[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[Boaz Brickner via cfe-commits]

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@@ -575,25 +575,42 @@ DiagnosticIDs::getDiagnosticSeverity(unsigned DiagID, SourceLocation Loc,
       DiagID != diag::fatal_too_many_errors && Diag.FatalsAsError)
     Result = diag::Severity::Error;
 
+  // Rest of the mappings are only applicable for diagnostics associated with a
+  // SourceLocation, bail out early for others.
+  if (!Diag.hasSourceManager())
+    return Result;
+
+  const auto &SM = Diag.getSourceManager();
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bricknerb wrote:

This is typically called SrcMgr and typically we keep the full name and don't use auto.

https://github.com/llvm/llvm-project/pull/112517