[clang] [LifetimeSafety] Warn when lifetimebound attribute is present on the definition but not on declaration (PR #197753)

[Utkarsh Saxena via cfe-commits]

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@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -fsyntax-only -Wlifetime-safety-validations -Wno-dangling -verify %s
+
+struct MyObj {
+  ~MyObj() {}
+};
+
+struct S {
+  MyObj data;
+  const MyObj &implicit_this_only(); // expected-warning {{'lifetimebound' attribute on the definition is not visible to callers; add it to this declaration instead}}
+  const MyObj &param_only(const MyObj &obj); // expected-warning {{'lifetimebound' attribute on the definition is not visible to callers; add it to this declaration instead}}
+  const MyObj &both(const MyObj &obj, bool); // expected-warning 2 {{'lifetimebound' attribute on the definition is not visible to callers; add it to this declaration instead}}
+};
+
+const MyObj &S::implicit_this_only() [[clang::lifetimebound]] { // expected-note {{'lifetimebound' attribute written on the definition is here}}
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usx95 wrote:

Suggestion for note text:
`'lifetimebound' attribute appears here on the definition`

https://github.com/llvm/llvm-project/pull/197753