Now bounds inside a path are parsed as DYN_TRAIT_TYPE, previously they would be
parsed as `PATH_TYPE` followed by `TYPE_BOUND_LIST`.
Basically this means `Box<T + 'f>` is now parsed almost the same as
`Box<dyn T + 'f>` with the exception of not having the `dyn` keyword.
These are now used when parsing type bounds. In addition parsing paths inside a
bound now does not recursively parse paths, rather they are treated as separate
bounds, separated by +.
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!
1034: HIR diagnostics API r=matklad a=matklad
This PR introduces diagnostics API for HIR, so we can now start issuing errors and warnings! Here are requirements that this solution aims to fulfill:
* structured diagnostics: rather than immediately rendering error to string, we provide a well-typed blob of data with error-description. These data is used by IDE to provide fixes
* open set diagnostics: there's no single enum with all possible diagnostics, which hopefully should result in better modularity
The `Diagnostic` trait describes "a diagnostic", which can be downcast to a specific diagnostic kind. Diagnostics are expressed in terms of macro-expanded syntax tree: they store pointers to syntax nodes. Diagnostics are self-contained: you don't need any context, besides `db`, to fully understand the meaning of a diagnostic.
Because diagnostics are tied to the source, we can't store them in salsa. So subsystems like type-checking produce subsystem-local diagnostic (which is a closed `enum`), which is expressed in therms of subsystem IR. A separate step converts these proto-diagnostics into `Diagnostic`, by merging them with source-maps.
Note that this PR stresses type-system quite a bit: we now type-check every function in open files to compute errors!
Discussion on Zulip: https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Fwg-rls-2.2E0/topic/Diagnostics.20API
Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>
