[compiler] Repro for interaction b/w outlining and idx

babel-plugin-idx enforces that its 2nd argument is an arrow function, so
outlining needs to skip over lambdas that are args to idx. This PR adds
a small repro highlighting the issue.

ghstack-source-id: b4627ec552056f33090e2f7bc0536a6006d79d18
Pull Request resolved: #30435

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.idx-outlining.expect.md

@@ -0,0 +1,27 @@
+
+## Input
+
+```javascript
+import idx from 'idx';
+
+function Component(props) {
+  // the lambda should not be outlined
+  const groupName = idx(props, _ => _.group.label);
+  return <div>{groupName}</div>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};
+
+```
+
+
+## Error
+
+```
+The second argument supplied to `idx` must be an arrow function. (This is an error on an internal node. Probably an internal error.)
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.idx-outlining.js

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+import idx from 'idx';
+
+function Component(props) {
+  // the lambda should not be outlined
+  const groupName = idx(props, _ => _.group.label);
+  return <div>{groupName}</div>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};