lean4-htt/tests/lean/run/issue2628.lean
Joachim Breitner b5122b6a7b feat: per-function termination hints
This change

 * moves `termination_by` and `decreasing_by` next to the function they
   apply to
 * simplify the syntax of `termination_by`
 * apply the `decreasing_by` goal to all goals at once, for better
   interactive use.

See the section in `RELEASES.md` for more details and migration advise.

This is a hard breaking change, requiring developers to touch every
`termination_by` in their code base. We decided to still do it as a
hard-breaking change, because supporting both old and new syntax at the
same time would be non-trivial, and not save that much. Moreover, this
requires changes to some metaprograms that developers might have
written, and supporting both syntaxes at the same time would make
_their_ migration harder.
2024-01-10 17:27:35 +01:00

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/-!
Test that PackMutual isn't confused when a recursive call has more arguments than is packed
into the unary argument, which can happen if the retturn type is a function type.
-/
namespace Ex1
mutual
def foo : Nat → Nat
| .zero => 0
| .succ n => (id bar) n
decreasing_by sorry
def bar : Nat → Nat
| .zero => 0
| .succ n => foo n
decreasing_by sorry
end
end Ex1
-- Same for n-ary functions
opaque id' : ∀ {α}, αα := id
namespace Ex2
mutual
def foo : Nat → Nat → Nat
| .zero, _m => 0
| .succ n, .zero => (id' (bar n)) .zero
| .succ n, m => (id' bar) n m
termination_by n m => (n,m)
decreasing_by all_goals sorry
def bar : Nat → Nat → Nat
| .zero, _m => 0
| .succ n, m => foo n m
termination_by n m => (n,m)
decreasing_by all_goals sorry
end
end Ex2
-- With extra arguments
namespace Ex3
mutual
def foo : Nat → Nat → Nat
| .zero => fun _ => 0
| .succ n => fun m => (id bar) n m
decreasing_by all_goals sorry
def bar : Nat → Nat → Nat
| .zero => fun _ => 0
| .succ n => fun m => foo n m
decreasing_by all_goals sorry
end
end Ex3
-- n-ary and with extra arguments
namespace Ex4
mutual
def foo : Nat → Nat → Nat → Nat
| .zero, _m => fun _ => 0
| .succ n, .zero => fun k => (id' (bar n)) .zero k
| .succ n, m => fun k => (id' bar) n m k
termination_by n m => (n,m)
decreasing_by all_goals sorry
def bar : Nat → Nat → Nat → Nat
| .zero, _m => fun _ => 0
| .succ n, m => fun k => foo n m k
termination_by n m => (n,m)
decreasing_by all_goals sorry
end
end Ex4
-- Check that eta-expansion works even if the function does not
-- have a function type
namespace Ex5
def FunType := Nat → Nat
mutual
def foo : FunType
| .zero => 0
| .succ n => (id bar) n
decreasing_by all_goals sorry
def bar : Nat → Nat
| .zero => 0
| .succ n => foo n
decreasing_by all_goals sorry
end
end Ex5
namespace Ex6
def Fun3Type := Nat → Nat → Nat
mutual
def foo : Nat → Nat → Nat → Nat
| .zero, _m => fun _ => 0
| .succ n, .zero => fun k => (id' (bar n)) .zero k
| .succ n, m => fun k => (id' bar) n m k
termination_by n m => (n,m)
decreasing_by all_goals sorry
def bar : Nat → Fun3Type
| .zero, _m => fun _ => 0
| .succ n, m => fun k => foo n m k
termination_by n m => (n,m)
decreasing_by all_goals sorry
end
end Ex6