[project @ 1999-06-28 16:23:28 by simonpj]

Fix lost specialisations.  There were two problems

	{-# SPECIALISE f :: Int -> Rational #-}
	fromIntegral	=  fromInteger . toInteger

This generates

	fromIntegral_spec = fromIntegral d

for some suitable dictionary d.  But since fromIntegral is small,
it got inlined into fromIntegral_spec, thus losing the specialised
call (fromIntegral d) that was the whole raison d'etre of fromIntegral_spec.
Haskish solution: add an inlne pragma for the _spec things:

	fromIntegral_spec = _inline_me (fromIntegral d)

Now we won't inline inside.  But this showed up a related problem.  The
typechecker tries to common up overloaded things, so it actually generates

	m = fromIntegral d
	fromIntegral_spec = _inline_me m

which is pretty stupid.  Using tcSimplifyToDicts (instead of tcSimplify)
in TcBinds.tcSpecSigs fixes this.

diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs
index a3177a2..3fb4cdf 100644 (file)
--- a/ghc/compiler/typecheck/TcBinds.lhs
+++ b/ghc/compiler/typecheck/TcBinds.lhs
@@ -16,7 +16,7 @@ import HsSyn          ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), InPat(..), Stmt
                          collectMonoBinders, andMonoBindList, andMonoBinds
                        )
 import RnHsSyn         ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
-import TcHsSyn         ( TcHsBinds, TcMonoBinds, TcId, zonkId )
+import TcHsSyn         ( TcHsBinds, TcMonoBinds, TcId, zonkId, mkHsLet )
 
 import TcMonad
 import Inst            ( Inst, LIE, emptyLIE, mkLIE, plusLIE, plusLIEs, InstOrigin(..),
@@ -27,7 +27,7 @@ import TcEnv          ( tcExtendLocalValEnv,
                          tcLookupTyCon, 
                          tcGetGlobalTyVars, tcExtendGlobalTyVars
                        )
-import TcSimplify      ( tcSimplify, tcSimplifyAndCheck )
+import TcSimplify      ( tcSimplify, tcSimplifyAndCheck, tcSimplifyToDicts )
 import TcMonoType      ( tcHsType, checkSigTyVars,
                          TcSigInfo(..), tcTySig, maybeSig, sigCtxt
                        )
@@ -837,6 +837,9 @@ tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
        -- the spec-pragma-id at the same time
     tcExpr (HsVar name) sig_ty                 `thenTc` \ (spec_expr, spec_lie) ->
 
+       -- Squeeze out any Methods (see comments with tcSimplifyToDicts)
+    tcSimplifyToDicts spec_lie                 `thenTc` \ (spec_lie1, spec_binds) ->
+
        -- Just specialise "f" by building a SpecPragmaId binding
        -- It is the thing that makes sure we don't prematurely 
        -- dead-code-eliminate the binding we are really interested in.
@@ -844,8 +847,8 @@ tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
 
        -- Do the rest and combine
     tcSpecSigs sigs                    `thenTc` \ (binds_rest, lie_rest) ->
-    returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id spec_expr,
-             lie_rest   `plusLIE`      spec_lie)
+    returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id (mkHsLet spec_binds spec_expr),
+             lie_rest   `plusLIE`      spec_lie1)
 
 tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
 tcSpecSigs []                = returnTc (EmptyMonoBinds, emptyLIE)