[clang] [clang] Diagnose dangling issues for the "Container<GSLPointer>" case. (PR #107213)

[Utkarsh Saxena via cfe-commits]

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@@ -525,3 +544,31 @@ void test() {
   std::string_view svjkk1 = ReturnStringView(StrCat("bar", "x")); // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
 }
 } // namespace GH100549
+
+namespace GH100526 {
+void test() {
+  std::vector<std::string_view> v1({std::string()}); // expected-warning {{object backing the pointer will be destroyed at the end}}
+  std::vector<std::string_view> v2({std::string(), std::string_view()}); // expected-warning {{object backing the pointer will be destroyed at the end}}
+  std::vector<std::string_view> v3({std::string_view(), std::string()}); // expected-warning {{object backing the pointer will be destroyed at the end}}
+
+  std::optional<std::string_view> o1 = std::string(); // expected-warning {{object backing the pointer}}
+
+  std::string s;
+  // This is a tricky use-after-free case, what it does:
+  //   1. make_optional creates a temporary "optional<string>"" object
+  //   2. the temporary object owns the underlying string which is copied from s.
+  //   3. the t3 object holds the view to the underlying string of the temporary object.
+  std::optional<std::string_view> o2 = std::make_optional(s); // expected-warning {{object backing the pointer}}
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usx95 wrote:

IIUC this is catching the case when a `Container<Pointer>` is constructed from temporary `Container<Owner>`
Can you also add a more intuitive case like `std::optional<std::string_view> o2 = std::optional<std::string>(s);`

https://github.com/llvm/llvm-project/pull/107213