[clang] [Coverage][Expansion] handle nested macros in scratch space (PR #89869)

[Wentao Zhang via cfe-commits]

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@@ -292,10 +292,36 @@ class CoverageMappingBuilder {
     return SM.getLocForEndOfFile(SM.getFileID(Loc));
   }
 
-  /// Find out where the current file is included or macro is expanded.
-  SourceLocation getIncludeOrExpansionLoc(SourceLocation Loc) {
-    return Loc.isMacroID() ? SM.getImmediateExpansionRange(Loc).getBegin()
-                           : SM.getIncludeLoc(SM.getFileID(Loc));
+  /// Find out where a macro is expanded. If the immediate result is a
+  /// <scratch space>, keep looking until the result isn't. Return the source
+  /// range of the found result, or std::nullopt if the while loop didn't get
+  /// executed, which means the location wasn't changed.
+  std::optional<SourceRange> getNonScratchExpansion(SourceLocation Loc) {
+    std::optional<SourceLocation> EndLoc = std::nullopt;
+    while (Loc.isMacroID() &&
+           SM.isWrittenInScratchSpace(SM.getSpellingLoc(Loc))) {
+      auto ExpansionRange = SM.getImmediateExpansionRange(Loc);
+      Loc = ExpansionRange.getBegin();
+      EndLoc = ExpansionRange.getEnd();
+    }
+    if (EndLoc.has_value())
+      return SourceRange(Loc, EndLoc.value());
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whentojump wrote:

> Actually returns CharSourceRange.

True. Ideally we can circulate around `CharSourceRange` without converting back and forth too much but I found it hard to make both two callers clean and straightforward. 

> You may rewind them 

I can do that, meanwhile I'll also seek if there's a better way



https://github.com/llvm/llvm-project/pull/89869