maybe I misread. I went with
> 95% of annotations in the average haskell codebase are unneeded for compilation
Like type aliases. They are not distinct types, so the compiler doesn't (can't) check that you're using the "right" name.
What I mean is that these annotations are going to prevent compilation if you get them wrong, but the compiler's type inference is good enough that you only need to provide types when there is ambiguity.
That means most of the type annotations written exist because developers find them useful for documentation.
> which happens to be checked against the compiler
as:
> the types aren't checked by the compiler, as my parent poster indicated.
(also type aliases are still checked. The check is less useful, but it's still a check)
> Why would any experienced programmer make such a blanket statement?
Because type annotations are less work than tests or documentation, don't suffer from falling out of sync like doc does, and because experience shows that haskell users typically find it useful to write types despite it not being necessary to compile. It would be surprising to skip types but invest in writing more complicated means of documenting and testing the software.