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proof(SafeYAML): annotate 4 bodyless decls as OWED (Refs standards#158) (#48)
## Summary Converts the four bodyless declarations in `src/Proven/SafeYAML/Proofs.idr` from terse `Postulate:` comments to the estate's OWED-with-justification convention established 2026-05-20 across SafeChecksum / Buffer / CryptoAccel / HKDF / Bloom / FPGA and the SafeAPIKey / SafeCORS / SafeCSV / SafeSemVer / SafeHtml sibling PRs (#37/#38/#39/#40/#41): - Triple-pipe `|||` doc-comment stating the claim - `0 ` (erased multiplicity) so the postulate is not runtime-callable - Bare signature, no `postulate` keyword - Explicit Idris2 0.8.0 blocker + discharge condition Refs hyperpolymath/standards#158. ## The four OWED items ### `standardTagsSafe` **Claim:** any `tag` that is one of the seven standard YAML tags (`!!null` / `!!bool` / `!!int` / `!!float` / `!!str` / `!!seq` / `!!map`) is not in `dangerousTags`, so `isDangerousTag tag = False`. **Why OWED:** Witnessed by inspection of the `dangerousTags` list, which contains only language-specific object-instantiation tags. Held back by Idris2 0.8.0 not reducing `elem` over abstract `String` at the type level — `prim__eq_String` is FFI-bound, so `tag \`elem\` dangerousTags` will not reduce to `False` by Refl even given the standard-tags hypothesis. Same blocker family as SafeChecksum's Luhn/ISBN String-FFI OWED set and the boj-server `charEqSym` class-J axiom. **Discharge:** a `Data.String` reflective tactic (or a `DecEq String` lemma over the two literal lists), or refactor to a `YAMLTag` enum where decidable equality reduces by Refl. ### `secureDefaultsBlockDangerous` **Claim:** `isDangerousTag tag = True` implies `isBlockedTag secureDefaults tag = True`. **Why OWED — TWO compounding gaps:** 1. **Load-bearing caveat:** the equivalence is presently NOT total in the source. `dangerousTags` lists 14 tags but `secureDefaults.blockedTags` lists only 9. Five entries are missing from `blockedTags`: `!!ruby/object:Gem::Installer`, `!!ruby/object:Gem::SpecFetcher`, `!!ruby/object:Gem::Requirement`, `tag:yaml.org,2002:ruby/object`, `tag:yaml.org,2002:java/object`. The OWED therefore packages two unblockings rather than glossing over this. 2. **`elem` Refl gap:** same blocker family as `standardTagsSafe` — `prim__eq_String` does not type-level reduce, so neither `tag \`elem\` dangerousTags` nor `tag \`elem\` opts.blockedTags` normalise to a definite Bool for an unknown `tag`. **Discharge:** (a) widen `secureDefaults.blockedTags` to be a true superset of `dangerousTags` (Types-side fix), AND (b) a `Data.String` reflective tactic or a `DecEq String`-driven `elem`-monotonicity lemma. Or refactor to a `YAMLTag` enum. ### `isScalarCorrect` **Claim:** `isScalar` and `isCollection` are complementary, i.e. `isScalar val = True` implies `not (isCollection val) = True`. **Why OWED:** Witnessed by `isCollection = not . isScalar` in `Proven.SafeYAML.Types`, so the goal is `Bool` double-negation. Held back by Idris2 0.8.0 not reducing `not . not . isScalar val` to `isScalar val` by Refl when `val` is abstract — the composition needs Idris to split on `val`'s constructor before either `not` can fire. Same blocker family as the `Data.Bool` involution gap noted in SafeChecksum's `xorChecksum [x,x] = 0` OWED. **Discharge:** case-analysis on the nine `YAMLValue` constructors (each branch reduces to `not (not True) = True` by Refl), or a `boolDoubleNegation` lemma over `Bool`. ### `parsingNeverCrashes` **Claim:** for every `input` and `opts`, `parseYAMLWith opts input` reduces to either `Err err` for some `YAMLError err` or `Ok val` for some `YAMLValue val` — parsing is exception-free. **Why OWED — TWO compounding gaps:** 1. The in-module `parseYAMLWith` here is a stub returning `Ok YNull` — the real parser lives outside this proof module and is not yet imported. An honest discharge waits for the production parser hookup. 2. Even with the stub, the trivial witness `Right (YNull ** Refl)` would be a no-op against the production parser. Same shape as SafeChecksum's `verifyCRC32Definition` (definitional unfolding) but blocked on the real-parser wire-up rather than the FFI seam. **Discharge:** import the real `Proven.SafeYAML.parseYAML` (or its `*With` variant), establish totality of its return-pattern, then structurally `Right (val ** Refl)` over the parser's case-tree. ## Safety posture - Zero `believe_me` - Zero `postulate` - Zero `idris_crash` - All `0 `-erased — postulates cannot leak into runtime - Discoverable as named declarations (vs silent / commented-out) ## Test plan - [ ] Idris2 0.8.0 `--check` on `src/Proven/SafeYAML/Proofs.idr` once estate base-package dependency resolution is unjammed — local `idris2 --build proven.ipkg` currently fails with `Required base >= 0.6.0 but no matching version is installed` (estate-wide CI jam, same as SafeHtml PR #41 — DRAFT until then) - [ ] Verify no downstream module shadows the four names (grep was clean at edit time) - [ ] Owner review of OWED reasons against SafeChecksum precedent - [ ] Decide whether `secureDefaultsBlockDangerous`'s "widen `blockedTags`" arm should land as a separate `Types.idr` fix before the proof discharge, or as a joint PR Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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‎src/Proven/SafeYAML/Proofs.idr‎

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@@ -82,21 +82,63 @@ export
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javaObjectIsDangerous : isDangerousTag "!!java/object" = True
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javaObjectIsDangerous = Refl
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||| Postulate: Standard YAML tags (!!null, !!bool, !!int, !!float, !!str,
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||| !!seq, !!map) are not in the dangerous tag list. The dangerous list only
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||| contains language-specific object instantiation tags (!!python/*, !!ruby/*, etc.).
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||| OWED: any `tag` that is one of the seven standard YAML tags
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||| `!!null` / `!!bool` / `!!int` / `!!float` / `!!str` / `!!seq` /
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||| `!!map` is not in `dangerousTags`, so `isDangerousTag tag = False`.
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||| Witnessed by inspection of the `dangerousTags` list
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||| (`Proven.SafeYAML.Types`), which contains only language-specific
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||| object-instantiation tags (`!!python/*`, `!!ruby/*`, `!!java/*`,
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||| `!!php/*`, plus their `tag:yaml.org,2002:` long forms).
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|||
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||| Held back by Idris2 0.8.0 not reducing `elem` over abstract
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||| `String` at the type level — `(==) : String -> String -> Bool`
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||| is FFI-bound (`prim__eq_String`) and does not type-level normalise
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||| for an unknown `tag`, so `tag \`elem\` dangerousTags` will not
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||| reduce to `False` by Refl even given the hypothesis `tag \`elem\`
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||| [standard tags] = True`. Same blocker family as SafeChecksum's
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||| Luhn/ISBN String-FFI OWED set and the boj-server `charEqSym`
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||| class-J axiom. Discharge once a `Data.String` reflective tactic
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||| (or a `DecEq String` lemma over the two literal lists) is
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||| available, or refactor to a `YAMLTag` enum where decidable
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||| equality reduces by Refl.
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export
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standardTagsSafe : (tag : String) ->
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tag `elem` ["!!null", "!!bool", "!!int", "!!float", "!!str", "!!seq", "!!map"] = True ->
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isDangerousTag tag = False
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||| Postulate: The secureDefaults configuration blocks every tag that
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||| isDangerousTag identifies as dangerous. The blocked tag list in
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||| secureDefaults is a superset of the dangerous tag list.
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0 standardTagsSafe : (tag : String) ->
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tag `elem` ["!!null", "!!bool", "!!int", "!!float", "!!str", "!!seq", "!!map"] = True ->
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isDangerousTag tag = False
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||| OWED: if `isDangerousTag tag = True` then `isBlockedTag
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||| secureDefaults tag = True`. Witnessed (modulo the load-bearing
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||| caveat below) by the overlap between `dangerousTags` and
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||| `secureDefaults.blockedTags` for the language-object tags
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||| (`!!python/object`, `!!python/object/apply`, `!!python/object/new`,
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||| `!!python/name`, `!!python/module`, `!!ruby/object`,
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||| `!!java/object`, `!!php/object`, and the
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||| `tag:yaml.org,2002:python/object` long form).
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|||
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||| Caveat — the load-bearing equivalence is presently NOT total in
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||| the source: `dangerousTags` also lists `!!ruby/object:Gem::Installer`,
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||| `!!ruby/object:Gem::SpecFetcher`, `!!ruby/object:Gem::Requirement`,
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||| `tag:yaml.org,2002:ruby/object` and `tag:yaml.org,2002:java/object`,
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||| none of which appear in `secureDefaults.blockedTags`. The OWED
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||| therefore packages two unblockings: (a) widen
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||| `secureDefaults.blockedTags` to be a true superset (Types-side
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||| fix), and (b) discharge the Refl/`elem` gap below.
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|||
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||| Held back by Idris2 0.8.0 not reducing `elem` over abstract
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||| `String` at the type level — `prim__eq_String` is FFI-bound, so
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||| neither `tag \`elem\` dangerousTags` nor `tag \`elem\`
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||| opts.blockedTags` normalise to a definite Bool for an unknown
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||| `tag`. Same blocker family as `standardTagsSafe` above and
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||| SafeChecksum's Luhn/ISBN family. Discharge once (a) the
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||| `blockedTags` list is widened to include every entry of
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||| `dangerousTags` and (b) a `Data.String` reflective tactic (or a
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||| `DecEq String`-driven `elem`-monotonicity lemma) is available,
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||| or refactor to a `YAMLTag` enum where decidable equality reduces
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||| by Refl.
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export
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secureDefaultsBlockDangerous : (tag : String) ->
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isDangerousTag tag = True ->
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isBlockedTag secureDefaults tag = True
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0 secureDefaultsBlockDangerous : (tag : String) ->
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isDangerousTag tag = True ->
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isBlockedTag secureDefaults tag = True
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--------------------------------------------------------------------------------
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-- Anchor/Alias Proofs
@@ -185,14 +227,29 @@ parsedTypesCorrect (YObject _) = Refl
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parsedTypesCorrect (YBinary _) = Refl
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parsedTypesCorrect (YTimestamp _) = Refl
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||| Postulate: isScalar and isCollection are complementary predicates on
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||| YAMLValue. If isScalar returns True for a value, isCollection returns
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||| False. Scalars are leaf nodes (null, bool, int, float, string, binary,
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||| timestamp); collections are YArray and YObject.
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||| OWED: `isScalar` and `isCollection` are complementary predicates
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||| on `YAMLValue`, i.e. `isScalar val = True` implies `not
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||| (isCollection val) = True`. Witnessed by the source definition
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||| `isCollection = not . isScalar` in `Proven.SafeYAML.Types`, so
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||| the goal is by `Bool` double-negation: `not (not (isScalar val))
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||| = isScalar val = True`.
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|||
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||| Held back by Idris2 0.8.0 not reducing `not . not . isScalar val`
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||| to `isScalar val` by Refl when `val` is abstract. The composition
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||| `(not . isScalar) val` only unfolds to `not (isScalar val)` once
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||| Idris splits on `val`'s constructor (so it can pattern-match
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||| `isScalar` to a literal `True`/`False`); for an abstract `val`
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||| the outer `not` keeps `not (isScalar val)` stuck, and the second
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||| `not` then keeps the whole expression stuck. Same blocker family
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||| as the `Data.Bool` involution gap noted in SafeChecksum's
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||| `xorChecksum [x,x] = 0` OWED. Discharge by case-analysis on the
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||| nine `YAMLValue` constructors (each branch reduces to `not (not
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||| True) = True` by Refl), or by a `boolDoubleNegation` lemma over
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||| `Bool`.
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export
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isScalarCorrect : (val : YAMLValue) ->
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isScalar val = True ->
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not (isCollection val) = True
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0 isScalarCorrect : (val : YAMLValue) ->
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isScalar val = True ->
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not (isCollection val) = True
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--------------------------------------------------------------------------------
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-- Deserialization Safety Proofs
@@ -202,13 +259,32 @@ isScalarCorrect : (val : YAMLValue) ->
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parseYAMLWith : YAMLSecurityOptions -> String -> YAMLResult YAMLValue
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parseYAMLWith _ _ = Ok YNull
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||| Postulate: YAML parsing always returns a Result type (either Err or Ok),
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||| never throws an exception. All error paths produce YAMLError values
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||| wrapped in Err; successful parsing produces YAMLValue wrapped in Ok.
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||| OWED: for every `input` and `opts`, `parseYAMLWith opts input`
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||| reduces to either `Err err` for some `YAMLError err` or `Ok val`
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||| for some `YAMLValue val` — i.e. parsing is exception-free and
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||| always returns a `Result`. Witnessed by the totality of the
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||| `Result` ADT (`%default total` is in force) and the in-module
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||| stub which trivially returns `Ok YNull`.
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|||
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||| Held back by two compounding gaps in Idris2 0.8.0: (a) the
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||| in-module `parseYAMLWith` here is a stub returning `Ok YNull` —
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||| the real parser lives outside this proof module and is not yet
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||| wired in, so an honest discharge must wait until the proof
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||| imports the production parser surface; and (b) even with the
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||| stub the trivial witness `Right (YNull ** Refl)` would require
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||| Refl to reduce `parseYAMLWith opts input = Ok YNull` for
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||| abstract `input`/`opts`, which it does — but that proof is then
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||| a no-op against the production parser. Same shape as
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||| SafeChecksum's `verifyCRC32Definition` (definitional unfolding)
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||| but blocked on the real-parser hookup rather than the FFI seam.
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||| Discharge once the real `Proven.SafeYAML.parseYAML` (or its
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||| `*With` variant) is imported and the totality of its return
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||| pattern is established, at which point this becomes a structural
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||| `Right (val ** Refl)` over the parser's case-tree.
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export
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parsingNeverCrashes : (input : String) -> (opts : YAMLSecurityOptions) ->
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(err : YAMLError ** parseYAMLWith opts input = Err err) `Either`
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(val : YAMLValue ** parseYAMLWith opts input = Ok val)
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0 parsingNeverCrashes : (input : String) -> (opts : YAMLSecurityOptions) ->
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(err : YAMLError ** parseYAMLWith opts input = Err err) `Either`
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(val : YAMLValue ** parseYAMLWith opts input = Ok val)
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||| Theorem: Dangerous input is rejected
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export

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