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Previously, when rustc was provided an async function that tried to
mutate through a shared reference to an implicit self (as shown in the
ui test), rustc would suggest modifying the parameter signature
to `&mut` + the fully qualified name of the ty (in the case of the repro
`S`). If a user modified their code to match the suggestion, the
compiler would not accept it.
This commit modifies the suggestion so that when rustc is provided the
ui test that is also attached in this commit, it suggests (correctly)
`&mut self`. We try to be careful about distinguishing between implicit
and explicit self annotations, since the latter seem to be handled
correctly already.
Fixes rust-lang/rust#93093
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In Rust, nesting method calls with both require `&mut` access to `self`
produces a borrow-check error:
error[E0499]: cannot borrow `*self` as mutable more than once at a time
--> src/lib.rs:7:14
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7 | self.foo(self.bar());
| ---------^^^^^^^^^^-
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| | | second mutable borrow occurs here
| | first borrow later used by call
| first mutable borrow occurs here
That's because Rust has a left-to-right evaluation order, and the method
receiver is passed first. Thus, the argument to the method cannot then
mutate `self`.
There's an easy solution to this error: just extract a local variable
for the inner argument:
let tmp = self.bar();
self.foo(tmp);
However, the error doesn't give any suggestion of how to solve the
problem. As a result, new users may assume that it's impossible to
express their code correctly and get stuck.
This commit adds a (non-structured) suggestion to extract a local
variable for the inner argument to solve the error. The suggestion uses
heuristics that eliminate most false positives, though there are a few
false negatives (cases where the suggestion should be emitted but is
not). Those other cases can be implemented in a future change.
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Fix a format_args span to be expansion
I found this while exploring solutions for rust-lang/rust-clippy#7843.
r? `@m-ou-se`
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Add a regression test for #80772
Closes #80772
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Add check that live_region is live in sanitize_promoted
This pull request fixes #88434 by adding a check in `sanitize_promoted` to ensure that only regions which are actually live are added to the `liveness_constraints` of the `BorrowCheckContext`.
To implement this change, I needed to add a method to `LivenessValues` which gets the elements contained by a region:
/// Returns an iterator of all the elements contained by the region `r`
crate fn get_elements(&self, row: N) -> impl Iterator<Item = Location> + '_
Then, inside `sanitize_promoted`, we check whether the iterator returned by this method is non-empty to ensure that the region is actually live at at least one location before adding that region to the `liveness_constraints` of the `BorrowCheckContext`.
This is my first pull request to the Rust repo, so any feedback on how I can improve this pull request or if there is a better way to fix this issue would be very appreciated.
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Use larger span for adjustment THIR expressions
Currently, we use a relatively 'small' span for THIR
expressions generated by an 'adjustment' (e.g. an autoderef,
autoborrow, unsizing). As a result, if a borrow generated
by an adustment ends up causing a borrowcheck error, for example:
```rust
let mut my_var = String::new();
let my_ref = &my_var
my_var.push('a');
my_ref;
```
then the span for the mutable borrow may end up referring
to only the base expression (e.g. `my_var`), rather than
the method call which triggered the mutable borrow
(e.g. `my_var.push('a')`)
Due to a quirk of the MIR borrowck implementation,
this doesn't always get exposed in migration mode,
but it does in many cases.
This commit makes THIR building consistently use 'larger'
spans for adjustment expressions. These spans are recoded
when we first create the adjustment during typecheck. For
example, an autoref adjustment triggered by a method call
will record the span of the entire method call.
The intent of this change it make it clearer to users
when it's the specific way in which a variable is
used (for example, in a method call) that produdes
a borrowcheck error. For example, an error message
claiming that a 'mutable borrow occurs here' might
be confusing if it just points at a usage of a variable
(e.g. `my_var`), when no `&mut` is in sight. Pointing
at the entire expression should help to emphasize
that the method call itself is responsible for
the mutable borrow.
In several cases, this makes the `#![feature(nll)]` diagnostic
output match up exactly with the default (migration mode) output.
As a result, several `.nll.stderr` files end up getting removed
entirely.
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Currently, we use a relatively 'small' span for THIR
expressions generated by an 'adjustment' (e.g. an autoderef,
autoborrow, unsizing). As a result, if a borrow generated
by an adustment ends up causing a borrowcheck error, for example:
```rust
let mut my_var = String::new();
let my_ref = &my_var
my_var.push('a');
my_ref;
```
then the span for the mutable borrow may end up referring
to only the base expression (e.g. `my_var`), rather than
the method call which triggered the mutable borrow
(e.g. `my_var.push('a')`)
Due to a quirk of the MIR borrowck implementation,
this doesn't always get exposed in migration mode,
but it does in many cases.
This commit makes THIR building consistently use 'larger'
spans for adjustment expressions
The intent of this change it make it clearer to users
when it's the specific way in which a variable is
used (for example, in a method call) that produdes
a borrowcheck error. For example, an error message
claiming that a 'mutable borrow occurs here' might
be confusing if it just points at a usage of a variable
(e.g. `my_var`), when no `&mut` is in sight. Pointing
at the entire expression should help to emphasize
that the method call itself is responsible for
the mutable borrow.
In several cases, this makes the `#![feature(nll)]` diagnostic
output match up exactly with the default (migration mode) output.
As a result, several `.nll.stderr` files end up getting removed
entirely.
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This reduces unhelpful diagnostics down the road.
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r=nagisa
rustc: use more correct span data in for loop desugaring
Fixes #82462
Before:
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
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LL | for x in DroppingSlice(&*v).iter(); {
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After:
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
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LL | };
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This seems like a reasonable fix: since the desugared "expr_drop_temps_mut" contains the entire desugared loop construct, its span should contain the entire loop construct as well.
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The definition order is already close to the span order, and only differs
in corner cases.
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When calling a method requiring a mutable self borrow on an inmutable
to a mutable borrow of the type, suggest making the binding mutable.
Fix #83241.
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Before:
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
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LL | for x in DroppingSlice(&*v).iter(); {
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After:
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
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LL | };
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This seems like a reasonable fix: since the desugared "expr_drop_temps_mut"
contains the entire desugared loop construct, its span should contain the
entire loop construct as well.
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Previously, we would set up the source lines for `match` expressions so
that the code generated to perform the test of the scrutinee was matched
to the line of the arm that required the test and then jump from the arm
block to the "next" block was matched to all of the lines in the `match`
expression.
While that makes sense, it has the side effect of causing strange
stepping behavior in debuggers.
I've changed the source information so that all of the generated tests
are sourced to `match {scrutinee}` and the jumps are sourced to the last
line of the block they are inside. This resolves the weird stepping
behavior in all debuggers and resolves some instances of "ambiguous
symbol" errors in WinDbg preventing the user from setting breakpoints at
`match` expressions.
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* On suggestions that include deletions, use a diff inspired output format
* When suggesting addition, use `+` as underline
* Color highlight modified span
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* Use more accurate span for `async move` suggestion
* Use more accurate span for deref suggestion
* Use `multipart_suggestion` more often
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Make const panic!("..") work in Rust 2021.
During const eval, this replaces calls to core::panicking::panic_fmt and std::panicking::being_panic_fmt with a call to a new const fn: core::panicking::const_panic_fmt. That function uses fmt::Arguments::as_str() to get the str and calls panic_str with that instead.
panic!() invocations with formatting arguments are still not accepted, as the creation of such a fmt::Arguments cannot be done in constant functions right now.
r? `@RalfJung`
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Suggest removing unnecessary &mut as help message
Closes #68697
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Stabilize bindings_after_at
attempting to stabilze bindings_after_at [#65490](https://github.com/rust-lang/rust/issues/65490), im pretty new to the whole thing so any pointers are greatly appreciated.
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Revert "Add missing brace"
This reverts commit 85ad773049536d7fed9a94ae0ac74f97135c8655.
Revert "Simplify base_expr"
This reverts commit 899aae465eb4ef295dc1eeb2603f744568e0768c.
Revert "Warn write-only fields"
This reverts commit d3c69a4c0dd98af2611b7553d1a65afef6a6ccb0.
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Add help on reinitialization between move and access
Fixes #83760
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Fixes #83760
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