[clang] [NFC][Clang] Adopt simplified `getTrailingObjects` in Expr.cpp/h (PR #140102)

[Erich Keane via cfe-commits]

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@@ -5043,16 +5037,18 @@ PseudoObjectExpr::PseudoObjectExpr(QualType type, ExprValueKind VK,
     : Expr(PseudoObjectExprClass, type, VK, OK_Ordinary) {
   PseudoObjectExprBits.NumSubExprs = semantics.size() + 1;
   PseudoObjectExprBits.ResultIndex = resultIndex + 1;
-
-  for (unsigned i = 0, e = semantics.size() + 1; i != e; ++i) {
-    Expr *E = (i == 0 ? syntax : semantics[i-1]);
-    getSubExprsBuffer()[i] = E;
-
-    if (isa<OpaqueValueExpr>(E))
-      assert(cast<OpaqueValueExpr>(E)->getSourceExpr() != nullptr &&
+  MutableArrayRef<Expr *> Trail = getTrailingObjects(semantics.size() + 1);
+  Trail[0] = syntax;
+  llvm::copy(semantics, Trail.drop_front().begin());
+
+#ifndef NDEBUG
+  llvm::for_each(semantics, [](const Expr *E) {
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erichkeane wrote:

wonder if an:

`assert(llvm::all_of(semantics, [](const Expr *E) { return !isa<OpaqueValueExpr>(E) || cast<OpaqueValueExpr>(E)->getSourceExpr() != nullptr; }) && "string stuff");`

would read better/be less intrusive?  WDYT?

https://github.com/llvm/llvm-project/pull/140102