Source-location tracking and diagnostics through the pipeline

[tetsuo-cpp]

Summary

Preserve Forth source locations on MLIR ops through translation and conversion so compile failures and debug dumps point at the offending word/line, not only opaque lowered IR.

Motivation

The parser has SMLoc / emitErrorAt for many syntax and control-flow errors. After lowering, pipeline failures and miscompiles are harder to attribute: stack/MemRef ops often lack useful FusedLoc / file-line mapping back to the .forth line.

For a stack language, “which word under/overflowed or lowered wrong?” is essential DX.

Proposed work

1. Attach FileLineColLoc (or equivalent) to every emitted forth.* op at parse time
2. Ensure conversion patterns propagate locations to new arith/memref/gpu ops (rewriter uses op.getLoc() consistently — audit and fix gaps)
3. warpforthc dumps: --debug-ir-after=convert-forth-to-memref style using standard MLIR pass instrumentation
4. Optional: print caret diagnostics for pipeline failures when locations remain

Acceptance criteria

• Audit: major Forth ops carry source locs out of the parser
• Sample conversion patterns preserve locs (LIT can check loc( in dump if stable)
• warpforthc supports IR dumping at stage boundaries (pass manager cl options wired or documented)
• At least one intentional lowering error demonstrates a Forth line in the diagnostic

Related

• Control-flow validation diagnostics (Add validation for mismatched control flow words #21 closed)
• Debug-mode runtime checks (separate)
• Opt pipeline expansion (dump stages help)