4 files changed, 38 insertions, 0 deletions
diff --git a/src/lib/corelib/language/itemreaderastvisitor.cpp b/src/lib/corelib/language/itemreaderastvisitor.cpp
index 15d8768c7..79f66687a 100644
--- a/src/lib/corelib/language/itemreaderastvisitor.cpp
+++ b/src/lib/corelib/language/itemreaderastvisitor.cpp
@@ -204,6 +204,13 @@ bool ItemReaderASTVisitor::visit(AST::UiScriptBinding *ast)
             throw ErrorInfo(Tr::tr("id: must be followed by identifier"));
         m_item->m_id = idExp->name.toString();
         m_file->ensureIdScope(m_itemPool);
+        ItemValueConstPtr existingId = m_file->idScope()->itemProperty(m_item->id());
+        if (existingId) {
+            ErrorInfo e(Tr::tr("The id '%1' is not unique.").arg(m_item->id()));
+            e.append(Tr::tr("First occurrence is here."), existingId->item()->location());
+            e.append(Tr::tr("Next occurrence is here."), m_item->location());
+            throw e;
+        }
         m_file->idScope()->setProperty(m_item->id(), ItemValue::create(m_item));
         return false;
     }
diff --git a/src/lib/corelib/language/testdata/id-uniqueness.qbs b/src/lib/corelib/language/testdata/id-uniqueness.qbs
new file mode 100644
index 000000000..cfbaf8548
--- /dev/null
+++ b/src/lib/corelib/language/testdata/id-uniqueness.qbs
@@ -0,0 +1,12 @@
+import qbs 1.0
+import "idusagebase.qbs" as DerivedProduct
+
+Project {
+    id: theProject
+    DerivedProduct {
+        id: baseProduct         // OK - even though 'baseProduct' is used in the base item.
+    }
+    DerivedProduct {
+        id: baseProduct         // ERROR
+    }
+}
diff --git a/src/lib/corelib/language/tst_language.cpp b/src/lib/corelib/language/tst_language.cpp
index f865190eb..b985940df 100644
--- a/src/lib/corelib/language/tst_language.cpp
+++ b/src/lib/corelib/language/tst_language.cpp
@@ -931,6 +931,24 @@ void TestLanguage::idUsage()
     QVERIFY(!exceptionCaught);
 }
 
+void TestLanguage::idUniqueness()
+{
+    bool exceptionCaught = false;
+    try {
+        defaultParameters.setProjectFilePath(testProject("id-uniqueness.qbs"));
+        loader->loadProject(defaultParameters);
+    }
+    catch (const ErrorInfo &e) {
+        exceptionCaught = true;
+        const QList<ErrorItem> items = e.items();
+        QCOMPARE(items.count(), 3);
+        QCOMPARE(items.at(0).toString(), QString::fromUtf8("The id 'baseProduct' is not unique."));
+        QVERIFY(items.at(1).toString().contains("id-uniqueness.qbs:6:5 First occurrence is here."));
+        QVERIFY(items.at(2).toString().contains("id-uniqueness.qbs:9:5 Next occurrence is here."));
+    }
+    QVERIFY(exceptionCaught);
+}
+
 void TestLanguage::importCollection()
 {
     bool exceptionCaught = false;
diff --git a/src/lib/corelib/language/tst_language.h b/src/lib/corelib/language/tst_language.h
index 995609180..c8d6e59f9 100644
--- a/src/lib/corelib/language/tst_language.h
+++ b/src/lib/corelib/language/tst_language.h
@@ -97,6 +97,7 @@ private slots:
     void identifierSearch_data();
     void identifierSearch();
     void idUsage();
+    void idUniqueness();
     void importCollection();
     void invalidBindingInDisabledItem();
     void itemPrototype();