4 files changed, 23 insertions, 11 deletions
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