Fix E0669: Non-const function call in const context

Sun, 02 Aug 2026 12:44:04 +0800

1. Symptoms

When you encounter error E0669, the Rust compiler produces output similar to the following:

error[E0669]: calls in constants are limited to inherent functions, structs, variants, and trait methods
  --> src/main.rs:6:5
   |
6  |     do_something();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The error message indicates that the function call cannot be evaluated at compile time because the called function lacks the const qualifier. The compiler explicitly states that constant evaluation contexts are restricted to inherent functions, struct constructors, enum variant constructors, and trait methods that have been marked as const.

E0669 on ErrorVault — Developer Error Code Dictionary

Fix E0669: Non-const function call in const context

1. Symptoms