fix: Handle single zero and decimal numbers correctly in lexer

Co-Authored-By: [email protected] <[email protected]>

Author: devin-ai-integration[bot]

jparse/lexer.go

@@ -430,7 +430,7 @@ func (l *lexer) scanNumber() token {
 		return token{Type: typeMinus, Value: "-", Position: pos}
 	}
 
-	// Handle special number formats (hex, binary, octal)
+		// Handle special number formats (hex, binary, octal)
 	if l.acceptRune('0') {
 		next := l.peek()
 		switch next {
@@ -452,15 +452,11 @@ func (l *lexer) scanNumber() token {
 				return token{Type: typeError, Value: "invalid hexadecimal number", Position: pos}
 			}
 			return token{Type: typeNumber, Value: l.input[pos:l.current], Position: pos}
-		}
-		// Handle leading zeros
-		if isDigit(next) {
-			l.acceptAll(isDigit)
-			if l.acceptRune('.') {
-				if !l.acceptAll(isDigit) {
-					l.backup()
-					return token{Type: typeNumber, Value: l.input[pos:l.current-1], Position: pos}
-				}
+		case '.':
+			l.nextRune()
+			if !l.acceptAll(isDigit) {
+				l.backup()
+				return token{Type: typeNumber, Value: "0", Position: pos}
 			}
 			if l.acceptRunes2('e', 'E') {
 				l.acceptRunes2('+', '-')
@@ -469,7 +465,34 @@ func (l *lexer) scanNumber() token {
 				}
 			}
 			return token{Type: typeNumber, Value: l.input[pos:l.current], Position: pos}
+		case 'e', 'E':
+			l.nextRune()
+			l.acceptRunes2('+', '-')
+			if !l.acceptAll(isDigit) {
+				return token{Type: typeError, Value: "invalid number literal", Position: pos}
+			}
+			return token{Type: typeNumber, Value: l.input[pos:l.current], Position: pos}
 		}
+		
+		// Handle single zero or leading zeros
+		if !isDigit(next) {
+			return token{Type: typeNumber, Value: "0", Position: pos}
+		}
+		
+		l.acceptAll(isDigit)
+		if l.acceptRune('.') {
+			if !l.acceptAll(isDigit) {
+				l.backup()
+				return token{Type: typeNumber, Value: l.input[pos:l.current-1], Position: pos}
+			}
+		}
+		if l.acceptRunes2('e', 'E') {
+			l.acceptRunes2('+', '-')
+			if !l.acceptAll(isDigit) {
+				return token{Type: typeError, Value: "invalid number literal", Position: pos}
+			}
+		}
+		return token{Type: typeNumber, Value: l.input[pos:l.current], Position: pos}
 	}
 
 	// Handle decimal point at start