From 92ea98da2f89348c3dfdc7d49594a4d876d06ba2 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 18 Mar 2019 05:27:17 +0100
Subject: Split List literal between empty and non-empty

---
 dhall_core/src/core.rs   | 25 ++++++++++++-------------
 dhall_core/src/parser.rs |  4 ++--
 2 files changed, 14 insertions(+), 15 deletions(-)

(limited to 'dhall_core')

diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs
index a3236eb..722506b 100644
--- a/dhall_core/src/core.rs
+++ b/dhall_core/src/core.rs
@@ -307,8 +307,10 @@ pub enum Expr<Note, Embed> {
     DoubleLit(Double),
     ///  `TextLit t                                ~  t`
     TextLit(InterpolatedText<Note, Embed>),
-    ///  `ListLit t [x, y, z]                      ~  [x, y, z] : List t`
-    ListLit(Option<SubExpr<Note, Embed>>, Vec<SubExpr<Note, Embed>>),
+    ///  [] : List t`
+    EmptyListLit(SubExpr<Note, Embed>),
+    ///  [x, y, z]
+    NEListLit(Vec<SubExpr<Note, Embed>>),
     ///  `OptionalLit t [e]                        ~  [e] : Optional t`
     ///  `OptionalLit t []                         ~  []  : Optional t`
     OptionalLit(Option<SubExpr<Note, Embed>>, Option<SubExpr<Note, Embed>>),
@@ -543,16 +545,12 @@ impl<S, A: Display> Expr<S, A> {
                 write!(f, ") → ")?;
                 d.fmt_b(f)
             }
-            &ListLit(ref t, ref es) => {
-                fmt_list("[", "]", es, f, |e, f| e.fmt(f))?;
-                match t {
-                    Some(t) => {
-                        write!(f, " : List ")?;
-                        t.fmt_e(f)?
-                    }
-                    None => {}
-                }
-                Ok(())
+            &EmptyListLit(ref t) => {
+                write!(f, "[] : List ")?;
+                t.fmt_e(f)
+            }
+            &NEListLit(ref es) => {
+                fmt_list("[", "]", es, f, |e, f| e.fmt(f))
             }
             &OptionalLit(ref t, ref es) => {
                 match es {
@@ -902,7 +900,8 @@ where
         DoubleLit(n) => DoubleLit(*n),
         TextLit(t) => TextLit(t.map(&map)),
         BinOp(o, x, y) => BinOp(*o, map(x), map(y)),
-        ListLit(t, es) => ListLit(opt(t), vec(es)),
+        EmptyListLit(t) => EmptyListLit(map(t)),
+        NEListLit(es) => NEListLit(vec(es)),
         OptionalLit(t, es) => OptionalLit(opt(t), opt(es)),
         Record(kts) => Record(btmap(kts)),
         RecordLit(kvs) => RecordLit(btmap(kvs)),
diff --git a/dhall_core/src/parser.rs b/dhall_core/src/parser.rs
index 9487ebc..6809aa2 100644
--- a/dhall_core/src/parser.rs
+++ b/dhall_core/src/parser.rs
@@ -650,7 +650,7 @@ rule!(empty_collection<RcExpr>;
     children!(x: str, y: expression) => {
        match x {
           "Optional" => bx(Expr::OptionalLit(Some(y), None)),
-          "List" => bx(Expr::ListLit(Some(y), vec![])),
+          "List" => bx(Expr::EmptyListLit(y)),
           _ => unreachable!(),
        }
     }
@@ -871,7 +871,7 @@ rule!(union_type_entry<(Label, RcExpr)>;
 
 rule!(non_empty_list_literal_raw<RcExpr>;
     children!(items*: expression) => {
-        bx(Expr::ListLit(None, items.collect()))
+        bx(Expr::NEListLit(items.collect()))
     }
 );
 
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