scopedLocalInsts.lean:12:6: error: failed to synthesize instance
  ToString A
scopedLocalInsts.lean:12:0: error: failed to synthesize
  Lean.Eval ?m
"A.mk 10 20"
scopedLocalInsts.lean:21:6: error: failed to synthesize instance
  ToString A
scopedLocalInsts.lean:21:0: error: failed to synthesize
  Lean.Eval ?m
"{ x := 10, y := 20 }"
scopedLocalInsts.lean:32:6: error: failed to synthesize instance
  ToString A
scopedLocalInsts.lean:32:0: error: failed to synthesize
  Lean.Eval ?m
"A.mk 10 20"