Improve granularity of UndecidableInstances
Currently, as a LANGUAGE pragma, UndecidableInstances can only be set once per file: Assuming that there are enough occasions where one would only need to enable it for one or two instances in a bigger source and considering that the warnings emitted if UndecidableInstances is not set are actually useful, it makes sense to support enabling the extension only on a per-instance basis.
proposed syntax:
{-# LANGUAGE UndecidableInstances #-}
[code]
{-# NOLANGUAGE UndecidableInstances #-}
Trac metadata
Trac field | Value |
---|---|
Version | 6.10.4 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
Architecture |