Add support for overloaded string literals.

[ghc-hetmet.git] / compiler / typecheck / TcPat.lhs

diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs
index f945292..4fe704a 100644 (file)
--- a/compiler/typecheck/TcPat.lhs
+++ b/compiler/typecheck/TcPat.lhs
@@ -555,7 +555,7 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside
        ; ex_tvs' <- tcInstSkolTyVars skol_info ex_tvs  -- Get location from monad,
                                                        -- not from ex_tvs
        ; let tenv     = zipTopTvSubst (univ_tvs ++ ex_tvs)
-                                     (ctxt_res_tys ++ mkTyVarTys ex_tvs')
+                                      (ctxt_res_tys ++ mkTyVarTys ex_tvs')
              eq_spec' = substEqSpec tenv eq_spec
              theta'   = substTheta  tenv theta
              arg_tys' = substTys    tenv arg_tys
@@ -813,6 +813,19 @@ tcOverloadedLit orig lit@(HsFractional r fr) res_ty
   = do         { expr <- newLitInst orig lit res_ty
        ; return (HsFractional r expr) }
 
+tcOverloadedLit orig lit@(HsIsString s fr) res_ty
+  | not (fr `isHsVar` fromStringName)  -- c.f. HsIntegral case
+  = do { str_ty <- tcMetaTy stringTyConName
+       ; fr' <- tcSyntaxOp orig fr (mkFunTy str_ty res_ty)
+       ; return (HsIsString s (HsApp (noLoc fr') (nlHsLit (HsString s)))) }
+
+  | Just expr <- shortCutStringLit s res_ty 
+  = return (HsIsString s expr)
+
+  | otherwise
+  = do         { expr <- newLitInst orig lit res_ty
+       ; return (HsIsString s expr) }
+
 newLitInst :: InstOrigin -> HsOverLit Name -> BoxyRhoType -> TcM (HsExpr TcId)
 newLitInst orig lit res_ty     -- Make a LitInst
   = do         { loc <- getInstLoc orig
@@ -919,13 +932,12 @@ sigPatCtxt pats bound_tvs pat_tys body_ty tidy_env
                 sep [ptext SLIT("When checking an existential match that binds"),
                      nest 4 (vcat (zipWith ppr_id show_ids tidy_tys)),
                      ptext SLIT("The pattern(s) have type(s):") <+> vcat (map ppr tidy_pat_tys),
-                     ptext SLIT("The body has type:") <+> ppr tidy_body_ty,
-                     ppr pats
+                     ptext SLIT("The body has type:") <+> ppr tidy_body_ty
                ]) }
   where
     bound_ids = collectPatsBinders pats
     show_ids = filter is_interesting bound_ids
-    is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs
+    is_interesting id = any (`elemVarSet` varTypeTyVars id) bound_tvs
 
     ppr_id id ty = ppr id <+> dcolon <+> ppr ty
        -- Don't zonk the types so we get the separate, un-unified versions