Is a fn -> coerces to a fn

Fixes #622.

second-edition/src/ch19-05-advanced-functions-and-closures.md

@@ -6,10 +6,10 @@ closures: function pointers, diverging functions, and returning closures.
 ### Function pointers
 
 We’ve talked about how to pass closures to functions, but you can pass regular
-functions to functions too! Functions have the type `fn`, with a lower case ‘f’
-not to be confused with the `Fn` closure trait. `fn` is called a *function
-pointer*. The syntax for specifying that a parameter is a function pointer is
-similar to that of closures, as shown in Listing 19-34:
+functions to functions too! Functions coerce to the type `fn`, with a lower
+case ‘f’ not to be confused with the `Fn` closure trait. `fn` is called a
+*function pointer*. The syntax for specifying that a parameter is a function
+pointer is similar to that of closures, as shown in Listing 19-34:
 
 <span class="filename">Filename: src/main.rs</span>