From 6ea0b6a42e0609dbb0ba80ca1ce638ca6cb506c4 Mon Sep 17 00:00:00 2001
From: Sathya Gunasekaran <gsathya.ceg@gmail.com>
Date: Mon, 16 Jan 2023 15:34:21 +0000
Subject: [PATCH] [alias] Don't alias primitives

---
 compiler/forget/src/HIR/HIR.ts                |  4 ++
 compiler/forget/src/Inference/InferAlias.ts   |  4 ++
 .../hir/primitive-alias-mutate.expect.md      | 50 +++++++++++++++++++
 .../fixtures/hir/primitive-alias-mutate.js    | 11 ++++
 4 files changed, 69 insertions(+)
 create mode 100644 compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.expect.md
 create mode 100644 compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.js

diff --git a/compiler/forget/src/HIR/HIR.ts b/compiler/forget/src/HIR/HIR.ts
index 99b4297bdb..e1fbeebb19 100644
--- a/compiler/forget/src/HIR/HIR.ts
+++ b/compiler/forget/src/HIR/HIR.ts
@@ -607,3 +607,7 @@ function phiTypeEquals(tA: Type, tB: Type): boolean {
 export function isObjectType(id: Identifier): boolean {
   return id.type.kind === "Object";
 }
+
+export function isPrimitiveType(id: Identifier): boolean {
+  return id.type.kind === "Primitive";
+}
diff --git a/compiler/forget/src/Inference/InferAlias.ts b/compiler/forget/src/Inference/InferAlias.ts
index 970e3fe2f6..6a1127369d 100644
--- a/compiler/forget/src/Inference/InferAlias.ts
+++ b/compiler/forget/src/Inference/InferAlias.ts
@@ -3,6 +3,7 @@ import {
   HIRFunction,
   Identifier,
   Instruction,
+  isPrimitiveType,
   LValue,
   Place,
 } from "../HIR/HIR";
@@ -33,6 +34,9 @@ function inferInstr(instr: Instruction, state: AliasAnalyser) {
   let alias: Place | null = null;
   switch (instrValue.kind) {
     case "Identifier": {
+      if (isPrimitiveType(instrValue.identifier)) {
+        return;
+      }
       alias = instrValue;
       break;
     }
diff --git a/compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.expect.md b/compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.expect.md
new file mode 100644
index 0000000000..47a727bf64
--- /dev/null
+++ b/compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.expect.md
@@ -0,0 +1,50 @@
+
+## Input
+
+```javascript
+function component(a) {
+  let x = "foo";
+  if (a) {
+    x = "bar";
+  } else {
+    x = "baz";
+  }
+  let y = x;
+  mutate(y);
+  return y;
+}
+
+```
+
+## Code
+
+```javascript
+function component(a) {
+  const $ = React.useMemoCache();
+  const x = "foo";
+  const c_0 = $[0] !== a;
+  let x$0;
+  if (c_0) {
+    x$0 = undefined;
+
+    if (a) {
+      const x$1 = "bar";
+      x$0 = x$1;
+    } else {
+      const x$2 = "baz";
+      x$0 = x$2;
+    }
+
+    $[0] = a;
+    $[1] = x$0;
+  } else {
+    x$0 = $[1];
+  }
+
+  const y = x$0;
+  mutate(y);
+  return y;
+}
+
+```
+      
\ No newline at end of file
diff --git a/compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.js b/compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.js
new file mode 100644
index 0000000000..f77284dcd9
--- /dev/null
+++ b/compiler/forget/src/__tests__/fixtures/hir/primitive-alias-mutate.js
@@ -0,0 +1,11 @@
+function component(a) {
+  let x = "foo";
+  if (a) {
+    x = "bar";
+  } else {
+    x = "baz";
+  }
+  let y = x;
+  mutate(y);
+  return y;
+}