Bug 52064 Content assist in "New Class" Dialog shows interfaces
Content Assist is available for the superclass in M7. However it also lists interfaces. If an interface is selected, the generated class "extends" it instead of "implementing" it.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/wizards/NewTypeWizardPage.java
protected String constructCUContent(ICompilationUnit cu, String typeContent, String lineDelimiter) throws CoreException {
		String typeComment= getTypeComment(cu, lineDelimiter);
		IPackageFragment pack= (IPackageFragment) cu.getParent();
		String content= CodeGeneration.getCompilationUnitContent(cu, typeComment, typeContent, lineDelimiter);
		if (content != null) {
			ASTParser parser= ASTParser.newParser(AST.JLS2);
			parser.setSource(content.toCharArray());
			CompilationUnit unit= (CompilationUnit) parser.createAST(null);
			if ((pack.isDefaultPackage() || unit.getPackage() != null) && !unit.types().isEmpty()) {
				return content;
			}
		}
		StringBuffer buf= new StringBuffer();
		if (!pack.isDefaultPackage()) {
			buf.append("package ").append(pack.getElementName()).append(';'); 
		}
		buf.append(lineDelimiter).append(lineDelimiter);
		if (typeComment != null) {
			buf.append(typeComment).append(lineDelimiter);
		}
		buf.append(typeContent);
		return buf.toString();
	}
	
	/**
	 * Returns the created type. The method only returns a valid type 
	 * after <code>createType</code> has been called.
	 * 
	 * @return the created type
	 * @see #createType(IProgressMonitor)