docs: Add exit-semantics design documentation#1080
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seebees wants to merge 1 commit intostrata-org:mainfrom
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docs: Add exit-semantics design documentation#1080seebees wants to merge 1 commit intostrata-org:mainfrom
seebees wants to merge 1 commit intostrata-org:mainfrom
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Adds a spec and decisions document for the small-step semantics of `exit` and labeled blocks in `Strata/DL/Imperative/StmtSemantics.lean`, plus two thin Lean files giving each spec requirement a descriptive public name. ## Documentation (`docs/design/exit-semantics/`) The spec uses RFC 2119 normative language only where an obligation maps to a specific Lean construct: - Preservation of well-formedness by every step, discharged by `step_preserves_exitsCoveredByBlocks`. - No-escape (exit does not leave a well-formed procedure body), discharged by `exitsCoveredByBlocks_noEscape` and its statement-list companion. Per-transition behavior is documented descriptively, since each transition is directly realized by a constructor of `StepStmt` and does not carry a separate normative obligation. The decisions document records six design choices and a future-work section, incorporating feedback from strata-org#993 and strata-org#869. ## Lean - `ExitProperties.lean` — seven per-transition lemmas (`exit_preserves_env`, `exit_skips_remaining`, `matching_block_consumes`, `nonmatching_exit_propagates`, `normal_block_completion`, `unlabeled_exit_consumed`, `block_body_steps`) plus two multi-step companions (`exit_eval`, `matching_block_eval`). - `ExitWellFormedness.lean` — `exit_target_in_labels` and `exit_none_has_enclosing` over `Stmt.exitsCoveredByBlocks`. Each lemma is a single-line proof over an existing `StepStmt` constructor or `Stmt.exitsCoveredByBlocks` definitional equation. No new mathematical content. Zero sorries. Also promotes `step_preserves_exitsCoveredByBlocks` from private to public so the spec's §4.3 requirement cites a public symbol. Tracks: strata-org#993
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Adds a spec and decisions document for the small-step semantics of
exitand labeled blocks inStrata/DL/Imperative/StmtSemantics.lean.The spec uses RFC 2119 normative language only where an obligation maps to a specific Lean construct:
step_preserves_exitsCoveredByBlocks.exitsCoveredByBlocks_noEscapeand its statement-list companion.Per-transition behavior is documented descriptively, since each transition is directly realized by a constructor of
StepStmtand does not carry a separate normative obligation.The decisions document records six design choices and a future-work section, incorporating feedback from #993 and #869.
Tracks: #993
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