Add proj-of-prop soundness test#36
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The exported theorem builds a proof of `False` via a projection from a
`Prop`-typed structure whose constructor was applied to an ill-typed
argument:
structure Wrapper : Prop where mk :: p : False
theorem badFalse : False := (Wrapper.mk True.intro).p
A checker that types a projection by inferring (rather than checking)
its structure — trusting the structure to be well-typed rather than
verifying the constructor's arguments against its binders — will accept
this and return `badFalse : False`. A sound checker must reject it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The previous version used `(Wrapper.mk True.intro).p` with `unchecked` + `debug.skipKernelTC`, but Lean's elaborator desugars `s.field` syntax into a call to the generated projection *function* (here `Wrapper.p`), never a raw `Expr.proj`. The exported declaration was therefore an `App`, which is caught by `infer_app`'s strict argument-type check -- so sound and unsound checkers all rejected it for the wrong reason. Construct the declaration programmatically instead, building the value as a literal `Expr.proj` around the ill-typed `Wrapper.mk True.intro`. Verified with `lka.py run`: the official Lean kernel rejects, nanoda and sonanoda both (incorrectly) accept. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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The exported theorem builds a proof of
Falsevia a projection from aProp-typed structure whose constructor was applied to an ill-typedargument:
A checker that types a projection by inferring (rather than checking)
its structure — trusting the structure to be well-typed rather than
verifying the constructor's arguments against its binders — will accept
this and return
badFalse : False. A sound checker must reject it.Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com