[NaN] handle NaN token as identifier (#475)

boa/src/builtins/array/tests.rs

@@ -452,12 +452,11 @@ fn fill() {
         String::from("4,2,3")
     );
 
-    // TODO: uncomment when NaN support is added
-    // forward(&mut engine, "a = [1, 2, 3];");
-    // assert_eq!(
-    //     forward(&mut engine, "a.fill(4, NaN, NaN).join()"),
-    //     String::from("1,2,3")
-    // );
+    forward(&mut engine, "a = [1, 2, 3];");
+    assert_eq!(
+        forward(&mut engine, "a.fill(4, NaN, NaN).join()"),
+        String::from("1,2,3")
+    );
 
     forward(&mut engine, "a = [1, 2, 3];");
     assert_eq!(

boa/src/builtins/mod.rs

@@ -8,6 +8,7 @@ pub mod error;
 pub mod function;
 pub mod json;
 pub mod math;
+pub mod nan;
 pub mod number;
 pub mod object;
 pub mod property;
@@ -36,6 +37,7 @@ pub fn init(global: &Value) {
     Boolean::init(global);
     json::init(global);
     math::init(global);
+    nan::init(global);
     Number::init(global);
     object::init(global);
     function::init(global);

boa/src/builtins/nan/mod.rs

@@ -0,0 +1,11 @@
+#[cfg(test)]
+mod tests;
+
+use crate::{builtins::value::Value, BoaProfiler};
+
+/// Initialize the `NaN` property on the global object.
+#[inline]
+pub fn init(global: &Value) {
+    let _timer = BoaProfiler::global().start_event("NaN", "init");
+    global.set_field("NaN", Value::from(f64::NAN));
+}

boa/src/builtins/nan/tests.rs

@@ -0,0 +1,10 @@
+use crate::exec;
+
+#[test]
+fn nan_exists_on_global_object_and_evaluates_to_nan_value() {
+    let scenario = r#"
+        NaN;
+        "#;
+
+    assert_eq!(&exec(scenario), "NaN");
+}

boa/src/syntax/lexer/mod.rs

@@ -660,7 +660,6 @@ impl<'a> Lexer<'a> {
                         "true" => TokenKind::BooleanLiteral(true),
                         "false" => TokenKind::BooleanLiteral(false),
                         "null" => TokenKind::NullLiteral,
-                        "NaN" => TokenKind::NumericLiteral(NumericLiteral::Rational(f64::NAN)),
                         slice => {
                             if let Ok(keyword) = FromStr::from_str(slice) {
                                 TokenKind::Keyword(keyword)

boa/src/syntax/lexer/tests.rs

@@ -387,19 +387,6 @@ fn check_decrement_advances_lexer_2_places() {
     );
 }
 
-#[test]
-fn check_nan() {
-    let mut lexer = Lexer::new("let a = NaN;");
-    lexer.lex().expect("failed to lex");
-
-    match lexer.tokens[3].kind {
-        TokenKind::NumericLiteral(NumericLiteral::Rational(a)) => {
-            assert!(a.is_nan());
-        }
-        ref other => panic!("Incorrect token kind found for NaN: {}", other),
-    }
-}
-
 #[test]
 fn numbers() {
     let mut lexer = Lexer::new(