[clang] Make [[clang::lifetimebound]] work for expressions coming from default arguments (PR #112047)

[via cfe-commits]

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@@ -34,13 +38,20 @@ namespace usage_ok {
   struct A {
     A();
     A(int);
+    A(const char*, const int& def3 [[clang::lifetimebound]] = 0); // #def3
     int *class_member() [[clang::lifetimebound]];
     operator int*() [[clang::lifetimebound]];
+    static const int &defaulted_param(const int &def4 [[clang::lifetimebound]] = 0); // #def4
+    static const int &defaulted_param2(const int &def5 [[clang::lifetimebound]] = defaulted_param()); // #def5
   };
 
   int *p = A().class_member(); // expected-warning {{temporary whose address is used as value of local variable 'p' will be destroyed at the end of the full-expression}}
   int *q = A(); // expected-warning {{temporary whose address is used as value of local variable 'q' will be destroyed at the end of the full-expression}}
   int *r = A(1); // expected-warning {{temporary whose address is used as value of local variable 'r' will be destroyed at the end of the full-expression}}
+  A a = A(""); // expected-warning {{temporary whose address is used as value of local variable 'a' will be destroyed at the end of the full-expression}} expected-note@#def3 {{initializing parameter 'def3' with default argument}}
+  const int &s = A::defaulted_param(); // expected-warning {{temporary bound to local reference 's' will be destroyed at the end of the full-expression}} expected-note@#def4 {{initializing parameter 'def4' with default argument}}
+  const int &t = A::defaulted_param2(); // expected-warning {{temporary bound to local reference 't' will be destroyed at the end of the full-expression}} expected-note@#def4 {{initializing parameter 'def4' with default argument}} expected-note@#def5 {{initializing parameter 'def5' with default argument}}
+  const int &u = defaultparam_array(); // expected-warning {{temporary bound to local reference 'u' will be destroyed at the end of the full-expression}} expected-note@#def2 {{initializing parameter 'p' with default argument}}
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higher-performance wrote:

Done, but neither of those cases trigger for me, and I'm not sure if they should either, since the return type is a value. If the return type is a reference then they do trigger.

https://github.com/llvm/llvm-project/pull/112047