[Elab.info] • command @ ⟨6, 0⟩-⟨6, 31⟩ @ Lean.Elab.Command.elabSetOption
      • [.] (Command.set_option "set_option" `trace.Elab.info []) @ ⟨6, 0⟩-⟨6, 26⟩
      • option trace.Elab.info @ ⟨6, 11⟩-⟨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} @ ⟨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} @ ⟨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} @ ⟨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} @ ⟨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⟩
      • match α, β, x, a with
        | α_1, .(α_1), Fam2.any, a => ?m x α_1 a
        | .(Nat), .(Nat), Fam2.nat n, a => n : β @ ⟨8, 2⟩-⟨10, 19⟩ @ Lean.Elab.Term.elabMatch
        • x : Fam2 α β @ ⟨8, 8⟩-⟨8, 9⟩ @ Lean.Elab.Term.elabIdent
          • [.] x : none @ ⟨8, 8⟩-⟨8, 9⟩
          • x : Fam2 α β @ ⟨8, 8⟩-⟨8, 9⟩
        • x : Fam2 α β @ ⟨8, 8⟩-⟨8, 9⟩ @ Lean.Elab.Term.elabIdent
          • [.] x : none @ ⟨8, 8⟩-⟨8, 9⟩
          • 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]]]) ([mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq]]]) @ ⟨9, 4⟩-⟨9, 12⟩
        • [.] a : some [mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq]]] @ ⟨8, 2⟩†-⟨10, 19⟩†
        • α (isBinder := true) : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
        • α : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
        • Fam2.any : Fam2 α α @ ⟨9, 4⟩†-⟨9, 12⟩†
          • α : Type @ ⟨9, 4⟩†-⟨9, 12⟩†
        • a (isBinder := true) : α @ ⟨8, 2⟩†-⟨10, 19⟩†
        • FVarAlias a
        • FVarAlias α
        • ?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]]]) ([mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq]]]) @ ⟨10, 4⟩-⟨10, 12⟩
        • [.] n : some Nat @ ⟨10, 13⟩-⟨10, 14⟩
        • [.] a : some [mdata _patWithRef: [mdata _inaccessible:1 [mdata _patWithRef: ?_uniq]]] @ ⟨8, 2⟩†-⟨10, 19⟩†
        • Nat : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
        • Nat : Type @ ⟨8, 2⟩†-⟨10, 19⟩†
        • Fam2.nat n : Fam2 Nat Nat @ ⟨10, 4⟩†-⟨10, 14⟩
          • n (isBinder := true) : Nat @ ⟨10, 13⟩-⟨10, 14⟩
        • a (isBinder := true) : Nat @ ⟨8, 2⟩†-⟨10, 19⟩†
        • FVarAlias a
        • FVarAlias n
        • 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⟩
[Elab.info] • command @ ⟨11, 0⟩-⟨11, 0⟩ @ Lean.Elab.Command.elabEoi