fix: Fix/GuessLex: refine through more casesOnApp/matcherApp #3176
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there was a check
if !Structural.recArgHasLooseBVarsAt recFnName fixedPrefixSize e then
that would avoid going through `.refineThrough`/`.addArg` for
matcher/casesOn applications. It seems it tries to detect when refining
the motive/param is pointless, but it was too eager, and cause confusion
with, for example, this reasonably reasonable function:
def foo : (n : Nat) → (i : Fin n) → Bool
| 0, _ => false
| 1, _ => false
| _+2, _ => foo 1 ⟨0, Nat.zero_lt_one⟩
decreasing_by simp_wf; simp_arith
In particular, the `GuessLex` code later expects that the (implict)
`PProd.casesOn` in the implementation of `foo._unary` will refine the
paramter, because else the (rather picky) `unpackArg` fails. But it also
prevents this from being provable.
So let's try without this shortcut.
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there was a check
that would avoid going through
.refineThrough/.addArgformatcher/casesOn applications. It seems it tries to detect when refining
the motive/param is pointless, but it was too eager, and cause confusion
with, for example, this reasonably reasonable function:
In particular, the
GuessLexcode later expects that the (implict)PProd.casesOnin the implementation offoo._unarywill refine theparamter, because else the (rather picky)
unpackArgfails. But it alsoprevents this from being provable.
So let's try without this shortcut.
Fixing this also revealed that
withRecAppswasn’t looking in all cornersof a matcherApp/casesOnApp.
Fixes #3175