[project @ 2003-07-09 11:08:03 by simonpj]

---------------------------------------
	Wibble to GHCi constraint simplification
	---------------------------------------

The new GHCi constraint-simplification story, with defaulting for
Show, Eq, Ord, should only apply to command-line expressions, not
to modules loaded by GHCi.

Hence new variant, TcSimplify.tcSimplifyInteractive

diff --git a/ghc/compiler/typecheck/TcSimplify.lhs b/ghc/compiler/typecheck/TcSimplify.lhs
index ff51c42..754af98 100644 (file)
--- a/ghc/compiler/typecheck/TcSimplify.lhs
+++ b/ghc/compiler/typecheck/TcSimplify.lhs
@@ -9,7 +9,8 @@
 module TcSimplify (
        tcSimplifyInfer, tcSimplifyInferCheck,
        tcSimplifyCheck, tcSimplifyRestricted,
-       tcSimplifyToDicts, tcSimplifyIPs, tcSimplifyTop,
+       tcSimplifyToDicts, tcSimplifyIPs, 
+       tcSimplifyTop, tcSimplifyInteractive,
        tcSimplifyBracket,
 
        tcSimplifyDeriv, tcSimplifyDefault,
@@ -1620,10 +1621,14 @@ It's OK: the final zonking stage should zap y to (), which is fine.
 
 
 \begin{code}
-tcSimplifyTop :: [Inst] -> TcM TcDictBinds
+tcSimplifyTop, tcSimplifyInteractive :: [Inst] -> TcM TcDictBinds
+tcSimplifyTop         wanteds = tc_simplify_top False {- Not interactive loop -} wanteds
+tcSimplifyInteractive wanteds = tc_simplify_top True  {- Interactive loop -}     wanteds
+
+
 -- The TcLclEnv should be valid here, solely to improve
 -- error message generation for the monomorphism restriction
-tcSimplifyTop wanteds
+tc_simplify_top is_interactive wanteds
   = getLclEnv                                                  `thenM` \ lcl_env ->
     traceTc (text "tcSimplifyTop" <+> ppr (lclEnvElts lcl_env))        `thenM_`
     simpleReduceLoop (text "tcSimplTop") reduceMe wanteds      `thenM` \ (frees, binds, irreds) ->
@@ -1674,8 +1679,7 @@ tcSimplifyTop wanteds
        addTopAmbigErrs (tidy_env, ambigs)      `thenM_`
 
        -- Disambiguate the ones that look feasible
-       getGhciMode                             `thenM` \ mode ->
-        mappM (disambigGroup mode) std_oks
+        mappM (disambigGroup is_interactive) std_oks
     )                                  `thenM` \ binds_ambig ->
 
     returnM (binds `andMonoBinds` andMonoBindList binds_ambig)
@@ -1722,11 +1726,11 @@ Since we're not using the result of @foo@, the result if (presumably)
 @void@.
 
 \begin{code}
-disambigGroup :: GhciMode 
+disambigGroup :: Bool  -- True <=> simplifying at top-level interactive loop
              -> [Inst] -- All standard classes of form (C a)
              -> TcM TcDictBinds
 
-disambigGroup ghci_mode dicts
+disambigGroup is_interactive dicts
   |   any std_default_class classes    -- Guaranteed all standard classes
          -- See comment at the end of function for reasons as to
          -- why the defaulting mechanism doesn't apply to groups that
@@ -1770,7 +1774,7 @@ disambigGroup ghci_mode dicts
 
     std_default_class cls
       =  isNumericClass cls
-      || (ghci_mode == Interactive && 
+      || (is_interactive && 
          classKey cls `elem` [showClassKey, eqClassKey, ordClassKey])
                -- In interactive mode, we default Show a to Show ()
                -- to avoid graututious errors on "show []"