LibJS: Plumb line and column information through Lexer / Parser

While debugging test failures, it's pretty frustrating to have to go do
printf debugging to figure out what test is failing right now. While
watching your JS Raytracer stream it seemed like this was pretty
furstrating as well. So I wanted to start working on improving the
diagnostics here.

In the future I hope we can eventually be able to plumb the info down
to the Error classes so any thrown exceptions will contain enough
metadata to know where they came from.

1 files changed, 12 insertions, 3 deletions

diff --git a/Libraries/LibJS/Lexer.cpp b/Libraries/LibJS/Lexer.cpp
index 94bf21ccc1..ddf2297306 100644
--- a/Libraries/LibJS/Lexer.cpp
+++ b/Libraries/LibJS/Lexer.cpp
@@ -39,7 +39,7 @@ HashMap<char, TokenType> Lexer::s_single_char_tokens;
 
 Lexer::Lexer(StringView source)
     : m_source(source)
-    , m_current_token(TokenType::Eof, StringView(nullptr), StringView(nullptr))
+    , m_current_token(TokenType::Eof, StringView(nullptr), StringView(nullptr), 0, 0)
 {
     if (s_keywords.is_empty()) {
         s_keywords.set("await", TokenType::Await);
@@ -146,6 +146,13 @@ void Lexer::consume()
         return;
     }
 
+    if (m_current_char == '\n') {
+        m_line_number++;
+        m_line_column = 1;
+    } else {
+        m_line_column++;
+    }
+
     m_current_char = m_source[m_position++];
 }
 
@@ -182,7 +189,7 @@ bool Lexer::is_block_comment_end() const
 void Lexer::syntax_error(const char* msg)
 {
     m_has_errors = true;
-    fprintf(stderr, "Syntax Error: %s\n", msg);
+    fprintf(stderr, "Syntax Error: %s (line: %zu, column: %zu)\n", msg, m_line_number, m_line_column);
 }
 
 Token Lexer::next()
@@ -317,7 +324,9 @@ Token Lexer::next()
     m_current_token = Token(
         token_type,
         m_source.substring_view(trivia_start - 1, value_start - trivia_start),
-        m_source.substring_view(value_start - 1, m_position - value_start));
+        m_source.substring_view(value_start - 1, m_position - value_start),
+        m_line_number,
+        m_line_column);
 
     return m_current_token;
 }