[project @ 2002-07-09 08:19:14 by simonpj]

Improve error message

	*** MERGE TO STABLE BRANCH ***

diff --git a/ghc/compiler/typecheck/TcExpr.lhs b/ghc/compiler/typecheck/TcExpr.lhs
index c5e33f3..b84b488 100644 (file)
--- a/ghc/compiler/typecheck/TcExpr.lhs
+++ b/ghc/compiler/typecheck/TcExpr.lhs
@@ -136,13 +136,13 @@ tcMonoExpr (HsIPVar ip) res_ty
 
 \begin{code}
 tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
- = tcHsSigType ExprSigCtxt poly_ty     `thenTc` \ sig_tc_ty ->
+ = tcAddErrCtxt (exprSigCtxt in_expr)  $
+   tcHsSigType ExprSigCtxt poly_ty     `thenTc` \ sig_tc_ty ->
    tcExpr expr sig_tc_ty               `thenTc` \ (expr', lie1) ->
 
        -- Must instantiate the outer for-alls of sig_tc_ty
        -- else we risk instantiating a ? res_ty to a forall-type
        -- which breaks the invariant that tcMonoExpr only returns phi-types
-   tcAddErrCtxt (exprSigCtxt in_expr)  $
    tcInstCall SignatureOrigin sig_tc_ty        `thenNF_Tc` \ (inst_fn, lie2, inst_sig_ty) ->
    tcSubExp res_ty inst_sig_ty         `thenTc` \ (co_fn, lie3) ->