Support aliased inline types

This allows adding aliased types to record fields without allowing illegal non-inline types such as record or variants.

grammar.js

@@ -318,6 +318,7 @@ module.exports = grammar({
       $.module_pack,
       $.unit,
       $.polymorphic_type,
+      alias($._as_aliasing_non_function_inline_type, $.as_aliasing_type)
     ),
 
     polymorphic_type: $ => seq(
@@ -706,6 +707,9 @@ module.exports = grammar({
 
     as_aliasing_type: $ => seq($._type, 'as', $.type_identifier),
 
+    _as_aliasing_non_function_inline_type: $ => 
+      prec(2, seq($._non_function_inline_type, 'as', $.type_identifier)),
+
     assert_expression: $ => prec.left(seq('assert', $.expression)),
 
     call_expression: $ => prec('call', seq(

test/corpus/type_declarations.txt

@@ -99,7 +99,9 @@ type t = {
 
   mutable x: int,
 
-  opt?: string
+  opt?: string,
+
+  env: {..} as 'env
 }
 
 type t = Mod.t = {a: int}
@@ -140,7 +142,13 @@ type t = {
         (record_type_field
           (property_identifier)
           (type_annotation
-            (type_identifier))))))
+          (type_identifier)))
+            (record_type_field
+              (property_identifier)
+                (type_annotation
+                  (as_aliasing_type
+                      (object_type)
+                      (type_identifier)))))))
   (type_declaration
     (type_binding
       (type_identifier)