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f959a02037
fixes #25725 This pull request makes significant improvements to symbol handling during transformation passes in the compiler, particularly for routines (procedures, iterators) and their parameters. The changes ensure that when routines are copied (for inlining, closure generation, etc.), all relevant symbols and type headers are also freshly copied and correctly owned, preventing subtle bugs from symbol reuse. Additionally, new regression tests are added to cover previously problematic iterator cases. **Improvements to symbol copying and ownership:** * Introduced `freshOwnedSym` to create a fresh copy of a symbol with a specified owner, ensuring that transformed routines and their parameters do not share symbols with the originals, which prevents accidental aliasing and ownership issues. * Refactored `freshVar` to use `freshOwnedSym`, centralizing fresh symbol creation logic. * Added `introduceNewRoutineHeaderSyms` and `copyRoutineTypeHeader` to ensure that when routines are copied, all parameter/result symbols and their types are also freshly copied and mapped, avoiding shared state between original and transformed routines. * Updated `introduceNewLocalVars` to use `freshOwnedSym` for routine symbols and to invoke the new header/type copying procedures, ensuring correctness in routine transformation. **Testing and regression coverage:** * Added new blocks to `tests/iter/titer_issues.nim` to test iterator transformation edge cases, including scenarios that previously led to symbol reuse bugs (e.g., bugs #25724 and #25725).