From 11138f5c1ffbb039285e2bbba39d0bb8319408cb Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Tue, 16 Mar 2021 20:34:40 +0100
Subject: [PATCH] LibJS: Throw RangeError on BigInt division/modulo by zero

https://tc39.es/ecma262/#sec-numeric-types-bigint-divide
https://tc39.es/ecma262/#sec-numeric-types-bigint-remainder
---
 Userland/Libraries/LibJS/Runtime/ErrorTypes.h |  1 +
 Userland/Libraries/LibJS/Runtime/Value.cpp    | 28 +++++++++++++------
 .../Tests/builtins/BigInt/bigint-basic.js     |  9 ++++++
 3 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/Userland/Libraries/LibJS/Runtime/ErrorTypes.h b/Userland/Libraries/LibJS/Runtime/ErrorTypes.h
index 1d4157855b..58bb2f2929 100644
--- a/Userland/Libraries/LibJS/Runtime/ErrorTypes.h
+++ b/Userland/Libraries/LibJS/Runtime/ErrorTypes.h
@@ -43,6 +43,7 @@
     M(Convert, "Cannot convert {} to {}")                                                                                               \
     M(ConvertUndefinedToObject, "Cannot convert undefined to object")                                                                   \
     M(DescChangeNonConfigurable, "Cannot change attributes of non-configurable property '{}'")                                          \
+    M(DivisionByZero, "Division by zero")                                                                                               \
     M(FunctionArgsNotObject, "Argument array must be an object")                                                                        \
     M(InOperatorWithObject, "'in' operator must be used on an object")                                                                  \
     M(InstanceOfOperatorBadPrototype, "'prototype' property of {} is not an object")                                                    \
diff --git a/Userland/Libraries/LibJS/Runtime/Value.cpp b/Userland/Libraries/LibJS/Runtime/Value.cpp
index 34d96e2a29..e29d40aa40 100644
--- a/Userland/Libraries/LibJS/Runtime/Value.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Value.cpp
@@ -882,27 +882,34 @@ Value mul(GlobalObject& global_object, Value lhs, Value rhs)
 
 Value div(GlobalObject& global_object, Value lhs, Value rhs)
 {
+    auto& vm = global_object.vm();
     auto lhs_numeric = lhs.to_numeric(global_object.global_object());
-    if (global_object.vm().exception())
+    if (vm.exception())
         return {};
     auto rhs_numeric = rhs.to_numeric(global_object.global_object());
-    if (global_object.vm().exception())
+    if (vm.exception())
         return {};
     if (both_number(lhs_numeric, rhs_numeric))
         return Value(lhs_numeric.as_double() / rhs_numeric.as_double());
-    if (both_bigint(lhs_numeric, rhs_numeric))
+    if (both_bigint(lhs_numeric, rhs_numeric)) {
+        if (rhs_numeric.as_bigint().big_integer() == BIGINT_ZERO) {
+            vm.throw_exception<RangeError>(global_object, ErrorType::DivisionByZero);
+            return {};
+        }
         return js_bigint(global_object.heap(), lhs_numeric.as_bigint().big_integer().divided_by(rhs_numeric.as_bigint().big_integer()).quotient);
-    global_object.vm().throw_exception<TypeError>(global_object.global_object(), ErrorType::BigIntBadOperatorOtherType, "division");
+    }
+    vm.throw_exception<TypeError>(global_object.global_object(), ErrorType::BigIntBadOperatorOtherType, "division");
     return {};
 }
 
 Value mod(GlobalObject& global_object, Value lhs, Value rhs)
 {
+    auto& vm = global_object.vm();
     auto lhs_numeric = lhs.to_numeric(global_object.global_object());
-    if (global_object.vm().exception())
+    if (vm.exception())
         return {};
     auto rhs_numeric = rhs.to_numeric(global_object.global_object());
-    if (global_object.vm().exception())
+    if (vm.exception())
         return {};
     if (both_number(lhs_numeric, rhs_numeric)) {
         if (lhs_numeric.is_nan() || rhs_numeric.is_nan())
@@ -912,9 +919,14 @@ Value mod(GlobalObject& global_object, Value lhs, Value rhs)
         auto trunc = (double)(i32)(index / period);
         return Value(index - trunc * period);
     }
-    if (both_bigint(lhs_numeric, rhs_numeric))
+    if (both_bigint(lhs_numeric, rhs_numeric)) {
+        if (rhs_numeric.as_bigint().big_integer() == BIGINT_ZERO) {
+            vm.throw_exception<RangeError>(global_object, ErrorType::DivisionByZero);
+            return {};
+        }
         return js_bigint(global_object.heap(), lhs_numeric.as_bigint().big_integer().divided_by(rhs_numeric.as_bigint().big_integer()).remainder);
-    global_object.vm().throw_exception<TypeError>(global_object.global_object(), ErrorType::BigIntBadOperatorOtherType, "modulo");
+    }
+    vm.throw_exception<TypeError>(global_object.global_object(), ErrorType::BigIntBadOperatorOtherType, "modulo");
     return {};
 }
 
diff --git a/Userland/Libraries/LibJS/Tests/builtins/BigInt/bigint-basic.js b/Userland/Libraries/LibJS/Tests/builtins/BigInt/bigint-basic.js
index 244bc44a92..eb96764d4f 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/BigInt/bigint-basic.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/BigInt/bigint-basic.js
@@ -87,4 +87,13 @@ describe("errors", () => {
             +123n;
         }).toThrowWithMessage(TypeError, "Cannot convert BigInt to number");
     });
+
+    test("division by zero", () => {
+        expect(() => {
+            1n / 0n;
+        }).toThrowWithMessage(RangeError, "Division by zero");
+        expect(() => {
+            1n % 0n;
+        }).toThrowWithMessage(RangeError, "Division by zero");
+    });
 });