C++: fix matching type with using from other namespace

example code:
struct S { int s; };

namespace std
{
    template <typename T>
    struct shared_ptr
    {
        T* operator->();
    };
}

namespace NS
{
    using std::shared_ptr;
}

int main()
{
    NS::shared_ptr<S> p;// for this shared_ptr
    return 0;
}

Fixes:
* find usages
* follow symbol
* highlighting
* marking

Task-number: QTCREATORBUG-7978
Change-Id: I28994c960b87ddd400e1d7b860fca6c6683bbb5a
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/libs/cplusplus/LookupContext.cpp

@@ -246,12 +246,13 @@ QList<LookupItem> LookupContext::lookupByUsing(const Name *name, Scope *scope) c
 {
     QList<LookupItem> candidates;
     // if it is a nameId there can be a using declaration for it
-    if (name->isNameId()) {
+    if (name->isNameId() || name->isTemplateNameId()) {
         for (unsigned i = 0, count = scope->memberCount(); i < count; ++i) {
             if (UsingDeclaration *u = scope->memberAt(i)->asUsingDeclaration()) {
                 if (const Name *usingDeclarationName = u->name()) {
                     if (const QualifiedNameId *q = usingDeclarationName->asQualifiedNameId()) {
-                        if (q->name() && q->name()->isEqualTo(name)) {
+                        if (q->name() && q->identifier() && name->identifier()
+                                && q->name()->identifier()->isEqualTo(name->identifier())) {
                             candidates = bindings()->globalNamespace()->find(q);
 
                             // if it is not a global scope(scope of scope is not equal 0)
@@ -267,6 +268,10 @@ QList<LookupItem> LookupContext::lookupByUsing(const Name *name, Scope *scope) c
                 }
             }
         }
+    } else if (const QualifiedNameId *q = name->asQualifiedNameId()) {
+        ClassOrNamespace *base = lookupType(q->base(), scope);
+        if (base && base->symbols().size() > 0 && base->symbols().first()->asScope())
+            return lookupByUsing(q->name(), base->symbols().first()->asScope());
     }
     return candidates;
 }

src/plugins/cpptools/cppchecksymbols.cpp

@@ -852,7 +852,10 @@ bool CheckSymbols::visit(QualifiedNameAST *ast)
                         addUse(ast->unqualified_name, CppHighlightingSupport::FunctionUse);
                 }
             } else {
-                maybeAddTypeOrStatic(binding->find(ast->unqualified_name->name), ast->unqualified_name);
+                QList<LookupItem> items = binding->find(ast->unqualified_name->name);
+                if (items.empty())
+                    items = _context.lookup(ast->name, enclosingScope());
+                maybeAddTypeOrStatic(items, ast->unqualified_name);
             }
 
             if (TemplateIdAST *template_id = ast->unqualified_name->asTemplateId())

tests/auto/cplusplus/checksymbols/tst_checksymbols.cpp

@@ -201,6 +201,7 @@ private slots:
     void test_alias_decl_QTCREATORBUG9386();
     void test_completion_enum_inside_block_inside_function_QTCREATORBUG5456();
     void test_completion_enum_inside_function_QTCREATORBUG5456();
+    void test_completion_using_inside_different_namespace_QTCREATORBUG7978();
 };
 
 void tst_CheckSymbols::test_checksymbols_TypeUse()
@@ -1821,5 +1822,41 @@ void tst_CheckSymbols::test_completion_enum_inside_function_QTCREATORBUG5456()
     TestData::check(source, expectedUses);
 }
 
+void tst_CheckSymbols::test_completion_using_inside_different_namespace_QTCREATORBUG7978()
+{
+    const QByteArray source =
+            "struct S {};\n"
+            "namespace std\n"
+            "{\n"
+            "    template <typename T> struct shared_ptr{};\n"
+            "}\n"
+            "namespace NS\n"
+            "{\n"
+            "    using std::shared_ptr;\n"
+            "}\n"
+            "void fun()\n"
+            "{\n"
+            "    NS::shared_ptr<S> p;\n"
+            "}\n"
+            ;
+
+    const QList<Use> expectedUses = QList<Use>()
+            << Use(1, 8, 1, CppHighlightingSupport::TypeUse)
+            << Use(2, 11, 3, CppHighlightingSupport::TypeUse)
+            << Use(4, 24, 1, CppHighlightingSupport::TypeUse)
+            << Use(4, 34, 10, CppHighlightingSupport::TypeUse)
+            << Use(6, 11, 2, CppHighlightingSupport::TypeUse)
+            << Use(8, 11, 3, CppHighlightingSupport::TypeUse)
+            << Use(8, 16, 10, CppHighlightingSupport::TypeUse)
+            << Use(10, 6, 3, CppHighlightingSupport::FunctionUse)
+            << Use(12, 5, 2, CppHighlightingSupport::TypeUse)
+            << Use(12, 9, 10, CppHighlightingSupport::TypeUse)
+            << Use(12, 20, 1, CppHighlightingSupport::TypeUse)
+            << Use(12, 23, 1, CppHighlightingSupport::LocalUse)
+            ;
+
+    TestData::check(source, expectedUses);
+}
+
 QTEST_APPLESS_MAIN(tst_CheckSymbols)
 #include "tst_checksymbols.moc"

tests/auto/cplusplus/findusages/tst_findusages.cpp

@@ -108,6 +108,8 @@ private Q_SLOTS:
     void using_insideNamespace();
     void using_insideFunction();
     void templatedFunction_QTCREATORBUG9749();
+
+    void usingInDifferentNamespace_QTCREATORBUG7978();
 };
 
 void tst_FindUsages::dump(const QList<Usage> &usages) const
@@ -866,5 +868,44 @@ void tst_FindUsages::templatedFunction_QTCREATORBUG9749()
     QCOMPARE(findUsages.usages().size(), 2);
 }
 
+void tst_FindUsages::usingInDifferentNamespace_QTCREATORBUG7978()
+{
+    const QByteArray src = "\n"
+            "struct S {};\n"
+            "namespace std\n"
+            "{\n"
+            "    template <typename T> struct shared_ptr{};\n"
+            "}\n"
+            "namespace NS\n"
+            "{\n"
+            "    using std::shared_ptr;\n"
+            "}\n"
+            "void fun()\n"
+            "{\n"
+            "    NS::shared_ptr<S> p;\n"
+            "}\n"
+            ;
+
+    Document::Ptr doc = Document::create("usingInDifferentNamespace_QTCREATORBUG7978");
+    doc->setUtf8Source(src);
+    doc->parse();
+    doc->check();
+
+    QVERIFY(doc->diagnosticMessages().isEmpty());
+    QCOMPARE(doc->globalSymbolCount(), 4U);
+
+    Snapshot snapshot;
+    snapshot.insert(doc);
+
+    Namespace *ns = doc->globalSymbolAt(1)->asNamespace();
+    QVERIFY(ns);
+    QCOMPARE(ns->memberCount(), 1U);
+    Template *templateClass = ns->memberAt(0)->asTemplate();
+
+    FindUsages findUsages(src, doc, snapshot);
+    findUsages(templateClass);
+    QCOMPARE(findUsages.usages().size(), 3);
+}
+
 QTEST_APPLESS_MAIN(tst_FindUsages)
 #include "tst_findusages.moc"