Added verify_exit_phi_no_collision() to contract_checks.rs for early detection
of ValueId collisions between exit PHIs and other instructions.
Problem detected:
- If exit_phi_builder uses builder.value_gen.next() (module-level) instead of
func.next_value_id() (function-level), ValueIds can collide:
Example:
- bb0: %1 = const 0 (counter init)
- bb3: %1 = phi ... (exit PHI - collision!)
Previous behavior:
- Error only detected at LLVM backend runtime
- Cryptic error: "Cannot overwrite PHI dst=1"
New behavior:
- Panic at Rust compile time (debug build)
- Clear error message with fix suggestion:
"Exit PHI dst %1 collides with instruction in block 0
Fix: Use func.next_value_id() in exit_phi_builder.rs"
Benefits:
- 🔥 Fail-Fast: Catch errors during Rust compilation, not LLVM execution
- 📋 Clear messages: Exact collision point + fix suggestion
- 🧪 Testable: verify_exit_phi_no_collision() can be unit tested
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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