Improve grammar for package declarations

Adds support for package blocks and package objects

corpus/definitions.txt

@@ -1,3 +1,37 @@
+================================
+Package
+================================
+
+package a.b
+package c {
+  object A
+}
+
+---
+
+(compilation_unit
+  (package_clause (package_identifier (identifier) (identifier)))
+  (package_clause (package_identifier (identifier))
+    (template_body
+      (object_definition (identifier)))))
+
+================================
+Package object
+================================
+
+package object d extends A {
+  val hello: String = "there"
+}
+
+---
+
+(compilation_unit
+  (package_object
+    (identifier)
+    (extends_clause (type_identifier))
+    (template_body
+      (val_definition (identifier) (type_identifier) (string)))))
+
 ================================
 Imports
 ================================

examples/Packages.scala

@@ -0,0 +1,9 @@
+package a.b
+package c {
+  object A
+}
+package c {
+  package object d {
+    val hello: String = "there"
+  }
+}

grammar.js

@@ -39,6 +39,7 @@ module.exports = grammar({
 
     _definition: $ => choice(
       $.package_clause,
+      $.package_object,
       $.class_definition,
       $.import_declaration,
       $.object_definition,
@@ -54,7 +55,22 @@ module.exports = grammar({
 
     package_clause: $ => seq(
       'package',
-      choice($.identifier, $.stable_identifier)
+      $.package_identifier,
+      // This is slightly more permissive than the EBNF in that it allows any
+      // kind of delcaration inside of the package blocks. As we're more
+      // concerned with the structure rather than the validity of the program
+      // we'll allow it.
+      optional($.template_body)
+    ),
+
+    package_identifier: $ => sep1(
+      '.', $.identifier
+    ),
+
+    package_object: $ => seq(
+      'package',
+      'object',
+      $._object_definition
     ),
 
     import_declaration: $ => seq(

src/grammar.json

@@ -15,6 +15,10 @@
           "type": "SYMBOL",
           "name": "package_clause"
         },
+        {
+          "type": "SYMBOL",
+          "name": "package_object"
+        },
         {
           "type": "SYMBOL",
           "name": "class_definition"
@@ -68,18 +72,63 @@
           "type": "STRING",
           "value": "package"
         },
+        {
+          "type": "SYMBOL",
+          "name": "package_identifier"
+        },
         {
           "type": "CHOICE",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "template_body"
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        }
+      ]
+    },
+    "package_identifier": {
+      "type": "SEQ",
       "members": [
         {
           "type": "SYMBOL",
           "name": "identifier"
         },
+        {
+          "type": "REPEAT",
+          "content": {
+            "type": "SEQ",
+            "members": [
+              {
+                "type": "STRING",
+                "value": "."
+              },
               {
                 "type": "SYMBOL",
-              "name": "stable_identifier"
+                "name": "identifier"
+              }
+            ]
+          }
         }
       ]
+    },
+    "package_object": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "package"
+        },
+        {
+          "type": "STRING",
+          "value": "object"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_object_definition"
         }
       ]
     },
@@ -90,6 +139,36 @@
           "type": "STRING",
           "value": "import"
         },
+        {
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "SYMBOL",
+              "name": "_import_expression"
+            },
+            {
+              "type": "REPEAT",
+              "content": {
+                "type": "SEQ",
+                "members": [
+                  {
+                    "type": "STRING",
+                    "value": ","
+                  },
+                  {
+                    "type": "SYMBOL",
+                    "name": "_import_expression"
+                  }
+                ]
+              }
+            }
+          ]
+        }
+      ]
+    },
+    "_import_expression": {
+      "type": "SEQ",
+      "members": [
         {
           "type": "CHOICE",
           "members": [