scopedLocalInsts.lean:12:6-12:39: error: failed to synthesize
  ToString A
use `set_option diagnostics true` to get diagnostic information
"A.mk 10 20"
scopedLocalInsts.lean:21:6-21:39: error: failed to synthesize
  ToString A
use `set_option diagnostics true` to get diagnostic information
"{ x := 10, y := 20 }"
scopedLocalInsts.lean:32:6-32:39: error: failed to synthesize
  ToString A
use `set_option diagnostics true` to get diagnostic information
"A.mk 10 20"