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
GridLayout layout = new GridLayout();
        layout.marginHeight = 10;
        layout.verticalSpacing = 5;
        layout.numColumns = 2;
        infoArea.setLayout(layout);
        GridData data = new GridData(GridData.FILL_BOTH);
        infoArea.setLayoutData(data);
        boolean wrapped = parser.isFormatWrapped();
        int HINDENT = 20;
        
        Display display = parent.getDisplay();
        Color background = JFaceColors.getBannerBackground(display);
        Color foreground = JFaceColors.getBannerForeground(display);
        infoArea.setBackground(background);
        int textStyle = SWT.MULTI | SWT.READ_ONLY;
        if (wrapped) {
            textStyle = textStyle | SWT.WRAP;
        }
        StyledText sampleStyledText = null;
        
        WelcomeItem item = getIntroItem();
        if (item != null) {
            StyledText styledText = new StyledText(infoArea, textStyle);
            this.texts.add(styledText);
            sampleStyledText = styledText;
            styledText.setCursor(null);
            JFaceColors.setColors(styledText, foreground, background);
            styledText.setText(getIntroItem().getText());
            setBoldRanges(styledText, item.getBoldRanges());
            setLinkRanges(styledText, item.getActionRanges());