#984: Syntax error shows in the wrong position
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Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Parser) | Version: 6.4.2
Severity: normal | Keywords: syntax parse case do
Difficulty: Unknown | Testcase:
Architecture: x86 | Os: Linux
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This bug concerns the behaviour of GHC on erroneous programs. GHC
recognizes the illegal syntax, but shows an unrelated error.
This problem is best illustrated in the following code:
{{{
f _ = do
x <- computation
case () of
_ ->
result <- computation
case () of () -> undefined
}}}
The error in this code is the missing "do" keyword on line 5, and the
compiler should suspect this when seeing the "<-" on line 6.
However, GHC gives the following error:
bug.hs:3:8: Parse error in pattern
This is misleading, since the line number is incorrect, and the syntax
error (as well is line 3) is unrelated to patterns.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/984>
GHC <http://www.haskell.org/ghc/>
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