[clang] [analyzer] Fix [[clang::suppress]] for tricky template specializations (PR #178441)

[Ziqing Luo via cfe-commits]

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@@ -182,6 +233,15 @@ bool BugSuppression::isSuppressed(const PathDiagnosticLocation &Location,
     // declaration that isn't TranslationUnitDecl, because we should respect
     // attributes on the entire declaration chain.
     while (true) {
+
+      // Template specializations (e.g., Wrapper<int>) should inherit
+      // suppression attributes from their primary template or partial
+      // specialization. Transform specializations to their template definitions
+      // before checking for suppressions or walking up the lexical parent
+      // chain.
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ziqingluo-90 wrote:

So far my understanding is:
- Template specialization is fine--it does inherit suppression attributes (according to the printed AST).
- The reason that we need this fix is that `getLexicalDeclContext` is not doing what we expect it to do. Though it may not be a bug in `getLexicalDeclContext` because I do not know if "lexical parent of a template specialization" is well defined.

https://github.com/llvm/llvm-project/pull/178441