[clang] 7337f29 - PR47555: Inheriting constructors are implicitly definable.

[Richard Smith via cfe-commits]

Author: Richard Smith
Date: 2020-09-16T18:11:18-07:00
New Revision: 7337f296194483e0959ff980049e2835e226f396

URL: https://github.com/llvm/llvm-project/commit/7337f296194483e0959ff980049e2835e226f396
DIFF: https://github.com/llvm/llvm-project/commit/7337f296194483e0959ff980049e2835e226f396.diff

LOG: PR47555: Inheriting constructors are implicitly definable.

Don't forget to define them if they're constexpr and used inside a
template; we might try to evaluate a call to them before the template is
instantiated.

Added: 
    

Modified: 
    clang/lib/Sema/SemaExpr.cpp
    clang/test/SemaCXX/cxx11-inheriting-ctors.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 9a4b3e31e850..c82febdbf3a7 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -16582,8 +16582,13 @@ static OdrUseContext isOdrUseContext(Sema &SemaRef) {
 }
 
 static bool isImplicitlyDefinableConstexprFunction(FunctionDecl *Func) {
-  return Func->isConstexpr() &&
-         (Func->isImplicitlyInstantiable() || !Func->isUserProvided());
+  if (!Func->isConstexpr())
+    return false;
+
+  if (Func->isImplicitlyInstantiable() || !Func->isUserProvided())
+    return true;
+  auto *CCD = dyn_cast<CXXConstructorDecl>(Func);
+  return CCD && CCD->getInheritedConstructor();
 }
 
 /// Mark a function referenced, and check whether it is odr-used

diff  --git a/clang/test/SemaCXX/cxx11-inheriting-ctors.cpp b/clang/test/SemaCXX/cxx11-inheriting-ctors.cpp
index 7d6f4f09f09c..5be428401fa0 100644
--- a/clang/test/SemaCXX/cxx11-inheriting-ctors.cpp
+++ b/clang/test/SemaCXX/cxx11-inheriting-ctors.cpp
@@ -133,3 +133,12 @@ namespace implicit_member_srcloc {
     S0<int> s0;
   }
 }
+
+namespace PR47555 {
+  struct A { constexpr A(int) {} };
+  struct B : A { using A::A; };
+  template<typename> void f() {
+    constexpr B b = 0;
+  };
+  template void f<int>();
+}