refactor(control_tree): Phase 125 P2-P4 introduce EnvLayout (writes+inputs) + Return(Variable) from inputs
Phase 125 P2: EnvLayout introduction
- Add EnvLayout struct (writes + inputs)
- from_contract() creates layout from StepTreeContract + available_inputs
- SSOT: inputs = reads ∩ available_inputs (deterministic order)
- No AST inference (don't capture from AST, use provided available_inputs)
Phase 125 P2: Builder env mapping
- lower_if_only_to_normalized: Use EnvLayout to create env map
- writes: Generate ValueId (as before)
- inputs: Reference ValueId from available_inputs (placeholder for P3)
- Function params: writes only (inputs come from outer scope)
Phase 125 P4: Return(Variable) resolution extended
- lower_return_value: Check env (writes + inputs)
- If found: return it (Phase 124 for writes, Phase 125 for inputs)
- If not found: Fail-Fast with structured error + hint
- Hint: "Pass as param, add to pinned capture, or define before if"
- Phase 125 errors return Ok(None) (out of scope, graceful degradation)
Unit tests:
- test_return_variable_from_env: PASS (Phase 124 regression)
- test_return_variable_out_of_scope: PASS (updated for Phase 125)
- test_return_variable_from_inputs_stub: PASS (P3 not wired yet)
- All 1160 lib tests PASS (no regression)
Note:
- P3 (available_inputs wiring) not implemented yet
- available_inputs is empty BTreeMap (stub)
- EnvLayout.inputs will be empty until P3 is wired
- Structured error tags: [phase125/return/var_not_in_env]
Ref: docs/development/current/main/phases/phase-125/README.md
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