Changes:
- `const_of_item()` was added to `Interner`, analogous to `type_of()`. No strongly-typed ID (yet).
- New solver trait lang item: `TrivialClone`.
- `TypeRelation` changed a bit, the code was copied from rustc.
Basically, we switch to expanding cfg_attr in AST form, filter irrelevant attributes from the item tree, and move hir-def attributes (non-item-tree) to be flag-based.
The main motivation is memory usage, although this also simplifies the code, and fixes some bugs around handling of `cfg_attr`s.
Major changes:
- `GoalSource::InstantiateHigherRanked` was removed.
- `Interner::UnevaluatedConstId` was introduced, allowing further simplifications due to better typing. Generally we don't represent unevaluated consts like we should, but it's still better.
- `PatternKind::NotNull` was introduced.
- Discussed in https://github.com/rust-lang/rust-analyzer/issues/21107
- Avoids activating an `attributes` feature to crates that do not use it
- Updates the 6 crates that use attributes feature to specify it in
their Cargo.toml: {hir,hir-def,hir-ty,ide-assists,ide-db,project-model}
Basically, we switch to expanding cfg_attr in AST form, filter irrelevant attributes from the item tree, and move hir-def attributes (non-item-tree) to be flag-based.
The main motivation is memory usage, although this also simplifies the code, and fixes some bugs around handling of `cfg_attr`s.
They have to do with diagnostics, we could probably not support them but we will also someday want good diagnostics.
The code is mostly copied from rustc.
The main changes are (there are some other small changes):
- Using a specific type for trait IDs in the new solver, allowing us to simplify a lot of code.
- Add `BoundConst` similar to `BoundTy` and `BoundRegion` (previously consts used `BoundVar` directly), due to a new trait requirement.
