#5728: Warnings from -fwarn-incomplete-record-updates even with all constructors
matched
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Reporter: mjo | Owner:
Type: bug | Status: new
Priority: normal | Milestone: _|_
Component: Compiler | Version: 7.4.1
Keywords: warnings | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Incorrect warning at
compile-time
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by maeder):
This language extension has the disadvantage that:
- the actual selector functions are shadowed and cannot be applied to
other values in subexpressions
- ".." binds variables that may conflict with other pattern variables,
so that extending the record may break my update-code (in separate
modules), like in:
{{{
{-# LANGUAGE RecordWildCards #-}
data Rec = Mt | Rec {a, b, c, d, e, f, g, h, i :: Int}
updA :: Int -> Rec -> Rec
updA i Rec { .. } = Rec { a = i, .. }
updA _ Mt = Mt
}}}
{{{
Rec.hs:5:6:
Conflicting definitions for `i'
Bound at: Rec.hs:5:6
Rec.hs:5:8-17
In an equation for `updA'
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5728#comment:4>
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