In ch3, section on Reading Type Errors, the error message presented for "one " :: Int
with IsString
seems non-standard, ie not from a minimal ghci session perhaps? Also note the space after e.
For all current GHC 9 versions I get;
ghci> "one" :: Int
<interactive>:1:1: error:
• Couldn't match type ‘[Char]’ with ‘Int’
Expected: Int
Actual: String
• In the expression: "one" :: Int
In an equation for ‘it’: it = "one" :: Int
(ghc-8.10 is slightly different but also no IsString.)
Of course it’s quite likely one will run into the IsString error IRL…