Add an isVirtualAsWritten AST matcher.

[klimek]

lg

[aaron.ballman]

FWIW, LGTM as well.

[thakis]

r258415, thanks!

docs/LibASTMatchersReference.html

 Given
   class A {
    public:
     virtual void x();
   };
   matches A::x
 </pre></td></tr>
 
+<tr><td>Matcher&lt<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXMethodDecl.html">CXXMethodDecl</a>&gt;</td><td class="name" onclick="toggle('isVirtualAsWritten0')"><a name="isVirtualAsWritten0Anchor">isVirtualAsWritten</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="isVirtualAsWritten0"><pre>Matches if the given method declaration has an explicit "virtual".
+
+Given
+  class A {
+   public:
+    virtual void x();
+  };
+  class B : public A {
+   public:
+    void x();
+  };
+  matches A::x but not B::x
+</pre></td></tr>
 
 <tr><td>Matcher&lt<a href="http://clang.llvm.org/doxygen/classclang_1_1CXXOperatorCallExpr.html">CXXOperatorCallExpr</a>&gt;</td><td class="name" onclick="toggle('hasOverloadedOperatorName1')"><a name="hasOverloadedOperatorName1Anchor">hasOverloadedOperatorName</a></td><td>StringRef Name</td></tr>
 <tr><td colspan="4" class="doc" id="hasOverloadedOperatorName1"><pre>Matches overloaded operator names.
 
 Matches overloaded operator names specified in strings without the
 "operator" prefix: e.g. "&lt;&lt;".
 
 Given:

include/clang/ASTMatchers/ASTMatchers.h

 ///     virtual void x();
 ///   };
 /// \endcode
 ///   matches A::x
 AST_MATCHER(CXXMethodDecl, isVirtual) {
   return Node.isVirtual();
 }
 
+/// \brief Matches if the given method declaration has an explicit "virtual".
+///
+/// Given
+/// \code
+///   class A {
+///    public:
+///     virtual void x();
+///   };
+///   class B : public A {
+///    public:
+///     void x();
+///   };
+/// \endcode
+///   matches A::x but not B::x
+AST_MATCHER(CXXMethodDecl, isVirtualAsWritten) {
+  return Node.isVirtualAsWritten();
+}
+
 /// \brief Matches if the given method or class declaration is final.
 ///
 /// Given:
 /// \code
 ///   class A final {};
 ///
 ///   struct B {
 ///     virtual void f();

lib/ASTMatchers/Dynamic/Registry.cpp

RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isProtected);
   REGISTER_MATCHER(isPublic);
   REGISTER_MATCHER(isPure);
   REGISTER_MATCHER(isStruct);
   REGISTER_MATCHER(isTemplateInstantiation);
   REGISTER_MATCHER(isUnion);
   REGISTER_MATCHER(isVariadic);
   REGISTER_MATCHER(isVirtual);
+  REGISTER_MATCHER(isVirtualAsWritten);
   REGISTER_MATCHER(isVolatileQualified);
   REGISTER_MATCHER(isWritten);
   REGISTER_MATCHER(labelStmt);
   REGISTER_MATCHER(lambdaExpr);
   REGISTER_MATCHER(lValueReferenceType);
   REGISTER_MATCHER(matchesName);
   REGISTER_MATCHER(matchesSelector);
   REGISTER_MATCHER(materializeTemporaryExpr);

unittests/ASTMatchers/ASTMatchersTest.cpp

 }
 
 TEST(Matcher, MatchesVirtualMethod) {
   EXPECT_TRUE(matches("class X { virtual int f(); };",
                       cxxMethodDecl(isVirtual(), hasName("::X::f"))));
   EXPECT_TRUE(notMatches("class X { int f(); };", cxxMethodDecl(isVirtual())));
 }
 
+TEST(Matcher, MatchesVirtualAsWrittenMethod) {
+  EXPECT_TRUE(matches("class A { virtual int f(); };"
+                      "class B : public A { int f(); };",
+                      cxxMethodDecl(isVirtualAsWritten(), hasName("::A::f"))));
+  EXPECT_TRUE(
+      notMatches("class A { virtual int f(); };"
+                 "class B : public A { int f(); };",
+                 cxxMethodDecl(isVirtualAsWritten(), hasName("::B::f"))));
+}
+
 TEST(Matcher, MatchesPureMethod) {
   EXPECT_TRUE(matches("class X { virtual int f() = 0; };",
                       cxxMethodDecl(isPure(), hasName("::X::f"))));
   EXPECT_TRUE(notMatches("class X { int f(); };", cxxMethodDecl(isPure())));
 }
 
 TEST(Matcher, MatchesCopyAssignmentOperator) {
   EXPECT_TRUE(matches("class X { X &operator=(X); };",