import {-# SOURCE #-} DsExpr ( dsExpr, dsLet )
import {-# SOURCE #-} Match ( matchSinglePat )
-import HsSyn ( Stmt(..), HsExpr(..), GRHSs(..), GRHS(..) )
+import HsSyn ( Stmt(..), HsExpr(..), GRHSs(..), GRHS(..), HsMatchContext(..) )
import TcHsSyn ( TypecheckedGRHSs, TypecheckedPat, TypecheckedStmt )
import CoreSyn ( CoreExpr )
import Type ( Type )
dsGuarded :: TypecheckedGRHSs -> DsM CoreExpr
dsGuarded grhss
- = dsGRHSs PatBindMatch [] grhss `thenDs` \ (err_ty, match_result) ->
+ = dsGRHSs PatBindRhs [] grhss `thenDs` \ (err_ty, match_result) ->
mkErrorAppDs nON_EXHAUSTIVE_GUARDS_ERROR_ID err_ty "" `thenDs` \ error_expr ->
extractMatchResult match_result error_expr
\end{code}
In contrast, @dsGRHSs@ produces a @MatchResult@.
\begin{code}
-dsGRHSs :: DsMatchKind -> [TypecheckedPat] -- These are to build a MatchContext from
+dsGRHSs :: HsMatchContext -> [TypecheckedPat] -- These are to build a MatchContext from
-> TypecheckedGRHSs -- Guarded RHSs
-> DsM (Type, MatchResult)
-> DsMatchContext -- Context
-> DsM MatchResult
-matchGuard (ExprStmt expr locn : should_be_null) ctx
+-- See comments with HsExpr.HsStmt re what an ExprStmt means
+-- Here we must be in a guard context (not do-expression, nor list-comp)
+
+matchGuard [ExprStmt expr locn] ctx
= putSrcLocDs locn (dsExpr expr) `thenDs` \ core_expr ->
returnDs (cantFailMatchResult core_expr)
+ -- Other ExprStmts must be guards
-- Turn an "otherwise" guard is a no-op
-matchGuard (GuardStmt (HsVar v) _ : stmts) ctx
+matchGuard (ExprStmt (HsVar v) _ : stmts) ctx
| v `hasKey` otherwiseIdKey
|| v `hasKey` trueDataConKey
= matchGuard stmts ctx
-matchGuard (GuardStmt expr locn : stmts) ctx
+matchGuard (ExprStmt expr locn : stmts) ctx
= matchGuard stmts ctx `thenDs` \ match_result ->
putSrcLocDs locn (dsExpr expr) `thenDs` \ pred_expr ->
returnDs (mkGuardedMatchResult pred_expr match_result)