Use the actual NaN value in the math package.

nevkontakte · nevkontakte · commit 5b30828c3703 · 2022-06-07T13:38:17.000+01:00
Apparently, under V8 division by zero literal and by zero assigned to a variable yields bitwise-different values of NaN, which broke some tests in `internal/fuzz`. Using an actual NaN value from the JavaScript runtime fixes the issue. Isolated example: https://jsfiddle.net/j3rtaz0o/1/. Note that Firefox doesn't seem to exhibit this issue.
diff --git a/compiler/natives/src/math/math.go b/compiler/natives/src/math/math.go
@@ -11,7 +11,12 @@ var math = js.Global.Get("Math")
 var _zero float64 = 0
 var posInf = 1 / _zero
 var negInf = -1 / _zero
-var nan = 0 / _zero
+
+// Usually, NaN can be obtained in JavaScript with `0 / 0` operation. However,
+// in V8, `0 / _zero` yields a bitwise-different value of NaN compared to the
+// default NaN or `0 / 0`. Unfortunately, Go compiler forbids division by zero,
+// so we have to get this value from prelude.
+var nan = js.Global.Get("$NaN").Float()
 
 func Acos(x float64) float64 {
 	return math.Call("acos", x).Float()
diff --git a/compiler/prelude/prelude.go b/compiler/prelude/prelude.go
@@ -7,6 +7,7 @@ const Prelude = prelude + numeric + types + goroutines + jsmapping
 
 const prelude = `Error.stackTraceLimit = Infinity;
 
+var $NaN = NaN;
 var $global, $module;
 if (typeof window !== "undefined") { /* web page */
   $global = window;
