This fixes#19978. The bug was introduced by 570325d, where if the type
of an Fn has not been inferred (strs[0] is "_") we slice from 1 to
0. We now explicitly check if `strs[0]` is a single element tuple.
in most cases, just the error message changed, but in some cases we
are reporting new errors that OUGHT to have been reported before but
we're overlooked (mostly involving the `'static` bound on `Send`).
(Previously, statically identifiable scopes/regions were solely
identified with NodeId's; this refactoring prepares for a future
where that 1:1 correspondence does not hold.)
region binding at the impl site, so for method types that come from impls,
it is necessary to liberate/instantiate late-bound regions at multiple
depths.
I wanted to embed an `Rc<TraitRef>`, but I was foiled by the current
static rules, which prohibit non-Sync values from being stored in
static locations. This means that the constants for `ty_int` and so
forth cannot be initialized.
Key points are:
1. `a + b` maps directly to `Add<A,B>`, where `A` and `B` are the types of `a` and `b`.
2. Indexing and slicing autoderefs consistently.
Diagnostics such as the following
```
mismatched types: expected `core::result::Result<uint,()>`, found `core::option::Option<<generic #1>>`
<anon>:6 let a: Result<uint, ()> = None;
^~~~
mismatched types: expected `&mut <generic #2>`, found `uint`
<anon>:7 f(42u);
^~~
```
tend to be fairly unappealing to new users. While specific type var IDs are valuable in
diagnostics that deal with more than one such variable, in practice many messages
only mention one. In those cases, leaving out the specific number makes the messages
slightly less terrifying.
In addition, type variables have been changed to use the type hole syntax `_` in diagnostics.
With a variable ID, they're printed as `_#id` (e.g. `_#1`). In cases where the ID is left out,
it's simply `_`. Integer and float variables have an additional suffix after the number, e.g.
`_#1i` or `_#3f`.
This adds a `Substs` field to `ty_unboxed_closure` and plumbs basic
handling of it throughout the compiler. trans now correctly
monomorphizes captured free variables and llvm function defs. This
fixes uses of unboxed closures which reference a free type or region
parameter from their environment in either their signature or free
variables. Closes#16791
Spring cleaning is here! In the Fall! This commit removes quite a large amount
of deprecated functionality from the standard libraries. I tried to ensure that
only old deprecated functionality was removed.
This is removing lots and lots of deprecated features, so this is a breaking
change. Please consult the deprecation messages of the deleted code to see how
to migrate code forward if it still needs migration.
[breaking-change]
- Unify the representations of `cat_upvar` and `cat_copied_upvar`
- In `link_reborrowed_region`, account for the ability of upvars to
change their mutability due to later processing. A map of recursive
region links we may want to establish in the future is maintained,
with the links being established when the kind of the borrow is
adjusted.
- When categorizing upvars, add an explicit deref that represents the
closure environment pointer for closures that do not take the
environment by value. The region for the implicit pointer is an
anonymous free region type introduced for this purpose. This
creates the necessary constraint to prevent unsound reborrows from
the environment.
- Add a note to categorizations to make it easier to tell when extra
dereferences have been inserted by an upvar without having to
perform deep pattern matching.
- Adjust borrowck to deal with the changes. Where `cat_upvar` and
`cat_copied_upvar` were previously treated differently, they are
now both treated roughly like local variables within the closure
body, as the explicit derefs now ensure proper behavior. However,
error diagnostics had to be changed to explicitly look through the
extra dereferences to avoid producing confusing messages about
references not present in the source code.
Closes issue #17403. Remaining work:
- The error diagnostics that result from failed region inference are
pretty inscrutible and should be improved.
Code like the following is now rejected:
let mut x = 0u;
let f = || &mut x;
let y = f();
let z = f(); // multiple mutable references to the same location
This also breaks code that uses a similar construction even if it does
not go on to violate aliasability semantics. Such code will need to
be reworked in some way, such as by using a capture-by-value closure
type.
[breaking-change]
