From be175a2b7551f0248f3401aa44f7a13ad3f6cfad Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Sat, 23 Feb 2019 00:59:58 -0800
Subject: [PATCH] Add more infrastructure for unify

---
 schala-lang/language/src/typechecking.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/schala-lang/language/src/typechecking.rs b/schala-lang/language/src/typechecking.rs
index d3edbb0..14c70a9 100644
--- a/schala-lang/language/src/typechecking.rs
+++ b/schala-lang/language/src/typechecking.rs
@@ -4,7 +4,7 @@ use std::rc::Rc;
 // -nope, ghc deliberately does typechecking before desugaring to core
 // cf. a history of haskell, peyton-jones
 
-use ena::unify::{UnifyKey, InPlaceUnificationTable, UnificationTable};
+use ena::unify::{UnifyKey, InPlaceUnificationTable, UnificationTable, EqUnifyValue};
 
 use crate::ast::*;
 use crate::util::ScopeStack;
@@ -60,13 +60,13 @@ pub enum Type {
 pub struct TypeVar(usize);
 
 impl UnifyKey for TypeVar {
-  type Value = ();
+  type Value = Option<TypeConst>;
   fn index(&self) -> u32 { self.0 as u32 }
   fn from_index(u: u32) -> TypeVar { TypeVar(u as usize) }
   fn tag() -> &'static str { "TypeVar" }
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum TypeConst {
   Unit,
   Nat,
@@ -78,6 +78,8 @@ pub enum TypeConst {
   UserDefined
 }
 
+impl EqUnifyValue for TypeConst { }
+
 macro_rules! ty {
   ($type_name:ident) => { Type::Const(TypeConst::$type_name) };
   ($t1:ident -> $t2:ident) => { Type::Arrow(Box::new(ty!($t1)), Box::new(ty!($t2))) };