CppEditor: Find implementations for pure virtual declaration

Clearly, if a user presses F2 on the declaration of an (unimplemented)
pure virtual function, they want to go to an implementation in a derived
class.

Fixes: QTCREATORBUG-10160
Change-Id: Ie8c4ff0001ab2c98a2d0e2ebc8d954cc928578c0
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

2 files changed, 36 insertions, 2 deletions

diff --git a/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp b/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
index 1355b2d178..17f2e364f9 100644
--- a/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
+++ b/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
@@ -1413,6 +1413,31 @@ void CppEditorPlugin::test_FollowSymbolUnderCursor_virtualFunctionCall_data()
             << OverrideItem(QLatin1String("CD1::virt"), 11)
             << OverrideItem(QLatin1String("CD2::virt"), 14));
 
+    /// Check: Cursor on unimplemented base declaration.
+    QTest::newRow("allOverrides from base declaration") << _(
+            "struct A { virtual void $@virt() = 0; };\n"
+            "\n"
+            "struct B : A { void virt(); };\n"
+            "void B::virt() {}\n"
+            "\n"
+            "struct C : B { void virt(); };\n"
+            "void C::virt() {}\n"
+            "\n"
+            "struct CD1 : C { void virt(); };\n"
+            "void CD1::virt() {}\n"
+            "\n"
+            "struct CD2 : C { void virt(); };\n"
+            "void CD2::virt() {}\n"
+            "\n"
+            "int f(A *o) { o->virt(); }\n"
+            "\n")
+        << (OverrideItemList()
+            << OverrideItem(QLatin1String("A::virt = 0"), 1)
+            << OverrideItem(QLatin1String("B::virt"), 4)
+            << OverrideItem(QLatin1String("C::virt"), 7)
+            << OverrideItem(QLatin1String("CD1::virt"), 10)
+            << OverrideItem(QLatin1String("CD2::virt"), 13));
+
     /// Check: Static type is derived class pointer, only overrides of sub classes are presented.
     QTest::newRow("possibleOverrides1") << _(
             "struct A { virtual void virt() = 0; };\n"
diff --git a/src/plugins/cpptools/cppfollowsymbolundercursor.cpp b/src/plugins/cpptools/cppfollowsymbolundercursor.cpp
index a21babf852..f7307b59c1 100644
--- a/src/plugins/cpptools/cppfollowsymbolundercursor.cpp
+++ b/src/plugins/cpptools/cppfollowsymbolundercursor.cpp
@@ -111,8 +111,17 @@ VirtualFunctionHelper::VirtualFunctionHelper(TypeOfExpression &typeOfExpression,
 bool VirtualFunctionHelper::canLookupVirtualFunctionOverrides(Function *function)
 {
     m_function = function;
-    if (!m_function || !m_baseExpressionAST || !m_expressionDocument || !m_document || !m_scope
-            || m_scope->isClass() || m_scope->isFunction() || m_snapshot.isEmpty()) {
+
+    if (!m_document || m_snapshot.isEmpty() || !m_function || !m_scope)
+        return false;
+
+    if (m_scope->isClass() && m_function->isPureVirtual()) {
+        m_staticClassOfFunctionCallExpression = m_scope->asClass();
+        return true;
+    }
+
+    if (!m_baseExpressionAST || !m_expressionDocument
+            || m_scope->isClass() || m_scope->isFunction()) {
         return false;
     }