995fa4766b
This PR refines the new wording of the "application type mismatch" error message to avoid ambiguity in references to the "final" argument in a subexpression that may be followed by additional arguments. It does so by replacing "final" with "last," rephrasing the message so that this adjective modifies the argument itself rather than the word "argument," and only displaying this wording when two arguments could be confused (determined by expression equality). These changes were motivated by a report that in cases where a function application `f a b c` fails to elaborate because `b` is incorrectly typed, the existing error message's reference to `b` being the "final" argument in the application `f a b` may create confusion because it is not the final argument in the full application expression.
54 lines
1.2 KiB
Text
54 lines
1.2 KiB
Text
/-- A `Vec` is just a `List α` of statically known size -/
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def Vec (α : Type _) (n : Nat) : Type _
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:= Fin n → α
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abbrev TypeVec : Nat → Type _
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:= Vec (Type _)
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/-- A dependent vector is a heterogeneous list of statically known size -/
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def DVec {n : Nat} (αs : TypeVec n) : Type _
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:= (i : Fin n) → (αs i)
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/-- A vector that repeats a single element `a` -/
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def Vec.const {α : Type _} (a : α) (n : Nat) : Vec α n
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:= fun _ => a
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/- `Vec` is defeq to a `DVec` with constant type -/
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unif_hint (α : Type _) (n : Nat) where
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|- Vec α n =?= DVec (Vec.const α n)
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namespace DVec
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def hd {n : Nat} {αs : TypeVec (n+1)} (v : DVec αs) : (αs 0)
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:= v 0
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end DVec
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namespace Vec
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export DVec (hd)
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end Vec
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def ts : TypeVec 1 := Vec.const Nat 1
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-- works
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example (v : DVec ts) : Nat :=
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v.hd
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-- works
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example (v : Vec Nat 1) : Nat :=
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DVec.hd v
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#check @Vec.hd
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-- Does not work: Aliases find that `v` could be the `TypeVec` argument since `TypeVec` is an abbrev for `Vec`.
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/--
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error: Application type mismatch: In the application
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@DVec.hd ?_ v
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the argument
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v
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has type
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Vec Nat 1 : Type
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but is expected to have type
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TypeVec (?_ + 1) : Type (_ + 1)
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-/
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#guard_msgs in set_option pp.mvars false in
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example (v : Vec Nat 1) : Nat :=
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v.hd
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