8424ddbb3e
This PR improves the “expected type mismatch” error message by omitting the type's types when they are defeq, and putting them into separate lines when not. I found it rather tediuos to parse the error message when the expected type is long, because I had to find the `:` in the middle of a large expression somewhere. Also, when both are of sort `Prop` or `Type` it doesn't add much value to print the sort (and it’s only one hover away anyways).
55 lines
1.2 KiB
Text
55 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
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of sort `Type` but is expected to have type
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TypeVec (?_ + 1)
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of sort `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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