From 72ad56209fe10e3120c19ca5b820ff267423ab1d Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Sat, 11 Apr 2020 15:41:21 +0100
Subject: spec: fix precedence of `===` and `with`

---
 CHANGELOG.md                                       |  1 +
 README.md                                          |  2 +-
 dhall-lang                                         |  2 +-
 dhall/build.rs                                     |  2 +-
 dhall/src/operations/kind.rs                       |  4 ++--
 dhall/src/syntax/ast/span.rs                       |  6 ++++++
 dhall/src/syntax/text/dhall.abnf                   | 22 ++++++++++++++--------
 dhall/src/syntax/text/parser.rs                    |  2 +-
 .../tests/parser/failure/unit/WithPrecedence1.txt  |  6 ++++++
 .../tests/parser/failure/unit/WithPrecedence2.txt  |  6 ++++++
 .../tests/parser/failure/unit/WithPrecedence3.txt  |  6 ++++++
 .../tests/parser/success/unit/WithPrecedence1B.txt |  1 +
 .../tests/parser/success/unit/WithPrecedence2B.txt |  1 +
 .../tests/parser/success/unit/WithPrecedence3B.txt |  1 +
 .../unit/operators/PrecedenceEquivalenceB.txt      |  1 +
 tests_buffer                                       |  1 -
 16 files changed, 49 insertions(+), 15 deletions(-)
 create mode 100644 dhall/tests/parser/failure/unit/WithPrecedence1.txt
 create mode 100644 dhall/tests/parser/failure/unit/WithPrecedence2.txt
 create mode 100644 dhall/tests/parser/failure/unit/WithPrecedence3.txt
 create mode 100644 dhall/tests/parser/success/unit/WithPrecedence1B.txt
 create mode 100644 dhall/tests/parser/success/unit/WithPrecedence2B.txt
 create mode 100644 dhall/tests/parser/success/unit/WithPrecedence3B.txt
 create mode 100644 dhall/tests/parser/success/unit/operators/PrecedenceEquivalenceB.txt

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 457c346..23997c5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 #### [Unreleased]
 
+- Adjust precedence of `===` and `with`
 - Fix running tests on Windows. Developing on this lib should now be possible on Windows.
 
 #### [0.5.3] - 2020-05-30
diff --git a/README.md b/README.md
index ab32536..cad82f8 100644
--- a/README.md
+++ b/README.md
@@ -169,7 +169,7 @@ same name as the corresponding test.
 
 I try to keep commit messages somewhat in the style of [Conventional
 Commits](https://www.conventionalcommits.org/en/v1.0.0). That means the commit
-message should start with `feat:`, `test:`, `doc:`, `fix:`, `style:`,
+message should start with `feat:`, `test:`, `spec:`, `doc:`, `fix:`, `style:`,
 `refactor:`, `chore:`, `perf:` or similar prefixes.
 
 A breaking change should be indicated with `!` before the `:`.
diff --git a/dhall-lang b/dhall-lang
index a53a620..b788d6d 160000
--- a/dhall-lang
+++ b/dhall-lang
@@ -1 +1 @@
-Subproject commit a53a620df888b97fe23598356be7157bda0c8e21
+Subproject commit b788d6dd2150eec49b6bdd0cc7de50e403fad889
diff --git a/dhall/build.rs b/dhall/build.rs
index 4fc8545..3dcdd5e 100644
--- a/dhall/build.rs
+++ b/dhall/build.rs
@@ -95,7 +95,7 @@ fn convert_abnf_to_pest() -> std::io::Result<()> {
             bool_or |
             import_alt
         }}
-        operator_expression = {{ with_expression ~ (whsp ~ operator ~ whsp ~ with_expression)* }}
+        operator_expression = {{ application_expression ~ (whsp ~ operator ~ whsp ~ application_expression)* }}
     "##
     )?;
 
diff --git a/dhall/src/operations/kind.rs b/dhall/src/operations/kind.rs
index 5415637..0ee9671 100644
--- a/dhall/src/operations/kind.rs
+++ b/dhall/src/operations/kind.rs
@@ -6,6 +6,8 @@ use crate::syntax::{trivial_result, Label};
 // pretty-printing to work correctly
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub enum BinOp {
+    /// x === y
+    Equivalence,
     /// `x ? y`
     ImportAlt,
     /// `x || y`
@@ -30,8 +32,6 @@ pub enum BinOp {
     BoolEQ,
     /// `x != y`
     BoolNE,
-    /// x === y
-    Equivalence,
 }
 
 /// Operations
diff --git a/dhall/src/syntax/ast/span.rs b/dhall/src/syntax/ast/span.rs
index e250602..ab3279b 100644
--- a/dhall/src/syntax/ast/span.rs
+++ b/dhall/src/syntax/ast/span.rs
@@ -66,6 +66,12 @@ impl Span {
                     end: max(x.end, y.end),
                 })
             }
+            (Parsed(_), Parsed(_)) => panic!(
+                "Tried to union incompatible spans: {:?} and {:?}",
+                self, other
+            ),
+            (Parsed(x), _) => Parsed(x.clone()),
+            (_, Parsed(x)) => Parsed(x.clone()),
             _ => panic!(
                 "Tried to union incompatible spans: {:?} and {:?}",
                 self, other
diff --git a/dhall/src/syntax/text/dhall.abnf b/dhall/src/syntax/text/dhall.abnf
index 1c3a980..861f7b3 100644
--- a/dhall/src/syntax/text/dhall.abnf
+++ b/dhall/src/syntax/text/dhall.abnf
@@ -757,6 +757,11 @@ expression =
     ; NOTE: Backtrack if parsing this alternative fails
     / operator-expression whsp arrow whsp expression
     
+    ; "a with x = b"
+    ;
+    ; NOTE: Backtrack if parsing this alternative fails
+    / with-expression
+    
     ; "merge e1 e2 : t"
     ;
     ; NOTE: Backtrack if parsing this alternative fails since we can't tell
@@ -792,9 +797,16 @@ let-binding = let whsp1 nonreserved-label whsp [ ":" whsp1 expression whsp ] "="
 empty-list-literal =
     "[" whsp [ "," whsp ] "]" whsp ":" whsp1 application-expression
 
-operator-expression = import-alt-expression
+with-expression =
+    import-expression 1*(whsp1 with whsp1 with-clause)
+
+with-clause =
+    any-label-or-some *(whsp "." whsp any-label-or-some) whsp "=" whsp operator-expression
+
+operator-expression = equivalent-expression
 
 ; Nonempty-whitespace to disambiguate `http://a/a?a`
+equivalent-expression    = import-alt-expression    *(whsp equivalent whsp import-alt-expression)
 import-alt-expression    = or-expression            *(whsp "?" whsp1 or-expression)
 or-expression            = plus-expression          *(whsp "||" whsp plus-expression)
 ; Nonempty-whitespace to disambiguate `f +2`
@@ -807,13 +819,7 @@ prefer-expression        = combine-types-expression *(whsp prefer whsp combine-t
 combine-types-expression = times-expression         *(whsp combine-types whsp times-expression)
 times-expression         = equal-expression         *(whsp "*" whsp equal-expression)
 equal-expression         = not-equal-expression     *(whsp "==" whsp not-equal-expression)
-not-equal-expression     = equivalent-expression    *(whsp "!=" whsp equivalent-expression)
-equivalent-expression    = with-expression          *(whsp equivalent whsp with-expression)
-
-with-expression = application-expression *(whsp1 with whsp1 with-clause)
-
-with-clause =
-    any-label-or-some *(whsp "." whsp any-label-or-some) whsp "=" whsp application-expression
+not-equal-expression     = application-expression   *(whsp "!=" whsp application-expression)
 
 
 ; Import expressions need to be separated by some whitespace, otherwise there
diff --git a/dhall/src/syntax/text/parser.rs b/dhall/src/syntax/text/parser.rs
index 1e1449c..e870db3 100644
--- a/dhall/src/syntax/text/parser.rs
+++ b/dhall/src/syntax/text/parser.rs
@@ -130,6 +130,7 @@ lazy_static::lazy_static! {
         use Rule::*;
         // In order of precedence
         let operators = vec![
+            equivalent,
             import_alt,
             bool_or,
             natural_plus,
@@ -142,7 +143,6 @@ lazy_static::lazy_static! {
             natural_times,
             bool_eq,
             bool_ne,
-            equivalent,
         ];
         PrecClimber::new(
             operators
diff --git a/dhall/tests/parser/failure/unit/WithPrecedence1.txt b/dhall/tests/parser/failure/unit/WithPrecedence1.txt
new file mode 100644
index 0000000..a1dfd31
--- /dev/null
+++ b/dhall/tests/parser/failure/unit/WithPrecedence1.txt
@@ -0,0 +1,6 @@
+ --> 1:24
+  |
+1 | { x = 0 } // { y = 1 } with x = 1␊
+  |                        ^---
+  |
+  = expected EOI, import_alt, bool_or, natural_plus, text_append, list_append, bool_and, natural_times, bool_eq, bool_ne, combine, combine_types, equivalent, prefer, arrow, import_hashed, or primitive_expression
diff --git a/dhall/tests/parser/failure/unit/WithPrecedence2.txt b/dhall/tests/parser/failure/unit/WithPrecedence2.txt
new file mode 100644
index 0000000..fefd172
--- /dev/null
+++ b/dhall/tests/parser/failure/unit/WithPrecedence2.txt
@@ -0,0 +1,6 @@
+ --> 1:15
+  |
+1 | foo { x = 0 } with x = 1␊
+  |               ^---
+  |
+  = expected EOI, import_alt, bool_or, natural_plus, text_append, list_append, bool_and, natural_times, bool_eq, bool_ne, combine, combine_types, equivalent, prefer, arrow, import_hashed, or primitive_expression
diff --git a/dhall/tests/parser/failure/unit/WithPrecedence3.txt b/dhall/tests/parser/failure/unit/WithPrecedence3.txt
new file mode 100644
index 0000000..418c669
--- /dev/null
+++ b/dhall/tests/parser/failure/unit/WithPrecedence3.txt
@@ -0,0 +1,6 @@
+ --> 1:22
+  |
+1 | { x = 0 } with x = 1 : T␊
+  |                      ^---
+  |
+  = expected EOI, import_alt, bool_or, natural_plus, text_append, list_append, bool_and, natural_times, bool_eq, bool_ne, combine, combine_types, equivalent, prefer, import_hashed, or primitive_expression
diff --git a/dhall/tests/parser/success/unit/WithPrecedence1B.txt b/dhall/tests/parser/success/unit/WithPrecedence1B.txt
new file mode 100644
index 0000000..5f22335
--- /dev/null
+++ b/dhall/tests/parser/success/unit/WithPrecedence1B.txt
@@ -0,0 +1 @@
+{ a = Some 1 } ⫽ { a = Some 2 } ⫽ { a = Some 3 }
diff --git a/dhall/tests/parser/success/unit/WithPrecedence2B.txt b/dhall/tests/parser/success/unit/WithPrecedence2B.txt
new file mode 100644
index 0000000..f945cc9
--- /dev/null
+++ b/dhall/tests/parser/success/unit/WithPrecedence2B.txt
@@ -0,0 +1 @@
+{ x = 0 } ⫽ { x = 1 + 1 }
diff --git a/dhall/tests/parser/success/unit/WithPrecedence3B.txt b/dhall/tests/parser/success/unit/WithPrecedence3B.txt
new file mode 100644
index 0000000..a801b24
--- /dev/null
+++ b/dhall/tests/parser/success/unit/WithPrecedence3B.txt
@@ -0,0 +1 @@
+foo::{ x = 0 } ⫽ { x = 1 }
diff --git a/dhall/tests/parser/success/unit/operators/PrecedenceEquivalenceB.txt b/dhall/tests/parser/success/unit/operators/PrecedenceEquivalenceB.txt
new file mode 100644
index 0000000..717c108
--- /dev/null
+++ b/dhall/tests/parser/success/unit/operators/PrecedenceEquivalenceB.txt
@@ -0,0 +1 @@
+2 + 3 * 4 ≡ 4 * 3 + 2
diff --git a/tests_buffer b/tests_buffer
index 3240b41..e01d7a7 100644
--- a/tests_buffer
+++ b/tests_buffer
@@ -11,7 +11,6 @@ From https://github.com/dhall-lang/dhall-lang/issues/280 :
     "${ not_really_an_expression ;-) }"
     ''${ not_an_expression ;-) }''
     {- {- -} 1
-{ x = 0 } with x = 1 + 1
 
 import:
 failure/
-- 
cgit v1.2.3