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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2011-12-05 04:44:13 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2011-12-05 04:44:13 +0000 |
| commit | 2e6dcdf711ebd50eef230a878014a5a9abd20e07 (patch) | |
| tree | d12c9675c1910b39224927a084e5685c8a1e1797 /compiler/deSugar/DsListComp.lhs | |
| parent | 22b317b1812cbb35d86872d7607de034bcf66fb2 (diff) | |
| download | haskell-2e6dcdf711ebd50eef230a878014a5a9abd20e07.tar.gz | |
Allow full constraint solving under a for-all (Trac #5595)
The main idea is that when we unify
forall a. t1 ~ forall a. t2
we get constraints from unifying t1~t2 that mention a.
We are producing a coercion witnessing the equivalence of
the for-alls, and inside *that* coercion we need bindings
for the solved constraints arising from t1~t2.
We didn't have way to do this before. The big change is
that here's a new type TcEvidence.TcCoercion, which is
much like Coercion.Coercion except that there's a slot
for TcEvBinds in it.
This has a wave of follow-on changes. Not deep but broad.
* New module TcEvidence, which now contains the HsWrapper
TcEvBinds, EvTerm etc types that used to be in HsBinds
* The typechecker works exclusively in terms of TcCoercion.
* The desugarer converts TcCoercion to Coercion
* The main payload is in TcUnify.unifySigmaTy. This is the
function that had a gross hack before, but is now beautiful.
* LCoercion is gone! Hooray.
Many many fiddly changes in conssequence. But it's nice.
Diffstat (limited to 'compiler/deSugar/DsListComp.lhs')
| -rw-r--r-- | compiler/deSugar/DsListComp.lhs | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/compiler/deSugar/DsListComp.lhs b/compiler/deSugar/DsListComp.lhs index 63d96fd465..4ad8006b39 100644 --- a/compiler/deSugar/DsListComp.lhs +++ b/compiler/deSugar/DsListComp.lhs @@ -19,6 +19,7 @@ import TcHsSyn import CoreSyn import MkCore +import TcEvidence import DsMonad -- the monadery used in the desugarer import DsUtils |