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Tips & Traps¶
The closest thing to describe Rust Enum is tagged Union. The Rust compiler adds an extra (up to) 8 bytes to the enum to store the discriminator. This is used to identify the variant currently stored in the enum. However, Rust does NOT guarantee that the memory layout of an enum is always a tag followed by a union. Instead, the Rust compiler retains the freedom to optimize the layout of types so that the code can be more memory efficient.