From 6642077368497583113d685d351ec93d230ffcad Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Thu, 20 Feb 2020 19:04:13 +0000
Subject: Add support for dotted field syntax

---
 README.md                                            |  1 +
 dhall-lang                                           |  2 +-
 dhall/build.rs                                       | 20 --------------------
 dhall/src/syntax/ast/span.rs                         |  3 ++-
 dhall/src/syntax/text/parser.rs                      | 13 ++++++++++++-
 dhall/tests/parser/failure/spacing/MergeNoSpace2.txt |  2 +-
 .../parser/failure/spacing/RecordTypeNoSpace.txt     |  2 +-
 7 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/README.md b/README.md
index 34878f4..e620e38 100644
--- a/README.md
+++ b/README.md
@@ -161,6 +161,7 @@ same name as the corresponding test.
 
 [???]
 
+- Add support for dotted field syntax
 - Disallow Natural literals with leading zeros
 - Add support for duplicate record fields
 - Update to supporting dhall v13.0.0
diff --git a/dhall-lang b/dhall-lang
index a1f2dc0..ec4fe8a 160000
--- a/dhall-lang
+++ b/dhall-lang
@@ -1 +1 @@
-Subproject commit a1f2dc019907ec001f28abbd05ca397bddb0975d
+Subproject commit ec4fe8ac58aa3d91f94223834ab6acfe57c3a425
diff --git a/dhall/build.rs b/dhall/build.rs
index 88a2145..7c62083 100644
--- a/dhall/build.rs
+++ b/dhall/build.rs
@@ -375,26 +375,6 @@ fn convert_abnf_to_pest() -> std::io::Result<()> {
     rules.remove("url_path");
     writeln!(&mut file, "url_path = _{{ path }}")?;
 
-    // TODO: workaround to simplify record parsing
-    rules.remove("non_empty_record_type_or_literal");
-    rules.remove("non_empty_record_literal");
-    rules.remove("non_empty_record_type");
-    writeln!(
-        &mut file,
-        "non_empty_record_type_or_literal = {{ non_empty_record_literal | \
-         non_empty_record_type }}"
-    )?;
-    writeln!(
-        &mut file,
-        "non_empty_record_literal = {{ record_literal_entry ~ (whsp ~ ^\",\" \
-         ~ whsp ~ record_literal_entry)*}}"
-    )?;
-    writeln!(
-        &mut file,
-        "non_empty_record_type = {{ record_type_entry ~ (whsp ~ ^\",\" ~ whsp \
-         ~ record_type_entry)* }}"
-    )?;
-
     // Work around some greediness issue in the grammar.
     rules.remove("missing");
     writeln!(
diff --git a/dhall/src/syntax/ast/span.rs b/dhall/src/syntax/ast/span.rs
index 6d017f6..7c004c5 100644
--- a/dhall/src/syntax/ast/span.rs
+++ b/dhall/src/syntax/ast/span.rs
@@ -18,8 +18,9 @@ pub(crate) struct ParsedSpan {
 pub(crate) enum Span {
     /// A location in the source text
     Parsed(ParsedSpan),
-    /// Desugaring of duplicate fields
+    /// Desugarings
     DuplicateRecordFieldsSugar,
+    DottedFieldSugar,
     /// For expressions obtained from decoding binary
     Decoded,
     /// For expressions constructed during normalization/typecheck
diff --git a/dhall/src/syntax/text/parser.rs b/dhall/src/syntax/text/parser.rs
index f74794b..ba64a75 100644
--- a/dhall/src/syntax/text/parser.rs
+++ b/dhall/src/syntax/text/parser.rs
@@ -915,7 +915,18 @@ impl DhallParser {
 
     fn record_literal_entry(input: ParseInput) -> ParseResult<(Label, Expr)> {
         Ok(match_nodes!(input.into_children();
-            [label(name), expression(expr)] => (name, expr)
+            [label(name), expression(expr)] => (name, expr),
+            [label(first_name), label(names).., expression(expr)] => {
+                // Desugar dotted field syntax into nested records
+                let expr = names.rev().fold(expr, |e, l| {
+                    let map = Some((l, e)).into_iter().collect();
+                    Expr::new(
+                        RecordLit(map),
+                        Span::DottedFieldSugar,
+                    )
+                });
+                (first_name, expr)
+            },
         ))
     }
 
diff --git a/dhall/tests/parser/failure/spacing/MergeNoSpace2.txt b/dhall/tests/parser/failure/spacing/MergeNoSpace2.txt
index 77314e0..96d937b 100644
--- a/dhall/tests/parser/failure/spacing/MergeNoSpace2.txt
+++ b/dhall/tests/parser/failure/spacing/MergeNoSpace2.txt
@@ -3,4 +3,4 @@
 1 | merge x(y)␊
   |       ^---
   |
-  = expected missing, non_empty_list_literal, double_quote_literal, single_quote_literal, if_, merge, NaN, Some_, toMap, assert, forall, numeric_double_literal, minus_infinity_literal, plus_infinity_literal, natural_literal, integer_literal, or import_hashed
+  = expected missing, double_quote_literal, single_quote_literal, if_, merge, non_empty_list_literal, NaN, Some_, toMap, assert, forall, numeric_double_literal, minus_infinity_literal, plus_infinity_literal, natural_literal, integer_literal, or import_hashed
diff --git a/dhall/tests/parser/failure/spacing/RecordTypeNoSpace.txt b/dhall/tests/parser/failure/spacing/RecordTypeNoSpace.txt
index f6427a4..9c1eaef 100644
--- a/dhall/tests/parser/failure/spacing/RecordTypeNoSpace.txt
+++ b/dhall/tests/parser/failure/spacing/RecordTypeNoSpace.txt
@@ -3,4 +3,4 @@
 1 | { x :T }␊
   |   ^---
   |
-  = expected non_empty_record_type_or_literal or empty_record_literal
+  = expected empty_record_literal or non_empty_record_type_or_literal
-- 
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