From 4c7deccba50cb6d46134362128e3cb25c693c153 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 23 Dec 2019 22:30:27 +0000
Subject: Update dhall-lang submodule

---
 dhall-lang                      |  2 +-
 dhall/build.rs                  |  8 ++++++++
 dhall/src/dhall.pest.visibility |  4 ++++
 dhall/src/syntax/text/parser.rs | 23 ++++++++++-------------
 4 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/dhall-lang b/dhall-lang
index 3b31dea..464b735 160000
--- a/dhall-lang
+++ b/dhall-lang
@@ -1 +1 @@
-Subproject commit 3b31dea1ba47f9de041a7288826f07a05a167ba7
+Subproject commit 464b7358545a0d5c10d0aa987fed94bedc7f5162
diff --git a/dhall/build.rs b/dhall/build.rs
index 70389bf..981e558 100644
--- a/dhall/build.rs
+++ b/dhall/build.rs
@@ -414,12 +414,20 @@ fn convert_abnf_to_pest() -> std::io::Result<()> {
     rules.remove("url_path");
     writeln!(&mut file, "url_path = _{{ path }}")?;
 
+    // Work around some greediness issue in the grammar.
     rules.remove("missing");
     writeln!(
         &mut file,
         r#"missing = {{ "missing" ~ !simple_label_next_char }}"#
     )?;
 
+    // Prefer my nice error message to illegible parse errors.
+    rules.remove("unicode_escape");
+    writeln!(
+        &mut file,
+        r#"unicode_escape = _{{ HEXDIG{{4}} | "{{" ~ HEXDIG+ ~ "}}" }}"#
+    )?;
+
     rules.remove("simple_label");
     writeln!(
         &mut file,
diff --git a/dhall/src/dhall.pest.visibility b/dhall/src/dhall.pest.visibility
index 41aa833..5d3b4c8 100644
--- a/dhall/src/dhall.pest.visibility
+++ b/dhall/src/dhall.pest.visibility
@@ -24,6 +24,10 @@ quoted_label
 double_quote_chunk
 double_quote_escaped
 # unicode_escape
+# unicode_suffix
+# unbraced_escape
+# braced_codepoint
+# braced_escape
 double_quote_char
 double_quote_literal
 single_quote_continue
diff --git a/dhall/src/syntax/text/parser.rs b/dhall/src/syntax/text/parser.rs
index d9e5c3b..27e0382 100644
--- a/dhall/src/syntax/text/parser.rs
+++ b/dhall/src/syntax/text/parser.rs
@@ -217,19 +217,18 @@ impl DhallParser {
             "t" => "\t".to_owned(),
             // "uXXXX" or "u{XXXXX}"
             s => {
-                use std::convert::{TryFrom, TryInto};
+                use std::convert::TryInto;
 
                 let s = &s[1..];
                 let s = if &s[0..1] == "{" {
                     &s[1..s.len() - 1]
                 } else {
-                    &s[0..s.len()]
+                    s
                 };
 
                 if s.len() > 8 {
                     Err(input.error(format!(
-                        "Escape sequences can't have more than 8 chars: \"{}\"",
-                        s
+                        "Escape sequences can't have more than 8 chars"
                     )))?
                 }
 
@@ -242,12 +241,10 @@ impl DhallParser {
                 // `s` has length 8, so `bytes` has length 4
                 let bytes: &[u8] = &hex::decode(s).unwrap();
                 let i = u32::from_be_bytes(bytes.try_into().unwrap());
-                let c = char::try_from(i).unwrap();
                 match i {
-                    0xD800..=0xDFFF => {
-                        let c_ecapsed = c.escape_unicode();
-                        Err(input.error(format!("Escape sequences can't contain surrogate pairs: \"{}\"", c_ecapsed)))?
-                    }
+                    0xD800..=0xDFFF => Err(input.error(format!(
+                        "Escape sequences can't contain surrogate pairs"
+                    )))?,
                     0x0FFFE..=0x0FFFF
                     | 0x1FFFE..=0x1FFFF
                     | 0x2FFFE..=0x2FFFF
@@ -264,12 +261,12 @@ impl DhallParser {
                     | 0xDFFFE..=0xDFFFF
                     | 0xEFFFE..=0xEFFFF
                     | 0xFFFFE..=0xFFFFF
-                    | 0x10_FFFE..=0x10_FFFF => {
-                        let c_ecapsed = c.escape_unicode();
-                        Err(input.error(format!("Escape sequences can't contain non-characters: \"{}\"", c_ecapsed)))?
-                    }
+                    | 0x10_FFFE..=0x10_FFFF => Err(input.error(format!(
+                        "Escape sequences can't contain non-characters"
+                    )))?,
                     _ => {}
                 }
+                let c: char = i.try_into().unwrap();
                 std::iter::once(c).collect()
             }
         })
-- 
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