From c00e7a2af2746061cdada5735b979bf04770aac9 Mon Sep 17 00:00:00 2001
From: Mofei Zhang <mofei.zhang@utexas.edu>
Date: Thu, 30 Mar 2023 18:43:55 -0400
Subject: [PATCH] [test] Test case for optional chaining in codegen

```js

// here, `a?.b.c` is a single optional chain

// (evaluates to undefined if a is nullish)

a?.b.c;

// here, 'a?.b` is an optional chain, and `.c` is an unconditional load

// (nullthrows if a is nullish)

(a?.b).c;

```

---

Next PR in stack will add a bailout for `(a?.b).c`.

(If we want to properly handle `(a?.b).c`, we might want to model optional
chains explicitly in the HIR. We currently assume that any `PropertyLoad` whose
lhs is an optional property load is read conditionally.)
---
 ...bug.optional-chaining-memberexpr.expect.md | 39 +++++++++++++++++++
 .../_bug.optional-chaining-memberexpr.js      |  7 ++++
 2 files changed, 46 insertions(+)
 create mode 100644 compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.expect.md
 create mode 100644 compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.js

diff --git a/compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.expect.md b/compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.expect.md
new file mode 100644
index 0000000000..b07e0c1380
--- /dev/null
+++ b/compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.expect.md
@@ -0,0 +1,39 @@
+
+## Input
+
+```javascript
+// Note that `a?.b.c` is semantically different from `(a?.b).c`
+// We should codegen the correct member expressions
+function Component(props) {
+  let x = props?.b.c;
+  let y = (props?.x).y;
+  return { x, y };
+}
+
+```
+
+## Code
+
+```javascript
+// Note that `a?.b.c` is semantically different from `(a?.b).c`
+// We should codegen the correct member expressions
+function Component(props) {
+  const $ = React.unstable_useMemoCache(3);
+  const x = (props?.b).c;
+  const y = (props?.x).y;
+  const c_0 = $[0] !== x;
+  const c_1 = $[1] !== y;
+  let t0;
+  if (c_0 || c_1) {
+    t0 = { x, y };
+    $[0] = x;
+    $[1] = y;
+    $[2] = t0;
+  } else {
+    t0 = $[2];
+  }
+  return t0;
+}
+
+```
+      
\ No newline at end of file
diff --git a/compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.js b/compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.js
new file mode 100644
index 0000000000..b3e9a1c49b
--- /dev/null
+++ b/compiler/forget/src/__tests__/fixtures/compiler/_bug.optional-chaining-memberexpr.js
@@ -0,0 +1,7 @@
+// Note that `a?.b.c` is semantically different from `(a?.b).c`
+// We should codegen the correct member expressions
+function Component(props) {
+  let x = props?.b.c;
+  let y = (props?.x).y;
+  return { x, y };
+}