Add support for block comments to lexer

src/lex.rs

@@ -163,7 +163,9 @@ fn scan_token(partial_source: &str, start_line: usize) -> Result<Consumed, ScanE
 
         Some(c @ '/') => {
             if next_matches(&mut source_chars, '/') {
-                return Ok(lex_comment_contents(&mut source_chars));
+                return Ok(lex_line_comment_contents(&mut source_chars));
+            } else if next_matches(&mut source_chars, '*') {
+                return lex_block_comment_contents(&mut source_chars, start_line);
             }
 
             Ok((TokenKind::Slash, c.to_string()))
@@ -237,7 +239,7 @@ fn scan_token(partial_source: &str, start_line: usize) -> Result<Consumed, ScanE
     })
 }
 
-fn lex_comment_contents<I: Iterator<Item = char>>(line_iter: &mut I) -> Consumed {
+fn lex_line_comment_contents<I: Iterator<Item = char>>(line_iter: &mut I) -> Consumed {
     let comment_length = length_until_end_of_line(line_iter);
     Consumed {
         span: Span {
@@ -248,6 +250,48 @@ fn lex_comment_contents<I: Iterator<Item = char>>(line_iter: &mut I) -> Consumed
     }
 }
 
+fn lex_block_comment_contents<I: Iterator<Item = char>>(
+    line_iter: &mut Peekable<I>,
+    start_line: usize,
+) -> Result<Consumed, ScanError> {
+    // We have already read 2 characters
+    let mut end_found = false;
+    let mut chars = 2;
+    let mut lines = 0;
+
+    let mut last = None;
+    for c in line_iter {
+        chars += 1;
+        let last_c = last;
+        last = Some(c);
+        if c == '\n' {
+            lines += 1;
+            continue;
+        }
+
+        if last_c == Some('*') && c == '/' {
+            end_found = true;
+            break;
+        }
+    }
+
+    if end_found {
+        Ok(Consumed {
+            token: None,
+            span: Span { lines, chars },
+        })
+    } else {
+        Err(ScanError {
+            span: Span { lines, chars },
+            error: ScriptError {
+                line: start_line,
+                location: String::new(),
+                message: "Unterminated block comment".to_string(),
+            },
+        })
+    }
+}
+
 fn lex_remaining_string_literal<I: Iterator<Item = char>>(
     line_iter: &mut I,
     start_line: usize,