Merge explicit and inferred param defaults (#1230)

Author: devongovett

__tests__/lib/infer/__snapshots__/params.js.snap

@@ -217,6 +217,21 @@ Array [
 ]
 `;
 
+exports[`inferParams 8`] = `
+Array [
+  Object {
+    "default": "4",
+    "lineNumber": 1,
+    "name": "x",
+    "title": "param",
+    "type": Object {
+      "name": "number",
+      "type": "NameExpression",
+    },
+  },
+]
+`;
+
 exports[`mergeTrees 1`] = `
 Object {
   "errors": Array [

__tests__/lib/infer/params.js

@@ -191,4 +191,15 @@ test('inferParams', function() {
       }
     `).params
   ).toEqual([]);
+
+  expect(
+    evaluate(
+      `
+    /** Test
+     * @param x
+    */
+    function f(x: number = 4) {}
+  `
+    ).params
+  ).toMatchSnapshot();
 });

src/infer/params.js

@@ -338,7 +338,9 @@ function combineTags(inferredTag, explicitTag) {
   let defaultValue;
   if (!explicitTag.type) {
     type = inferredTag.type;
-  } else if (!explicitTag.default && inferredTag.default) {
+  }
+
+  if (!explicitTag.default && inferredTag.default) {
     defaultValue = inferredTag.default;
   }