Fix E0506: cannot assign twice to borrowed content

Sun, 09 Aug 2026 22:20:04 +0800

1. Symptoms

When the Rust compiler encounters error E0506, you will see the following diagnostic message in your build output:

error[E0506]: cannot assign twice to borrowed content
  --> src/main.rs:XX:YY
   |
LL |     let r = &s;
   |          -- borrow of `s` occurs here
...
LL |     s = String::from("reassignment");
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed `s` occurs here

The compiler identifies two distinct locations in your code: the line where the borrow begins and the line where the problematic reassignment occurs. The error message emphasizes that the content of s is borrowed at the first location, and attempting to assign a new value at the second location violates Rust’s ownership rules.

E0506 on ErrorVault — Developer Error Code Dictionary

Fix E0506: cannot assign twice to borrowed content

1. Symptoms