Improvements to the core glsl language

Are there plans to improve the glsl language. This could be from simple features like default parameters for functions, till more complex ones like interfaces/classes and/or templates? It seems to me that there was no progress made in this direction in the last couple of years. Features like these would make it much easier to write clean and compact code. If there is already an ongoing discussion, please refer me to it.

No file, test, or entry point is identified. First review the core GLSL specification and the issue discussion, then determine whether the requested default parameters, interfaces/classes, or templates have an existing proposal; a concrete scope and acceptance criteria would be needed before implementation can be considered done.

Written by the indexing model from the issue text.