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rust/tests/ui/borrowck/suggest-local-var-imm-and-mut.stderr

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Suggest using a temporary variable to fix borrowck errors 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 | 7 | self.foo(self.bar()); | ---------^^^^^^^^^^- | | | | | | | 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.
2021-03-15 17:09:06 -05:00
error[E0502]: cannot borrow `*self` as mutable because it is also borrowed as immutable
--> $DIR/suggest-local-var-imm-and-mut.rs:12:22
|
LL | self.foo(self.bar());
Do not set up wrong span for adjustments
2023-06-22 15:30:23 -05:00
| ---- --- ^^^^^^^^^^ mutable borrow occurs here
| | |
Suggest using a temporary variable to fix borrowck errors 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 | 7 | self.foo(self.bar()); | ---------^^^^^^^^^^- | | | | | | | 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.
2021-03-15 17:09:06 -05:00
| | immutable borrow later used by call
| immutable borrow occurs here
error[E0502]: cannot borrow `*self` as mutable because it is also borrowed as immutable
--> $DIR/suggest-local-var-imm-and-mut.rs:24:29
|
LL | Self::foo(self, Self::bar(self));
| --------- ---- ^^^^^^^^^^^^^^^ mutable borrow occurs here
| | |
| | immutable borrow occurs here
| immutable borrow later used by call
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0502`.
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