[clang] [ASTMatcher] Fix redundant macro expansion checks in getExpansionLocOfMacro (PR #117143)

[Aaron Ballman via cfe-commits]

================
@@ -697,27 +698,61 @@ static bool isTokenAtLoc(const SourceManager &SM, const LangOptions &LangOpts,
   return !Invalid && Text == TokenText;
 }
 
-std::optional<SourceLocation>
-getExpansionLocOfMacro(StringRef MacroName, SourceLocation Loc,
-                       const ASTContext &Context) {
+namespace {
+struct SourceLocationHash {
+  std::size_t operator()(const SourceLocation &Loc) const {
+    return Loc.getHashValue();
+  }
+};
+
+struct SourceLocationEqual {
+  bool operator()(const SourceLocation &LHS, const SourceLocation &RHS) const {
+    return LHS == RHS;
+  }
+};
+
+} // namespace
+
+static std::optional<SourceLocation> getExpansionLocOfMacroRecursive(
+    StringRef MacroName, SourceLocation Loc, const ASTContext &Context,
+    std::unordered_set<SourceLocation, SourceLocationHash, SourceLocationEqual>
+        &CheckedLocations) {
   auto &SM = Context.getSourceManager();
   const LangOptions &LangOpts = Context.getLangOpts();
   while (Loc.isMacroID()) {
+    if (CheckedLocations.count(Loc)) {
+      return std::nullopt;
+    }
----------------
AaronBallman wrote:

```suggestion
    if (CheckedLocations.count(Loc))
      return std::nullopt;
```
We have very odd coding style rules, sorry. :-)

https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

https://github.com/llvm/llvm-project/pull/117143