440.lean:1:21-1:22: error: don't know how to synthesize placeholder
context:
⊢ True
440.lean:4:29-4:30: error: don't know how to synthesize placeholder
context:
x : Nat
⊢ Nat
f : Nat → Nat
440.lean:11:0-11:9: error: cannot evaluate code because it uses 'sorry' and/or contains errors