2 Sep
2017
2 Sep
'17
8:53 a.m.
On Sat, 2 Sep 2017, Artyom wrote:
Background
IsString is a class that is used with the -XOverloadedStrings extension to support string literals of types other than String - for instance, with the IsString Text instance in scope, you can write "foobar" :: Text and it will compile.
String literals are still allowed to be empty. That is, "" :: NonEmpty Char would now be accepted but would be undefined. It's pretty easy for a user to make a non-empty literal empty if he does not know the code and he would not notice that "" is actually undefined in this context. Thus I think the original programmer should make explicit the problem either by the ugly ('f' :| "oobar") notation or using a partial function like (nonEmptyString "foobar").