Comprehensively support trailing commas in std/core macros
I carefully organized the changes into four commits:
* Test cases
* Fixes for `macro_rules!` macros
* Fixes for builtin macros
* Docs for builtins
**I can easily scale this back to just the first two commits for now if such is desired.**
### Breaking (?) changes
* This fixes#48042, which is a breaking change that I hope people can agree is just a bugfix for an extremely dark corner case.
* To fix five of the builtins, this changes `syntax::ext::base::get_single_str_from_tts` to accept a trailing comma, and revises the documentation so that this aspect is not surprising. **I made this change under the (hopefully correct) understanding that `libsyntax` is private rustc implementation detail.** After reviewing all call sites (which were, you guessed it, *precisely those five macros*), I believe the revised semantics are closer to the intended spirit of the function.
### Changes which may require concensus
Up until now, it could be argued that some or all the following macros did not conceptually take a comma-separated list, because they only took one argument:
* **`cfg(unix,)`** (most notable since cfg! is unique in taking a meta tag)
* **`include{,_bytes,_str}("file.rs",)`** (in item form this might be written as "`include!{"file.rs",}`" which is even slightly more odd)
* **`compile_error("message",);`**
* **`option_env!("PATH",)`**
* **`try!(Ok(()),)`**
So I think these particular changes may require some sort of consensus. **All of the fixes for builtins are included this list, so if we want to defer these decisions to later then I can scale this PR back to just the first two commits.**
### Other notes/general requests for comment
* Do we have a big checklist somewhere of "things to do when adding macros?" My hope is for `run-pass/macro-comma-support.rs` to remain comprehensive.
* Originally I wanted the tests to also comprehensively forbid double trailing commas. However, this didn't work out too well: [see this gist and the giant FIXME in it](https://gist.github.com/ExpHP/6fc40e82f3d73267c4e590a9a94966f1#file-compile-fail_macro-comma-support-rs-L33-L50)
* I did not touch `select!`. It appears to me to be a complete mess, and its trailing comma mishaps are only the tip of the iceberg.
* There are [some compile-fail test cases](5fa97c35da/src/test/compile-fail/macro-comma-behavior.rs (L49-L52)) that didn't seem to work (rustc emits errors, but compile-fail doesn't acknowledge them), so they are disabled. Any clues? (Possibly related: These happen to be precisely the set of errors which are tagged by rustc as "this error originates in a macro outside of the current crate".)
---
Fixes#48042Closes#46241
When unnecessarily using a fat arrow after an if condition, suggest the
removal of it.
When finding an if statement with no block, point at the `if` keyword to
provide more context.
When finding:
```rust
match &Some(3) {
&None => 1
&Some(2) => { 3 }
_ => 2
}
```
provide the following diagnostic:
```
error: expected one of `,`, `.`, `?`, `}`, or an operator, found `=>`
--> $DIR/missing-comma-in-match.rs:15:18
|
X | &None => 1
| -- - help: missing comma
| |
| while parsing the match arm starting here
X | &Some(2) => { 3 }
| ^^ expected one of `,`, `.`, `?`, `}`, or an operator here
```
Rustc explain
Fixes#48041.
To make the review easier, I separated tests update to code update. Also, I used this script to generate new ui tests stderr:
```python
from os import listdir
from os.path import isdir, isfile, join
PATH = "src/test/ui"
def do_something(path):
files = [join(path, f) for f in listdir(path)]
for f in files:
if isdir(f):
do_something(f)
continue
if not isfile(f) or not f.endswith(".stderr"):
continue
x = open(f, "r")
content = x.read().strip()
if "error[E" not in content:
continue
errors = dict()
for y in content.splitlines():
if y.startswith("error[E"):
errors[y[6:11]] = True
errors = sorted(errors.keys())
if len(errors) < 1:
print("weird... {}".format(f))
continue
if len(errors) > 1:
content += "\n\nYou've got a few errors: {}".format(", ".join(errors))
content += "\nIf you want more information on an error, try using \"rustc --explain {}\"".format(errors[0])
else:
content += "\n\nIf you want more information on this error, try using \"rustc --explain {}\"".format(errors[0])
content += "\n"
x = open(f, "w")
x.write(content)
do_something(PATH)
```
This is named for the issue as it's testing the specific details of that
bug. It's a bit tricky as the ICE requires multiple files and debug info
enabled to trigger.
This ensures that the entry function is never elided due to inlining, even with `inline(always)`. Fixes#47783.
There were a couple of possible ways of addressing this issue; I simply picked the one that seemed most direct. A warning could be appropriate, but considering using inlining hints in other places it doesn't apply also throws no warnings, and it seems like an edge case anyway, I haven't added one for now.
test: Fix s390x-unknown-linux-gnu atomic-lock-free test not run for systemz
The s390-unknown-linux-gnu atomic-lock-free test is currently run for ```LLVM_COMPONENTS == powerpc```. I assume it was meant to be run for ```LLVM_COMPONENTS == systemz```, so let's fix this.
rustdoc: don't crash when an external trait's docs needs to import another trait
Fixes https://github.com/rust-lang/rust/issues/48414
When resolving intra-paths for an item, rustdoc needs to have information about their items on hand, for proper bookkeeping. When loading a path for an external item, it needs to load these items from their host crate, since their information isn't otherwise available. This includes resolving paths for those docs. which can cause this process to recurse. Rustdoc keeps a map of external traits in a `RefCell<HashMap<DefId, Trait>>`, and it keeps a borrow of this active when importing an external trait. In the linked crash, this led to a RefCell borrow error, panic, and ICE.
This PR manually releases the borrow while importing the trait, and also keeps a list of traits being imported at the given moment. The latter keeps rustdoc from infinitely recursing as it tries to import the same trait repeatedly.
Allow two-phase borrows of &mut self in ops
We need two-phase borrows of ops to be in the initial NLL release since without them lots of existing code will break. Fixes#48129.
CC @pnkfelix and @nikomatsakis
r? @pnkfelix
Fix borrow checker unsoundness with unions
Fixes#45157. After discussion with @nikomatsakis on Gitter, this PR only adds a test since the original issue was resolved elsewhere.
r? @nikomatsakis
Remove "static item recursion checking" in favor of relying on cycle checks in the query engine
Tests are changed to use the cycle check error message instead. Some duplicate tests are removed.
r? @eddyb
