[clang-tools-extra] [clang-tidy] Speed up deduplicating warnings from alias checks (PR #174237)

[Victor Chernyakin via cfe-commits]

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@@ -760,9 +758,9 @@ struct LessClangTidyError {
     const tooling::DiagnosticMessage &M1 = LHS.Message;
     const tooling::DiagnosticMessage &M2 = RHS.Message;
 
-    return std::tie(M1.FilePath, M1.FileOffset, LHS.DiagnosticName,
-                    M1.Message) <
-           std::tie(M2.FilePath, M2.FileOffset, RHS.DiagnosticName, M2.Message);
+    return std::tie(M1.FilePath, M1.FileOffset, M1.Message,
+                    LHS.DiagnosticName) <
+           std::tie(M2.FilePath, M2.FileOffset, M2.Message, RHS.DiagnosticName);
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localspook wrote:

Having `DiagnosticName` (i.e. the check name) last means sorting using this predicate puts duplicate diagnostics into consecutive runs. This enables us to do away with the `UniqueErrorSet` in `removeDuplicatedDiagnosticsOfAliasCheckers`.

https://github.com/llvm/llvm-project/pull/174237