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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