Parse async blocks (#44)

* Parse async blocks

* Await blocks ca also have move

Author: GrayJack

corpus/async.txt

@@ -48,3 +48,24 @@ futures.await?.function().await?;
             (await_expression (identifier)))
           (field_identifier))
         (arguments)))))
+
+============================================
+Async Block
+============================================
+
+async {}
+async { let x = 10; }
+async move {}
+
+---
+
+(source_file
+  (async_block
+    (block))
+  (async_block
+    (block
+      (let_declaration
+        (identifier)
+        (integer_literal))))
+  (async_block
+    (block)))

grammar.js

@@ -844,6 +844,7 @@ module.exports = grammar({
 
     _expression_ending_with_block: $ => choice(
       $.unsafe_block,
+      $.async_block,
       $.block,
       $.if_expression,
       $.if_let_expression,
@@ -1188,6 +1189,12 @@ module.exports = grammar({
       $.block
     ),
 
+    async_block: $ => seq(
+      'async',
+      optional("move"),
+      $.block
+    ),
+
     block: $ => seq(
       '{',
       repeat($._statement),

src/grammar.json

@@ -4662,6 +4662,10 @@
           "type": "SYMBOL",
           "name": "unsafe_block"
         },
+        {
+          "type": "SYMBOL",
+          "name": "async_block"
+        },
         {
           "type": "SYMBOL",
           "name": "block"
@@ -6881,6 +6885,31 @@
         }
       ]
     },
+    "async_block": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "async"
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "STRING",
+              "value": "move"
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "SYMBOL",
+          "name": "block"
+        }
+      ]
+    },
     "block": {
       "type": "SEQ",
       "members": [

src/node-types.json

@@ -105,6 +105,10 @@
         "type": "assignment_expression",
         "named": true
       },
+      {
+        "type": "async_block",
+        "named": true
+      },
       {
         "type": "await_expression",
         "named": true
@@ -594,6 +598,21 @@
       }
     }
   },
+  {
+    "type": "async_block",
+    "named": true,
+    "fields": {},
+    "children": {
+      "multiple": false,
+      "required": true,
+      "types": [
+        {
+          "type": "block",
+          "named": true
+        }
+      ]
+    }
+  },
   {
     "type": "attribute_item",
     "named": true,
@@ -759,6 +778,10 @@
           "type": "_expression",
           "named": true
         },
+        {
+          "type": "async_block",
+          "named": true
+        },
         {
           "type": "block",
           "named": true
@@ -3201,6 +3224,10 @@
           "type": "_expression",
           "named": true
         },
+        {
+          "type": "async_block",
+          "named": true
+        },
         {
           "type": "block",
           "named": true