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Simon Marlow authored
This commit replaces the old yacc parser with a Happy-generated one. Notes: - The generated .hs file is *big*. Best to use a recent version of Happy, and even better to add the -c flag to use unsafeCoerce# with ghc (versions 4.02+ please). - The lexer has grown all sorts of unsightly growths and should be put down as soon as possible. - Parse errors may result in strange diagnostics. I'm looking into this. - HsSyn now contains a few extra constructors due to the way patterns are parsed as expressions in the parser. - The layout rule is implemented according to the Haskell report. I found a couple of places in the libraries where we previously weren't adhering to this - in particular the rule about "nested contexts must be more indented than outer contexts". The rule is necessary to disambiguate in the presence of empty declaration lists.
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