From 78b9649d46c91f377cfc799aecb74cb017f72c36 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Fri, 11 Feb 2011 18:13:20 +0000
Subject: [PATCH] Poison the relational operators ==, !=, <, <=, >=, > on
 llvm::Optional objects, since they'll end up using the implicit conversion to
 "bool" and causing some very "fun" surprises.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125380 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/ADT/Optional.h | 54 +++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/include/llvm/ADT/Optional.h b/include/llvm/ADT/Optional.h
index 34e54a07a0e..ee8b69f3d12 100644
--- a/include/llvm/ADT/Optional.h
+++ b/include/llvm/ADT/Optional.h
@@ -61,6 +61,60 @@ template <typename T>
 struct simplify_type<Optional<T> >
   : public simplify_type<const Optional<T> > {};
 
+/// \brief Poison comparison between two \c Optional objects. Clients needs to
+/// explicitly compare the underlying values and account for empty \c Optional
+/// objects.
+///
+/// This routine will never be defined. It returns \c void to help diagnose 
+/// errors at compile time.
+template<typename T, typename U>
+void operator==(const Optional<T> &X, const Optional<U> &Y);
+
+/// \brief Poison comparison between two \c Optional objects. Clients needs to
+/// explicitly compare the underlying values and account for empty \c Optional
+/// objects.
+///
+/// This routine will never be defined. It returns \c void to help diagnose 
+/// errors at compile time.
+template<typename T, typename U>
+void operator!=(const Optional<T> &X, const Optional<U> &Y);
+
+/// \brief Poison comparison between two \c Optional objects. Clients needs to
+/// explicitly compare the underlying values and account for empty \c Optional
+/// objects.
+///
+/// This routine will never be defined. It returns \c void to help diagnose 
+/// errors at compile time.
+template<typename T, typename U>
+void operator<(const Optional<T> &X, const Optional<U> &Y);
+
+/// \brief Poison comparison between two \c Optional objects. Clients needs to
+/// explicitly compare the underlying values and account for empty \c Optional
+/// objects.
+///
+/// This routine will never be defined. It returns \c void to help diagnose 
+/// errors at compile time.
+template<typename T, typename U>
+void operator<=(const Optional<T> &X, const Optional<U> &Y);
+
+/// \brief Poison comparison between two \c Optional objects. Clients needs to
+/// explicitly compare the underlying values and account for empty \c Optional
+/// objects.
+///
+/// This routine will never be defined. It returns \c void to help diagnose 
+/// errors at compile time.
+template<typename T, typename U>
+void operator>=(const Optional<T> &X, const Optional<U> &Y);
+
+/// \brief Poison comparison between two \c Optional objects. Clients needs to
+/// explicitly compare the underlying values and account for empty \c Optional
+/// objects.
+///
+/// This routine will never be defined. It returns \c void to help diagnose 
+/// errors at compile time.
+template<typename T, typename U>
+void operator>(const Optional<T> &X, const Optional<U> &Y);
+
 } // end llvm namespace
 
 #endif