From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Tue, 14 Feb 2017 23:27:44 +0000 (+0000)
Subject: Do not implicitly instantiate the definition of a class template specialization
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=44d0f7062d219377f1c93ada5ae676baf40381c1;p=clang

Do not implicitly instantiate the definition of a class template specialization
that has been explicitly specialized!

We assume in various places that we can tell the template specialization kind
of a class type by looking at the declaration produced by TagType::getDecl.
That was previously not quite true: for an explicit specialization, we could
have first seen a template-id denoting the specialization (with a use that does
not trigger an implicit instantiation of the defintiion) and then seen the
first explicit specialization declaration. TagType::getDecl would previously
return an arbitrary declaration when called on a not-yet-defined class; it
now consistently returns the most recent declaration in that case.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@295118 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index 8f22a1b197..1d064b135e 100644
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -3023,8 +3023,10 @@ static TagDecl *getInterestingTagDecl(TagDecl *decl) {
     if (I->isCompleteDefinition() || I->isBeingDefined())
       return I;
   }
-  // If there's no definition (not even in progress), return what we have.
-  return decl;
+  // If there's no definition (not even in progress), return the most recent
+  // declaration. This is important for template specializations, in order to
+  // pick the declaration with the most complete TemplateSpecializationKind.
+  return decl->getMostRecentDecl();
 }
 
 TagDecl *TagType::getDecl() const {
diff --git a/test/SemaTemplate/explicit-specialization-member.cpp b/test/SemaTemplate/explicit-specialization-member.cpp
index f302836c7e..4300ceb17e 100644
--- a/test/SemaTemplate/explicit-specialization-member.cpp
+++ b/test/SemaTemplate/explicit-specialization-member.cpp
@@ -57,3 +57,14 @@ template<typename T> struct Helper {
 template<typename T> void Helper<T>::func<2>() {} // expected-error {{cannot specialize a member}} \
                                                   // expected-error {{no function template matches}}
 }
+
+namespace b35070233 {
+  template <typename T> struct Cls {
+    static void f() {}
+  };
+
+  void g(Cls<int>);
+
+  template<> struct Cls<int>; // expected-note {{forward declaration}}
+  template<> void Cls<int>::f(); // expected-error {{incomplete type}}
+}