From d4d27296fc6af92b2a637f3851ddfa0933796a63 Mon Sep 17 00:00:00 2001
From: Yiyu Lin <linyiyu1992@gmail.com>
Date: Thu, 14 May 2020 02:17:54 +0800
Subject: [PATCH] fix `NaN` is lexed as identifier, not as a number (#397)

close #393
---
 boa/src/syntax/lexer/mod.rs   |  1 +
 boa/src/syntax/lexer/tests.rs | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/boa/src/syntax/lexer/mod.rs b/boa/src/syntax/lexer/mod.rs
index cda968f4e15..c0696df90d9 100644
--- a/boa/src/syntax/lexer/mod.rs
+++ b/boa/src/syntax/lexer/mod.rs
@@ -592,6 +592,7 @@ 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)
diff --git a/boa/src/syntax/lexer/tests.rs b/boa/src/syntax/lexer/tests.rs
index a50bc3b5b63..dcf2131aec9 100644
--- a/boa/src/syntax/lexer/tests.rs
+++ b/boa/src/syntax/lexer/tests.rs
@@ -369,6 +369,19 @@ 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_eq!(a.is_nan(), true);
+        }
+        _ => assert!(false),
+    }
+}
+
 #[test]
 fn numbers() {
     let mut lexer = Lexer::new(