From 6b5154696d7481a04ad4cb4dfd979a8a9010dc40 Mon Sep 17 00:00:00 2001
From: Yu-Hsi Chiang <arbuz.tw@gmail.com>
Date: Sun, 1 Oct 2017 23:57:54 +0800
Subject: [PATCH] Add a `FromParam` instance for String.

---
 fn/src/Web/Fn.hs | 4 ++++
 fn/test/Spec.hs  | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/fn/src/Web/Fn.hs b/fn/src/Web/Fn.hs
index 6b5ba7d..03ae8b1 100644
--- a/fn/src/Web/Fn.hs
+++ b/fn/src/Web/Fn.hs
@@ -423,6 +423,10 @@ instance FromParam Text where
   fromParam [x] = Right x
   fromParam [] = Left ParamMissing
   fromParam _ = Left ParamTooMany
+instance {-# INCOHERENT #-} FromParam String where
+  fromParam [t] = Right (T.unpack t)
+  fromParam [] = Left ParamMissing
+  fromParam _ = Left ParamTooMany
 instance FromParam Int where
   fromParam [t] = case decimal t of
                     Left _ -> Left ParamUnparsable
diff --git a/fn/test/Spec.hs b/fn/test/Spec.hs
index ce55a63..4fee779 100644
--- a/fn/test/Spec.hs
+++ b/fn/test/Spec.hs
@@ -170,6 +170,8 @@ main = hspec $ do
   describe "parameter parsing" $
     do it "should parse Text" $
          fromParam ["hello"] `shouldBe` Right ("hello" :: Text)
+       it "should parse String" $
+         fromParam ["hello"] `shouldBe` Right ("hello" :: String)
        it "should parse Int" $
          do fromParam ["1"] `shouldBe` Right (1 :: Int)
             fromParam ["2011"] `shouldBe` Right (2011 :: Int)