For scalable struct types, we do not know the exact size of the struct. Do not use memcpy for struct copy. We use extractvalue and insertvalue for the purpose.
nit: missing "a": is a sizeless type
Are SrcVec and DestVec the right names here? It took me a while to realise they're not vector types.
We could define Vec inside the loop?
I don't know if getContext().getASTRecordLayout(Record).getFieldCount() is expensive to compute, but this may be recomputing it on every iteration.