diff --git a/src/plugins/coreplugin/editormanager/documentmodel.cpp b/src/plugins/coreplugin/editormanager/documentmodel.cpp
index fb6bf689493..7aa24d4c852 100644
--- a/src/plugins/coreplugin/editormanager/documentmodel.cpp
+++ b/src/plugins/coreplugin/editormanager/documentmodel.cpp
@@ -76,9 +76,8 @@ void DocumentModelPrivate::addEntry(DocumentModel::Entry *entry)
         fixedPath = DocumentManager::filePathKey(fileName.toString(), DocumentManager::ResolveLinks);
 
     // replace a non-loaded entry (aka 'suspended') if possible
-    int previousIndex = indexOfFilePath(fileName);
-    if (previousIndex >= 0) {
-        DocumentModel::Entry *previousEntry = m_entries.at(previousIndex);
+    DocumentModel::Entry *previousEntry = DocumentModel::entryForFilePath(fileName);
+    if (previousEntry) {
         const bool replace = !entry->isSuspended && previousEntry->isSuspended;
         if (replace) {
             previousEntry->isSuspended = false;
@@ -180,13 +179,16 @@ QIcon DocumentModelPrivate::lockedIcon()
     return icon;
 }
 
-int DocumentModelPrivate::indexOfFilePath(const Utils::FileName &filePath) const
+Utils::optional<int> DocumentModelPrivate::indexOfFilePath(const Utils::FileName &filePath) const
 {
     if (filePath.isEmpty())
-        return -1;
+        return Utils::nullopt;
     const QString fixedPath = DocumentManager::filePathKey(filePath.toString(),
                                                            DocumentManager::ResolveLinks);
-    return m_entries.indexOf(m_entryByFixedPath.value(fixedPath));
+    const int index = m_entries.indexOf(m_entryByFixedPath.value(fixedPath));
+    if (index < 0)
+        return Utils::nullopt;
+    return index;
 }
 
 void DocumentModelPrivate::removeDocument(int idx)
@@ -210,11 +212,14 @@ void DocumentModelPrivate::removeDocument(int idx)
     delete entry;
 }
 
-int DocumentModelPrivate::indexOfDocument(IDocument *document) const
+Utils::optional<int> DocumentModelPrivate::indexOfDocument(IDocument *document) const
 {
-    return Utils::indexOf(m_entries, [&document](DocumentModel::Entry *entry) {
+    const int index = Utils::indexOf(m_entries, [&document](DocumentModel::Entry *entry) {
         return entry->document == document;
     });
+    if (index < 0)
+        return Utils::nullopt;
+    return index;
 }
 
 Qt::ItemFlags DocumentModelPrivate::flags(const QModelIndex &index) const
@@ -292,14 +297,14 @@ void DocumentModelPrivate::itemChanged()
 {
     IDocument *document = qobject_cast<IDocument *>(sender());
 
-    int idx = indexOfDocument(document);
-    if (idx < 0)
+    const Utils::optional<int> idx = indexOfDocument(document);
+    if (!idx)
         return;
     const QString fileName = document->filePath().toString();
     QString fixedPath;
     if (!fileName.isEmpty())
         fixedPath = DocumentManager::filePathKey(fileName, DocumentManager::ResolveLinks);
-    DocumentModel::Entry *entry = m_entries.at(idx);
+    DocumentModel::Entry *entry = m_entries.at(idx.value());
     bool found = false;
     // The entry's fileName might have changed, so find the previous fileName that was associated
     // with it and remove it, then add the new fileName.
@@ -316,8 +321,8 @@ void DocumentModelPrivate::itemChanged()
     }
     if (!found && !fixedPath.isEmpty())
         m_entryByFixedPath[fixedPath] = entry;
-    if (!disambiguateDisplayNames(m_entries.at(idx))) {
-        QModelIndex mindex = index(idx + 1/*<no document>*/, 0);
+    if (!disambiguateDisplayNames(m_entries.at(idx.value()))) {
+        QModelIndex mindex = index(idx.value() + 1/*<no document>*/, 0);
         emit dataChanged(mindex, mindex);
     }
 }
@@ -507,7 +512,7 @@ QList<IEditor *> DocumentModel::editorsForDocuments(const QList<IDocument *> &do
     return result;
 }
 
-int DocumentModel::indexOfDocument(IDocument *document)
+Utils::optional<int> DocumentModel::indexOfDocument(IDocument *document)
 {
     return d->indexOfDocument(document);
 }
@@ -520,10 +525,10 @@ DocumentModel::Entry *DocumentModel::entryForDocument(IDocument *document)
 
 DocumentModel::Entry *DocumentModel::entryForFilePath(const Utils::FileName &filePath)
 {
-    const int index = d->indexOfFilePath(filePath);
-    if (index < 0)
+    const Utils::optional<int> index = d->indexOfFilePath(filePath);
+    if (!index)
         return nullptr;
-    return d->m_entries.at(index);
+    return d->m_entries.at(index.value());
 }
 
 QList<IDocument *> DocumentModel::openedDocuments()
@@ -533,10 +538,10 @@ QList<IDocument *> DocumentModel::openedDocuments()
 
 IDocument *DocumentModel::documentForFilePath(const QString &filePath)
 {
-    const int index = d->indexOfFilePath(Utils::FileName::fromString(filePath));
-    if (index < 0)
-        return 0;
-    return d->m_entries.at(index)->document;
+    const Utils::optional<int> index = d->indexOfFilePath(Utils::FileName::fromString(filePath));
+    if (!index)
+        return nullptr;
+    return d->m_entries.at(index.value())->document;
 }
 
 QList<IEditor *> DocumentModel::editorsForFilePath(const QString &filePath)
@@ -560,11 +565,14 @@ int DocumentModel::entryCount()
     return d->m_entries.count();
 }
 
-int DocumentModel::rowOfDocument(IDocument *document)
+Utils::optional<int> DocumentModel::rowOfDocument(IDocument *document)
 {
     if (!document)
         return 0 /*<no document>*/;
-    return indexOfDocument(document) + 1/*<no document>*/;
+    const Utils::optional<int> index = indexOfDocument(document);
+    if (index)
+        return index.value() + 1/*correction for <no document>*/;
+    return Utils::nullopt;
 }
 
 QList<DocumentModel::Entry *> DocumentModel::entries()
diff --git a/src/plugins/coreplugin/editormanager/documentmodel.h b/src/plugins/coreplugin/editormanager/documentmodel.h
index e0b14ed3aa2..73e75f71caf 100644
--- a/src/plugins/coreplugin/editormanager/documentmodel.h
+++ b/src/plugins/coreplugin/editormanager/documentmodel.h
@@ -29,6 +29,7 @@
 #include "../id.h"
 
 #include <utils/fileutils.h>
+#include <utils/optional.h>
 
 QT_BEGIN_NAMESPACE
 class QAbstractItemModel;
@@ -63,11 +64,11 @@ public:
     };
 
     static Entry *entryAtRow(int row);
-    static int rowOfDocument(IDocument *document);
+    static Utils::optional<int> rowOfDocument(IDocument *document);
 
     static int entryCount();
     static QList<Entry *> entries();
-    static int indexOfDocument(IDocument *document);
+    static Utils::optional<int> indexOfDocument(IDocument *document);
     static Entry *entryForDocument(IDocument *document);
     static Entry *entryForFilePath(const Utils::FileName &filePath);
     static QList<IDocument *> openedDocuments();
diff --git a/src/plugins/coreplugin/editormanager/documentmodel_p.h b/src/plugins/coreplugin/editormanager/documentmodel_p.h
index 98223e63ed5..ae6ff016fa5 100644
--- a/src/plugins/coreplugin/editormanager/documentmodel_p.h
+++ b/src/plugins/coreplugin/editormanager/documentmodel_p.h
@@ -58,8 +58,8 @@ public:
     void addEntry(DocumentModel::Entry *entry);
     void removeDocument(int idx);
 
-    int indexOfFilePath(const Utils::FileName &filePath) const;
-    int indexOfDocument(IDocument *document) const;
+    Utils::optional<int> indexOfFilePath(const Utils::FileName &filePath) const;
+    Utils::optional<int> indexOfDocument(IDocument *document) const;
 
     bool disambiguateDisplayNames(DocumentModel::Entry *entry);
 
diff --git a/src/plugins/coreplugin/editormanager/openeditorsview.cpp b/src/plugins/coreplugin/editormanager/openeditorsview.cpp
index 5d1b7870b60..c644baaeb93 100644
--- a/src/plugins/coreplugin/editormanager/openeditorsview.cpp
+++ b/src/plugins/coreplugin/editormanager/openeditorsview.cpp
@@ -30,6 +30,7 @@
 
 #include <coreplugin/actionmanager/actionmanager.h>
 #include <coreplugin/actionmanager/command.h>
+#include <utils/qtcassert.h>
 
 #include <QApplication>
 #include <QMenu>
@@ -70,15 +71,15 @@ OpenEditorsWidget::~OpenEditorsWidget()
 
 void OpenEditorsWidget::updateCurrentItem(IEditor *editor)
 {
-    IDocument *document = editor ? editor->document() : 0;
-    QModelIndex index = m_model->index(DocumentModel::indexOfDocument(document), 0);
-    if (!index.isValid()) {
+    if (!editor) {
         clearSelection();
         return;
     }
-    setCurrentIndex(index);
+    const Utils::optional<int> index = DocumentModel::indexOfDocument(editor->document());
+    if (QTC_GUARD(index))
+        setCurrentIndex(m_model->index(index.value(), 0));
     selectionModel()->select(currentIndex(),
-                                              QItemSelectionModel::ClearAndSelect | QItemSelectionModel::Rows);
+                             QItemSelectionModel::ClearAndSelect | QItemSelectionModel::Rows);
     scrollTo(currentIndex());
 }
 
diff --git a/src/plugins/coreplugin/editortoolbar.cpp b/src/plugins/coreplugin/editortoolbar.cpp
index b41245cd251..3383325e4cd 100644
--- a/src/plugins/coreplugin/editortoolbar.cpp
+++ b/src/plugins/coreplugin/editortoolbar.cpp
@@ -320,7 +320,9 @@ void EditorToolBar::setMenuProvider(const EditorToolBar::MenuProvider &provider)
 void EditorToolBar::setCurrentEditor(IEditor *editor)
 {
     IDocument *document = editor ? editor->document() : 0;
-    d->m_editorList->setCurrentIndex(DocumentModel::rowOfDocument(document));
+    const Utils::optional<int> index = DocumentModel::rowOfDocument(document);
+    if (QTC_GUARD(index))
+        d->m_editorList->setCurrentIndex(index.value());
 
     // If we never added the toolbar from the editor,  we will never change
     // the editor, so there's no need to update the toolbar either.
@@ -332,8 +334,11 @@ void EditorToolBar::setCurrentEditor(IEditor *editor)
 
 void EditorToolBar::updateEditorListSelection(IEditor *newSelection)
 {
-    if (newSelection)
-        d->m_editorList->setCurrentIndex(DocumentModel::rowOfDocument(newSelection->document()));
+    if (newSelection) {
+        const Utils::optional<int> index = DocumentModel::rowOfDocument(newSelection->document());
+        if (QTC_GUARD(index))
+            d->m_editorList->setCurrentIndex(index.value());
+    }
 }
 
 void EditorToolBar::changeActiveEditor(int row)
@@ -403,7 +408,9 @@ void EditorToolBar::updateDocumentStatus(IDocument *document)
         return;
     }
 
-    d->m_editorList->setCurrentIndex(DocumentModel::rowOfDocument(document));
+    const Utils::optional<int> index = DocumentModel::rowOfDocument(document);
+    if (QTC_GUARD(index))
+        d->m_editorList->setCurrentIndex(index.value());
 
     if (document->filePath().isEmpty()) {
         d->m_lockButton->setIcon(QIcon());
diff --git a/src/plugins/fakevim/fakevimplugin.cpp b/src/plugins/fakevim/fakevimplugin.cpp
index d8c92a13ebb..04c6e9e0ab0 100644
--- a/src/plugins/fakevim/fakevimplugin.cpp
+++ b/src/plugins/fakevim/fakevimplugin.cpp
@@ -73,6 +73,7 @@
 #include <utils/hostosinfo.h>
 #include <utils/qtcassert.h>
 #include <utils/pathchooser.h>
+#include <utils/qtcassert.h>
 #include <utils/savedaction.h>
 #include <utils/stylehelper.h>
 
@@ -2209,9 +2210,12 @@ void FakeVimPluginPrivate::highlightMatches(FakeVimHandler *, const QString &nee
 int FakeVimPluginPrivate::currentFile() const
 {
     IEditor *editor = EditorManager::currentEditor();
-    if (!editor)
-        return -1;
-    return DocumentModel::indexOfDocument(editor->document());
+    if (editor) {
+        const Utils::optional<int> index = DocumentModel::indexOfDocument(editor->document());
+        if (QTC_GUARD(index))
+            return index.value();
+    }
+    return -1;
 }
 
 void FakeVimPluginPrivate::switchToFile(int n)