[clang][Tooling] Get rid of a hack in SymbolOccurrences, NFCI

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

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Basic/SourceLocation.cpp b/clang/lib/Basic/SourceLocation.cpp
index fde1399..6f64120 100644
--- a/clang/lib/Basic/SourceLocation.cpp
+++ b/clang/lib/Basic/SourceLocation.cpp
@@ -42,6 +42,14 @@ void PrettyStackTraceLoc::print(raw_ostream &OS) const {
 // SourceLocation
 //===----------------------------------------------------------------------===//
 
+static_assert(std::is_trivially_destructible<SourceLocation>::value,
+              "SourceLocation must be trivially destructible because it is "
+              "used in unions");
+
+static_assert(std::is_trivially_destructible<SourceRange>::value,
+              "SourceRange must be trivially destructible because it is "
+              "used in unions");
+
 unsigned SourceLocation::getHashValue() const {
   return llvm::DenseMapInfo<unsigned>::getHashValue(ID);
 }