[hir] Traverse function to capture deps, not just body node

Technically there is a body node created for implicit return expression in a 
arrow function, so the existing logic should've worked fine. But there seems to 
be a Babel bug, so let's work around it by traversing the function. 

Added a test case that captures a dep as a param -- this is currently 
unsupported  and also something that would've been ignored before this PR. Added 
a failing test to make sure we think about this case when we add support for 
default params.

compiler/packages/babel-plugin-react-forget/src/HIR/BuildHIR.ts

@@ -3058,7 +3058,7 @@ function gatherCapturedDeps(
     }
   }
 
-  fn.get("body").traverse({
+  fn.traverse({
     Expression(path) {
       visit(path);
     },

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.nested-function-with-param-as-captured-dep.expect.md

@@ -0,0 +1,29 @@
+
+## Input
+
+```javascript
+function Foo() {
+  (function t() {
+    let x = {};
+    return function a(x = () => {}) {
+      return x;
+    };
+  })();
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Foo,
+  params: [],
+  isComponent: false,
+};
+
+```
+
+
+## Error
+
+```
+[ReactForget] Todo: (BuildHIR::node.lowerReorderableExpression) Expression type 'ArrowFunctionExpression' cannot be safely reordered (4:4)
+```
+          
+      

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.nested-function-with-param-as-captured-dep.ts

@@ -0,0 +1,14 @@
+function Foo() {
+  (function t() {
+    let x = {};
+    return function a(x = () => {}) {
+      return x;
+    };
+  })();
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Foo,
+  params: [],
+  isComponent: false,
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/lambda-return-expression.expect.md

@@ -18,11 +18,22 @@ export const FIXTURE_ENTRYPOINT = {
 
 ```
 
+## Code
 
-## Error
+```javascript
+import { invoke } from "shared-runtime";
+
+function useFoo() {
+  const x = {};
+  const result = invoke(() => x);
+  console.log(result);
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [],
+  isComponent: false,
+};
 
 ```
-[ReactForget] Invariant: Expected value for identifier `16` to be initialized. (5:5)
-```
-