From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Tue, 21 May 2013 22:29:20 +0000 (+0000)
Subject: PR16090: C++1y: treat undeduced 'auto' as a literal type, so that constexpr
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bdaeaed3e3293f1915cdf336f406d4d391331039;p=clang

PR16090: C++1y: treat undeduced 'auto' as a literal type, so that constexpr
function templates can use it as a return type.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182433 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index eacf367818..004e31af17 100644
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -1196,6 +1196,11 @@ bool Type::isLiteralType(ASTContext &Ctx) const {
     return true;
   }
 
+  // If this type hasn't been deduced yet, then conservatively assume that
+  // it'll work out to be a literal type.
+  if (isa<AutoType>(BaseTy->getCanonicalTypeInternal()))
+    return true;
+
   return false;
 }
 
diff --git a/test/SemaCXX/constant-expression-cxx1y.cpp b/test/SemaCXX/constant-expression-cxx1y.cpp
index ea0c9e6526..23b5d0b460 100644
--- a/test/SemaCXX/constant-expression-cxx1y.cpp
+++ b/test/SemaCXX/constant-expression-cxx1y.cpp
@@ -708,3 +708,10 @@ namespace switch_stmt {
   static_assert(test_copy("hello world", 10), "");
   static_assert(test_copy("hello world", 10), "");
 }
+
+namespace deduced_return_type {
+  constexpr auto f() { return 0; }
+  template<typename T> constexpr auto g(T t) { return t; }
+  static_assert(f() == 0, "");
+  static_assert(g(true), "");
+}