Fresh type var

schala-lang/language/src/typechecking.rs

@@ -30,7 +30,7 @@ pub type TypeName = Rc<String>;
 pub struct TypeContext<'a> {
   variable_map: ScopeStack<'a, Rc<String>, Type>,
   unification_table: InPlaceUnificationTable<TypeVar>,
-  //evar_count: u32
+  type_var_count: usize,
 }
 
 /// `InferResult` is the monad in which type inference takes place.
@@ -207,7 +207,7 @@ impl<'a> TypeContext<'a> {
     TypeContext { 
       variable_map: ScopeStack::new(None),
       unification_table: UnificationTable::new(),
-      //evar_count: 0
+      type_var_count: 0,
     }
   }
 
@@ -372,6 +372,12 @@ impl<'a> TypeContext<'a> {
       (a, b) => TypeError::new(format!("{:?} and {:?} do not unify", a, b)),
     }
   }
+
+  fn fresh_type_variable(&mut self) -> TypeVar {
+    let n = self.type_var_count;
+    self.type_var_count += 1;
+    TypeVar(n)
+  }
 }
 
 #[cfg(test)]