In the new frontend,
```lean
@[macroInline] def or : Bool → Bool → Bool
| true, _ => true
| false, b => b
```
is compiled as
```lean
def or (x y : Bool) : Bool :=
or.match_1 _ x y (fun _ => true) (fun b => b)
```
Thus, the `[macroInline]` attribute does not guarantee that `y` is
evalutated only when `x` is `false`. The new definition does.
This issue was not exposed before because the compiler has an
optimization that float let-decls when they are used in a single
branch.
@Kha We have talked about removing `macroInline`, and defining
functions such as `or` as
```lean
@[inline] def or (x : Bool) (y : Unit -> Bool) : Bool :=
match x with
| true => true
| false => y ()
```
and define `x || y` as notation for `or x (fun _ => y)`.
I think this is the way to go for polymorphic operators such as `<|>`,
but I am not sure about `or`. New users will probably be puzzled by
it. In particular when they are writing proofs.
