[Elab.info] command @ ⟨6, 0⟩-⟨6, 31⟩ @ Lean.Elab.Command.elabSetOption
  [.] (Command.set_option "set_option" `trace.Elab.info) @ ⟨6, 0⟩-⟨6, 26⟩
1018unknowMVarIssue.lean:9:18-9:19: error: don't know how to synthesize placeholder
context:
α✝ β : Type
x : Fam2 α✝ β
α : Type
a : α
⊢ α
[Elab.info] command @ ⟨7, 0⟩-⟨10, 19⟩ @ Lean.Elab.Command.elabDeclaration
  α : Type @ ⟨7, 13⟩-⟨7, 14⟩ @ Lean.Elab.Term.elabIdent
    [.] `α : some Sort.{?_uniq.311} @ ⟨7, 13⟩-⟨7, 14⟩
    α : Type @ ⟨7, 13⟩-⟨7, 14⟩
  a (isBinder := true) : α @ ⟨7, 9⟩-⟨7, 10⟩
  α : Type @ ⟨7, 13⟩-⟨7, 14⟩ @ Lean.Elab.Term.elabIdent
    [.] `α : some Sort.{?_uniq.317} @ ⟨7, 13⟩-⟨7, 14⟩
    α : Type @ ⟨7, 13⟩-⟨7, 14⟩
  a (isBinder := true) : α @ ⟨7, 9⟩-⟨7, 10⟩
  Fam2 α β : Type 1 @ ⟨7, 21⟩-⟨7, 29⟩ @ Lean.Elab.Term.elabApp
    [.] `Fam2 : some Sort.{?_uniq.319} @ ⟨7, 21⟩-⟨7, 25⟩
    Fam2 : Type → Type → Type 1 @ ⟨7, 21⟩-⟨7, 25⟩
    α : Type @ ⟨7, 26⟩-⟨7, 27⟩ @ Lean.Elab.Term.elabIdent
      [.] `α : some Type @ ⟨7, 26⟩-⟨7, 27⟩
      α : Type @ ⟨7, 26⟩-⟨7, 27⟩
    β : Type @ ⟨7, 28⟩-⟨7, 29⟩ @ Lean.Elab.Term.elabIdent
      [.] `β : some Type @ ⟨7, 28⟩-⟨7, 29⟩
      β : Type @ ⟨7, 28⟩-⟨7, 29⟩
  x (isBinder := true) : Fam2 α β @ ⟨7, 17⟩-⟨7, 18⟩
  β : Type @ ⟨7, 33⟩-⟨7, 34⟩ @ Lean.Elab.Term.elabIdent
    [.] `β : some Sort.{?_uniq.321} @ ⟨7, 33⟩-⟨7, 34⟩
    β : Type @ ⟨7, 33⟩-⟨7, 34⟩
  _example (isBinder := true) : {α β : Type} → α → Fam2 α β → β @ ⟨7, 0⟩†-⟨10, 19⟩†
  a (isBinder := true) : α @ ⟨7, 9⟩-⟨7, 10⟩
  x (isBinder := true) : Fam2 α β @ ⟨7, 17⟩-⟨7, 18⟩
  _example.match_1 (fun α β x a => β) α β x a (fun α_1 a => ?m x α_1 a) fun n a =>
    n : <failed-to-infer-type> @ ⟨8, 2⟩-⟨10, 19⟩ @ Lean.Elab.Term.elabMatch
    x : Fam2 α β @ ⟨8, 8⟩-⟨8, 9⟩
    [.] `Fam2.any : none @ ⟨9, 4⟩-⟨9, 12⟩
    [.] `Fam2.any : none @ ⟨9, 4⟩-⟨9, 12⟩
    @Fam2.any : {α : Type} → Fam2 α α @ ⟨9, 4⟩-⟨9, 12⟩
    [.] `Fam2.nat : none @ ⟨10, 4⟩-⟨10, 12⟩
    Fam2.nat : Nat → Fam2 Nat Nat @ ⟨10, 4⟩-⟨10, 12⟩
    [.] `n : none @ ⟨10, 13⟩-⟨10, 14⟩
    [.] `Fam2.any : none @ ⟨9, 4⟩-⟨9, 12⟩
    [.] `Fam2.any : none @ ⟨9, 4⟩-⟨9, 12⟩
    @Fam2.any : {α : Type} → Fam2 α α @ ⟨9, 4⟩-⟨9, 12⟩
    [.] `a : none @ ⟨8, 2⟩†-⟨10, 19⟩†
    [.] `Fam2.any : some Fam2 ([mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq.652]]]) ([mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq.653]]]) @ ⟨9, 4⟩-⟨9, 12⟩
    [.] `a : some [mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq.652]]] @ ⟨8, 2⟩†-⟨10, 19⟩†
    α (isBinder := true) : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
    α : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
    α : Type @ ⟨9, 4⟩†-⟨9, 12⟩†
    Fam2.any : Fam2 α α @ ⟨9, 4⟩†-⟨9, 12⟩†
    a (isBinder := true) : α @ ⟨8, 2⟩†-⟨10, 19⟩†
    ?m x α a : α @ ⟨9, 18⟩-⟨9, 19⟩ @ Lean.Elab.Term.elabHole
    [.] `Fam2.nat : none @ ⟨10, 4⟩-⟨10, 12⟩
    Fam2.nat : Nat → Fam2 Nat Nat @ ⟨10, 4⟩-⟨10, 12⟩
    [.] `n : none @ ⟨10, 13⟩-⟨10, 14⟩
    [.] `a : none @ ⟨8, 2⟩†-⟨10, 19⟩†
    [.] `Fam2.nat : some Fam2 ([mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq.684]]]) ([mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq.685]]]) @ ⟨10, 4⟩-⟨10, 12⟩
    [.] `n : some Nat @ ⟨10, 13⟩-⟨10, 14⟩
    [.] `a : some [mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq.684]]] @ ⟨8, 2⟩†-⟨10, 19⟩†
    Nat : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
    Nat : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
    n (isBinder := true) : Nat @ ⟨10, 13⟩-⟨10, 14⟩
    Fam2.nat n : Fam2 Nat Nat @ ⟨10, 4⟩†-⟨10, 14⟩
    a (isBinder := true) : Nat @ ⟨8, 2⟩†-⟨10, 19⟩†
    n : Nat @ ⟨10, 18⟩-⟨10, 19⟩ @ Lean.Elab.Term.elabIdent
      [.] `n : some Nat @ ⟨10, 18⟩-⟨10, 19⟩
      n : Nat @ ⟨10, 18⟩-⟨10, 19⟩
  @_example (isBinder := true) : {α β : Type} → α → Fam2 α β → β @ ⟨7, 0⟩-⟨7, 7⟩