Editor: Validate trigger from snippets xml

Fixes: QTCREATORBUG-24415
Change-Id: Ic99355220bf1948af8a17d6ce017924eba3fc3ba
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/texteditor/snippets/snippet.cpp

@@ -25,6 +25,7 @@
 
 #include "snippet.h"
 
+#include <utils/algorithm.h>
 #include <utils/templateengine.h>
 
 #include <QTextDocument>
@@ -105,6 +106,13 @@ const QString &Snippet::trigger() const
     return m_trigger;
 }
 
+bool Snippet::isValidTrigger(const QString &trigger)
+{
+    if (trigger.isEmpty() || trigger.at(0).isNumber())
+        return false;
+    return Utils::allOf(trigger, [](const QChar &c) { return c.isLetterOrNumber() || c == '_'; });
+}
+
 void Snippet::setContent(const QString &content)
 {
     m_content = content;