Before this commit, `Parse`s for original file ended up two times in
salsa's db: first, when we parse original file, and second, when we
parse macro or a file.
Given that parse trees are the worst ofenders in terms of memory, it
makes sense to make sure we store them only once.
We use panics for cancellation, so we could trigger panic while
holding the solver. std::sync::Mutex will be poisoned as a result,
which and all further attempts to use solver (from other threads) will
panic as well.
This commit switches to parking_lot::Mutex which just unlocks on panic.
Currently, when expanding macros, we look at the source code
directly (we invoke ast_id_to_node query via to_node method).
This is less then ideal, because it make us re-expand macros after
every source change.
This commit establishes a salsa-firewall: a query to get macro call's
token tree. Unlike the syntax tree, token tree changes only if we
actually modify the macro itself.
- make it possible to get parent trait from method
- add 'obligation' machinery for checking that a type implements a
trait (and inferring facts about type variables from that)
- handle type parameters of traits (to a certain degree)
- improve the hacky implements check to cover enough cases to exercise the
handling of traits with type parameters
- basic canonicalization (will probably also be done by Chalk)
This solves the problem of "macro expansion can't call into name
resolution, because name resolution calls back into macro expansion"
Because we store macro def as a part of call id, macro expansion just
knows the def!