* d...@veryhaha.com <d...@veryhaha.com> [161013 08:42]:
> https://golang.org/ref/spec#Type_assertions
>     var x interface{} = 7  // x has dynamic type int and value 7
>     i := x.(int)           // i has type int and value 7
>     type I interface { m() }
>     var y I
>     s := y.(string)        // illegal: string does not implement I (missing 
> method m)
>     r := y.(io.Reader)     // r has type io.Reader and y must implement 
> both I and io.Reader
> I don't understand the comment of the last line. Can someone explain it for 
> me?

To expand on what Jan Mercl said, the spec separates x.(T) into two
cases:  T is not an interface type, and T is an interface type.  The
example above (from the spec) is giving an example of each case.  The
compiler can detect the first case, but the second case must be checked
at runtime.


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