[clang] [clang] Implement lifetime analysis for lifetime_capture_by(X) (PR #115921)

[Utkarsh Saxena via cfe-commits]

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@@ -793,3 +793,108 @@ void test13() {
 }
 
 } // namespace GH100526
+
+namespace lifetime_capture_by {
+struct S {
+  const int *x;
+  void captureInt(const int&x [[clang::lifetime_capture_by(this)]]) { this->x = &x; }
+  void captureSV(std::string_view sv [[clang::lifetime_capture_by(this)]]);
+};
+///////////////////////////
+// Detect dangling cases.
+///////////////////////////
+void captureInt(const int&x [[clang::lifetime_capture_by(s)]], S&s);
+void captureRValInt(int&&x [[clang::lifetime_capture_by(s)]], S&s);
+void noCaptureInt(int x [[clang::lifetime_capture_by(s)]], S&s);
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usx95 wrote:

SG. I will add an error diagnositc on use of this annotation on non-reference and non-view types. But I prefer to do this in a followup PR.

https://github.com/llvm/llvm-project/pull/115921