Drop-Trait on ErrorVault — Developer Error Code Dictionary

Fix E0493: Destructor Cannot Be Called in Constant Function

Sat, 08 Aug 2026 22:20:04 +0800

1. Symptoms

When the Rust compiler encounters E0493, it produces an error message indicating that a destructor cannot be invoked during constant evaluation. The compiler provides context about which type’s destructor is problematic and where the invalid call occurs.

Typical compiler output looks like this:

error[E0493]: destructor of `MyStruct` cannot be called in constant function
  --> src/main.rs:10:5
   |
10 |     drop(value);
   |     ^^^^^^^^^^^ calling the destructor of `MyStruct` in constant function

The error manifests in several common scenarios. When using the drop function on a type that implements Drop inside a const fn, the compiler rejects the code. Similarly, when a constant initialization implicitly requires destructor execution, such as when a const value goes out of scope during const evaluation, the same error appears. Explicit calls to std::mem::drop within constant contexts also trigger this error when the dropped type has a custom destructor.

Fix E0796: Destructor Names Must Not Be Used Outside of Their Trait

Tue, 28 Jul 2026 00:44:04 +0800

1. Symptoms

When the Rust compiler encounters error E0796, you will see a message similar to the following in your build output:

error[E0796]: destructor names must not be used outside of their trait
  --> src/main.rs:10:5
   |
10 |     SomeType::drop(some_instance);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot call a destructor by name
   |
   = note: this error occurs if you try to call a destructor directly.
     Use the `std::mem::drop` function or implement the `Drop` trait instead.

The compiler will reject the code and halt compilation at the point where you attempted to invoke the destructor. Common patterns that trigger this error include explicit calls to TypeName::drop(), attempting to manually run cleanup code through the destructor mechanism, or trying to access drop-related internals directly from user code. The error message explicitly guides developers toward the std::mem::drop function as the idiomatic alternative for explicitly dropping values.

Fix E0161: the trait bound `Drop + Sized` is not satisfied

Wed, 22 Jul 2026 10:20:04 +0800

1. Symptoms

When the Rust compiler encounters error E0161, you will see output similar to the following in your terminal or IDE:

error[E0161]: the trait bound `Drop + Sized` is not satisfied
  --> src/main.rs:10:5
   |
10 |     fn drop(&mut self) { }
   |     ^^^^^^ unsized types have no automatic `Drop` implementations
   |
   = note: unsized types have no automatic `Drop` implementations
   = note: this error occurs because the type has a `Drop` implementation in the
     standard library, but not all its fields implement `Sized`
     = help: consider moving the `Drop` implementation to a wrapper type

The error message indicates that you are attempting to use a feature that requires the Sized bound, but the type in question is unsized. Unsized types in Rust include trait objects (dyn Trait), slices ([T]), and the string slice type (str). These types do not have a known size at compile time, which prevents certain operations that require knowing the exact memory layout of a type.