From 25ee8102471b26a04774bb882761cc0d07f42536 Mon Sep 17 00:00:00 2001
From: Brian Smith <brian@dbsoft.org>
Date: Wed, 19 Jul 2023 02:17:04 -0500
Subject: [PATCH] Issue #1240 - Part 5a - BigInt to Number conversion.
 https://bugzilla.mozilla.org/show_bug.cgi?id=1466893

---
 js/src/jsnum.cpp | 40 +++++++++++++++++++++++++++++++++++-----
 js/src/jsnum.h   | 14 ++++++++++++++
 2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/js/src/jsnum.cpp b/js/src/jsnum.cpp
index f103f4dc79..62f694c216 100644
--- a/js/src/jsnum.cpp
+++ b/js/src/jsnum.cpp
@@ -524,15 +524,21 @@ Number(JSContext* cx, unsigned argc, Value* vp)
     bool isConstructing = args.isConstructing();
 
     if (args.length() > 0) {
-        if (!ToNumber(cx, args[0]))
+        // BigInt proposal section 6.2, steps 2a-c.
+        if (!ToNumeric(cx, args[0]))
             return false;
-        args.rval().set(args[0]);
-    } else {
-        args.rval().setInt32(0);
+        if (args[0].isBigInt())
+            args[0].setNumber(BigInt::numberValue(args[0].toBigInt()));
     }
 
-    if (!isConstructing)
+    if (!isConstructing) {
+        if (args.length() > 0) {
+            args.rval().set(args[0]);
+        } else {
+            args.rval().setInt32(0);
+        }
         return true;
+    }
 
     RootedObject newTarget(cx, &args.newTarget().toObject());
     RootedObject proto(cx);
@@ -1492,6 +1498,30 @@ js::ToInt8Slow(JSContext *cx, const HandleValue v, int8_t *out)
     return true;
 }
 
+// BigInt proposal section 3.1.6
+bool
+js::ToNumericSlow(ExclusiveContext* cx, MutableHandleValue vp)
+{
+    MOZ_ASSERT(!vp.isNumber());
+    MOZ_ASSERT(!vp.isBigInt());
+
+    // Step 1.
+    if (!vp.isPrimitive()) {
+        if (!cx->isJSContext())
+            return false;
+        if (!ToPrimitive(cx->asJSContext(), JSTYPE_NUMBER, vp))
+            return false;
+    }
+
+    // Step 2.
+    if (vp.isBigInt()) {
+        return true;
+    }
+
+    // Step 3.
+    return ToNumber(cx->asJSContext(), vp);
+}
+
 /*
  * Convert a value to an uint8_t, according to the ToUInt8() function in ES6
  * ECMA-262, 7.1.10. Return converted value in *out on success, false on failure.
diff --git a/js/src/jsnum.h b/js/src/jsnum.h
index f169a9c38d..295d237c22 100644
--- a/js/src/jsnum.h
+++ b/js/src/jsnum.h
@@ -362,6 +362,20 @@ ToNumber(ExclusiveContext* cx, HandleValue v, double* out)
     return ToNumberSlow(cx, v, out);
 }
 
+bool
+ToNumericSlow(ExclusiveContext* cx, JS::MutableHandleValue vp);
+
+// BigInt proposal section 3.1.6
+MOZ_ALWAYS_INLINE MOZ_MUST_USE bool
+ToNumeric(ExclusiveContext* cx, JS::MutableHandleValue vp)
+{
+    if (vp.isNumber())
+        return true;
+    if (vp.isBigInt())
+        return true;
+    return ToNumericSlow(cx, vp);
+}
+
 void FIX_FPU();
 
 } /* namespace js */