[clang] [analyzer] Fix [[clang::suppress]] for template instantiations (PR #168954)

[Balázs Benics via cfe-commits]

================
@@ -1,4 +1,27 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=core -verify %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify %s
+
+void clang_analyzer_warnIfReached();
+
+struct Clazz {
+  template <typename T>
+  static void templated_memfn();
+};
+
+// This must come before the 'templated_memfn' is defined!
+static void instantiate() {
+  Clazz::templated_memfn<int>();
+}
+
+template <typename T>
+void Clazz::templated_memfn() {
+  // When we report a bug in a function, we traverse the lexical decl context
+  // of it while looking for suppression attributes to record what source
----------------
steakhal wrote:

> Eg. you dereference a null smart pointer, and the warning is in the implementation of the overloaded dereference operator, so it'd make a lot of sense to put suppression at the call site of the dereference operator, so that you could keep getting warnings about the rest of null dereferences through that operator.

Eh, I'm not sure. Wouldn't that mean that in practice most callsites would need that attribute? Like if there is a branch in that definition, that happens to be triggered from almost all callsites. At that point, it would be very inconvenient to apply a suppression attribute at the callsites.

I agree that it feels niche.

https://github.com/llvm/llvm-project/pull/168954