Implement filter loop

corpus/filter.txt

@@ -0,0 +1,79 @@
+==================
+Filter Loop
+==================
+
+filter i in [1, 2, 3] {
+  i <= 1 
+}
+
+---
+
+(root
+  (item
+    (statement
+      (filter
+        (identifier)
+        (expression
+          (value
+            (list
+              (expression
+                (value
+                  (integer)))
+              (expression
+                (value
+                  (integer)))
+              (expression
+                (value
+                  (integer))))))
+        (item
+          (statement
+            (expression
+              (logic
+                (expression
+                  (identifier))
+                (logic_operator)
+                (expression
+                  (value
+                    (integer)))))))))))
+
+==================
+Filter Loop Assignment
+==================
+
+list = filter i in ["one", "two", "three"] {
+  i == "one"
+}
+
+---
+
+(root
+  (item
+    (statement
+      (assignment
+        (identifier)
+        (assignment_operator)
+        (statement
+          (filter
+            (identifier)
+            (expression
+              (value
+                (list
+                  (expression
+                    (value
+                      (string)))
+                  (expression
+                    (value
+                      (string)))
+                  (expression
+                    (value
+                      (string))))))
+            (item
+              (statement
+                (expression
+                  (logic
+                    (expression
+                      (identifier))
+                    (logic_operator)
+                    (expression
+                      (value
+                        (string)))))))))))))

grammar.js

@@ -19,6 +19,7 @@ module.exports = grammar({
       $.async,
       $.for,
       $.transform,
+      $.filter,
     ),
   
     comment: $ => seq(/[#]+.*/),
@@ -195,6 +196,16 @@ module.exports = grammar({
       '}',
     ),
 
+    filter: $ => seq(
+      'filter',
+      $.identifier,
+      'in',
+      $.expression,
+      '{',
+      $.item,
+      '}',
+    ),
+
     tool: $ => choice(
       'assert',
       'assert_equal',

src/grammar.json

@@ -62,6 +62,10 @@
         {
           "type": "SYMBOL",
           "name": "transform"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "filter"
         }
       ]
     },
@@ -792,6 +796,39 @@
         }
       ]
     },
+    "filter": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "filter"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "identifier"
+        },
+        {
+          "type": "STRING",
+          "value": "in"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "expression"
+        },
+        {
+          "type": "STRING",
+          "value": "{"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "item"
+        },
+        {
+          "type": "STRING",
+          "value": "}"
+        }
+      ]
+    },
     "tool": {
       "type": "CHOICE",
       "members": [

src/node-types.json

@@ -117,6 +117,29 @@
       ]
     }
   },
+  {
+    "type": "filter",
+    "named": true,
+    "fields": {},
+    "children": {
+      "multiple": true,
+      "required": true,
+      "types": [
+        {
+          "type": "expression",
+          "named": true
+        },
+        {
+          "type": "identifier",
+          "named": true
+        },
+        {
+          "type": "item",
+          "named": true
+        }
+      ]
+    }
+  },
   {
     "type": "for",
     "named": true,
@@ -402,6 +425,10 @@
           "type": "expression",
           "named": true
         },
+        {
+          "type": "filter",
+          "named": true
+        },
         {
           "type": "for",
           "named": true