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.
Introduce macro sub-namespaces and `macro_use` prelude
This PR implements two mechanisms needed for correct macro name resolution: macro sub-namespace and `macro_use` prelude.
- [macro sub-namespaces][subns-ref]
Macros have two sub-namespaces: one for function-like macro and the other for those in attributes (including custom derive macros). When we're resolving a macro name for function-like macro, we should ignore non-function-like macros, and vice versa.
This helps resolve single-segment macro names because we can (and should, as rustc does) fallback to names in preludes when the name in the current module scope is in different sub-namespace.
- [`macro_use` prelude][prelude-ref]
`#[macro_use]`'d extern crate declarations (including the standard library) bring their macros into scope, but they should not be prioritized over local macros (those defined in place and those explicitly imported).
We have been bringing them into legacy (textual) macro scope, which has the highest precedence in name resolution. This PR introduces the `macro_use` prelude in crate-level `DefMap`s, whose precedence is lower than local macros but higher than the standard library prelude.
The first 3 commits are drive-by fixes/refactors.
Fixes#8828 (prelude)
Fixes#12505 (prelude)
Fixes#12734 (prelude)
Fixes#13683 (prelude)
Fixes#13821 (prelude)
Fixes#13974 (prelude)
Fixes#14254 (namespace)
[subns-ref]: https://doc.rust-lang.org/reference/names/namespaces.html#sub-namespaces
[prelude-ref]: https://doc.rust-lang.org/reference/names/preludes.html#macro_use-prelude
Refactor symbol index
Closes https://github.com/rust-lang/rust-analyzer/issues/14677
instead of eagerly fetching the source data in symbol index we do it lazily now, this shouldn't make it much more expensive as we had to parse the source most of the time anyways even after fetching.
fix: ide: exclude sized in go-to actions in hover
fixes#13163
i opted to just simply omit `Sized` entirely from go-to actions, as opposed to including it if even someone writes an explicit `T: Sized`, as i think a go-to on Sized is of dubious value practically.
Fix explicit deref problems in closure capture
fix the `need-mut` part of #14562
Perhaps surprisingly, it wasn't unique immutable borrow. The code still doesn't emit any of them, and I think those won't happen in edition 2021 (which is currently the only thing implemented), since we always capture `&mut *x` instead of `&mut x`. But I'm not very sure about it.
