The class `SymbolOccurrences` can store either a single `SourceRange`
in-place or multiple `SourceRanges` on the heap. In the latter case
the number of source ranges is stored in the internal representation
of the beginning `SourceLocation` of the in-place `SourceRange`
object.
This change gets rid of such hack by placing `SourceRange` in a union
which holds either a valid `SourceRange` or an `unsigned int` (a number
of ranges).
The change also adds `static_assert`s that check that `SourceRange` and
`SourceLocation` are trivially destructible (this is required for the
current patch and for D94237 which has already been committed).
Reviewed By: MarkMurrayARM, simon_tatham
Differential Revision: https://reviews.llvm.org/D94599
a0e30914f8