[compiler] Fixture to show current behavior of nested function declarations

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/function-decl-nested.expect.md

@@ -0,0 +1,83 @@
+
+## Input
+
+```javascript
+import {useRef} from 'react';
+
+function C(x) {
+  function g(x) {
+    return 2;
+  }
+  g();
+  function f() {
+    return x.x;
+  }
+  function h(x) {
+    return 2;
+  }
+  return <>{h(f)}</>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{x: 1}],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+import { useRef } from "react";
+
+function C(x) {
+  const $ = _c(5);
+  const g = function g(x_0) {
+    return 2;
+  };
+
+  g();
+  let t0;
+  if ($[0] !== x.x) {
+    t0 = function f() {
+      return x.x;
+    };
+    $[0] = x.x;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  const f = t0;
+  let t1;
+  if ($[2] === Symbol.for("react.memo_cache_sentinel")) {
+    t1 = function h(x_1) {
+      return 2;
+    };
+    $[2] = t1;
+  } else {
+    t1 = $[2];
+  }
+  const h = t1;
+
+  const t2 = h(f);
+  let t3;
+  if ($[3] !== t2) {
+    t3 = <>{t2}</>;
+    $[3] = t2;
+    $[4] = t3;
+  } else {
+    t3 = $[4];
+  }
+  return t3;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{ x: 1 }],
+};
+
+```
+
+### Eval output
+(kind: ok) 2

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/function-decl-nested.js

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+import {useRef} from 'react';
+
+function C(x) {
+  function g(x) {
+    return 2;
+  }
+  g();
+  function f() {
+    return x.x;
+  }
+  function h(x) {
+    return 2;
+  }
+  return <>{h(f)}</>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{x: 1}],
+};