[clang] [clang-tools-extra] Reland "[clang] Don't add documentation comments to the AST if not requested (#206363)" (PR #221605)

[via cfe-commits]

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@@ -589,6 +589,12 @@ class DiagnosticsEngine : public RefCountedBase<DiagnosticsEngine> {
     return GetDiagStateForLoc(Loc);
   }
 
+  /// Returns whether \p Loc is in a system header and/or a system macro, as a
+  /// value in [0, 4). Severity depends on this through
+  /// DiagnosticIDs::shouldSuppressAsSystemWarning(), so a cache keyed on
+  /// getDiagStateKeyForLoc() must take it into account as well.
+  unsigned getDiagStateSystemClassForLoc(SourceLocation Loc) const;
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AnonMiraj wrote:

Didn't think of it

https://github.com/llvm/llvm-project/pull/221605