fix: allow decorators before type and declarations

See #133

Author: nkrkv

grammar.js

@@ -241,13 +241,19 @@ module.exports = grammar({
         choice('=', '+='),
         optional('private'),
         $._type,
-        optional(seq(
-          'and',
-          $._type_declaration
-        )),
+        repeat(alias($._type_declaration_and, $.type_declaration)),
       )),
     ),
 
+    _type_declaration_and: $ => seq(
+      // New line here not necessary terminates the statement,
+      // show this doubt to the parser
+      repeat($._newline),
+      repeat($.decorator),
+      'and',
+      $._type_declaration
+    ),
+
     type_parameters: $ => seq(
       '<',
       commaSep1t($.type_identifier),

test/corpus/decorators.txt

@@ -67,3 +67,34 @@ let onResult = () => @doesNotRaise Belt.Array.getExn([], 0)
           (array)
           (number))))))
 
+============================================
+Decorator before type `and`
+============================================
+
+@deriving
+type foo = {
+  foo: string
+}
+@deriving
+and bar = {bar: int}
+
+
+@deriving @hello and baz = {baz: float}
+
+---
+
+(source_file
+  (decorated
+    (decorator (decorator_identifier))
+    (type_declaration
+      (type_identifier)
+      (record_type (record_type_field (property_identifier) (type_annotation (type_identifier))))
+      (type_declaration
+        (decorator (decorator_identifier))
+        (type_identifier)
+        (record_type (record_type_field (property_identifier) (type_annotation (type_identifier)))))
+      (type_declaration
+        (decorator (decorator_identifier))
+        (decorator (decorator_identifier))
+        (type_identifier)
+        (record_type (record_type_field (property_identifier) (type_annotation (type_identifier))))))))

test/corpus/type_declarations.txt

@@ -385,15 +385,16 @@ and teacher = {
         (property_identifier)
         (type_annotation
           (type_identifier))))
-    (type_identifier)
-    (record_type
-      (record_type_field
-        (property_identifier)
-        (type_annotation
-          (generic_type
-            (type_identifier)
-            (type_arguments
-              (type_identifier))))))))
+    (type_declaration
+      (type_identifier)
+      (record_type
+        (record_type_field
+          (property_identifier)
+          (type_annotation
+            (generic_type
+              (type_identifier)
+              (type_arguments
+                (type_identifier)))))))))
 
 
 ===========================================