-- The SyntaxExprs in here are used *only* for do-notation and monad
-- comprehensions, which have rebindable syntax. Otherwise they are unused.
data StmtLR idL idR
- = LastStmt -- Always the last Stmt in ListComp, MonadComp, PArrComp, DoExpr, MDoExpr
+ = LastStmt -- Always the last Stmt in ListComp, MonadComp, PArrComp,
+ -- and (after the renamer) DoExpr, MDoExpr
-- Not used for GhciStmt, PatGuard, which scope over other stuff
(LHsExpr idR)
(SyntaxExpr idR) -- The return operator, used only for MonadComp
-- with type (forall a. a -> m a)
-- See notes [Monad Comprehensions]
-- After renaming, the ids are the binders
- -- bound by the stmts and used after them
+ -- bound by the stmts and used after themp
- -- "qs, then f by e" ==> TransformStmt qs binders f (Just e) (return) (>>=)
- -- "qs, then f" ==> TransformStmt qs binders f Nothing (return) (>>=)
- | TransformStmt
- [LStmt idL] -- Stmts are the ones to the left of the 'then'
-
- [idR] -- After renaming, the Ids are the binders occurring
- -- within this transform statement that are used after it
-
- (LHsExpr idR) -- "then f"
-
- (Maybe (LHsExpr idR)) -- "by e" (optional)
-
- (SyntaxExpr idR) -- The 'return' function for inner monad
- -- comprehensions
- (SyntaxExpr idR) -- The '(>>=)' operator.
- -- See Note [Monad Comprehensions]
-
- | GroupStmt {
- grpS_stmts :: [LStmt idL], -- Stmts to the *left* of the 'group'
+ | TransStmt {
+ trS_form :: TransForm,
+ trS_stmts :: [LStmt idL], -- Stmts to the *left* of the 'group'
-- which generates the tuples to be grouped
- grpS_bndrs :: [(idR, idR)], -- See Note [GroupStmt binder map]
+ trS_bndrs :: [(idR, idR)], -- See Note [TransStmt binder map]
- grpS_by :: Maybe (LHsExpr idR), -- "by e" (optional)
-
- grpS_using :: LHsExpr idR,
- grpS_explicit :: Bool, -- True <=> explicit "using f"
- -- False <=> implicit; grpS_using is filled in with
- -- 'groupWith' (list comprehensions) or
- -- 'groupM' (monad comprehensions)
-
- -- Invariant: if grpS_explicit = False, then grp_by = Just e
- -- That is, we can have group by e
- -- group using f
- -- group by e using f
-
- grpS_ret :: SyntaxExpr idR, -- The 'return' function for inner monad
- -- comprehensions
- grpS_bind :: SyntaxExpr idR, -- The '(>>=)' operator
- grpS_fmap :: SyntaxExpr idR -- The polymorphic 'fmap' function for desugaring
+ trS_using :: LHsExpr idR,
+ trS_by :: Maybe (LHsExpr idR), -- "by e" (optional)
+ -- Invariant: if trS_form = GroupBy, then grp_by = Just e
+
+ trS_ret :: SyntaxExpr idR, -- The monomorphic 'return' function for
+ -- the inner monad comprehensions
+ trS_bind :: SyntaxExpr idR, -- The '(>>=)' operator
+ trS_fmap :: SyntaxExpr idR -- The polymorphic 'fmap' function for desugaring
+ -- Only for 'group' forms
} -- See Note [Monad Comprehensions]
-- Recursive statement (see Note [How RecStmt works] below)
-- be quite as simple as (m (tya, tyb, tyc)).
}
deriving (Data, Typeable)
+
+data TransForm -- The 'f' below is the 'using' function, 'e' is the by function
+ = ThenForm -- then f or then f by e
+ | GroupFormU -- group using f or group using f by e
+ | GroupFormB -- group by e
+ -- In the GroupByFormB, trS_using is filled in with
+ -- 'groupWith' (list comprehensions) or
+ -- 'groupM' (monad comprehensions)
+ deriving (Data, Typeable)
\end{code}
Note [The type of bind in Stmts]
So we must be careful not to make assumptions about the type.
In particular, the monad may not be uniform throughout.
-Note [GroupStmt binder map]
+Note [TransStmt binder map]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The [(idR,idR)] in a GroupStmt behaves as follows:
+The [(idR,idR)] in a TransStmt behaves as follows:
* Before renaming: []
ppr stmt = pprStmt stmt
pprStmt :: (OutputableBndr idL, OutputableBndr idR) => (StmtLR idL idR) -> SDoc
-pprStmt (LastStmt expr _) = ppr expr
+pprStmt (LastStmt expr _) = ifPprDebug (ptext (sLit "[last]")) <+> ppr expr
pprStmt (BindStmt pat expr _ _) = hsep [ppr pat, ptext (sLit "<-"), ppr expr]
pprStmt (LetStmt binds) = hsep [ptext (sLit "let"), pprBinds binds]
pprStmt (ExprStmt expr _ _ _) = ppr expr
pprStmt (ParStmt stmtss _ _ _) = hsep (map doStmts stmtss)
where doStmts stmts = ptext (sLit "| ") <> ppr stmts
-pprStmt (TransformStmt stmts bndrs using by _ _)
- = sep (ppr_lc_stmts stmts ++ [pprTransformStmt bndrs using by])
-
-pprStmt (GroupStmt { grpS_stmts = stmts, grpS_by = by, grpS_using = using, grpS_explicit = explicit })
- = sep (ppr_lc_stmts stmts ++ [pprGroupStmt by using explicit])
+pprStmt (TransStmt { trS_stmts = stmts, trS_by = by, trS_using = using, trS_form = form })
+ = sep (ppr_lc_stmts stmts ++ [pprTransStmt by using form])
pprStmt (RecStmt { recS_stmts = segment, recS_rec_ids = rec_ids
, recS_later_ids = later_ids })
, nest 2 (ppr using)
, nest 2 (pprBy by)]
-pprGroupStmt :: OutputableBndr id => Maybe (LHsExpr id)
- -> LHsExpr id -> Bool
+pprTransStmt :: OutputableBndr id => Maybe (LHsExpr id)
+ -> LHsExpr id -> TransForm
-> SDoc
-pprGroupStmt by using explicit
- = sep [ ptext (sLit "then group"), nest 2 (pprBy by), nest 2 pp_using ]
- where
- pp_using | explicit = ptext (sLit "using") <+> ppr using
- | otherwise = empty
+pprTransStmt by using ThenForm
+ = sep [ ptext (sLit "then"), nest 2 (ppr using), nest 2 (pprBy by)]
+pprTransStmt by _ GroupFormB
+ = sep [ ptext (sLit "then group"), nest 2 (pprBy by) ]
+pprTransStmt by using GroupFormU
+ = sep [ ptext (sLit "then group"), nest 2 (pprBy by), nest 2 (ptext (sLit "using") <+> ppr using)]
pprBy :: OutputableBndr id => Maybe (LHsExpr id) -> SDoc
pprBy Nothing = empty
-----------------
pprStmtContext GhciStmt = ptext (sLit "interactive GHCi command")
-pprStmtContext DoExpr = ptext (sLit "'do' expression")
-pprStmtContext MDoExpr = ptext (sLit "'mdo' expression")
+pprStmtContext DoExpr = ptext (sLit "'do' block")
+pprStmtContext MDoExpr = ptext (sLit "'mdo' block")
pprStmtContext ListComp = ptext (sLit "list comprehension")
pprStmtContext MonadComp = ptext (sLit "monad comprehension")
pprStmtContext PArrComp = ptext (sLit "array comprehension")
pprStmtInCtxt :: (OutputableBndr idL, OutputableBndr idR)
=> HsStmtContext idL -> StmtLR idL idR -> SDoc
-pprStmtInCtxt ctxt stmt = hang (ptext (sLit "In a stmt of") <+> pprAStmtContext ctxt <> colon)
- 4 (ppr_stmt stmt)
+pprStmtInCtxt ctxt (LastStmt e _)
+ | isListCompExpr ctxt -- For [ e | .. ], do not mutter about "stmts"
+ = hang (ptext (sLit "In the expression:")) 2 (ppr e)
+
+pprStmtInCtxt ctxt stmt
+ = hang (ptext (sLit "In a stmt of") <+> pprAStmtContext ctxt <> colon)
+ 2 (ppr_stmt stmt)
where
-- For Group and Transform Stmts, don't print the nested stmts!
- ppr_stmt (GroupStmt { grpS_by = by, grpS_using = using
- , grpS_explicit = explicit }) = pprGroupStmt by using explicit
- ppr_stmt (TransformStmt _ bndrs using by _ _) = pprTransformStmt bndrs using by
- ppr_stmt stmt = pprStmt stmt
+ ppr_stmt (TransStmt { trS_by = by, trS_using = using
+ , trS_form = form }) = pprTransStmt by using form
+ ppr_stmt stmt = pprStmt stmt
\end{code}
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