From 960223bfc3fd1c2ac4608b837fb83f3bc6b5fd16 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Mon, 28 Jun 1999 16:23:28 +0000
Subject: [PATCH] [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.
---
ghc/compiler/typecheck/TcBinds.lhs | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs
index a3177a29bda2..3fb4cdf07231 100644
--- 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)
--
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