-/// Once allocated, Types are never free'd, unless they are an abstract type
-/// that is resolved to a more concrete type.
-///
-/// Types themself don't have a name, and can be named either by:
-/// - using SymbolTable instance, typically from some Module,
-/// - using convenience methods in the Module class (which uses module's
-/// SymbolTable too).
-///
-/// Opaque types are simple derived types with no state. There may be many
-/// different Opaque type objects floating around, but two are only considered
-/// identical if they are pointer equals of each other. This allows us to have
-/// two opaque types that end up resolving to different concrete types later.
-///
-/// Opaque types are also kinda weird and scary and different because they have
-/// to keep a list of uses of the type. When, through linking, parsing, or
-/// bitcode reading, they become resolved, they need to find and update all
-/// users of the unknown type, causing them to reference a new, more concrete
-/// type. Opaque types are deleted when their use list dwindles to zero users.
-///
-/// @brief Root of type hierarchy
-class Type : public AbstractTypeUser {