Fix PR11848: decree that an alias template contains an unexpanded parameter pack

iff its substitution contains an unexpanded parameter pack. This has the effect
that we now reject declarations such as this (which we used to crash when
expanding):

  template<typename T> using Int = int;
  template<typename ...Ts> void f(Int<Ts> ...ints);

The standard is inconsistent on how this case should be treated.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148905 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index 7b30c500c6e2c7a6e4c232e5163fde55d47d3b8a..b6ce59e977d97605e4d188bfb7ecfaf7216aff01 100644 (file)
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -1889,7 +1889,9 @@ TemplateSpecializationType(TemplateName T,
          Canon.isNull()? T.isDependent() : Canon->isDependentType(),
          Canon.isNull()? T.isDependent() 
                        : Canon->isInstantiationDependentType(),
-         false, T.containsUnexpandedParameterPack()),
+         false,
+         Canon.isNull()? T.containsUnexpandedParameterPack()
+                       : Canon->containsUnexpandedParameterPack()),
     Template(T), NumArgs(NumArgs) {
   assert(!T.getAsDependentTemplateName() && 
          "Use DependentTemplateSpecializationType for dependent template-name");
@@ -1922,7 +1924,7 @@ TemplateSpecializationType(TemplateName T,
     if (Args[Arg].getKind() == TemplateArgument::Type &&
         Args[Arg].getAsType()->isVariablyModifiedType())
       setVariablyModified();
-    if (Args[Arg].containsUnexpandedParameterPack())
+    if (Canon.isNull() && Args[Arg].containsUnexpandedParameterPack())
       setContainsUnexpandedParameterPack();
 
     new (&TemplateArgs[Arg]) TemplateArgument(Args[Arg]);

diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 2b96a1c7447f02414a2f660aa0198b8714d55e71..e183f1f1c1d7d8cbb8fffd08755eb6122a060c1b 100644 (file)
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1510,7 +1510,7 @@ ParmVarDecl *Sema::SubstParmVarDecl(ParmVarDecl *OldParm,
   // FIXME: When OldParm is a parameter pack and NewParm is not a parameter
   // pack, we actually have a set of instantiated locations. Maintain this set!
   if (OldParm->isParameterPack() && !NewParm->isParameterPack()) {
-    // Add the new parameter to 
+    // Add the new parameter to the instantiated parameter pack.
     CurrentInstantiationScope->InstantiatedLocalPackArg(OldParm, NewParm);
   } else {
     // Introduce an Old -> New mapping

diff --git a/test/SemaTemplate/alias-templates.cpp b/test/SemaTemplate/alias-templates.cpp
index 79d6849a6efeb18def5ff4c131c8fc3922b29a8a..c0f9e21b3530c3bec44678a28e06e4301257e1bf 100644 (file)
--- a/test/SemaTemplate/alias-templates.cpp
+++ b/test/SemaTemplate/alias-templates.cpp
@@ -68,3 +68,36 @@ itt::thing ith(itr);
 
 itt::rebind<bool> btr;
 itt::rebind_thing<bool> btt(btr);
+
+namespace PR11848 {
+  template<typename T> using U = int;
+
+  template<typename T, typename ...Ts>
+  void f(U<T> i, U<Ts> ...is) { // expected-error {{type 'U<Ts>' (aka 'int') of function parameter pack does not contain any unexpanded parameter packs}}
+    return i + f<Ts...>(is...); // expected-error {{pack expansion does not contain any unexpanded parameter packs}}
+  }
+
+  template<typename ...Ts>
+  struct S {
+    S(U<Ts>...ts); // expected-error {{does not contain any unexpanded parameter packs}}
+  };
+
+  template<typename T>
+  struct Hidden1 {
+    template<typename ...Ts>
+    Hidden1(typename T::template U<Ts> ...ts);
+  };
+
+  template<typename T, typename ...Ts>
+  struct Hidden2 {
+    Hidden2(typename T::template U<Ts> ...ts);
+  };
+
+  struct Hide {
+    template<typename T> using U = int;
+  };
+
+  // FIXME: This case crashes clang at the moment.
+  //Hidden1<Hide> h1;
+  Hidden2<Hide, double, char> h2(1, 2);
+}