Bug 117925 [Intro] Misleading exception message in WelcomeEditor.init()
... it says it expects an IFileEditorInput, but it actually checks for WelcomeEditorInput. Suggested patch appended.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/WelcomeEditor.java
* Returns whether the "save as" operation is supported by this editor.
     * <p>
     * Subclasses must override this method to implement the open-save-close lifecycle
     * for an editor.  For greater details, see <code>IEditorPart</code>
     * </p>
     *
     * @see IEditorPart
     */
    public boolean isSaveAsAllowed() {
        return false;
    }
    /**
     * Read the contents of the welcome page
     * 
     * @param is the <code>InputStream</code> to parse
     * @throws IOException if there is a problem parsing the stream.
     */
    public void read(InputStream is) throws IOException {
        try {
            parser = new WelcomeParser();
        } catch (ParserConfigurationException e) {
            throw (IOException) (new IOException().initCause(e));
        } catch (SAXException e) {
            throw (IOException) (new IOException().initCause(e));
        }
        parser.parse(is);
    }
    /**
     * Reads the welcome file
     */