This adds support for dropping cleanups for temporary values when they
are moved somewhere else. It then adds wraps most copy operations
(return, put in data structure, box, etc) in a way that will fall back
to a move when it is safe.
This saves a lot of taking/dropping, shaving over a megabyte off the
stage2/rustc binary size.
In some cases, most notably function returns, we could detect that the
returned value is a local variable, and can thus be safely moved even
though it is not a temporary. This will require putting some more
information in lvals.
I did not yet handle function arguments, since the logic for passing
them looked too convoluted to touch. I'll probably try that in the
near future, since it's bound to be a big win.
src/comp/syntax is currently just a sub-module of rustc, but it will,
in the near future, be its own crate. This includes:
- The AST data structure
- The parser
- The pretty-printer
- Visit, walk, and fold
- The syntax extension system
- Some utility stuff that should be in the stdlib*
*) Stdlib extensions currently require a snapshot before they can be
used, and the win build is very broken right now. This is temporary
and will be cleaned up when one of those problems goes away.
A lot of code was moved by this patch, mostly towards a more organized
layout. Some package paths did get longer, and I guess the new layout
will take some getting used to. Sorry about that!
Please try not to re-introduce any dependencies in syntax/ on any of
the other src/comp/ subdirs.
Non-copyability is not enforced yet, and something is still flaky with
dropping of the internal value, so don't actually use them yet. I'm
merging this in so that I don't have to keep merging against new
patches.
This involved, in part, changing the ast::def type so that a def_fn
has a "purity" field. This lets the typechecker determine whether
functions defined in other crates are pure.
It also required updating some error messages in tests. As a test
for cross-crate constrained functions, I added a safe_slice function
to std::str (slice(), with one of the asserts replaced with a
function precondition) and some test cases (various versions of
fn-constraint.rs) that call it. Also, I changed "fn" to "pred" for
some of the boolean functions in std::uint.
This will replace the various node_id-to-node mappings done in several
other passes. This commit already uses the new map in resolve, dropping
the ast_map that was built there before.
This reduces some redundancy in the AST data structures and cruft in
the code that works with them. To get a def_id from a node_id, apply
ast::local_def, which adds the local crate_num to the given node_id.
Most code only deals with crate-local node_ids, and won't have to
create def_ids at all.
Revert "rustc: Export only what's needed from middle::ty"
This reverts commit 4255d58aa5db2a05362c4435a0e807205e1b8ed7.
Revert "rustc: Make name resolution errors less fatal"
This reverts commit b8ab9ea89c16c60237e7660804f4321f59ae0435.
Revert "rustc: Make import resolution errors less fatal"
This reverts commit 92a8ae94b971206bf0502da3dc5f416fcb24cc36.
Revert "rustc: Export only what's used from middle::resolve"
This reverts commit 4539a2cf7ad99851a165c98ed2f4e4a475cffd7d.
Revert "rustc: Re-introduce session.span_err, session.err"
This reverts commit 7fe9a88e31ae07f2fd89f6715efedd7e3edf49e6.
Revert "rustc: Rename session.span_err -> span_fatal, err -> fatal"
This reverts commit c394a7f49ac29a099994e243017065de2ff97f2a.
Most of the fields in an AST item were present in all variants. Things
could be simplified considerably by putting them in the rec rather
than in the variant tags.
I added a "resolved" version of the ast::constr type -- ty::constr_def
-- that has a def_id field instead of an ann_field. This is more
consistent with other types and eliminates some checking.
Incidentally, I removed the def_map argument to the top-level function
in middle::alias, since the ty::ctxt already has a def_map field.
Since the decl in a for or for-each loop must always be a local
decl, I changed the AST to express this. Fewer potential match
failures and "the impossible happened" error messages = yay!
Generate appropriate constraints for calls to functions with
preconditions, and reject calls where those constraints don't
hold true in the prestate.
...by which I mean that it works for one test case :-)
The old system tried to ensure that the location an alias pointed at
would retain its type. That turned out to not be strong enough in the
face of aliases to the inside of tags.
The new system instead proves that values pointed to by aliases are
not replaced (or invalidated in some other way) at all. It knows of
two sufficient conditions for this, and tries to prove at least of
them:
A) The alias is 'immutably rooted' in a local, and this local is not
reassigned for the lifetime of the alias. Immutably rooted means
the alias refers to the local itself, or to something reachable
from the local through immutable dereferencing.
B) No value whose type might include the type of the 'inner mutable
element' of the thing the alias refers to (for example, the box in
rec(mutable x = @mutable int)) is from the outer scope is accessed
for the lifetime of the alias. This means for functions, no other
argument types may include the alias's inner mutable type. For alt,
for each, and for, it means the body does not refer to any locals
originating from outside their scope that include this type.
The lifetime of an alias in an alt, for each, or for body is defined
as the range from its definition to its last use, not to the point
where it goes out of scope. This makes working around these
restrictions somewhat less annoying. For example, you can assign to
your alt-ed value you don't refer to any bindings afterwards.
This litters aberrations like 'alt({foo.bar}) { ... }' and f({*baz})
though the code (mostly in trans.rs). These are a way to explicitly
copy the given value so that it can be safely aliased. At some point
we'll probably want a more explicit copy operator.
