如何减少 GHC 类型错误消息的大小？

Question

例如，

test/Spec.hs:42:18: error:
    • No instance for (genvalidity-0.8.0.0:Data.GenValidity.GenUnchecked
                         (Decl UnkindedType Identifier Location))
        arising from a use of ‘forAllUnchecked’
    • In the second argument of ‘it’, namely
        ‘(forAllUnchecked
            (\ decls
               -> shouldBe
                    (either
                       (const ())
                       (const ())
        ... 50 (literally) more lines ...

太长了，我必须向上滚动我的终端/消息查看器才能看到发生了什么。我只需要行号和列。

是否有一个 GHC 标志让它输出这个？

test/Spec.hs:42:18: error:
    • No instance for (genvalidity-0.8.0.0:Data.GenValidity.GenUnchecked
                         (Decl UnkindedType Identifier Location))
        arising from a use of ‘forAllUnchecked’

这给了我我需要的一切。

Answer 1

到目前为止，我想出的最好的是：

-dppr-user-length=0 -dppr-cols=10000

产生

test/Spec.hs:42:18: error:
    • No instance for (genvalidity-0.8.0.0:Data.GenValidity.GenUnchecked (Decl UnkindedType Identifier Location)) arising from a use of ‘forAllUnchecked’
    • In the second argument of ‘it’, namely ‘(forAllUnchecked (\ decls -> ...))’
      In a stmt of a 'do' block: it "Compiler terminates" (forAllUnchecked (\ decls -> ...))
      In the second argument of ‘describe’, namely ‘(do ...)’
   |
42 |                 (forAllUnchecked
   |                  ^^^^^^^^^^^^^^^...

它仍然占用空间，但比以前少得多。我会接受更好的答案。