The alias checker works by ensuring that any value to which an alias
is created is rooted in some way that ensures it outlives the alias.
It is now disallowed to create an alias to the content of a mutable
box, or to a box hanging off a mutable field. There is also machinery
in place to prevent assignment to local variables whenever they are
the root of a live alias.
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.
Hello from SFO Terminal 3!
unify_fn_common had the expected and actual types reversed in one
place. This was causing the type of an occurence of a function f
with type fn(int) -> T to be set to fn(_|_) -> T at a call site like
f(fail); I think this was also making some of the type error messages
come out backwards, but I haven't checked.
Also: ty_bot does not contain pointers
This makes it possible to pass the location of that space through to
nested blocks, resulting in less copying, taking, and dropping.
This makes the compiler slightly faster and 19k smaller.
A FIXME is to use 'move' semantics when returning the values from the
block -- don't bump the refcount and drop it again for the returning
block, but simply assign ownership to the receiver. To do this, we'll
need a way to (safely) scrub things from a block's cleanup list.
A non-returning call should have a postcondition in which all predicates
are true -- not just a poststate. Otherwise, alt expressions where
one or more branches terminate in a non-returning call and others
initialize a variable get rejected.
Includes a test case.
* Non-returning calls should set all predicates to be true, not
just the "this function returns" predicate
* Fixed a bug in the expr_alt case in tstate.states that wasn't updating
the changed flag properly, then fixed *another* bug that was updating
it too enthusiastically, but was masked by the first bug.
Changed the typechecker to correctly typecheck the declared variable
type in a for or for-each loop against the vector element type (for
a for loop) or the iterator type (for a for-each loop). Added a
test case.
