[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
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)
[NLL] Returns are interesting for free regions
Based on #53088 - creating now to get feedback.
Closes#51175
* Make assigning to the return type interesting.
* Use "returning this value" instead of "return" in error messages.
* Prefer one of the explanations that we have a name for to a generic interesting cause in some cases.
* Treat causes that involve the destination of a call like assignments.
Make some ported cfail tests robust w.r.t. NLL
Updated the most glaring instances of weak tests w.r.t. NLL that came from #53196.
See also the bulletpoint list on #53351.
make more ported compile fail tests more robust w.r.t. NLL
This is similar to PR #53369, except it covers a disjoint (and much smaller) set of tests that I needed to look at more carefully before being 100% certain they were the same kind of issue.
by strengthening the tests there.
In almost all cases the strengthening amount to just encoding a use
that models the original lexical lifetime. A more invasive revision
was made in one case where it seems the actual issue is MIR-borrowck's
greater "knowledge" of unreachable code in the control flow...
optimize redundant borrows and escaping paths in NLL
This builds on https://github.com/rust-lang/rust/pull/53168 and adds a commit that addresses https://github.com/rust-lang/rust/issues/53176 -- or at least I think it does. I marked this as WIP because I want to see the test results (and measure the performance). I also want to double check we're not adding in any unsoundness here.
Add help message for missing `IndexMut` impl
Code:
```rust
let mut map = HashMap::new();
map.insert("peter", 23);
map["peter"] = 27;
```
Before:
```
error[E0594]: cannot assign to immutable indexed content
--> src/main.rs:7:5
|
7 | map["peter"] = 27;
| ^^^^^^^^^^^^^^^^^ cannot borrow as mutable
```
With this change (just the `help` was added):
```
error[E0594]: cannot assign to immutable indexed content
--> index-error.rs:7:5
|
7 | map["peter"] = 27;
| ^^^^^^^^^^^^^^^^^ cannot borrow as mutable
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for std::collections::HashMap<&str, i32>
```
---
Yesterday I did some pair programming with a Rust-beginner. We created a type and implemented `Index` for it. Trying to modify the value returned by the index operation returns in a rather vague error that was not very clear for the Rust beginner. So I tried to improve the situation.
## Notes/questions for reviewers:
- Is the formulation OK like that? I'm fine with changing it.
- Can we be absolutely sure that `IndexMut` is actually not implemented in the case my `help` message is added? I'm fairly sure myself, but there could be some cases I didn't think of. Also, I don't know the compiler very well, so I don't know what exactly certain enum variants are used for.
- It would be nice to test if `IndexMut` is in fact not implemented for the type, but I couldn't figure out how to check that. If you think that additional check would be beneficial, could you tell me how to check if a trait is implemented?
- Do you think I should change the error message instead of only adding an additional help message?
revert #52991
Reverts https://github.com/rust-lang/rust/pull/52991 which is flawed. I have an idea how to fix it but might as well revert first since it is so wildly flawed. That's what I get for opening PRs while on PTO =)
r? @pnkfelix
Fix NLL migration mode so that reports region errors when necessary.
The code here was trying to be clever, and say "lets not report diagnostics when we 'know' NLL will report an error about them in the future."
The problem is that in migration mode, when no error was reported here, the NLL error that we "knew" was coming was downgraded to a warning (!).
Thus causing #53026
(I hope it is the only instance of such a scenario, but we will see.)
Anyway, this PR fixes that by only doing the "clever" skipping of region error reporting when we are not in migration mode. As noted in the FIXME, I'm not really thrilled with this band-aid, but it is small enough to be back-ported easily if that is necessary.
Rather than make a separate test for issue 53026, I just took the test that uncovered this in a first place, and extended it (via our revisions system) to explicitly show all three modes in action: AST-borrowck, NLL, and NLL migration mode.
(To be honest I hope not to have to add such revisions to many tests. Instead I hope to adopt some sort of new `compare-mode` for either borrowck=migrate or for the 2018 edition as a whole.)
Fix#53026
[NLL] Use smaller spans for errors involving closure captures
Closes#51170Closes#46599
Error messages involving closures now point to the captured variable/closure args.
r? @pnkfelix
avoid computing liveness for locals that escape into statics
Fixes#52713
I poked at this on the plane and I think it's working -- but I want to do a bit more investigation and double check. The idea is to identify those local variables where the entire value will "escape" into the return -- for them, we don't need to compute liveness, since we know that the outlives relations from the return type will force those regions to be equal to free regions. This should help with html5ever in particular.
- [x] test performance
- [x] verify correctness
- [x] add comments
r? @pnkfelix
cc @lqd
Namely, the code here was trying to be clever, and say "lets not
report diagnostics when we 'know' NLL will report an error about them
in the future."
The problem is that in migration mode, when no error was reported here,
the NLL error that we "knew" was coming was downgraded to a warning (!).
This fixes that by only doing the "clever" skipping of region error reporting
when we are not in migration mode.
Rather than make a separate test for issue 53026, I just took the test
that uncovered this in a first place, and extended it (via our
revisions system) to explicitly show all three modes in action:
ACT-borrowck, NLL, and NLL migration mode.
(Tto be honest I hope not to have to add such revisions to many tests.
Instead I hope to adopt some sort of new `compare-mode` for either
borrowck=migrate or for the 2018 edition as a whole.)
NLL: On "cannot move out of type" error, print original before rewrite
NLL: On "cannot move out of type" error, print original source before rewrite.
* Arguably this change is sometimes injecting noise into the output (namely in the cases where the suggested rewrite is inline with the suggestion and we end up highlighting the original source code). I would not be opposed to something more aggressive/dynamic, like revising the suggestion code to automatically print the original source when necessary (e.g. when the error does not have a span that includes the span of the suggestion).
* Also, as another note on this change: The doc comment for `Diagnostic::span_suggestion` says:
```rust
/// The message
///
/// * should not end in any punctuation (a `:` is added automatically)
/// * should not be a question
/// * should not contain any parts like "the following", "as shown"
```
* but the `:` is *not* added when the emitted line appears out-of-line relative to the suggestion. I find that to be an unfortunate UI experience.
----
As a drive-by fix, also changed code to combine multiple suggestions for a pattern into a single multipart suggestion (which vastly improves user experience IMO).
----
Includes the updates to expected NLL diagnostics.
Fix#52877
* Arguably this change is sometimes injecting noise into the output
(namely in the cases where the suggested rewrite is inline with the
suggestion and we end up highlighting the original source code).
I would not be opposed to something more aggressive/dynamic, like
revising the suggestion code to automatically print the original
source when necessary (e.g. when the error does not have a span
that includes the span of the suggestion).
* Also, as another note on this change: The doc comment for `Diagnostic::span_suggestion`
says:
/// The message
///
/// * should not end in any punctuation (a `:` is added automatically)
/// * should not be a question
/// * should not contain any parts like "the following", "as shown"
but the `:` is *not* added when the emitted line appears
out-of-line relative to the suggestion. I find that to be an
unfortunate UI experience.
----
As a drive-by fix, also changed code to combine multiple suggestions
for a pattern into a single multipart suggestion (which vastly
improves user experience IMO).
----
Includes the updates to expected NLL diagnostics.
[NLL] Use better spans in some errors
* Use the span of the discriminant and patterns for "fake" statements created to properly check matches. I plan to special case these soon, but this felt like a good first step
* Use the span of the statement, rather than the initialization, when reporting move errors for `let x = ...`, which avoids giving an unhelpful suggestion to use `&{ }`.
r? @nikomatsakis cc @pnkfelix
[NLL] make temp for each candidate in `match` arm
In NLL, `ref mut` patterns leverage the two-phase borrow infrastructure to allow the shared borrows within a guard before the "activation" of the mutable borrow when we begin execution of the match arm's body. (There is further discussion of this on PR #50783.)
To accommodate the restrictions we impose on two-phase borrows (namely that there is a one-to-one mapping between each activation and the original initialization), this PR is making separate temps for each candidate pattern. So in an arm like this:
```rust
PatA(_, ref mut ident) |
PatB(ref mut ident) |
PatC(_, _, ref mut ident) |
PatD(ref mut ident) if guard_stuff(ident) => ...
```
instead of 3 temps (two for the guard and one for the arm body), we now have 4 + 2 temps associated with `ident`: one for each candidate plus the actual temp that the guard uses directly, and then the sixth is the temp used in the arm body.
Fix#51348
