Revert "Recover arrow type detection"

This reverts commit 153cf8dab3b80aba30ac3adfd44e4be251494ea2.

2 files changed, 19 insertions, 47 deletions

diff --git a/dhall_syntax/src/core.rs b/dhall_syntax/src/core.rs
index 389f037..c8a2425 100644
--- a/dhall_syntax/src/core.rs
+++ b/dhall_syntax/src/core.rs
@@ -60,7 +60,7 @@ pub enum Const {
 /// The `Int` field is a DeBruijn index.
 /// See dhall-lang/standard/semantics.md for details
 #[derive(Debug, Clone, PartialEq, Eq)]
-pub struct Var<VarLabel>(pub VarLabel, pub usize);
+pub struct Var<Label>(pub Label, pub usize);
 
 // Definition order must match precedence order for
 // pretty-printing to work correctly
@@ -529,19 +529,6 @@ impl<'a> From<&'a Label> for Var<Label> {
     }
 }
 
-/// Trait for things that capture a label used for variables.
-/// Allows normalization to be generic in whether to alpha-normalize or not.
-pub trait VarLabel: std::fmt::Display + Clone {
-    /// Is `self` the default variable (i.e. "_") ?
-    fn is_underscore_var(&self) -> bool;
-}
-
-impl VarLabel for Label {
-    fn is_underscore_var(&self) -> bool {
-        &String::from(self) == "_"
-    }
-}
-
 /// `shift` is used by both normalization and type-checking to avoid variable
 /// capture by shifting variable indices
 /// See https://github.com/dhall-lang/dhall-lang/blob/master/standard/semantics.md#shift
diff --git a/dhall_syntax/src/printer.rs b/dhall_syntax/src/printer.rs
index 6ebd537..9cc1b46 100644
--- a/dhall_syntax/src/printer.rs
+++ b/dhall_syntax/src/printer.rs
@@ -3,11 +3,8 @@ use itertools::Itertools;
 use std::fmt::{self, Display};
 
 /// Generic instance that delegates to subexpressions
-impl<SE, L, E> Display for ExprF<SE, L, E>
-where
-    SE: Display + Clone,
-    L: VarLabel,
-    E: Display,
+impl<SE: Display + Clone, L: Display + Clone, E: Display> Display
+    for ExprF<SE, L, E>
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         use crate::ExprF::*;
@@ -18,9 +15,10 @@ where
             BoolIf(a, b, c) => {
                 write!(f, "if {} then {} else {}", a, b, c)?;
             }
-            Pi(a, b, c) if a.is_underscore_var() => {
-                write!(f, "{} → {}", b, c)?;
-            }
+            // TODO: arrow type
+            // Pi(a, b, c) if &String::from(a) == "_" => {
+            //     write!(f, "{} → {}", b, c)?;
+            // }
             Pi(a, b, c) => {
                 write!(f, "∀({} : {}) → {}", a, b, c)?;
             }
@@ -131,34 +129,23 @@ enum PrintPhase {
 #[derive(Clone)]
 struct PhasedExpr<'a, L, S, A>(&'a SubExpr<L, S, A>, PrintPhase);
 
-impl<'a, L, S, A> Display for PhasedExpr<'a, L, S, A>
-where
-    L: VarLabel,
-    S: Clone,
-    A: Display + Clone,
+impl<'a, L: Display + Clone, S: Clone, A: Display + Clone> Display
+    for PhasedExpr<'a, L, S, A>
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         self.0.as_ref().fmt_phase(f, self.1)
     }
 }
 
-impl<'a, L, S, A> PhasedExpr<'a, L, S, A>
-where
-    L: VarLabel,
-    S: Clone,
-    A: Display + Clone,
+impl<'a, L: Display + Clone, S: Clone, A: Display + Clone>
+    PhasedExpr<'a, L, S, A>
 {
     fn phase(self, phase: PrintPhase) -> PhasedExpr<'a, L, S, A> {
         PhasedExpr(self.0, phase)
     }
 }
 
-impl<L, S, A> Expr<L, S, A>
-where
-    L: VarLabel,
-    S: Clone,
-    A: Display + Clone,
-{
+impl<L: Display + Clone, S: Clone, A: Display + Clone> Expr<L, S, A> {
     fn fmt_phase(
         &self,
         f: &mut fmt::Formatter,
@@ -192,11 +179,12 @@ where
         // Annotate subexpressions with the appropriate phase, defaulting to Base
         let phased_self = match self.map_ref_simple(|e| PhasedExpr(e, Base)) {
             Pi(a, b, c) => {
-                if a.is_underscore_var() {
-                    Pi(a, b.phase(Operator), c)
-                } else {
+                // TODO: arrow type
+                // if &String::from(&a) == "_" {
+                //     Pi(a, b.phase(Operator), c)
+                // } else {
                 Pi(a, b, c)
-                }
+                // }
             }
             Merge(a, b, c) => Merge(
                 a.phase(Import),
@@ -232,11 +220,8 @@ where
     }
 }
 
-impl<L, S, A> Display for SubExpr<L, S, A>
-where
-    L: VarLabel,
-    S: Clone,
-    A: Display + Clone,
+impl<L: Display + Clone, S: Clone, A: Display + Clone> Display
+    for SubExpr<L, S, A>
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         self.as_ref().fmt_phase(f, PrintPhase::Base)