This trait provides features for owned heap analysis, which is used to determine if a type owns
memory on heap. Owned heap should be automatically released by default.
This is the type for storing the heap analysis results.
The result is represented as a hashmap, where the key is DefId and the value contains the
information of whether the type contains data on heap.
Since a type could be a enumerate type, the value is represented as a vec, indicating the heap
information of each variant.
Also, because it may contain type parameters or generic types,
the heap information is a tuple containing the information of each type parameter.