Split the type context into a global and a local (inference-only) one.
After this change, each `InferCtxt` creates its own local type interner for types with inference by-products.
Most of the code which handles both a global and a local interner uses `'gcx` and `'tcx` for them.
A reference to the type context in that situation (e.g. `infcx.tcx`) is `TyCtxt<'a, 'gcx, 'tcx>`.
The global type context which used to be `&'a TyCtxt<'tcx>` is now `TyCtxt<'a, 'tcx, 'tcx>`.
In order to minimize the number of extra lifetime parameters, many functions became methods.
Where possible (some inherent impls), lifetime parameters were added on the impl, not each method.
As inference by-products no longer escape their inference contexts, memory usage is lower.
Example of `-Z time-passes` excerpt for `librustc`, stage1 (~100MB gains):
Before "rustc: Split local type contexts interners from the global one.":
```
time: 0.395; rss: 335MB item-types checking
time: 15.392; rss: 472MB item-bodies checking
time: 0.000; rss: 472MB drop-impl checking
time: 1.140; rss: 478MB const checking
time: 0.139; rss: 478MB privacy checking
time: 0.024; rss: 478MB stability index
time: 0.072; rss: 478MB intrinsic checking
time: 0.038; rss: 478MB effect checking
time: 0.255; rss: 478MB match checking
time: 0.128; rss: 484MB liveness checking
time: 1.372; rss: 484MB rvalue checking
time: 1.404; rss: 597MB MIR dump
time: 0.809; rss: 599MB MIR passes
```
After:
```
time: 0.467; rss: 337MB item-types checking
time: 17.443; rss: 395MB item-bodies checking
time: 0.000; rss: 395MB drop-impl checking
time: 1.423; rss: 401MB const checking
time: 0.141; rss: 401MB privacy checking
time: 0.024; rss: 401MB stability index
time: 0.116; rss: 401MB intrinsic checking
time: 0.038; rss: 401MB effect checking
time: 0.382; rss: 401MB match checking
time: 0.132; rss: 407MB liveness checking
time: 1.678; rss: 407MB rvalue checking
time: 1.614; rss: 503MB MIR dump
time: 0.957; rss: 512MB MIR passes
```
**NOTE**: Functions changed to methods weren't re-indented to keep this PR easier to review.
Once approved, the changes will be mechanically performed.
However, indentation changes of function arguments are there - and I believe there's a way to hide whitespace-only changes in diffs on GitHub.
rustdoc: remove artificial indentation of doctest code
The indentation makes the examples look nicer when printed (when is this done?), but breaks tests using multi-line string literals.
Fixes: #25944
borrowck: do not suggest to change "&mut self" to "&mut mut self"
Matching the snippet string might not be the cleanest, but matching
the AST node instead seems to end in a lot of nested `if let`s, so I
don't know what's better.
Of course it's entirely possible that there is another API altogether
that I just don't know of?
Fixes#31424.
resolve: do not modify span of non-importable name
This span modification is probably leftover from a time when import spans were assigned differently.
With this change, error spans for the following are properly reported:
```
use abc::one_el;
use abc::{a, bbb, cccccc};
use a_very_long_name::{el, el2};
```
before (spans only):
```
x.rs:3 use abc::one_el;
^~~
x.rs:4 use abc::{a, bbb, cccccc};
^~~
x.rs:4 use abc::{a, bbb, cccccc};
^~~
x.rs:4 use abc::{a, bbb, cccccc};
^~~
(internal compiler error: unprintable span)
(internal compiler error: unprintable span)
```
after:
```
x.rs:3 use abc::one_el;
^~~~~~~~~~~
x.rs:4 use abc::{a, bbb, cccccc};
^
x.rs:4 use abc::{a, bbb, cccccc};
^~~
x.rs:4 use abc::{a, bbb, cccccc};
^~~~~~
x.rs:5 use a_very_long_name::{el, el2};
^~
x.rs:5 use a_very_long_name::{el, el2};
^~~
```
Fixes: #33464
Preparatory refactorings for collector-driven trans.
This is a set of refactorings that allows to do translation item collection and partitioning before LocalCrateContext instances or LLVM modules are generated. As a consequence we can now create LocalCrateContexts already with knowledge of the codegen unit it will be used for. This is a preparation step for driving trans by the results of codegen unit partitioning.
