Add associative map constraints and range refinement

editors/tree-sitter-decodal/grammar.js

@@ -2,6 +2,7 @@
 // doc/manual/souce/language/grammar.md.
 
 const PREC = {
+  AS: 0,
   DEFAULT: 1,
   PATCH: 2,
   COMPOSE: 3,
@@ -53,6 +54,7 @@ module.exports = grammar({
       $.identifier,
       $.regex_literal,
       $.comparison_constraint,
+      $.map_constraint,
       $.object,
       $.array_constraint,
       $.array,
@@ -66,6 +68,7 @@ module.exports = grammar({
       $.unary_expression,
       $.binary_expression,
       $.default_expression,
+      $.as_expression,
     ),
 
     literal: $ => choice(
@@ -100,6 +103,13 @@ module.exports = grammar({
       '}',
     ),
 
+    map_constraint: $ => seq(
+      '{',
+      '...',
+      field('value', $._expression),
+      '}',
+    ),
+
     field_definition: $ => seq(
       field('path', $.field_path),
       '=',
@@ -125,12 +135,12 @@ module.exports = grammar({
       ']',
     ),
 
-    let_expression: $ => seq(
+    let_expression: $ => prec.right(seq(
       'let',
       repeat(seq($.field_definition, ';')),
       'in',
       field('body', $._expression),
-    ),
+    )),
 
     function_expression: $ => prec.right(seq(
       '(',
@@ -237,5 +247,11 @@ module.exports = grammar({
       'default',
       field('fallback', $._expression),
     )),
+
+    as_expression: $ => prec.left(PREC.AS, seq(
+      field('narrower', $._expression),
+      'as',
+      field('wider', $._expression),
+    )),
   },
 });