TextEditor: avoid creating an highlighter to check a type

check the type after construcing the highlighter instead and save that
information.

Change-Id: I7d942dae4be8471dba90dd266267ff7fa1b6f440
Reviewed-by: Artem Sokolovskii <artem.sokolovskii@qt.io>

src/plugins/texteditor/syntaxhighlighterrunner.cpp

@@ -6,6 +6,7 @@
 #include "fontsettings.h"
 #include "textdocumentlayout.h"
 #include "texteditorsettings.h"
+#include "highlighter.h"
 
 #include <utils/textutils.h>
 
@@ -92,13 +93,13 @@ public:
 
     void rehighlight() { m_highlighter->rehighlight(); }
 
-signals:
-    void resultsReady(const QList<SyntaxHighlighter::Result> &result);
-
-private:
     std::unique_ptr<SyntaxHighlighter> m_highlighter;
     QTextDocument *m_document = nullptr;
     FontSettings m_fontSettings;
+
+signals:
+    void resultsReady(const QList<SyntaxHighlighter::Result> &result);
+
 };
 
 // ----------------------------- BaseSyntaxHighlighterRunner --------------------------------------
@@ -110,6 +111,8 @@ BaseSyntaxHighlighterRunner::BaseSyntaxHighlighterRunner(
     : d(new SyntaxHighlighterRunnerPrivate(creator, document, fontSettings))
     , m_document(document)
 {
+    m_useGenericHighlighter = qobject_cast<Highlighter *>(d->m_highlighter.get());
+
     if (document == nullptr)
         return;
 
@@ -176,6 +179,11 @@ void BaseSyntaxHighlighterRunner::changeDocument(int from, int charsRemoved, int
     });
 }
 
+bool BaseSyntaxHighlighterRunner::useGenericHighlighter() const
+{
+    return m_useGenericHighlighter;
+}
+
 void BaseSyntaxHighlighterRunner::setExtraFormats(
     const QMap<int, QList<QTextLayout::FormatRange>> &formatMap)
 {