From 77af0bbc171618f48531cc6b1d77e18089928885 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 13 Aug 2019 20:54:15 +0200
Subject: Stop tracking the absence of Embed values at the type level

---
 dhall_syntax/src/core/context.rs |  2 +-
 dhall_syntax/src/core/expr.rs    | 16 ++--------------
 dhall_syntax/src/core/visitor.rs | 15 +--------------
 dhall_syntax/src/printer.rs      |  6 ------
 4 files changed, 4 insertions(+), 35 deletions(-)

(limited to 'dhall_syntax')

diff --git a/dhall_syntax/src/core/context.rs b/dhall_syntax/src/core/context.rs
index eeec121..6844baa 100644
--- a/dhall_syntax/src/core/context.rs
+++ b/dhall_syntax/src/core/context.rs
@@ -4,7 +4,7 @@ use std::hash::Hash;
 
 /// A `(Context a)` associates `Text` labels with values of type `a`
 ///
-/// The `Context` is used for type-checking when `(a = Expr X)`
+/// The `Context` is used for type-checking when `(a = Expr)`
 ///
 /// * You create a `Context` using `empty` and `insert`
 /// * You transform a `Context` using `fmap`
diff --git a/dhall_syntax/src/core/expr.rs b/dhall_syntax/src/core/expr.rs
index 0cbece3..e08d816 100644
--- a/dhall_syntax/src/core/expr.rs
+++ b/dhall_syntax/src/core/expr.rs
@@ -10,9 +10,9 @@ pub type Double = NaiveDouble;
 
 /// An empty type
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub enum X {}
+pub enum Void {}
 
-pub fn trivial_result<T>(x: Result<T, X>) -> T {
+pub fn trivial_result<T>(x: Result<T, Void>) -> T {
     match x {
         Ok(x) => x,
         Err(e) => match e {},
@@ -351,12 +351,6 @@ impl<E> Expr<E> {
     }
 }
 
-impl Expr<X> {
-    pub fn absurd<E>(&self) -> Expr<E> {
-        self.visit(&mut visitor::AbsurdVisitor)
-    }
-}
-
 impl<E> SubExpr<E> {
     pub fn as_ref(&self) -> &Expr<E> {
         &self.0.as_ref().0
@@ -416,12 +410,6 @@ impl<E> SubExpr<E> {
     }
 }
 
-impl SubExpr<X> {
-    pub fn absurd<T>(&self) -> SubExpr<T> {
-        SubExpr::from_expr_no_span(self.as_ref().absurd())
-    }
-}
-
 impl<E> Clone for SubExpr<E> {
     fn clone(&self) -> Self {
         SubExpr(Rc::clone(&self.0))
diff --git a/dhall_syntax/src/core/visitor.rs b/dhall_syntax/src/core/visitor.rs
index 50ec68a..e39e95b 100644
--- a/dhall_syntax/src/core/visitor.rs
+++ b/dhall_syntax/src/core/visitor.rs
@@ -243,7 +243,7 @@ impl<'a, T, SE1, SE2, E1, E2> ExprFFallibleVisitor<'a, SE1, SE2, E1, E2>
 where
     T: ExprFInFallibleVisitor<'a, SE1, SE2, E1, E2>,
 {
-    type Error = X;
+    type Error = Void;
 
     fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error> {
         Ok(self.0.visit_subexpr(subexpr))
@@ -379,16 +379,3 @@ where
         (self.0)(embed)
     }
 }
-
-pub struct AbsurdVisitor;
-
-impl<'a, 'b, E> ExprFInFallibleVisitor<'a, SubExpr<X>, SubExpr<E>, X, E>
-    for &'b mut AbsurdVisitor
-{
-    fn visit_subexpr(&mut self, subexpr: &'a SubExpr<X>) -> SubExpr<E> {
-        SubExpr::from_expr_no_span(subexpr.as_ref().visit(&mut **self))
-    }
-    fn visit_embed(self, embed: &'a X) -> E {
-        match *embed {}
-    }
-}
diff --git a/dhall_syntax/src/printer.rs b/dhall_syntax/src/printer.rs
index 95eafe5..25d4ca8 100644
--- a/dhall_syntax/src/printer.rs
+++ b/dhall_syntax/src/printer.rs
@@ -491,9 +491,3 @@ impl<Label: Display> Display for V<Label> {
         Ok(())
     }
 }
-
-impl Display for X {
-    fn fmt(&self, _: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        match *self {}
-    }
-}
-- 
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