proc_macro::Group::span_open and span_close
Before this addition, every delimited group like `(`...`)` `[`...`]` `{`...`}` has only a single Span that covers the full source location from opening delimiter to closing delimiter. This makes it impossible for a procedural macro to trigger an error pointing to just the opening or closing delimiter. The Rust compiler does not seem to have the same limitation:
```rust
mod m {
type T =
}
```
```console
error: expected type, found `}`
--> src/main.rs:3:1
|
3 | }
| ^
```
On that same input, a procedural macro would be forced to trigger the error on the last token inside the block, on the entire block, or on the next token after the block, none of which is really what you want for an error like above.
This commit adds `group.span_open()` and `group.span_close()` which access the Span associated with just the opening delimiter and just the closing delimiter of the group. Relevant to Syn as we implement real error messages for when parsing fails in a procedural macro: https://github.com/dtolnay/syn/issues/476.
```diff
impl Group {
fn span(&self) -> Span;
+ fn span_open(&self) -> Span;
+ fn span_close(&self) -> Span;
}
```
Fixes#48187
r? @alexcrichton
rustc_codegen_llvm: don't assume offsets are always aligned.
Fixes#53728 by taking into account not just overall type alignment and the field's alignment when determining whether a field is aligned or not ("packed"), but also the field's offset within the type.
Previously, rustc assumed that the offset was always at least as aligned as `min(struct.align, field.align)`. However, there's no real reason to have that assumption, and it obviously can't always be true after we implement `#[repr(align(N), pack(K))]`. There's also a case today where that assumption is not true, involving niche discriminants in enums:
Suppose that we have the code in #53728:
```Rust
#[repr(u16)]
enum DeviceKind {
Nil = 0,
}
#[repr(packed)]
struct DeviceInfo {
endianness: u8,
device_kind: DeviceKind,
}
struct Wrapper {
device_info: DeviceInfo,
data: u32
}
```
Observe the layout of `Option<Wrapper>`. It has an alignment of 4 because of the `u32`. `device_info.device_kind` is a good niche field to use, which means the enum ends up with this layout:
```
size = 8
align = 4
fields = [
{ offset=1, type=u16 } // discriminant, .<Some>.device_info.device_kind
]
```
And here we have an discriminant with alignment 2 (`u16`) but offset 1.
rustc_resolve: only prepend CrateRoot to a non-keyword segment.
Fixes#53770 by treating `use` paths as absolute in a finer-grained manner, specifically:
```rust
use {a, crate::b, self::c, super::d};
```
Used to be interpreted as if it were (when `uniform_paths` is not enabled):
```rust
use ::{a, crate::b, self::c, super::d};
```
With this PR, the `CrateRoot` pseudo-keyword indicating an absolute path is only inserted when the first path segment is found (if it's not a keyword), i.e. the example behaves like:
```rust
use {::a, crate::b, self::c, super::d};
```
This should (finally) make `use {path};` fully equivalent to `use path;`.
r? @petrochenkov cc @cramertj @joshtriplett @nikomatsakis
Rollup of 10 pull requests
Successful merges:
- #53315 (use `NonZeroU32` in `newtype_index!`macro, change syntax)
- #53932 ([NLL] Remove base_place)
- #53942 (Rewrite `precompute_borrows_out_of_scope` for fewer hash table lookups.)
- #53973 (Have rust-lldb look for the rust-enabled lldb)
- #53981 (Implement initializer() for FileDesc)
- #53987 (rustbuild: allow configuring llvm version suffix)
- #53993 (rustc_resolve: don't record uniform_paths canaries as reexports.)
- #54007 (crates that provide a `panic_handler` are exempt from the `unused_extern_crates` lint)
- #54040 (update books for next release)
- #54050 (Update `petgraph` dependency to 0.4.13 to fix build with nightly)
[NLL] Remove base_place
This function was supposed to make `Box` less special. But
* I think that the consensus is that MIR borrowck is going to fully special case `Box`
* It wasn't implemented correctly, it's looking at the type of the wrong `Place`, resulting in weird behaviour:
```rust
#![feature(nll)]
type A = Box<i32>; // If this is changed to another type then this will compile.
pub fn foo(x: Box<(String, A)>) {
let a = x.0; // This will compile if these lines are swapped
let b = x.1;
}
```
r? @nikomatsakis
stabilize #[panic_handler]
closes#44489
### Update(2018-09-07)
This was proposed for stabilization in https://github.com/rust-lang/rust/issues/44489#issuecomment-398965881 and its FCP with disposition to merge / accept is nearly over. The summary of what's being stabilized can be found in https://github.com/rust-lang/rust/issues/44489#issuecomment-416645946
Documentation PRs:
- Reference. https://github.com/rust-lang-nursery/reference/pull/362
- Nomicon. https://github.com/rust-lang-nursery/nomicon/pull/75
---
`#[panic_implementation]` was implemented recently in #50338. `#[panic_implementation]` is basically the old `panic_fmt` language item but in a less error prone (\*) shape. There are still some issues and questions to sort out around this feature (cf. #44489) but this PR is meant to start a discussion about those issues / questions with the language team.
(\*) `panic_fmt` was not type checked; changes in its function signature caused serious, silent binary size regressions like the one observed in #43054
Some unresolved questions from #44489:
> Should the Display of PanicInfo format the panic information as "panicked at 'reason',
> src/main.rs:27:4", as "'reason', src/main.rs:27:4", or simply as "reason".
The current implementation formats `PanicInfo` as the first alternative, which is how panic messages are formatted by the `std` panic handler. The `Display` implementation is more than a convenience: `PanicInfo.message` is unstable so it's not possible to replicate the `Display` implementation on stable.
> Is this design compatible, or can it be extended to work, with unwinding implementations for
> no-std environments?
I believe @whitequark made more progress with unwinding in no-std since their last comment in #44489. Perhaps they can give us an update?
---
Another unresolved question is where this feature should be documented. The feature currently doesn't have any documentation.
cc @rust-lang/lang
cc @jackpot51 @alevy @phil-opp
This allows it to print out the "late-bound regions" from the closure
context more easily. Besides, all the state that is being printed it
is private to the `UniversalRegions`.
[nll] teach SCC about `'static`
r? @nikomatsakis
I think this is right? I am seeing better performance on the `html5ever` benchmark but I'd like a perf run to quantify the exact speedup. There's a few ui tests failing due to changes in the error messages. The main issue seems to be that returns aren't being detected correctly?
`mir_check_cast_unsize.rs` before:
```
error: unsatisfied lifetime constraints
--> mir_check_cast_unsize.rs:17:46
|
17 | fn bar<'a>(x: &'a u32) -> &'static dyn Debug {
| ________--____________________________________^
| | |
| | lifetime `'a` defined here
18 | | //~^ ERROR unsatisfied lifetime constraints
19 | | x
20 | | //~^ WARNING not reporting region error due to nll
21 | | }
| |_^ return requires that `'a` must outlive `'static`
```
`mir_check_cast_unsize.rs` after:
```
error: unsatisfied lifetime constraints
--> mir_check_cast_unsize.rs:19:5
|
17 | fn bar<'a>(x: &'a u32) -> &'static dyn Debug {
| -- lifetime `'a` defined here
18 | //~^ ERROR unsatisfied lifetime constraints
19 | x
| ^ cast requires that `'a` must outlive `'static`
```
Rollup of 17 pull requests
Successful merges:
- #53299 (Updated core/macros.rs to note it works in a no_std environment.)
- #53376 (Cross reference io::copy and fs::copy in docs.)
- #53455 (Individual docs for {from,to}_*_bytes)
- #53550 (librustc_lint: In recursion warning, change 'recurring' to 'recursing')
- #53860 (Migrate (some) of run-pass/ to ui)
- #53874 (Implement Unpin for Box, Rc, and Arc)
- #53895 (tidy: Cleanups and clippy warning fixes)
- #53946 (Clarify `ManuallyDrop` docs)
- #53948 (Minimized clippy test from when NLL disabled two-phase borrows)
- #53959 (Add .git extension to submodule paths missing it)
- #53966 (A few cleanups and minor improvements to mir/dataflow)
- #53967 (propagate build.python into cmake)
- #53979 (Remove `#[repr(transparent)]` from atomics)
- #53991 (Add unchecked_shl/shr check for intrinsics to fix miri's test suit)
- #53992 (migrate run-pass/borrowck to ui/run-pass)
- #53994 (migrate run-pass/*/ to ui/run-pass)
- #54023 (update clippy submodule)
Migrate (some) of run-pass/ to ui
This is a step towards addressing #53764. Much still remains.
I went through a large portion of the `*.rs` files that were directly stored into `src/test/run-pass/` and moved them into various subdirectories of a newly created `src/test/ui/run-pass/`.
(yes, it would have perhaps been nice to meld it more directly with directories already in `src/test/ui/`; but the sad truth is that opens up the reality of filename collisions, and one of my short term goals for resolving #53764 is to keep the *filenames* invariant, even as their parents directories and contents are mildly revised...)
librustc_lint: In recursion warning, change 'recurring' to 'recursing'
The existing wording seems incorrect.
Aside: This warning, 'function cannot return without recursing' is not perfectly clear - it implies that the function _can_ return, it's just got to recurse. But really the fn cannot return period. Clearer wording: 'function recurses infinitely; it cannot return'; or 'function is infinitely self-recursive; it cannot return, and this is probably an error'. I like that.
rustc_resolve: allow `use crate_name;` under `uniform_paths`.
Specifically, `use crate_name;` and `use crate_name::{self, ...};` are now allowed, whereas previously there would produce a (false positive) ambiguity error, as the ambiguity detection code was seeing the `crate_name` import as a locally-available definition to conflict with the crate.
r? @petrochenkov cc @aturon @joshtriplett @Centril
Don't reduce E0161 to a warning in NLL migrate mode
This error has been on stable for a while, and allowing such code cause the compile to later ICE (since we can't codegen it). Errors `box UNSIZED EXPR` with unsized locals because it's not compatible with the current evaluation order (create the box before evaluating the expressions).
cc #53469 (fixes the ICE in this case)
cc @qnighy
Fix issue #52475: Make loop detector only consider reachable memory
As [suggested](https://github.com/rust-lang/rust/pull/51702#discussion_r197585664) by @oli-obk `alloc_id`s should be ignored by traversing all `Allocation`s in interpreter memory at a given moment in time, beginning by `ByRef` locals in the stack.
- [x] Generalize the implementation of `Hash` for `EvalSnapshot` to traverse `Allocation`s
- [x] Generalize the implementation of `PartialEq` for `EvalSnapshot` to traverse `Allocation`s
- [x] Commit regression tests
Fixes#52626
Fixes https://github.com/rust-lang/rust/issues/52849
