FAQ: small improvement in 'this type' answer (#2195)

Author: SethTisue

_overviews/FAQ/index.md

@@ -229,7 +229,12 @@ For an in-depth treatment of types vs. classes, see the blog post
 
 ### How can a method in a superclass return a value of the “current” type?
 
-Possible solutions include F-bounded polymorphism
+First, note that using `this.type` won't work. People often try that,
+but `this.type` means "the singleton type of this instance", a
+different and too-specific meaning.  Only `this` itself has the
+type `this.type`; other instances do not.
+
+What does work? Possible solutions include F-bounded polymorphism
 _(familiar to Java programmers)_, type members,
 and the [typeclass pattern](http://tpolecat.github.io/2013/10/12/typeclass.html).