cannot move out of borrowed content
cannot move out of borrowed content in Rust means you attempted to transfer ownership of a value that you only have a reference (&T or &mut T) to, which would leave the referenced memory in an uninitialized state.
How do I fix cannot move out of borrowed content?
To fix cannot move out of borrowed content in Rust, locate the line causing the error and check the values right before it runs. Most occurrences happen because of extracting a string from a borrowed struct field. Apply a defensive check or safe fallback, make sure collections or objects exist before access, and verify return values from upstream functions.
What does cannot move out of borrowed content mean?
Rust strictly tracks ownership. When you borrow a reference to a struct or collection, you do not own the underlying memory. Moving a non-Copy type (such as String or Vec) out of a reference would deallocate or invalidate the original owner's data.
Why does cannot move out of borrowed content happen?
1. Extracting a String from a borrowed struct field
Moving field 'name' out of &User leaves the struct partially moved and broken.
Breaks
fn get_name(user: &User) -> String {
user.name // cannot move out of borrowed user!
}Works
fn get_name(user: &User) -> String {
user.name.clone() // clone to create a new owned instance
}2. Taking an item out of a vector via indexing
Indexing vec[0] produces a reference &T, not an owned T.
Breaks
let item = vec[0]; // cannot move out of vec[0]!Works
let item = vec.remove(0); // or vec.pop(), or vec[0].clone()How to find it in your own code
Use .clone() to produce an owned copy if the type implements Clone. If you own the container, use methods designed for extraction like Option::take(), std::mem::replace(), or Vec::remove(). Implement the Copy trait for lightweight types.
Try it: fix this bug
mediumMatch arm unconditionally matches because variable name binds a new pattern instead of comparing
fn match_expected_code(actual: i32, expected: i32) -> bool {
match actual {
// 'expected' here binds a new local variable shadowing the parameter!
expected => true,
_ => false,
}
}
fn main() {
println!("{}", match_expected_code(404, 200));
}More challenges with this error
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