qsf file, quartus will ignore any user libraries (or namespaces as you like to call them) and just throw everything in the work library.

If you post your whole code and project, maybe it will be clearer what you're doing..