Keywords are now only recognized in contexts where they are valid. The
lexer no longer recognizes them, all words are lexed as IDENT tokens,
that get interpreted by the parser.
This commit reinstates the requirement that the predicate in a
"check" must be a manifest call to a special kind of function
declared with the new "pred" keyword instead of "fn". Preds must
have a boolean return type and can only call other preds; they
can't have any effects (as enforced by the typechecker).
The arguments to a predicate in a check expression must be
slot variables or literals.
This giant commit changes the syntax of Rust to use "assert" for
"check" expressions that didn't mean anything to the typestate
system, and continue using "check" for checks that are used as
part of typestate checking.
Most of the changes are just replacing "check" with "assert" in test
cases and rustc.
Mostly:
* Merciless refactoring of trans.rs so that trans_call can work for
self-calls as well as other kinds of calls
Also:
* Various changes to go with having idents, rather than exprs, in
expr_call_self AST nodes
* Added missing case for SELF token to token.to_str()
and literals with the 'f32' or 'f64' suffixes work as well. In
addition, logging things with the f32 or f64 type works. (float is
still assumed to be a synonym for f64).
