fix: plus signs in certain contexts were missing

Author: amaanq

Cargo.toml

@@ -12,13 +12,13 @@ edition = "2018"
 
 build = "bindings/rust/build.rs"
 include = [
-  "common",
-  "bindings/rust",
-  "typescript/grammar.js",
-  "typescript/src",
-  "tsx/grammar.js",
-  "tsx/src",
-  "queries"
+	"common",
+	"bindings/rust",
+	"typescript/grammar.js",
+	"typescript/src",
+	"tsx/grammar.js",
+	"tsx/src",
+	"queries",
 ]
 
 [lib]

common/define-grammar.js

@@ -618,6 +618,7 @@ module.exports = function defineGrammar(dialect) {
       ),
 
       omitting_type_annotation: $ => seq('-?:', $._type),
+      adding_type_annotation: $ => seq('+?:', $._type),
       opting_type_annotation: $ => seq('?:', $._type),
       type_annotation: $ => seq(':', $._type),
 
@@ -933,7 +934,7 @@ module.exports = function defineGrammar(dialect) {
       index_signature: $ => seq(
         optional(
           seq(
-            field("sign", optional("-")),
+            field("sign", optional(choice("-", "+"))),
             'readonly'
           )
         ),
@@ -953,6 +954,7 @@ module.exports = function defineGrammar(dialect) {
         field('type', choice(
           $.type_annotation,
           $.omitting_type_annotation,
+          $.adding_type_annotation,
           $.opting_type_annotation
         ))
       ),