surprising error message with bang pattern
the following code
f3 :: [Int] -> IO Int
f3 x = return (sum x)
f4 :: [Int] -> IO Int
f4 !x = return (sum x) gives The type signature for ‘f4’ lacks an accompanying binding for the second function (the two functions are exactly the same except for the added bang). I do not understand bang patterns well, but would expect a more instructive error message. without the type definition, the second function f4 compiles with the bang).
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.0.2 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | Linux |
| Architecture | x86_64 (amd64) |
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information