From 10525b6015a37d26e38f32298888811f223cf7a1 Mon Sep 17 00:00:00 2001
From: Mike Vitousek <mmvitousek@gmail.com>
Date: Wed, 14 Aug 2024 16:56:49 -0400
Subject: [PATCH] [compiler] Support for member expression inc/decrement

Test Plan:
Builds support for a.x++ and friends. Similar to a.x += y, emits it as an assignment expression.

[ghstack-poisoned]
---
 .../src/HIR/BuildHIR.ts                       | 51 +++++++++++++++++++
 .../compiler/error.todo-kitchensink.expect.md |  4 --
 .../fixtures/compiler/member-inc.expect.md    | 44 ++++++++++++++++
 .../__tests__/fixtures/compiler/member-inc.js | 14 +++++
 4 files changed, 109 insertions(+), 4 deletions(-)
 create mode 100644 compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.expect.md
 create mode 100644 compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.js

diff --git a/compiler/packages/babel-plugin-react-compiler/src/HIR/BuildHIR.ts b/compiler/packages/babel-plugin-react-compiler/src/HIR/BuildHIR.ts
index 8ed71b5e62a7e..945a265f487c9 100644
--- a/compiler/packages/babel-plugin-react-compiler/src/HIR/BuildHIR.ts
+++ b/compiler/packages/babel-plugin-react-compiler/src/HIR/BuildHIR.ts
@@ -2396,6 +2396,57 @@ function lowerExpression(
     case 'UpdateExpression': {
       let expr = exprPath as NodePath<t.UpdateExpression>;
       const argument = expr.get('argument');
+      if (argument.isMemberExpression()) {
+        const binaryOperator = expr.node.operator === '++' ? '+' : '-';
+        const leftExpr = argument as NodePath<t.MemberExpression>;
+        const {object, property, value} = lowerMemberExpression(
+          builder,
+          leftExpr,
+        );
+
+        // Store the previous value to a temporary
+        const previousValuePlace = lowerValueToTemporary(builder, value);
+        // Store the new value to a temporary
+        const updatedValue = lowerValueToTemporary(builder, {
+          kind: 'BinaryExpression',
+          operator: binaryOperator,
+          left: {...previousValuePlace},
+          right: lowerValueToTemporary(builder, {
+            kind: 'Primitive',
+            value: 1,
+            loc: GeneratedSource,
+          }),
+          loc: leftExpr.node.loc ?? GeneratedSource,
+        });
+
+        // Save the result back to the property
+        let newValuePlace;
+        if (typeof property === 'string') {
+          newValuePlace = lowerValueToTemporary(builder, {
+            kind: 'PropertyStore',
+            object: {...object},
+            property,
+            value: {...updatedValue},
+            loc: leftExpr.node.loc ?? GeneratedSource,
+          });
+        } else {
+          newValuePlace = lowerValueToTemporary(builder, {
+            kind: 'ComputedStore',
+            object: {...object},
+            property: {...property},
+            value: {...updatedValue},
+            loc: leftExpr.node.loc ?? GeneratedSource,
+          });
+        }
+
+        return {
+          kind: 'LoadLocal',
+          place: expr.node.prefix
+            ? {...newValuePlace}
+            : {...previousValuePlace},
+          loc: exprLoc,
+        };
+      }
       if (!argument.isIdentifier()) {
         builder.errors.push({
           reason: `(BuildHIR::lowerExpression) Handle UpdateExpression with ${argument.type} argument`,
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.todo-kitchensink.expect.md b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.todo-kitchensink.expect.md
index ba32831cbb884..d8360455bb303 100644
--- a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.todo-kitchensink.expect.md
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.todo-kitchensink.expect.md
@@ -104,10 +104,6 @@ Todo: (BuildHIR::lowerStatement) Handle ArrayPattern inits in ForOfStatement (38
 
 Todo: (BuildHIR::lowerStatement) Handle ObjectPattern inits in ForOfStatement (40:40)
 
-Todo: (BuildHIR::lowerExpression) Handle UpdateExpression with MemberExpression argument (49:49)
-
-Todo: (BuildHIR::lowerExpression) Handle UpdateExpression with MemberExpression argument (50:50)
-
 Todo: (BuildHIR::node.lowerReorderableExpression) Expression type `MemberExpression` cannot be safely reordered (57:57)
 
 Todo: (BuildHIR::node.lowerReorderableExpression) Expression type `BinaryExpression` cannot be safely reordered (53:53)
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.expect.md b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.expect.md
new file mode 100644
index 0000000000000..b8d4de7e84573
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.expect.md
@@ -0,0 +1,44 @@
+
+## Input
+
+```javascript
+//@flow
+
+component Foo() {
+  let x = {a: 1};
+  x.a++;
+  x.a--;
+  console.log(++x.a);
+  console.log(x.a++);
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Foo,
+  params: [],
+};
+
+```
+
+## Code
+
+```javascript
+function Foo() {
+  const x = { a: 1 };
+  x.a = x.a + 1;
+  x.a = x.a - 1;
+  console.log((x.a = x.a + 1));
+  const t0 = x.a;
+  x.a = t0 + 1;
+  console.log(t0);
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Foo,
+  params: [],
+};
+
+```
+      
+### Eval output
+(kind: ok) 
+logs: [2,2]
\ No newline at end of file
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.js b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.js
new file mode 100644
index 0000000000000..c5b649a3d4944
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/member-inc.js
@@ -0,0 +1,14 @@
+//@flow
+
+component Foo() {
+  let x = {a: 1};
+  x.a++;
+  x.a--;
+  console.log(++x.a);
+  console.log(x.a++);
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Foo,
+  params: [],
+};