title: Restricting string literals to Text only
body: <p>I'm aware that the <code>OverloadedStrings</code> language pragma wraps an implicit <code>fromString</code> around all string literals. What I'd like to do is not actually <em>overload</em> strings, but merely change their meaning so that they are <em>always</em> turned into <code>Text</code>, and therefore, using a string literal as a list of characters should result in a type error.</p>
  
  <p>It appears to be impossible to import the <code>IsString</code> class without also importing the <code>String</code> instance for that class. Does ghc provide some way for me to restrict string literals to <code>Text</code> only?</p>