What we now do is to create a region variable for each &
expression (and also each borrow). The lifetime of this
variable will be checked by borrowck to ensure it is not greater
than the lifetime of the underlying data. This both leads to
shorter lifetimes in some cases but also longer in others,
such as taking the address to the interior of unique boxes
tht are rooted in region pointers (e.g., returning a pointer
to the interior of a sendable map).
This may lead to issue #2977 if the rvalue is not POD, because
we may drop the data in trans sooner than borrowck expects us
to. Need to work out precisely where that fix ought to occur.
Rewrote bitv as a class that uses a 32-bit int as its representation
for bit vectors of 32 bits or less, and a vector (the old representation)
otherwise. I didn't benchmark very much, but a bit of informal benchmarking
suggested this is a win.
Closes#2341
Previously, resolve was allowing impls, traits or classes that were
nested within a fn to refer to upvars, as well as referring to type
parameters bound by the fn. Fixing this required adding a new kind of
def: def_typaram_binder, which can refer to any of an impl, trait or
class that has bound ty params. resolve uses this to enforce that
methods can refer to their parent item's type parameters, but not to
outer items' type parameters; other stages ignore it. I also made
sure that impl, trait and class methods get checked inside a
MethodRibKind thing so as to forbid upvars, and changed the definition
of MethodRibKind so that its second argument is an optional node_id
(so that required trait method signatures can be checked with a
MethodRibKind as well).
New style is allow(foo), warn(foo), deny(foo) and forbid(foo),
mirrored by -A foo, -W foo, -D foo and -F foo on command line.
These replace -W no-foo, -W foo, -W err-foo, respectively.
Forbid is new, and means "deny, and you can't override it".
resolve3 wasn't checking this. Added test cases. Also added a helpful informational
message in the case where you have a variable binding that you probably think
refers to a variant that you forgot to import.
This is easier to do in resolve than in typeck because there's code in typeck
that assumes that each of the patterns binds the same number of variables.
