+Consider
+\begin{verbatim}
+ a `op1` b `op2` c
+\end{verbatim}
+@(compareFixity op1 op2)@ tells which way to arrange appication, or
+whether there's an error.
+
+\begin{code}
+compareFixity :: Fixity -> Fixity
+ -> (Bool, -- Error please
+ Bool) -- Associate to the right: a op1 (b op2 c)
+compareFixity (Fixity prec1 dir1) (Fixity prec2 dir2)
+ = case prec1 `compare` prec2 of
+ GT -> left
+ LT -> right
+ EQ -> case (dir1, dir2) of
+ (InfixR, InfixR) -> right
+ (InfixL, InfixL) -> left
+ _ -> error_please
+ where
+ right = (False, True)
+ left = (False, False)
+ error_please = (True, False)
+\end{code}
+
+%************************************************************************
+%* *
+\subsubsection{Literals}
+%* *
+%************************************************************************
+
+When literals occur we have to make sure
+that the types and classes they involve
+are made available.
+
+\begin{code}
+litFVs (HsChar c) = returnRn (unitFV charTyCon_name)
+litFVs (HsCharPrim c) = returnRn (unitFV (getName charPrimTyCon))
+litFVs (HsString s) = returnRn (mkFVs [listTyCon_name, charTyCon_name])
+litFVs (HsStringPrim s) = returnRn (unitFV (getName addrPrimTyCon))
+litFVs (HsInt i) = returnRn (unitFV (getName intTyCon))
+litFVs (HsIntPrim i) = returnRn (unitFV (getName intPrimTyCon))
+litFVs (HsFloatPrim f) = returnRn (unitFV (getName floatPrimTyCon))
+litFVs (HsDoublePrim d) = returnRn (unitFV (getName doublePrimTyCon))
+litFVs (HsLitLit l bogus_ty) = lookupOrigName cCallableClass_RDR `thenRn` \ cc ->
+ returnRn (unitFV cc)
+litFVs lit = pprPanic "RnExpr.litFVs" (ppr lit) -- HsInteger and HsRat only appear
+ -- in post-typechecker translations
+
+rnOverLit (HsIntegral i from_integer)
+ = lookupOccRn from_integer `thenRn` \ from_integer' ->
+ (if inIntRange i then
+ returnRn emptyFVs
+ else
+ lookupOrigNames [plusInteger_RDR, timesInteger_RDR]
+ ) `thenRn` \ ns ->
+ returnRn (HsIntegral i from_integer', ns `addOneFV` from_integer')
+
+rnOverLit (HsFractional i n)
+ = lookupOccRn n `thenRn` \ n' ->
+ lookupOrigNames [ratioDataCon_RDR, plusInteger_RDR, timesInteger_RDR] `thenRn` \ ns' ->
+ -- We have to make sure that the Ratio type is imported with
+ -- its constructor, because literals of type Ratio t are
+ -- built with that constructor.
+ -- The Rational type is needed too, but that will come in
+ -- when fractionalClass does.
+ -- The plus/times integer operations may be needed to construct the numerator
+ -- and denominator (see DsUtils.mkIntegerLit)
+ returnRn (HsFractional i n', ns' `addOneFV` n')
+\end{code}
+
+%************************************************************************
+%* *
+\subsubsection{Assertion utils}
+%* *
+%************************************************************************
+
+\begin{code}
+mkAssertExpr :: RnMS (RenamedHsExpr, FreeVars)
+mkAssertExpr =
+ lookupOrigName assertErr_RDR `thenRn` \ name ->
+ getSrcLocRn `thenRn` \ sloc ->
+
+ -- if we're ignoring asserts, return (\ _ e -> e)
+ -- if not, return (assertError "src-loc")
+
+ if opt_IgnoreAsserts then
+ getUniqRn `thenRn` \ uniq ->
+ let
+ vname = mkSysLocalName uniq SLIT("v")
+ expr = HsLam ignorePredMatch
+ loc = nameSrcLoc vname
+ ignorePredMatch = Match [] [WildPatIn, VarPatIn vname] Nothing
+ (GRHSs [GRHS [ExprStmt (HsVar vname) loc] loc]
+ EmptyBinds Nothing)
+ in
+ returnRn (expr, unitFV name)
+ else
+ let
+ expr =
+ HsApp (HsVar name)
+ (HsLit (HsString (_PK_ (showSDoc (ppr sloc)))))
+
+ in
+ returnRn (expr, unitFV name)
+
+\end{code}
+
+%************************************************************************
+%* *
+\subsubsection{Errors}
+%* *
+%************************************************************************
+