When a `borrowing` or `consuming` parameter is captured by a closure,
we emit references to the binding within the closure as if it is non-implicitly
copyable, but we didn't mark the bindings inside the closure for move-only
checking to ensure the uses were correct, so improper consumes would go
undiagnosed and lead to assertion failures, compiler crashes, and/or
miscompiles. Fixes rdar://127382105
It works well enough now that it should be an acceptable replacement for both
borrowing and consuming switches that works in more correct situations than the
previous implementation. This does however expose a few known issues that I'll
try to fix in follow ups:
- overconsumes cause verifier errors instead of raising diagnostics (rdar://125381446)
- cases with multiple pattern labels aren't yet supported (rdar://125188955)
- copyable types with the `borrowing` or `consuming` modifiers should probably use
noncopyable pattern matching.
The `BorrowingSwitch` flag is still necessary to enable the surface-level syntax
changes (switches without `consume` and the `_borrowing` modifier, for instance).
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
- replaces "move-only" terminology with "noncopyable"
- replaces compiler jargon like "guaranteed parameters"
and "lvalue" with corresponding language-level notions
- simplifies diagnostics about closures.
and probably more.
rdar://109281444
Specifically, previously if we emitted an error we just dumped all of the
consuming uses. Now instead for each consuming use that needs a copy, we perform
a search for a specific boundary use (consuming or non-consuming) that is
reachable from the former and emit a specialized error for it. Thus we emit for
the two consuming case the normal consumed twice error, and now for
non-consuming errors we emit the "use after consume" error.
The reason to do the first is to ensure that when I enable -sil-verify-all, we
do not have errors due to a copy_value of a move only type.
The reason to do the second thing is that:
1. If we have a move only type that is no implicit copy, I am in a subsequent
commit going to emit a type checker error saying that one cannot do this. When
we implement consuming/borrowing bindings/etc, we can make this looser if it
gets into the way.
2. If we have a copyable no implicit copy type, then any structural accesses
that we may want to do that would require a destructure must be to a copyable
type which is ok to copy as long as we do the unwrap from the first thing.
rdar://104929957
move only types will already be checked by the move only checker and said
checker will still see move_value as a consume so we are just eliminating an
unnecessary double diagnostic.
rdar://102056097
The reason why we are doing this is that we are really accessing a getter on the
type. The error would be necessarily done inside the getter where any
consumption would happen. So it shouldn't be on the move only value itself.
I am renaming this since as we add more true move only types to the compiler, it
may be confusing that these are testing no implicit copy and not true move only
types.
