As with the lexical flag, when creating an alloc_stack corresponding to
an alloc_box, transfer the var_decl flag from any begin_borrow users of
the box.
I was originally hoping to reuse mark_must_check for multiple types of checkers.
In practice, this is not what happened... so giving it a name specifically to do
with non copyable types makes more sense and makes the code clearer.
Just a pure rename.
Vars of such types should be given lexical `alloc_stack`s by
`AllocBoxToStack` which requires that the `alloc_box` insts formed for
them have an associated borrow scope which in turn requires that type
lowering for move only structs and enums have their lexical bits set.
rdar://110901430
As part of SE-390, you're required to write either:
- `consume self`
- pass self as a `consuming` parameter to a function
- `discard self`
before the function ends in a context that contains a
`discard self` somewhere. This prevents people from accidentally
invoking the deinit due to implicit destruction of `self` before
exiting the function.
rdar://106099027
SE-390 concluded with choosing the keyword discard rather than forget for
the statement that disables the deinit of a noncopyable type. This commit
adds parsing support for `discard self` and adds a deprecation warning for
`_forget self`.
rdar://108859077
