Flow opaque type 6.x backport (#6081)

* Flow opaque type backport

* Add tests for strip types, comments, and babel-generator

* Fix failing tests, run scripts

* Bump babylon to 6.18.0

packages/babel-types/src/definitions/flow.js

@@ -103,6 +103,14 @@ defineType("DeclareTypeAlias", {
   }
 });
 
+defineType("DeclareOpaqueType", {
+  visitor: ["id", "typeParameters", "supertype"],
+  aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
+  fields: {
+    // todo
+  }
+});
+
 defineType("DeclareVariable", {
   visitor: ["id"],
   aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
@@ -111,6 +119,14 @@ defineType("DeclareVariable", {
   }
 });
 
+defineType("DeclareExportDeclaration", {
+  visitor: ["declaration", "specifiers", "source"],
+  aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
+  fields: {
+    // todo
+  },
+});
+
 defineType("ExistentialTypeParam", {
   aliases: ["Flow"]
 });
@@ -236,6 +252,14 @@ defineType("TypeAlias", {
   }
 });
 
+defineType("OpaqueType", {
+  visitor: ["id", "typeParameters", "impltype", "supertype"],
+  aliases: ["Flow", "FlowDeclaration", "Statement", "Declaration"],
+  fields: {
+    // todo
+  }
+});
+
 defineType("TypeAnnotation", {
   visitor: ["typeAnnotation"],
   aliases: ["Flow"],

packages/babel-types/src/retrievers.js

@@ -70,6 +70,7 @@ getBindingIdentifiers.keys = {
   DeclareVariable: ["id"],
   InterfaceDeclaration: ["id"],
   TypeAlias: ["id"],
+  OpaqueType: ["id"],
 
   CatchClause: ["param"],
   LabeledStatement: ["label"],