Add associative map constraints and range refinement

editors/lezer-decodal/decodal.grammar

@@ -5,7 +5,12 @@ Statement {
   Expression Semicolon?
 }
 
-Expression { DefaultExpression }
+Expression { AsExpression }
+
+AsExpression {
+  DefaultExpression |
+  AsExpression !as As DefaultExpression
+}
 
 DefaultExpression {
   PatchExpression |
@@ -70,6 +75,7 @@ PrimaryExpression {
   Literal |
   Identifier |
   ComparisonConstraint |
+  MapConstraint |
   Object |
   ArrayConstraint |
   Array |
@@ -85,6 +91,7 @@ CompareOperator { EqualEqual | BangEqual | Lt | Lte | Gt | Gte }
 ComparisonConstraint { (Lt | Lte | Gt | Gte) Expression }
 
 Object { LBrace (FieldDefinition (Semicolon FieldDefinition)* Semicolon?)? RBrace }
+MapConstraint { LBrace Ellipsis Expression RBrace }
 FieldDefinition { FieldPath Equal Expression }
 FieldPath { Identifier !fieldPath (Dot Identifier)* }
 
@@ -104,8 +111,11 @@ Pattern { Underscore | Expression }
 
 ImportExpression { Import String }
 
+As { @specialize<Identifier, "as"> }
+
 @precedence {
   fieldPath @left,
+  as @left,
   default @right,
   patch @left,
   compose @left,