The Rust function core::slice::cmp::memcmp has the symbol name memcmp, which is the intrinsic it compiles to. The intrinsic uses void* pointers (which is the type stored in the symbol table), but they are *const u8 on the Rust side. This means that we cannot trust the type in the symbol table, so we have to use the output of codegen_function_sig to generate the correct Rust type, which adds redundancy and confusion.

Maybe the correct solution for this would be to treat core::slice::cmp::memcmp as an intrinsic. Currently, the instance returned is InstanceDef::Item, not InstanceDef::Intrinsic, so Kani generates code as for a normal function, but still has the problem of mismatched types.

This was discovered in #1338..