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  • #14112

Closed
Open
Opened Aug 14, 2017 by Carter Schonwald@carterDeveloper

bang patterns on pattern synonyms? (left vs right hand sides)

I'm trying to define my own fancy strict maybe types, and so i've written some pattern synonyms to wrap them up.

imagine my surprise when i find i can write bang patterns on the *right* hand side, but not the left hand!

data MyMaybe a = JustC a | NothingC

pattern MyJust :: a -> MyMaybe a
-- pattern MyJust !a = JustC a -- this fails
pattern MyJust a = JustC !a -- this is fine

is this deliberate or a leakage of how desugaring works?

Trac metadata
Trac field Value
Version 8.2.1
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
Assignee
Assign to
8.4.1
Milestone
8.4.1 (Past due)
Assign milestone
Time tracking
None
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None
Reference: ghc/ghc#14112