ex1 (heq : foo = bar) (P : Nat → Prop) (h : P foo) : P bar
substFails.lean:6:67-6:74: error: invalid `▸` notation, expected result type of cast is 
  P 4
however, the equality 
  heq
of type 
  foo = bar
does not contain the expected result type on either the left or the right hand side
substFails.lean:8:67-8:74: error: invalid `▸` notation, the equality
  heq
has type 
  foo = bar
but neither side of the equality is mentioned in the type
  P 3
substFails.lean:9:67-9:74: error: invalid `▸` notation, expected result type of cast is 
  P 4
however, the equality 
  heq
of type 
  foo = bar
does not contain the expected result type on either the left or the right hand side
ex7 (heq : bar = foo) (P : Nat → Prop) (h : P foo) : P bar
substFails.lean:14:67-14:74: error: invalid `▸` notation, expected result type of cast is 
  P 4
however, the equality 
  heq
of type 
  bar = foo
does not contain the expected result type on either the left or the right hand side
substFails.lean:16:67-16:74: error: invalid `▸` notation, the equality
  heq
has type 
  bar = foo
but neither side of the equality is mentioned in the type
  P 3
substFails.lean:17:67-17:74: error: invalid `▸` notation, expected result type of cast is 
  P 4
however, the equality 
  heq
of type 
  bar = foo
does not contain the expected result type on either the left or the right hand side