[clang] [clang-tools-extra] [libcxx] [clang] fix diagnostic printing of expressions ignoring LangOpts (PR #134693)

[Erich Keane via cfe-commits]

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@@ -7379,6 +7379,14 @@ class RecoveryExpr final : public Expr,
   friend class ASTStmtWriter;
 };
 
+/// Insertion operator for diagnostics.  This allows sending
+/// Expr into a diagnostic with <<.
+inline const StreamingDiagnostic &operator<<(const StreamingDiagnostic &DB,
+                                             const Expr *E) {
+  DB.AddTaggedVal(reinterpret_cast<uint64_t>(E), DiagnosticsEngine::ak_expr);
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erichkeane wrote:

`intptr_t` /`uintptr_t` I think avoids any 'round trip' errors by standard, but I think `uint64_t` is going to be the same type ANYWAY so this is probably harmless at least.  I think the suggestion to use `intptr_t`/`uintptr_t` is a good one that should happen.

https://github.com/llvm/llvm-project/pull/134693