Pattern matching as currently implemented is consuming, but that's not
necessarily what we want to be the default behavior when borrowing pattern
matching is implemented. When a binding of noncopyable type is pattern-matched,
require it to be annotated with the `consume` operator explicitly. That way,
when we introduce borrowing pattern matching later, we have the option to make
`switch x` do the right thing without subtly changing the behavior of existing
code. rdar://110073984
this also fixes a bug where sometimes we simply emit
'consumed here' twice and other times we'd said 'other
consume here' for the same "consumed more than once"
message. so I went through and changed all of the 2nd
consumes into "consumed again".
rdar://109281444
- refer to a "consuming use" as simply a "consume", to reserve "use" for non-consuming uses.
- refer to "non-consuming uses" as just a "use".
- don't call it a "user defined deinit" and instead a "deinitializer" to match Sema
- be specific about what binding a closure is capturing that is preventing consumption.
rdar://109281444
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
