: {- empty -} { [] }
| cvtopdecls { $1 }
--- tuple expressions: things that can appear unparenthesized as long as they're
+-- "texp" is short for tuple expressions:
+-- things that can appear unparenthesized as long as they're
-- inside parens or delimitted by commas
texp :: { LHsExpr RdrName }
: exp { $1 }
- -- Technically, this should only be used for bang patterns,
- -- but we can be a little more liberal here and avoid parens
- -- inside tuples
- | infixexp qop { LL $ SectionL $1 $2 }
+
+ -- Note [Parsing sections]
+ -- ~~~~~~~~~~~~~~~~~~~~~~~
+ -- We include left and right sections here, which isn't
+ -- technically right according to Haskell 98. For example
+ -- (3 +, True) isn't legal
+ -- However, we want to parse bang patterns like
+ -- (!x, !y)
+ -- and it's convenient to do so here as a section
+ -- Then when converting expr to pattern we unravel it again
+ -- Meanwhile, the renamer checks that real sections appear
+ -- inside parens.
+ | infixexp qop { LL $ SectionL $1 $2 }
| qopm infixexp { LL $ SectionR $1 $2 }
- -- view patterns get parenthesized above
+
+ -- View patterns get parenthesized above
| exp '->' exp { LL $ EViewPat $1 $3 }
texps :: { [LHsExpr RdrName] }
mkNegAppRn e' neg_name `thenM` \ final_e ->
returnM (final_e, fv_e `plusFV` fv_neg)
-rnExpr (HsPar e)
- = rnLExpr e `thenM` \ (e', fvs_e) ->
- returnM (HsPar e', fvs_e)
-
+------------------------------------------
-- Template Haskell extensions
-- Don't ifdef-GHCI them because we want to fail gracefully
-- (not with an rnExpr crash) in a stage-1 compiler.
returnM (expr'', fvs_qq `plusFV` fvs_expr)
#endif /* GHCI */
-rnExpr section@(SectionL expr op)
- = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
- rnLExpr op `thenM` \ (op', fvs_op) ->
- checkSectionPrec InfixL section op' expr' `thenM_`
- returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr)
+---------------------------------------------
+-- Sections
+-- See Note [Parsing sections] in Parser.y.pp
+rnExpr (HsPar (L loc (section@(SectionL {}))))
+ = do { (section', fvs) <- rnSection section
+ ; return (HsPar (L loc section'), fvs) }
+
+rnExpr (HsPar (L loc (section@(SectionR {}))))
+ = do { (section', fvs) <- rnSection section
+ ; return (HsPar (L loc section'), fvs) }
-rnExpr section@(SectionR op expr)
- = rnLExpr op `thenM` \ (op', fvs_op) ->
- rnLExpr expr `thenM` \ (expr', fvs_expr) ->
- checkSectionPrec InfixR section op' expr' `thenM_`
- returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr)
+rnExpr (HsPar e)
+ = do { (e', fvs_e) <- rnLExpr e
+ ; return (HsPar e', fvs_e) }
+rnExpr expr@(SectionL {})
+ = do { addErr (sectionErr expr); rnSection expr }
+rnExpr expr@(SectionR {})
+ = do { addErr (sectionErr expr); rnSection expr }
+
+---------------------------------------------
rnExpr (HsCoreAnn ann expr)
= rnLExpr expr `thenM` \ (expr', fvs_expr) ->
returnM (HsCoreAnn ann expr', fvs_expr)
rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other)
-- HsWrap
-\end{code}
+----------------------
+-- See Note [Parsing sections] in Parser.y.pp
+rnSection :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
+rnSection section@(SectionR op expr)
+ = do { (op', fvs_op) <- rnLExpr op
+ ; (expr', fvs_expr) <- rnLExpr expr
+ ; checkSectionPrec InfixR section op' expr'
+ ; return (SectionR op' expr', fvs_op `plusFV` fvs_expr) }
+
+rnSection section@(SectionL expr op)
+ = do { (expr', fvs_expr) <- rnLExpr expr
+ ; (op', fvs_op) <- rnLExpr op
+ ; checkSectionPrec InfixL section op' expr'
+ ; return (SectionL expr' op', fvs_op `plusFV` fvs_expr) }
+
+rnSection other = pprPanic "rnSection" (ppr other)
+\end{code}
%************************************************************************
%* *
msg = ptext (sLit "Illegal transform or grouping in") <+> pprStmtContext ctxt
---------
+sectionErr :: HsExpr RdrName -> SDoc
+sectionErr expr
+ = hang (ptext (sLit "A section must be enclosed in parentheses"))
+ 2 (ptext (sLit "thus:") <+> (parens (ppr expr)))
+
patSynErr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
patSynErr e = do { addErr (sep [ptext (sLit "Pattern syntax in expression context:"),
nest 4 (ppr e)])