Merge inferred return type like we do for params. Refs #359 (#604)

Author: tmcw

lib/infer/return.js

@@ -14,7 +14,9 @@ var findTarget = require('./finders').findTarget,
  */
 module.exports = function () {
   return shouldSkipInference(function inferReturn(comment) {
-    if (comment.returns) {
+    if (Array.isArray(comment.returns) &&
+      comment.returns.length &&
+      comment.returns[0].type) {
       return comment;
     }
     var path = findTarget(comment.context.ast);
@@ -29,9 +31,14 @@ module.exports = function () {
     if (t.isFunction(fn) &&
       fn.returnType &&
       fn.returnType.typeAnnotation) {
-      comment.returns = [{
-        type: flowDoctrine(fn.returnType.typeAnnotation)
-      }];
+      var returnType = flowDoctrine(fn.returnType.typeAnnotation);
+      if (comment.returns) {
+        comment.returns[0].type = returnType;
+      } else {
+        comment.returns = [{
+          type: returnType
+        }];
+      }
     }
     return comment;
   });

test/fixture/merge-infered-type.input.js

@@ -2,7 +2,7 @@
  * Add five to `x`.
  *
  * @param x The number to add five to.
- * @returns {number} x plus five.
+ * @returns x plus five.
  */
 function addFive(x: number): number {
   return x + 5;

test/fixture/merge-infered-type.output.json

@@ -98,10 +98,7 @@
         "title": "returns",
         "description": "x plus five.",
         "lineNumber": 4,
-        "type": {
-          "type": "NameExpression",
-          "name": "number"
-        }
+        "type": null
       }
     ],
     "loc": {