Add "mixed" Flow type

"mixed" is one of the base types listed here:

http://flowtype.org/docs/base-types.html

So this commit adds support for it.

src/acorn/plugins/flow.js

@@ -415,6 +415,9 @@ pp.flow_identToTypeAnnotation = function (start, node, id) {
     case "boolean":
       return this.finishNode(node, "BooleanTypeAnnotation")
 
+    case "mixed":
+      return this.finishNode(node, "MixedTypeAnnotation")
+
     case "number":
       return this.finishNode(node, "NumberTypeAnnotation")
 

src/babel/generation/generators/flow.js

@@ -103,6 +103,10 @@ export function IntersectionTypeAnnotation(node, print) {
   print.join(node.types, { separator: " & " });
 }
 
+export function MixedTypeAnnotation() {
+  this.push("mixed");
+}
+
 export function NullableTypeAnnotation(node, print) {
   this.push("?");
   print.plain(node.typeAnnotation);

src/babel/types/alias-keys.json

@@ -93,6 +93,7 @@
   "InterfaceExtends":            ["Flow"],
   "InterfaceDeclaration":        ["Flow", "Statement", "Declaration"],
   "IntersectionTypeAnnotation":  ["Flow"],
+  "MixedTypeAnnotation":         ["Flow"],
   "NullableTypeAnnotation":      ["Flow"],
   "NumberTypeAnnotation":        ["Flow"],
   "StringLiteralTypeAnnotation": ["Flow"],

src/babel/types/visitor-keys.json

@@ -91,6 +91,7 @@
   "InterfaceExtends":            ["id", "typeParameters"],
   "InterfaceDeclaration":        ["id", "typeParameters", "extends", "body"],
   "IntersectionTypeAnnotation":  ["types"],
+  "MixedTypeAnnotation":         [],
   "NullableTypeAnnotation":      ["typeAnnotation"],
   "NumberTypeAnnotation":        [],
   "StringLiteralTypeAnnotation": [],