Makes check for defaultProps more specific (#37)

* adds failing test for this expression example

* does not try and convert all assignment expressions

Author: petegleeson

__snapshots__/test.js.snap

@@ -821,6 +821,36 @@ Object {
 }
 `;
 
+exports[`flow class with this expression 1`] = `
+Object {
+  "component": Object {
+    "kind": "generic",
+    "value": Object {
+      "kind": "object",
+      "members": Array [
+        Object {
+          "default": Object {
+            "kind": "number",
+            "value": 1,
+          },
+          "key": Object {
+            "kind": "id",
+            "name": "ok",
+          },
+          "kind": "property",
+          "optional": false,
+          "value": Object {
+            "kind": "number",
+          },
+        },
+      ],
+      "referenceIdName": "Props",
+    },
+  },
+  "kind": "program",
+}
+`;
+
 exports[`flow default class export 1`] = `
 Object {
   "component": Object {

index.js

@@ -213,11 +213,8 @@ function convertReactComponentFunction(path, context) {
     path.hub.file.path.traverse({
       // look for MyComponent.defaultProps = ...
       AssignmentExpression(assignmentPath) {
-        const component = convert(assignmentPath.get('left'), {
-          ...context,
-          mode: 'value'
-        });
-        if (component.object.referenceIdName === name) {
+        const left = assignmentPath.get('left.object');
+        if (left.isIdentifier() && left.node.name === name) {
           let initialConversion = convert(assignmentPath.get('right'), {
             ...context,
             mode: 'value'

test.js

@@ -1300,6 +1300,36 @@ const TESTS = [
         }
       }
     `
+  },
+  {
+    name: 'flow class with this expression',
+    typeSystem: 'flow',
+    code: `
+    type Props = {
+      ok: number
+    }
+    
+    class FieldInner extends React.Component<Props> {
+      unregisterField = () => {};
+    
+      componentDidMount() {
+        this.unregisterField = this.register();
+      }
+    
+      componentWillUnmount() {
+        this.unregisterField();
+      }
+    }
+    
+    const Field = (props: Props) => <FieldInner {...props} />;
+    
+    Field.defaultProps = {
+      ok: 1
+    };
+    
+    export default Field;
+    
+    `
   }
 ];