One of the primary platforms for the `armv7-unknown-linux-gnueabihf` target,
Linux distributions, do not enable NEON extensions by default. This PR disables
that feature by defualt but enables the `d16` feature which enables VFP3D16 that
distributions do enable.
Closes#35590
Part of #29365
explain that std::mem::drop in prelude will invoke Drop
change "prelude" -> "the prelude"; change links to reference-style
move link references to links' section
Restructure metadata encoder to track deps precisely
This issue restructures meta-data encoding to track dependencies very precisely. It uses a cute technique I hope to spread elsewhere, where we can guard the data flowing into a new dep-graph task and ensure that it is not "leaking" information from the outside, which would result in missing edges. There are no tests because we don't know of any bugs in the old system, but it's clear that there was leaked data.
The commit series is standalone, but the refactorings are kind of "windy". It's a good idea to read the comment in `src/librustc_metadata/index_builder.rs` to get a feeling for the overall strategy I was aiming at.
In several cases, I wound up adding some extra hashtable lookups, I think primarily for looking up `AdtDef` instances. We could remove these by implementing `DepGraphRead` for an `AdtDef` and then having it register a read to the adt-defs table, I guess, but I doubt it is really noticeable.
Eventually I think I'd like to extend this pattern to the dep-graph more generally, since it effectively guarantees that data cannot leak.
Fixes#35111.
r? @michaelwoerister
Move 'doesn't live long enough' errors to labels
This patch moves the "doesn't live long enough" region-style errors to instead use labels.
An example follows.
Before:
```
error: `x` does not live long enough
--> src/test/compile-fail/send-is-not-static-ensures-scoping.rs:26:18
|
26 | let y = &x;
| ^
|
note: reference must be valid for the block at 23:10...
--> src/test/compile-fail/send-is-not-static-ensures-scoping.rs:23:11
|
23 | fn main() {
| ^
note: ...but borrowed value is only valid for the block suffix following statement 0 at 25:18
--> src/test/compile-fail/send-is-not-static-ensures-scoping.rs:25:19
|
25 | let x = 1;
| ^
```
After:
```
error: `x` does not live long enough
--> src/test/compile-fail/send-is-not-static-ensures-scoping.rs:26:18
|
26 | let y = &x;
| ^ does not live long enough
...
32 | };
| - borrowed value only valid until here
...
35 | }
| - borrowed value must be valid until here
```
r? @nikomatsakis
