diff options
| author | Simon Marlow <marlowsd@gmail.com> | 2013-09-27 20:59:41 +0100 |
|---|---|---|
| committer | Simon Marlow <marlowsd@gmail.com> | 2013-10-01 11:45:46 +0100 |
| commit | aab65608f9a26990b2c5083e4b65b9d1f6c9b48a (patch) | |
| tree | 6af79a93a7e17dedf73f3e9d66e9a522ce6c0ece /compiler/parser/Parser.y.pp | |
| parent | c0f89a1b536d9cd3640803138d5f794982049cce (diff) | |
| download | haskell-aab65608f9a26990b2c5083e4b65b9d1f6c9b48a.tar.gz | |
Add layout to MultiWayIf (#7783)
This makes it possible to write
x = if | False -> if | False -> 1
| False -> 2
| True -> 3
Layout normally inserts semicolons between declarations at the same
indentation level, so I added optional semicolons to the syntax for
guards in MultiWayIf syntax. This is a bit of a hack, but the
alternative (a special kind of layout that doesn't insert semicolons)
seemed worse, or at least equally bad.
Diffstat (limited to 'compiler/parser/Parser.y.pp')
| -rw-r--r-- | compiler/parser/Parser.y.pp | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/compiler/parser/Parser.y.pp b/compiler/parser/Parser.y.pp index ea192a0060..c2ddf452cc 100644 --- a/compiler/parser/Parser.y.pp +++ b/compiler/parser/Parser.y.pp @@ -1459,7 +1459,7 @@ exp10 :: { LHsExpr RdrName } | 'if' exp optSemi 'then' exp optSemi 'else' exp {% checkDoAndIfThenElse $2 $3 $5 $6 $8 >> return (LL $ mkHsIf $2 $5 $8) } - | 'if' gdpats {% hintMultiWayIf (getLoc $1) >> + | 'if' ifgdpats {% hintMultiWayIf (getLoc $1) >> return (LL $ HsMultiIf placeHolderType (reverse $ unLoc $2)) } | 'case' exp 'of' altslist { LL $ HsCase $2 (mkMatchGroup (unLoc $4)) } | '-' fexp { LL $ NegApp $2 noSyntaxExpr } @@ -1754,6 +1754,19 @@ gdpats :: { Located [LGRHS RdrName (LHsExpr RdrName)] } : gdpats gdpat { LL ($2 : unLoc $1) } | gdpat { L1 [$1] } +-- optional semi-colons between the guards of a MultiWayIf, because we use +-- layout here, but we don't need (or want) the semicolon as a separator (#7783). +gdpatssemi :: { Located [LGRHS RdrName (LHsExpr RdrName)] } + : gdpatssemi gdpat optSemi { sL (comb2 $1 $2) ($2 : unLoc $1) } + | gdpat optSemi { L1 [$1] } + +-- layout for MultiWayIf doesn't begin with an open brace, because it's hard to +-- generate the open brace in addition to the vertical bar in the lexer, and +-- we don't need it. +ifgdpats :: { Located [LGRHS RdrName (LHsExpr RdrName)] } + : '{' gdpatssemi '}' { LL (unLoc $2) } + | gdpatssemi close { $1 } + gdpat :: { LGRHS RdrName (LHsExpr RdrName) } : '|' guardquals '->' exp { sL (comb2 $1 $>) $ GRHS (unLoc $2) $4 } |