[clang] [Clang] fix missing source location for ':' error in macro-expanded case statements (PR #143460)

[Eli Friedman via cfe-commits]

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@@ -833,9 +833,23 @@ StmtResult Parser::ParseCaseStatement(ParsedStmtContext StmtCtx,
           << FixItHint::CreateReplacement(ColonLoc, ":");
     } else {
       SourceLocation ExpectedLoc = PP.getLocForEndOfToken(PrevTokLocation);
+      SourceLocation ExprLoc =
+          LHS.get() ? LHS.get()->getExprLoc() : SourceLocation();
+
+      if (ExpectedLoc.isInvalid() && ExprLoc.isMacroID()) {
+        ExpectedLoc = PP.getSourceManager().getSpellingLoc(ExprLoc);
+      }
+
       Diag(ExpectedLoc, diag::err_expected_after)
           << "'case'" << tok::colon
           << FixItHint::CreateInsertion(ExpectedLoc, ":");
+
+      if (ExprLoc.isMacroID()) {
+        Diag(ExprLoc, diag::note_macro_expansion)
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efriedma-quic wrote:

We usually let the diagnostic infrastructure generate this sort of note; trying to write it out is likely to get it wrong.

https://github.com/llvm/llvm-project/pull/143460