GHC HEAD no longer reports inaccessible code
Given this A.hs:
{-# LANGUAGE GADTs #-}
module A where
f :: Bool ~ Int => a -> b
f x = x
I get:
ezyang@sabre:~$ ghc-head --version
The Glorious Glasgow Haskell Compilation System, version 8.1.20161010
ezyang@sabre:~$ ghc-head --make A.hs
[1 of 1] Compiling A ( A.hs, A.o )
A.hs:4:1: warning: [-Woverlapping-patterns]
Pattern match is redundant
In an equation for ‘f’: f x = ...
In contrast:
ezyang@sabre:~$ ghc-8.0 --make A.hs
[1 of 1] Compiling A ( A.hs, A.o )
A.hs:3:6: error:
• Couldn't match type ‘Bool’ with ‘Int’
Inaccessible code in
the type signature for:
f :: Bool ~ Int => a -> b
• In the ambiguity check for ‘f’
To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
In the type signature:
f :: Bool ~ Int => a -> b
Is this expected? I'd expect at least a warning!
Trac metadata
Trac field | Value |
---|---|
Version | 8.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | goldfire |
Operating system | |
Architecture |