fix: panic related to invalid property access in goMapObject

Ignore errors when converting a property name to the key type for goMapObject
during a getOwnProperty operation, as a property which fails conversion to the
target's key type could not possibly be a member of it.

fixes #488

type_go_map.go

@@ -47,7 +47,21 @@ func (o goMapObject) toValue(value Value) reflect.Value {
 
 func goMapGetOwnProperty(obj *object, name string) *property {
 	goObj := obj.value.(*goMapObject)
-	value := goObj.value.MapIndex(goObj.toKey(name))
+
+	// an error here means that the key referenced by `name` could not possibly
+	// be a property of this object, so it should be safe to ignore this error
+	//
+	// TODO: figure out if any cases from
+	// https://go.dev/ref/spec#Comparison_operators meet the criteria of 1)
+	// being possible to represent as a string, 2) being possible to reconstruct
+	// from a string, and 3) having a meaningful failure case in this context
+	// other than "key does not exist"
+	key, err := stringToReflectValue(name, goObj.keyType.Kind())
+	if err != nil {
+		return nil
+	}
+
+	value := goObj.value.MapIndex(key)
 	if value.IsValid() {
 		return &property{obj.runtime.toValue(value.Interface()), 0o111}
 	}

value_test.go

@@ -77,6 +77,42 @@ func TestToValue(t *testing.T) {
 			value, _ = vm.ToValue(&tmp2)
 			is(value, "undefined")
 		}
+
+		{
+			m := map[int64]string{0: "foo", 1: "bar"}
+			value, err := vm.ToValue(m)
+			is(err, nil)
+			v0, err := value.Object().Get("0")
+			is(err, nil)
+			is(v0, m[0])
+			v1, err := value.Object().Get("1")
+			is(err, nil)
+			is(v1, m[1])
+			missing, err := value.Object().Get("2")
+			is(err, nil)
+			is(missing, UndefinedValue())
+			invalid, err := value.Object().Get("xxx")
+			is(err, nil)
+			is(invalid, UndefinedValue())
+		}
+
+		{
+			m := map[uint64]string{0: "foo", 1: "bar"}
+			value, err := vm.ToValue(m)
+			is(err, nil)
+			v0, err := value.Object().Get("0")
+			is(err, nil)
+			is(v0, m[0])
+			v1, err := value.Object().Get("1")
+			is(err, nil)
+			is(v1, m[1])
+			missing, err := value.Object().Get("2")
+			is(err, nil)
+			is(missing, UndefinedValue())
+			invalid, err := value.Object().Get("xxx")
+			is(err, nil)
+			is(invalid, UndefinedValue())
+		}
 	})
 }
 
@@ -295,6 +331,18 @@ func TestExport(t *testing.T) {
 			vm.Set("abc", abc)
 			is(test(`abc;`).export(), abc)
 		}
+
+		{
+			abc := map[int64]string{0: "foo", 1: "bar"}
+			vm.Set("abc", abc)
+			is(test(`abc;`).export(), abc)
+		}
+
+		{
+			abc := map[uint64]string{0: "foo", 1: "bar"}
+			vm.Set("abc", abc)
+			is(test(`abc;`).export(), abc)
+		}
 	})
 }