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`).
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.
Various miscellaneous changes pushing towards HRTB support:
1. Update parser and adjust ast to support `for<'a,'b>` syntax, both in closures and trait bounds. Warn on the old syntax (not error, for stage0).
2. Refactor TyTrait representation to include a TraitRef.
3. Purge `once_fns` feature gate and `once` keyword.
r? @pcwalton
This is a [breaking-change]:
- The `once_fns` feature is now officially deprecated. Rewrite using normal closures or unboxed closures.
- The new `for`-based syntax now issues warnings (but not yet errors):
- `fn<'a>(T) -> U` becomes `for<'a> fn(T) -> U`
- `<'a> |T| -> U` becomes `for<'a> |T| -> U`
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.
- When selecting an implicit trait impl for an unboxed closure, plumb
through and use the substitutions from impl selection instead of
using those from the current param environment in trans, which may
be incorrect.
- When generating a function declaration for an unboxed closure, plumb
through the substitutions from the param environment of the closure
as above. Also normalize the type to avoid generating duplicate
declarations due to regions being inconsistently replaced with
ReStatic elsewhere.
- Do not place the closure type in the self param space when
translating the unboxed closure callee, etc. It is not actually
used, and doing so conflicts with the self substitution from
default trait methods.
Closes#18661Closes#18685
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
Change to resolve and update compiler and libs for uses.
[breaking-change]
Enum variants are now in both the value and type namespaces. This means that
if you have a variant with the same name as a type in scope in a module, you
will get a name clash and thus an error. The solution is to either rename the
type or the variant.
The implementation essentially desugars during type collection and AST
type conversion time into the parameter scheme we have now. Only fully
qualified names--e.g. `<T as Foo>::Bar`--are supported.
lifetime bounds. This doesn't really cause any difficulties, because
we already had to accommodate the fact that multiple implicit bounds
could accumulate. Object types still require precisely one lifetime
bound. This is a pre-step towards generalized where clauses (once you
have lifetime bounds in where clauses, it is harder to restrict them
to exactly one).
