[clang] [analyzer] Fix timing of `PostStmt<CXXDeleteExpr>` (PR #215828)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-static-analyzer-1

Author: Donát Nagy (NagyDonat)

<details>
<summary>Changes</summary>

When `ExprEngine::Visit` visits a statement, it usually first invokes the `PreStmt` callbacks, then performs the statement-specific visitation logic, then finally invokes the `PostStmt` callbacks.

Before this commit, `CXXDeleteExpr` did not follow this regular pattern, because it invoked the `PostStmt` callbacks before the statement-specific logic. This exceptional logic was introduced in 2020 by commit 9d69072fb80755a0029a01c74892b4bf03f20f65 and I confirmed with the author of that commit that the unusual order is not intentional -- it is just an accidental mistake.

This commit ensures that `CXXDeleteExpr` also follows the standard order by swapping the `PostStmt` step and the `VisitCXXDeleteExpr()` call.

As no (upstream) checkers use the `PostStmt<CXXDeleteExpr>` callback, this is -- in practice -- a non-functional change. (The inconsistency was spotted by Gábor Tóthvári in the source code.)

---
Full diff: https://github.com/llvm/llvm-project/pull/215828.diff


1 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Core/ExprEngine.cpp (+4-4) 


``````````diff
diff --git a/clang/lib/StaticAnalyzer/Core/ExprEngine.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngine.cpp
index 328ed5b23dd83..dd1088d1aaafb 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngine.cpp
@@ -2133,12 +2133,12 @@ void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred,
       ExplodedNodeSet PreVisit;
       const auto *CDE = cast<CXXDeleteExpr>(S);
       getCheckerManager().runCheckersForPreStmt(PreVisit, Pred, S, *this);
-      ExplodedNodeSet PostVisit;
-      getCheckerManager().runCheckersForPostStmt(PostVisit, PreVisit, S, *this);
 
-      for (const auto i : PostVisit)
-        VisitCXXDeleteExpr(CDE, i, Dst);
+      ExplodedNodeSet PostVisit;
+      for (const auto i : PreVisit)
+        VisitCXXDeleteExpr(CDE, i, PostVisit);
 
+      getCheckerManager().runCheckersForPostStmt(Dst, PostVisit, S, *this);
       break;
     }
       // FIXME: ChooseExpr is really a constant.  We need to fix

``````````

</details>


https://github.com/llvm/llvm-project/pull/215828