tl;dr:Adrian discusses the issue of memory fragmentation in Rust, particularly when using Enums with different-sized variants explaining that one of the biggest motivators for efficient Enum arrays has been compilers, as "Big ASTs can incur a hefty performance penalty during compilation." The article suggests using a "struct-of-arrays" (SoA) approach or creating one vector per variant, termed as "array of variant arrays" (AoVA), to mitigate fragmentation.