[ASTMatchers] isTemplateInstantiation: also match explicit instantiation declaration.

Summary:
Example:
template <typename T> class X {}; class A {};
// Explicit instantiation declaration.
extern template class X<A>;

Reviewers: bkramer

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D43567

llvm-svn: 325678

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -4649,6 +4649,10 @@ AST_MATCHER_P(UsingShadowDecl, hasTargetDecl,
 /// \code
 ///   template <typename T> class X {}; class A {}; template class X<A>;
 /// \endcode
+/// or
+/// \code
+///   template <typename T> class X {}; class A {}; extern template class X<A>;
+/// \endcode
 /// cxxRecordDecl(hasName("::X"), isTemplateInstantiation())
 ///   matches the template instantiation of X<A>.
 ///
@@ -4666,7 +4670,9 @@ AST_POLYMORPHIC_MATCHER(isTemplateInstantiation,
                                                         CXXRecordDecl)) {
   return (Node.getTemplateSpecializationKind() == TSK_ImplicitInstantiation ||
           Node.getTemplateSpecializationKind() ==
-          TSK_ExplicitInstantiationDefinition);
+              TSK_ExplicitInstantiationDefinition ||
+          Node.getTemplateSpecializationKind() ==
+              TSK_ExplicitInstantiationDeclaration);
 }
 
 /// \brief Matches declarations that are template instantiations or are inside

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

@@ -1623,6 +1623,14 @@ TEST(IsTemplateInstantiation, MatchesExplicitClassTemplateInstantiation) {
       "template class X<A>;",
     cxxRecordDecl(isTemplateInstantiation(), hasDescendant(
       fieldDecl(hasType(recordDecl(hasName("A"))))))));
+
+  // Make sure that we match the instantiation instead of the template
+  // definition by checking whether the member function is present.
+  EXPECT_TRUE(
+      matches("template <typename T> class X { void f() { T t; } };"
+              "extern template class X<int>;",
+              cxxRecordDecl(isTemplateInstantiation(),
+                            unless(hasDescendant(varDecl(hasName("t")))))));
 }
 
 TEST(IsTemplateInstantiation,