NLL: change compare-mode=nll to use borrowck=migrate
Fixes#55118.
This PR is split into two parts:
The first commit is a minor change that fixes a flaw in the existing `borrowck=migrate` implementation whereby a lint that was promoted to an error in the AST borrow checker would result in the same lint from the NLL borrow checker being downgraded to a warning in migrate mode. This PR fixes this by ensuring lints are exempt from buffering in the NLL borrow checker.
The second commit updates `compiletest` to make the NLL compare mode use `-Z borrowck=migrate` rather than `-Z borrowck=mir`. The third commit shows all the test output changes that result from this.
r? @pnkfelix
reject partial init and reinit of uninitialized data
Reject partial initialization of uninitialized structured types (i.e. structs and tuples) and also reject partial *reinitialization* of such types.
Fix#54986Fix#54499
cc #21232
This commit updates the test output for the updated NLL compare mode
that uses `-Z borrowck=migrate` rather than `-Z borrowck=mir`. The
previous commit changes `compiletest` and this commit only updates
`.nll.stderr` files.
[NLL] Check user types are well-formed
Also contains a change of span for AscribeUserType.
I'm not quite sure if this was what @nikomatsakis was thinking.
Closes#54620
r? @nikomatsakis
Better Diagnostic for Trait Object Capture
Part of #52663.
This commit enhances `LaterUseKind` detection to identify when a borrow
is captured by a trait object which helps explain why there is a borrow
error.
r? @nikomatsakis
cc @pnkfelix
Now when a `FnMut` closure is returning a closure that contains a
reference to a captured variable, we provide an error that makes it more
clear what is happening.
[NLL] Improve closure region bound errors
Previously, we would report free region errors that originate from closure with the span of the closure and a "closure body requires ..." message. This is now updated to use a reason and span from inside the closure.
This commit updates the captured trait object search logic to look for
unsized casts to boxed types rather than for functions that returned
trait objects.
NLL: temps in block tail expression diagnostic
This change adds a diagnostic that explains when temporaries in a block tail expression live longer than block local variables that they borrow, and attempts to suggest turning the tail expresion into a statement (either by adding a semicolon at the end, when its result value is clearly unused, or by introducing a `let`-binding for the result value and then returning that).
Fix#54556
[NLL] Improve "borrow later used here" messages
* In the case of two conflicting borrows, the later used message says which borrow it's referring to
* If the later use is a function call (from the users point of view) say that the later use is for the call. Point just to the function.
r? @pnkfelix
Closes#48643
Give a special message when the later use is from a call. Use the span
of the callee instead of the whole expression. For conflicting borrow
messages say that the later use is of the first borrow.
NLL fails to suggest "try removing `&mut` here"
Fixes#51191.
This PR adds ``try removing `&mut` here`` suggestions to functions where a mutable borrow is being taken of a `&mut self` or a `self: &mut Self`. This PR also enables the suggestion for adding a `mut` pattern to by-value implicit self arguments without `mut` patterns already.
r? @nikomatsakis
This commit improves mutability error suggestions by suggesting the
removal of `&mut` where a mutable borrow is being taken of a `&mut self`
or a `self: &mut Self`.
This commit adds an `ImplicitSelfKind` to the HIR and the MIR that keeps
track of whether a implicit self argument is immutable by-value, mutable
by-value, immutable reference or mutable reference so that the addition
of the `mut` keyword can be suggested for the immutable by-value case.
This commit special cases the move out of borrowed content error,
previously:
```
error[E0507]: cannot move out of borrowed content
--> src/main.rs:7:10
|
7 | drop(x.field);
| ^ cannot move out of borrowed content
```
to instead mention that it is a move out of a `Rc`/`Arc` which is more
helpful:
```
error[E0507]: cannot move out of an `Rc`
--> src/main.rs:7:10
|
7 | drop(x.field);
| ^ cannot move out of an `Rc`
```
[NLL] Get Polonius borrow check to work in simple cases
* Restores the generation of outlives facts from subtyping.
* Restore liveness facts.
* Generate invalidates facts at the start point of each location,
where we check for errors.
* Add a small test for simple cases (previously these cases have compiled, and more recently ICEd).
Closes#54212
cc #53142 (will need test)
### Known limitations
* Two phase borrows aren't implemented for Polonius yet
* Invalidation facts haven't been updated for some of the recent changes to make `Drop` terminators access fewer things.
* Fact generation is not as optimized as it could be.
* Around 30 tests fail in compare mode, often tests that are ignored in nll compare mode
r? @nikomatsakis
NLL: regression test for "dropck: track order of destruction for r-value temporaries"
Once this lands, we can remove the E-needstest from #22323.
(We shouldn't close the bug itself, however, because we are leaving the NLL-fixed-by-NLL bugs open until NLL is turned on by default.)
* Restores the generation of outlives facts from subtyping.
* Restore liveness facts.
* Generate invalidates facts at the start point of each location,
where we check for errors.
* Add a small test for simple cases.
Before, if we had a projection like `<T as Foo<'0>>::Bar: 'x` and a
where clause like `<T as Foo<'a>>::Bar: 'a`, we considered those to
have nothing to do with one another. Therefore, we would use the
"overconstrained" path of adding `T: 'x` and `'0: 'x` requirements. We
now do a "fuzzy" match where we erase regions first and hence we see
the env bound `'a`.
Previously, we would split the drop access into multiple checks for each
field of a struct/tuple/closure and through `Box` dereferences. This
changes this to check if the borrow is accessed by the drop in
places_conflict.
This also allows us to handle enums in a simpler way, since we don't
have to construct any new places.
