Conflicting definitions error does not print explicit quantifiers when necessary
```hs
-- Y.hs-boot
{-# LANGUAGE ScopedTypeVariables #-}
module Y where
f :: forall a b. (a, b)
-- YY.hs
module YY where
import {-# SOURCE #-} Y
-- Y.hs
{-# LANGUAGE ScopedTypeVariables #-}
module Y where
import YY
f :: forall b a. (a, b)
f = undefined
```
I get the following unhelpful error:
```
ezyang@sabre:~$ ghc-8.0 --make Y.hs -fforce-recomp
[1 of 3] Compiling Y[boot] ( Y.hs-boot, Y.o-boot )
[2 of 3] Compiling YY ( YY.hs, YY.o )
[3 of 3] Compiling Y ( Y.hs, Y.o )
Y.hs-boot:3:1: error:
Identifier ‘f’ has conflicting definitions in the module
and its hs-boot file
Main module: f :: (a, b)
Boot file: f :: (a, b)
The two types are different
```
Yes this example is purposely shooting itself in the foot, but in the wild I encountered an un-annotated type which inferred a different quantifier ordering than what I expected, and I subsequently spent a while puzzling over the error message. `-fprint-explicit-foralls` is a sufficient workaround.
issue