PR18746: If a constexpr function has a dependent return type and no return
statements, don't diagnose; the return type might end up being 'void'.
Patch by Rahul Jain! Tiny tweaks by me.
llvm-svn: 206929
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 96c6360..197518f 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -1175,10 +1175,12 @@
} else {
if (ReturnStmts.empty()) {
// C++1y doesn't require constexpr functions to contain a 'return'
- // statement. We still do, unless the return type is void, because
+ // statement. We still do, unless the return type might be void, because
// otherwise if there's no return statement, the function cannot
// be used in a core constant expression.
- bool OK = getLangOpts().CPlusPlus1y && Dcl->getReturnType()->isVoidType();
+ bool OK = getLangOpts().CPlusPlus1y &&
+ (Dcl->getReturnType()->isVoidType() ||
+ Dcl->getReturnType()->isDependentType());
Diag(Dcl->getLocation(),
OK ? diag::warn_cxx11_compat_constexpr_body_no_return
: diag::err_constexpr_body_no_return);
diff --git a/clang/test/SemaCXX/cxx1y-deduced-return-type.cpp b/clang/test/SemaCXX/cxx1y-deduced-return-type.cpp
index d3308b3..6086416 100644
--- a/clang/test/SemaCXX/cxx1y-deduced-return-type.cpp
+++ b/clang/test/SemaCXX/cxx1y-deduced-return-type.cpp
@@ -261,6 +261,13 @@
namespace Constexpr {
constexpr auto f1(int n) { return n; }
+ template<typename T> struct X { constexpr auto f() {} }; // PR18746
+ template<typename T> struct Y { constexpr T f() {} }; // expected-note {{control reached end of constexpr function}}
+ void f() {
+ X<int>().f();
+ Y<void>().f();
+ constexpr int q = Y<int>().f(); // expected-error {{must be initialized by a constant expression}} expected-note {{in call to '&Y<int>()->f()'}}
+ }
struct NonLiteral { ~NonLiteral(); } nl; // expected-note {{user-provided destructor}}
constexpr auto f2(int n) { return nl; } // expected-error {{return type 'Constexpr::NonLiteral' is not a literal type}}
}