From cb345fb2d62fe95e189e698b2c70b0caf93719b3 Mon Sep 17 00:00:00 2001
From: Lukas Taegert-Atkinson <lukas.taegert-atkinson@tngtech.com>
Date: Fri, 28 Apr 2023 22:03:58 +0200
Subject: [PATCH] Ensure arguments are deoptimized when arguments variable is
 used

---
 src/ast/nodes/shared/FunctionBase.ts          |  5 +++++
 src/ast/nodes/shared/FunctionNode.ts          |  5 +++++
 src/ast/variables/ArgumentsVariable.ts        | 22 +++++++++++++++++++
 .../deoptimize-via-arguments/_config.js       |  3 +++
 .../samples/deoptimize-via-arguments/main.js  | 17 ++++++++++++++
 5 files changed, 52 insertions(+)
 create mode 100644 test/function/samples/deoptimize-via-arguments/_config.js
 create mode 100644 test/function/samples/deoptimize-via-arguments/main.js

diff --git a/src/ast/nodes/shared/FunctionBase.ts b/src/ast/nodes/shared/FunctionBase.ts
index f1298c0a2f6..c1fa969f3b2 100644
--- a/src/ast/nodes/shared/FunctionBase.ts
+++ b/src/ast/nodes/shared/FunctionBase.ts
@@ -54,8 +54,11 @@ export default abstract class FunctionBase extends NodeBase {
 					argument.deoptimizePath(UNKNOWN_PATH);
 				} else if (parameter instanceof Identifier) {
 					parameters[position][0].addEntityToBeDeoptimized(argument);
+					this.addArgumentToBeDeoptimized(argument);
 				} else if (parameter) {
 					argument.deoptimizePath(UNKNOWN_PATH);
+				} else {
+					this.addArgumentToBeDeoptimized(argument);
 				}
 			}
 		} else {
@@ -181,6 +184,8 @@ export default abstract class FunctionBase extends NodeBase {
 		super.parseNode(esTreeNode);
 	}
 
+	protected addArgumentToBeDeoptimized(_argument: ExpressionEntity) {}
+
 	protected applyDeoptimizations() {}
 
 	protected abstract getObjectEntity(): ObjectEntity;
diff --git a/src/ast/nodes/shared/FunctionNode.ts b/src/ast/nodes/shared/FunctionNode.ts
index 809b0a64ccb..3385ef2b37b 100644
--- a/src/ast/nodes/shared/FunctionNode.ts
+++ b/src/ast/nodes/shared/FunctionNode.ts
@@ -5,6 +5,7 @@ import FunctionScope from '../../scopes/FunctionScope';
 import type { ObjectPath, PathTracker } from '../../utils/PathTracker';
 import type BlockStatement from '../BlockStatement';
 import Identifier, { type IdentifierWithVariable } from '../Identifier';
+import type { ExpressionEntity } from './Expression';
 import { UNKNOWN_EXPRESSION } from './Expression';
 import FunctionBase from './FunctionBase';
 import { type IncludeChildren } from './Node';
@@ -95,6 +96,10 @@ export default class FunctionNode extends FunctionBase {
 		this.id?.declare('function', this);
 	}
 
+	protected addArgumentToBeDeoptimized(argument: ExpressionEntity) {
+		this.scope.argumentsVariable.addArgumentToBeDeoptimized(argument);
+	}
+
 	protected getObjectEntity(): ObjectEntity {
 		if (this.objectEntity !== null) {
 			return this.objectEntity;
diff --git a/src/ast/variables/ArgumentsVariable.ts b/src/ast/variables/ArgumentsVariable.ts
index eb26d5da75f..1b13d6c9c08 100644
--- a/src/ast/variables/ArgumentsVariable.ts
+++ b/src/ast/variables/ArgumentsVariable.ts
@@ -1,16 +1,38 @@
 import type { AstContext } from '../../Module';
 import type { NodeInteraction } from '../NodeInteractions';
 import { INTERACTION_ACCESSED } from '../NodeInteractions';
+import type { ExpressionEntity } from '../nodes/shared/Expression';
 import { UNKNOWN_EXPRESSION } from '../nodes/shared/Expression';
 import type { ObjectPath } from '../utils/PathTracker';
+import { UNKNOWN_PATH } from '../utils/PathTracker';
 import LocalVariable from './LocalVariable';
 
 export default class ArgumentsVariable extends LocalVariable {
+	private deoptimizedArguments: ExpressionEntity[] = [];
+
 	constructor(context: AstContext) {
 		super('arguments', null, UNKNOWN_EXPRESSION, context);
 	}
 
+	addArgumentToBeDeoptimized(argument: ExpressionEntity): void {
+		if (this.included) {
+			argument.deoptimizePath(UNKNOWN_PATH);
+		} else {
+			this.deoptimizedArguments.push(argument);
+		}
+	}
+
 	hasEffectsOnInteractionAtPath(path: ObjectPath, { type }: NodeInteraction): boolean {
 		return type !== INTERACTION_ACCESSED || path.length > 1;
 	}
+
+	include() {
+		if (!this.included) {
+			super.include();
+			for (const argument of this.deoptimizedArguments) {
+				argument.deoptimizePath(UNKNOWN_PATH);
+			}
+			this.deoptimizedArguments.length = 0;
+		}
+	}
 }
diff --git a/test/function/samples/deoptimize-via-arguments/_config.js b/test/function/samples/deoptimize-via-arguments/_config.js
new file mode 100644
index 00000000000..c71d20260b1
--- /dev/null
+++ b/test/function/samples/deoptimize-via-arguments/_config.js
@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'deoptimize call parameters when arguments variable is used'
+};
diff --git a/test/function/samples/deoptimize-via-arguments/main.js b/test/function/samples/deoptimize-via-arguments/main.js
new file mode 100644
index 00000000000..1b9072bb086
--- /dev/null
+++ b/test/function/samples/deoptimize-via-arguments/main.js
@@ -0,0 +1,17 @@
+function mutate(a) {
+	arguments[0].x = true;
+	arguments[1].x = true;
+}
+
+var obj1 = {
+	x: false
+};
+
+var obj2 = {
+	x: false
+};
+
+mutate(obj1, obj2);
+
+assert.ok(obj1.x ? true : false);
+assert.ok(obj2.x ? true : false);