[Underspecified semantics] Type check defaults at declaration.
Fixes #46669. See the test for code that compiles on stable but will no longer compile. This falls under a "Underspecified language semantics" fix. **Needs crater**.
On type and trait declarations, we currently allow anything that name checks as a type parameter default. That allows the user to write a default that can never be applied, or even a default that may conditionally be applied depending on the type of another parameter. Mostly this just defers the error to use sites, but also allows clever hacks such as `Foo<T, U = <T as Iterator>::Item>` where `U` will be able to apply it's default only when `T: Iterator`. Maybe that means this bug is a feature, but it's a fiddly behaviour that seems undesirable.
This PR validates defaults at declaration sites by ensuring all predicates on the parameter are valid for the default. With the exception of `Self: Sized` which we don't want to check to allow things like `trait Add<RHS = Self>`.
Given a trait predicate, if all params appearing in the LHS have
defaults then it should be a backwards compatible predicate. We verify
that by checking the WF of predicate with all defaults substituted
simultaneously.
Fix error-format to properly send JSON to stdout
Since we take Cargo's JSON messages as well we need to specifically send
rustc's messages out so we don't hide them.
r? @Manishearth
Ensure main() always has external linkage
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.
Restrict the Termination impls to simplify stabilization
Make a minimal commitment in preparation for stabilization. More impls, or broader ones, are likely in future, but are not necessary at this time and are more controversial.
cc https://github.com/rust-lang/rust/issues/48453#issuecomment-368155082
r? @nikomatsakis
Handle gdb command failure gracefully in compiletest
Previously, if the gdb command was available, but threw an error, compiletest would panic. This is obviously not good. Now, gdb is treated as missing if calling `gdb --version` does not output anything on stdout.
Add support for powerpc-unknown-linux-gnuspe
This PR adds support for the embedded PowerPC variant "e500". On Linux, this architecture is usually called "powerpcspe", it is a 32-bit PowerPC architecture. The main difference between normal 32-bit PowerPC and PowerPCSPE is the lack of Altivec instructions and the additional SPE instruction set.
This architecture is supported in Debian through an unofficial port.
RefCell: document panics in Clone, PartialEq, PartialOrd, Ord.
This fixes#47400 by adding:
```rust
/// # Panics
///
/// Panics if the value is currently mutably borrowed.
```
to said impls. They may panic since they call `.borrow()`.
Add non-panicking variants of pow for integer types
Currently, calling pow may panic in case of overflow, and the function does not have non-panicking counterparts. Thus, it would be beneficial to add those in.
Closes#48291.
Relevant tracking issue: #48320
Report non-standard compile flags on ICE
Some ICEs (such as the recent #48248) only happens when a non-standard compiler flag is provided to rustc, but users don't always report the used flags. This can slow down reproducing the issue, so this PR shows all the non-standard compiler flags in the ICE error message.
For example, the output of #48248 with this PR is:
```
error: internal compiler error: [...]
thread 'rustc' panicked at [...]
note: Run with `RUST_BACKTRACE=1` for a backtrace.
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: [...]
note: rustc 1.25.0-dev running on x86_64-unknown-linux-gnu
note: compiler flags: -C link-dead-code
```
### Open questions
* At the moment, only `-C` and `-Z` flags are shown by default, and all the ones provided by cargo in a standard build are ignored: I did this to only show the flags that probably caused the ICE, and to remove some noise from the message. This removed flags like `opt-level` and `debuginfo` though, could those be useful for reproducing ICEs?
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](https://github.com/ExpHP/rust/blob/5fa97c35da2f0ee/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
rustdoc: Foldable impl blocks
Addresses #40363, #45720, #24483, #23986 and so on
* Expands and refactors collapseDocs and toggleAllDocs
* Adds [-] toggle to all impls (including inherent impl)
* Makes it hiding though main css file, not though element inline style
May need to be addressed:
* "[-]" and anchor link copier are overlaid a bit
* Inherent methods are also hidden by the global [-] toggle.
* Auto-collapsing "Iterator" and so on by default is not implemented yet
* Tested only shallowly and only in Chromiuim
* No tests. Are there tests for css/js part here?
* The new implementation may be a bit slower.
What next steps are need to be done before the integration?
Anonymize some line numbers in UI test output
New unstable flag `-Z ui-testing` is introduced. This flag changes diagnostic output of the compiler *in some way* making it more suitable for UI testing (this is intentionally vague).
At the moment this flag anonymizes line numbers at line starts thus solving the largest issue with UI test diffs. If diffs continue to be too noisy, some other tweaks could be applied (e.g. anonymizing lines/columns in `--> $DIR/file.rs:line:column`), but this needs some time and experience (we shouldn't diverge too much from the actual output in general).
If comment `// disable-ui-testing-normalization` is added to an UI test, then `-Z ui-testing` is not passed.
Closes https://github.com/rust-lang/rust/issues/46643
