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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2017-03-10 11:46:50 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2017-03-10 16:05:21 +0000 |
| commit | 48d1866e9051e52b80c9c88547bd66d66483f1d5 (patch) | |
| tree | 72047939e1bad05062f7518db97b6c999d32c948 /compiler/typecheck/TcBinds.hs | |
| parent | 7e96526ac2ef5987ecb03217d3d616b6281c1441 (diff) | |
| download | haskell-48d1866e9051e52b80c9c88547bd66d66483f1d5.tar.gz | |
Improve error messages for skolems
In error messages like this
• Couldn't match type ‘c’ with ‘f0 (a -> b)’
‘c’ is a rigid type variable bound by
the type signature for:
f :: ((a -> b) -> b) -> forall c. c -> a
we need to take case both to actually show that 'forall c',
and to make sure that its name lines with the 'c' in the
error message.
This has been shaky for some time, and this commit puts it on solid
ground. See TcRnTypes: Note [SigSkol SkolemInfo]
The main changes are
* SigSkol gets an extra field that records the way in which the
type signature was skolemised.
* The type in SigSkol is now the /un/-skolemised version
* pprSkolemInfo uses the info to make the tidy type line up
nicely
Lots of error message wibbles!
Diffstat (limited to 'compiler/typecheck/TcBinds.hs')
| -rw-r--r-- | compiler/typecheck/TcBinds.hs | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/compiler/typecheck/TcBinds.hs b/compiler/typecheck/TcBinds.hs index 201da00504..942bf96988 100644 --- a/compiler/typecheck/TcBinds.hs +++ b/compiler/typecheck/TcBinds.hs @@ -687,13 +687,13 @@ tcPolyCheck prag_fn , fun_matches = matches })) = setSrcSpan sig_loc $ do { traceTc "tcPolyCheck" (ppr poly_id $$ ppr sig_loc) - ; (tv_prs, theta, tau) <- tcInstType (tcInstSigTyVars sig_loc) poly_id + ; (tv_prs, theta, tau) <- tcInstType tcInstSkolTyVars poly_id -- See Note [Instantiate sig with fresh variables] ; mono_name <- newNameAt (nameOccName name) nm_loc ; ev_vars <- newEvVars theta ; let mono_id = mkLocalId mono_name tau - skol_info = SigSkol ctxt (mkPhiTy theta tau) + skol_info = SigSkol ctxt (idType poly_id) tv_prs skol_tvs = map snd tv_prs ; (ev_binds, (co_fn, matches')) |