[ ghc-Bugs-1075259 ] Wrong overlapped pattern warning for n+k Pattern

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Bugs item #1075259, was opened at 2004-11-29 06:00
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Category: Compiler (Parser)
Group: 6.2.2
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: Wrong overlapped pattern warning for n+k Pattern

Initial Comment:
compiling:

  module Overlap where

  f (n+1) = 2
  f 0     = 1

emits wrongly:

    Warning: Pattern match(es) are overlapped
             In the definition of `f': f 0 = ...


The Patterns are disjoint, aren't they? At least  "f 0"
yields "1" when evaluated and negative inputs for f are
rejected. However the warning is not emitted if the two
equations are given in reversed order.

Christian (maeder at tzi.de)


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