refutable let bindings produce "irrefutable pattern failed" errors
In ghc-8.2.2 (probably since ghc-8.0.1), strict pattern matches in let bindings produce "Irrefutable pattern failed" errors.
GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help
Prelude> :set -XBangPatterns
Prelude> let ![] = [1] in 1
*** Exception: <interactive>:2:5-13: Irrefutable pattern failed for pattern []
In ghc-7.10.2, normal pattern match failures were produced.
GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help
Prelude> :set -XBangPatterns
Prelude> let ![] = [1] in 1
*** Exception: <interactive>:3:5-13: Non-exhaustive patterns in pattern binding
To my mind, the latter error makes much more sense; the effect of the ! is to make the pattern an ordinary, refutable one. Could the old behavior be restored?
Trac metadata
Trac field | Value |
---|---|
Version | 8.2.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
Architecture |