#   Set: pp::colors
  Set: pp::unicode
Proof state:
a : Bool, b : Bool, H : b ⊢ a ∨ b
## Proof state:
a : Bool, b : Bool, H : b ⊢ a
## Proof state:
a : Bool, b : Bool, H : b ⊢ b
## stdin:9:0 error: failed to backtrack
Proof state:
a : Bool, b : Bool, H : b ⊢ b
## Proof state:
no goals
##   Proved: T2
# theorem T2 (a b : Bool) (H : b) : a ∨ b := or_intror a H
#