Rust errors / Everything else
Rust compiler error · checked with rustc 1.99.0
Rust error E0301: #### Note: this error code is no longer emitted by the compiler
What it means#### Note: this error code is no longer emitted by the compiler.
Retired: rustc no longer emits this error code. You may still see it in old answers, books and CI logs from older toolchains; the explanation below is kept for reference.
The compiler team's explanation
Note: this error code is no longer emitted by the compiler.
Mutable borrows are not allowed in pattern guards, because matching cannot have side effects. Side effects could alter the matched object or the environment on which the match depends in such a way, that the match would not be exhaustive. For instance, the following would not match any arm if mutable borrows were allowed:
match Some(()) {
None => { },
option if option.take().is_none() => {
/* impossible, option is `Some` */
},
Some(_) => { } // When the previous match failed, the option became `None`.
}From rustc --explain E0301 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
Related errors
- E0061this function takes N arguments but M were supplied
- E0412cannot find type in this scope
- E0515cannot return reference to local variable
- E0728await is only allowed inside async functions and blocks
- E0267`break` inside of a closure
- E0268`break` outside of a loop or labeled block
- E0317`if` may be missing an `else` clause
- E0320overflow while adding drop-check rules for `A<T>`
Up next
Often hit nextE0061: this function takes N arguments but M were suppliedA related error from the same family.Read it next →Did this answer your question?