get_os and get_arch were failing to return a value in the error
case; they were also assuming that strings are indexed from 1. No
idea how they ever worked, but anyway, fixed.
* Reorganized typestate into several modules.
* Made typestate check that any function with a non-nil return type
returns a value. For now, the check is a warning and not an error
(see next item).
* Added a "bot" type (prettyprinted as _|_), for constructs like be, ret, break, cont, and
fail that don't locally return a value that can be inspected. "bot"
is distinct from "nil". There is no concrete syntax for _|_, while
the concrete syntax for the nil type is ().
* Added support to the parser for a ! annotation on functions whose
result type is _|_. Such a function is required to have either a
fail or a call to another ! function that is reached in all control
flow paths. The point of this annotation is to mark functions like
unimpl() and span_err(), so that an alt with a call to err() in one
case isn't a false positive for the return-value checker. I haven't
actually annotated anything with it yet.
* Random bugfixes:
* * Fixed bug in trans::trans_binary that was throwing away the
cleanups for nested subexpressions of an and or or
(tests: box-inside-if and box-inside-if2).
** In typeck, unify the expected type arguments of a tag with the
actual specified arguments.
Possibly, at some point, we should add a state-passing variant of
walk, or a wrapper that makes it easier to thread state. (See the
repetetive pop_state_for_* functions in this commit.)
One step closer to removing fold and having a single, immutable AST.
Resolve still uses fold, because it has to detect and transform
expr_field expressions. If we go through on our plan of moving to a
different syntax for module dereferencing, the parser can spit out
expr_field expressions, and resolve can move to walk.
(I am truly sorry for the things I did in typestate_check.rs. I expect
we'll want to change that to walk as well in the near future, at which
point it should probably pass around a context record, which could
hold the def_map.)
I changed instantiate to print out a more helpful error message,
which required passing it a session argument. To avoid
threading extra arguments through a lot of functions,
I added a session field to ty_ctxt.
