fix: deduplicate fields and types in completion
Fixes#15024
- `hir_ty::autoderef()` (which is only meant to be used outside `hir-ty`) now deduplicates types and completely resolves inference variables within.
- field completion now deduplicates fields of the same name and only picks such field of the first type in the deref chain.
Emit `'_` for lifetime generics in `HirDisplay`
This makes the generated code not linted by `rust_2018_idioms` lint. But that is an allow by default lint, so should we do this? Maybe we should only do this for `DisplayTarget::SourceCode`?
fix: consider outer binders when folding captured items' type
Fixes#14966
Basically, the crash is caused by us producing a broken type and passing it to chalk: `&dyn for<type> [for<> Implemented(^1.0: A<^0.0>)]` (notice the innermost bound var `^0.0` has no corresponding binder). It's created in `CapturedItemWithoutTy::with_ty()`, which didn't consider outer binders when folding types to replace placeholders with bound variables.
The fix is one-liner, but I've also refactored the surrounding code a little.
- use `DefWithBodyId::as_generic_def_id()`
- add comments on `InferenceResult` invariant
- move local helper function to bottom to comply with style guide
MIR episode 5
This PR inits drop support (it is very broken at this stage, some things are dropped multiple time, drop scopes are wrong, ...) and adds stdout support (`println!` doesn't work since its expansion is dummy, but `stdout().write(b"hello world\n")` works if you use `RA_SYSROOT_HACK`) for interpreting. There is no useful unit test that it can interpret yet, but it is a good sign that it didn't hit a major road block yet.
In MIR lowering, it adds support for slice pattern and anonymous const blocks, and some fixes so that we can evaluate `SmolStr::new_inline` in const eval. With these changes, 57 failed mir body remains.
