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Avoid core::mem::forget usage

Description​

The core::mem::forget function usage is a bad practice.

Exploit Scenario​

Consider the following ink! contract:

   #[ink(message)]
   pub fn forget_value(&mut self) {
       let forgotten_value = self.value;
       self.value = false;
       core::mem::forget(forgotten_value);
   }

The problem arises from the use of the core::mem::forget function. This function is used to forget about a value without running its destructor. This is a bad practice because it can lead to memory leaks, resource leaks and logic errors.

The vulnerable code example can be found here.

Remediation​

Use the pattern let _ = forgotten_value; or the .drop() method instead of core::mem::forget(forgotten_value);.

References​