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

[Boaz Brickner via cfe-commits]

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@@ -1199,6 +1207,21 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
       break;
     }
 
+    case LK_LifetimeCapture: {
+      if (!MTE)
+        return false;
+      assert(shouldLifetimeExtendThroughPath(Path) ==
+                 PathLifetimeKind::NoExtend &&
+             "No lifetime extension in function calls");
+      if (CapEntity->Entity != nullptr)
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bricknerb wrote:

Seems like we typically (see line 1211 for example) don't compare to nullptr.

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