Add enhancement proposal for unused code which appears

after removing unused code.

enhancement_proposals/dep_3.md

@@ -0,0 +1,18 @@
+# DEP 3 - Removal of unused code might create new unused code
+**Status**: Proposed
+**Type**: Feature
+**Created**: 2024-04-16
+
+## Problem statement
+Additional unused code could appear after removal of unused code, since
+some code might have been used by code, which was not used.
+
+## Considered solutions
+These solutions are possible:
+- apply deadcode multiple times till the output does not change in two consequtive runs.
+- intelligently mark which code parts are unused and dont mark code as used, if it is used only by the code, which is unused.
+
+## Chosen soluton
+Intelligent code tracking should be implemented, to make this algorithm more efficient.
+Implementation details should still be considered:
+- Code usage tree might have to be constructed with actual links to usages, which might require a lot of memory.