Add mapping to unelaborated types. UnelaboratedTypeOf(Decl)

[GorNishanov]

typedef int MyInt;
MyInt* x;

The IPR declaration of x knows it is type int*, information about MyInt is discarded.
We would like to have a mapping that allows to discover what user has written to declare x.
Maybe something like:

Optional<Type> UnelaboratedTypeOf(const Decl&);

If an alias/typedef was involved, the UnelaboratedTypeOf(Decl) will give As_type(MyInt)* type.

[GabrielDosReis]

I agree that declarations, being generative, are places where additional declarative semantics fluff can be added. However the type asked for here is still elaborated -- imagine uses of template aliases (one still wants elaboration). There is a delicate balance to strike here between syntax and semantics. Ideally there should be a separate syntax tree that is mapped to the semantics (IPR), and there should be (ideally) a way to query the original alias type used to declare a name in the IPR decl node.