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SPEC: Diagnostics and Lowering

4. Non-goals

  • full modal-group validation beyond the current supported motion rule
  • units and distance-mode completeness
  • full RS274NGC expression/macro support
  • full subprogram execution semantics in the original v0.1 scope

5. Diagnostics

  • syntax errors are reported with 1-based line and column
  • syntax messages should be actionable and prefixed with syntax error:
  • semantic diagnostics include explicit correction hints

Current semantic error examples:

  • mixed Cartesian and polar coordinates in one G0/G1 line
  • multiple motion commands in one line
  • invalid G4 block composition
  • invalid dwell mode/value combinations

Planned Siemens compatibility diagnostics:

  • malformed skip-level marker
  • invalid assignment-shape diagnostics for Siemens = rules

6. Message Lowering

Current supported paths:

  • parse -> AIL
  • parse -> AIL -> packets
  • parse -> messages as a compatibility surface

Legacy note:

  • older batch message/session APIs remain for compatibility and tooling
  • the public execution architecture is centered on ExecutionSession

Result model

  • diagnostics
  • lowered instructions or packets/messages
  • rejected lines for fail-fast policies

JSON schema notes

  • top-level schema_version
  • ordered payload lists
  • deterministic diagnostics
  • deterministic rejected_lines

Packet stage

Packet result shape:

  • packets
  • diagnostics
  • rejected_lines

Current packetization converts motion and dwell AIL instructions. Non-motion instructions are skipped with warning diagnostics where appropriate.

6.1 Control-Flow AIL and Executor

AIL may include:

  • label
  • goto
  • branch_if

Structured control flow is lowered into explicit linear control flow with generated labels and gotos.

Runtime/executor contract:

  • branch resolution uses injected resolver interfaces
  • condition evaluation may be:
    • true
    • false
    • pending
    • error
  • variable references are preserved structurally for runtime resolution
  • skip-level execution is applied at lowering/execution time from configured active levels

Executor state model:

  • ready
  • blocked
  • completed
  • fault

Target resolution behavior:

  • GOTOF: forward-only
  • GOTOB: backward-only
  • GOTO: forward, then backward
  • GOTOC: non-faulting unresolved-target variant

Simple system-variable goto targets are still unresolved in the v0 executor model and follow the fault-or-continue behavior of the opcode.