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
label.setLayoutData(gd);
            if (imageLabel == null) {
                imageLabel = label;
            }
            StyledText styledText = new StyledText(infoArea, textStyle);
            this.texts.add(styledText);
            sampleStyledText = styledText;
            styledText.setCursor(null);
            JFaceColors.setColors(styledText, foreground, background);
            styledText.setText(items[i].getText());
            setBoldRanges(styledText, items[i].getBoldRanges());
            setLinkRanges(styledText, items[i].getActionRanges());
            setLinkRanges(styledText, items[i].getHelpRanges());
            gd = new GridData(GridData.FILL_HORIZONTAL);
            gd.verticalAlignment = GridData.VERTICAL_ALIGN_BEGINNING;
            gd.verticalSpan = 2;
            styledText.setLayoutData(gd);
            styledText.setData(items[i]);
            addListeners(styledText);
            Label spacer = new Label(infoArea, SWT.NONE);
            spacer.setBackground(background);
            gd = new GridData(GridData.VERTICAL_ALIGN_BEGINNING);
            gd.horizontalSpan = 2;
            spacer.setLayoutData(gd);
            
            MenuManager menuMgr = new MenuManager("#PopUp"); 
            menuMgr.add(copyAction);
            styledText.setMenu(menuMgr.createContextMenu(styledText));
        }
        lastText = sampleStyledText;