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6eaa7fb576
Detect borrow checker errors where `.clone()` would be an appropriate user action
When a value is moved twice, suggest cloning the earlier move:
```
error[E0509]: cannot move out of type `U2`, which implements the `Drop` trait
--> $DIR/union-move.rs:49:18
|
LL | move_out(x.f1_nocopy);
| ^^^^^^^^^^^
| |
| cannot move out of here
| move occurs because `x.f1_nocopy` has type `ManuallyDrop<RefCell<i32>>`, which does not implement the `Copy` trait
|
help: consider cloning the value if the performance cost is acceptable
|
LL | move_out(x.f1_nocopy.clone());
| ++++++++
```
When a value is borrowed by an `fn` call, consider if cloning the result of the call would be reasonable, and suggest cloning that, instead of the argument:
```
error[E0505]: cannot move out of `a` because it is borrowed
--> $DIR/variance-issue-20533.rs:53:14
|
LL | let a = AffineU32(1);
| - binding `a` declared here
LL | let x = bat(&a);
| -- borrow of `a` occurs here
LL | drop(a);
| ^ move out of `a` occurs here
LL | drop(x);
| - borrow later used here
|
help: consider cloning the value if the performance cost is acceptable
|
LL | let x = bat(&a).clone();
| ++++++++
```
otherwise, suggest cloning the argument:
```
error[E0505]: cannot move out of `a` because it is borrowed
--> $DIR/variance-issue-20533.rs:59:14
|
LL | let a = ClonableAffineU32(1);
| - binding `a` declared here
LL | let x = foo(&a);
| -- borrow of `a` occurs here
LL | drop(a);
| ^ move out of `a` occurs here
LL | drop(x);
| - borrow later used here
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let x = foo(&a);
LL + let x = foo(a.clone());
|
```
This suggestion doesn't attempt to square out the types between what's cloned and what the `fn` expects, to allow the user to make a determination on whether to change the `fn` call or `fn` definition themselves.
Special case move errors caused by `FnOnce`:
```
error[E0382]: use of moved value: `blk`
--> $DIR/once-cant-call-twice-on-heap.rs:8:5
|
LL | fn foo<F:FnOnce()>(blk: F) {
| --- move occurs because `blk` has type `F`, which does not implement the `Copy` trait
LL | blk();
| ----- `blk` moved due to this call
LL | blk();
| ^^^ value used here after move
|
note: `FnOnce` closures can only be called once
--> $DIR/once-cant-call-twice-on-heap.rs:6:10
|
LL | fn foo<F:FnOnce()>(blk: F) {
| ^^^^^^^^ `F` is made to be an `FnOnce` closure here
LL | blk();
| ----- this value implements `FnOnce`, which causes it to be moved when called
```
Account for redundant `.clone()` calls in resulting suggestions:
```
error[E0507]: cannot move out of dereference of `S`
--> $DIR/needs-clone-through-deref.rs:15:18
|
LL | for _ in self.clone().into_iter() {}
| ^^^^^^^^^^^^ ----------- value moved due to this method call
| |
| move occurs because value has type `Vec<usize>`, which does not implement the `Copy` trait
|
note: `into_iter` takes ownership of the receiver `self`, which moves value
--> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
help: you can `clone` the value and consume it, but this might not be your desired behavior
|
LL | for _ in <Vec<usize> as Clone>::clone(&self).into_iter() {}
| ++++++++++++++++++++++++++++++ ~
```
We use the presence of `&mut` values in a move error as a proxy for the user caring about side effects, so we don't emit a clone suggestion in that case:
```
error[E0505]: cannot move out of `s` because it is borrowed
--> $DIR/borrowck-overloaded-index-move-index.rs:53:7
|
LL | let mut s = "hello".to_string();
| ----- binding `s` declared here
LL | let rs = &mut s;
| ------ borrow of `s` occurs here
...
LL | f[s] = 10;
| ^ move out of `s` occurs here
...
LL | use_mut(rs);
| -- borrow later used here
```
We properly account for `foo += foo;` errors where we *don't* suggest `foo.clone() += foo;`, instead suggesting `foo += foo.clone();`.
---
Each commit can be reviewed in isolation. There are some "cleanup" commits, but kept them separate in order to show *why* specific changes were being made, and their effect on tests' output.
Fix #49693, CC #64167.
|
||
|---|---|---|
| .. | ||
| assignment-of-clone-call-on-ref-due-to-missing-bound.fixed | ||
| assignment-of-clone-call-on-ref-due-to-missing-bound.rs | ||
| assignment-of-clone-call-on-ref-due-to-missing-bound.stderr | ||
| borrow-closures-instead-of-move.rs | ||
| borrow-closures-instead-of-move.stderr | ||
| issue-22536-copy-mustnt-zero.rs | ||
| issue-22536-copy-mustnt-zero.stderr | ||
| issue-34721.fixed | ||
| issue-34721.rs | ||
| issue-34721.stderr | ||
| issue-46099-move-in-macro.rs | ||
| issue-46099-move-in-macro.stderr | ||
| issue-72649-uninit-in-loop.rs | ||
| issue-72649-uninit-in-loop.stderr | ||
| issue-75904-move-closure-loop.rs | ||
| issue-75904-move-closure-loop.stderr | ||
| issue-99470-move-out-of-some.rs | ||
| issue-99470-move-out-of-some.stderr | ||
| move-1-unique.rs | ||
| move-2-unique.rs | ||
| move-2.rs | ||
| move-3-unique.rs | ||
| move-4-unique.rs | ||
| move-4.rs | ||
| move-arg-2-unique.rs | ||
| move-arg-2.rs | ||
| move-arg.rs | ||
| move-deref-coercion.rs | ||
| move-deref-coercion.stderr | ||
| move-fn-self-receiver.rs | ||
| move-fn-self-receiver.stderr | ||
| move-guard-same-consts.rs | ||
| move-guard-same-consts.stderr | ||
| move-in-guard-1.rs | ||
| move-in-guard-1.stderr | ||
| move-in-guard-2.rs | ||
| move-in-guard-2.stderr | ||
| move-into-dead-array-1.rs | ||
| move-into-dead-array-1.stderr | ||
| move-into-dead-array-2.rs | ||
| move-into-dead-array-2.stderr | ||
| move-nullary-fn.rs | ||
| move-of-addr-of-mut.rs | ||
| move-of-addr-of-mut.stderr | ||
| move-out-of-array-1.rs | ||
| move-out-of-array-1.stderr | ||
| move-out-of-array-ref.rs | ||
| move-out-of-array-ref.stderr | ||
| move-out-of-field.rs | ||
| move-out-of-slice-1.rs | ||
| move-out-of-slice-1.stderr | ||
| move-out-of-slice-2.rs | ||
| move-out-of-slice-2.stderr | ||
| move-out-of-tuple-field.rs | ||
| move-out-of-tuple-field.stderr | ||
| move-scalar.rs | ||
| moves-based-on-type-access-to-field.rs | ||
| moves-based-on-type-access-to-field.stderr | ||
| moves-based-on-type-block-bad.rs | ||
| moves-based-on-type-block-bad.stderr | ||
| moves-based-on-type-capture-clause-bad.rs | ||
| moves-based-on-type-capture-clause-bad.stderr | ||
| moves-based-on-type-capture-clause.rs | ||
| moves-based-on-type-cyclic-types-issue-4821.rs | ||
| moves-based-on-type-cyclic-types-issue-4821.stderr | ||
| moves-based-on-type-distribute-copy-over-paren.rs | ||
| moves-based-on-type-distribute-copy-over-paren.stderr | ||
| moves-based-on-type-exprs.rs | ||
| moves-based-on-type-exprs.stderr | ||
| moves-based-on-type-match-bindings.rs | ||
| moves-based-on-type-match-bindings.stderr | ||
| moves-based-on-type-move-out-of-closure-env-issue-1965.rs | ||
| moves-based-on-type-move-out-of-closure-env-issue-1965.stderr | ||
| moves-based-on-type-no-recursive-stack-closure.rs | ||
| moves-based-on-type-no-recursive-stack-closure.stderr | ||
| moves-based-on-type-tuple.rs | ||
| moves-based-on-type-tuple.stderr | ||
| moves-sru-moved-field.rs | ||
| moves-sru-moved-field.stderr | ||
| needs-clone-through-deref.fixed | ||
| needs-clone-through-deref.rs | ||
| needs-clone-through-deref.stderr | ||
| nested-loop-moved-value-wrong-continue.rs | ||
| nested-loop-moved-value-wrong-continue.stderr | ||
| pin-mut-reborrow-infer-var-issue-107419.fixed | ||
| pin-mut-reborrow-infer-var-issue-107419.rs | ||
| pin-mut-reborrow-infer-var-issue-107419.stderr | ||
| pin-mut-reborrow.fixed | ||
| pin-mut-reborrow.rs | ||
| pin-mut-reborrow.stderr | ||
| recreating-value-in-loop-condition.rs | ||
| recreating-value-in-loop-condition.stderr | ||
| suggest-clone-when-some-obligation-is-unmet.fixed | ||
| suggest-clone-when-some-obligation-is-unmet.rs | ||
| suggest-clone-when-some-obligation-is-unmet.stderr | ||
| suggest-clone.fixed | ||
| suggest-clone.rs | ||
| suggest-clone.stderr | ||
| use_of_moved_value_clone_suggestions.rs | ||
| use_of_moved_value_clone_suggestions.stderr | ||
| use_of_moved_value_copy_suggestions.fixed | ||
| use_of_moved_value_copy_suggestions.rs | ||
| use_of_moved_value_copy_suggestions.stderr | ||