hakorune/docs/development/issues/llvm_binop_string_mismatch.md

LLVM lowering: string + int causes binop type mismatch

Status: open

Summary

• When compiling code that concatenates a string literal with a non-string (e.g., integer), LLVM object emission fails with a type mismatch in binop.
• Example from apps/ny-map-llvm-smoke/main.hako: print("Map: v=" + v) and print("size=" + s).

Environment

• LLVM 18 / inkwell 0.5.0
• Phase 11.2 lowering

Repro

1. Run: NYASH_LLVM_ARRAY_SMOKE=1 ./tools/llvm_smoke.sh release (or build/link the map smoke similarly)
2. Observe: ❌ LLVM object emit error: binop type mismatch

Expected

• String concatenation should be lowered to a safe runtime shim (e.g., NyRT string builder or nyash_string_concat) that accepts (i8* string, i64/int) and returns i8*.

Observed

• + binop is currently generated as integer addition for non-float operands, leading to a type mismatch when one side is a pointer (string) and the other is integer.

Plan

1. Introduce string-like detection in lowering: if either operand is String (or pointer from nyash_string_new), route to a NyRT concat shim.
2. Provide NyRT APIs:
   • nyash.string.concat_ss(i8*, i8*) -> i8*
   • nyash.string.concat_si(i8*, i64) -> i8*
   • Optional: concat_sf, concat_sb (format helpers)
3. As an interim simplification for smoke, emit print("..." ) in two steps to avoid mixed-type + until the concat shim is ready.

CI

• Keep apps/ny-llvm-smoke OFF by default. Re-enable once concat shim lands and binop lowering is updated.