---input---
a//c1
 //c2
label://c3
a // c4
label: implicit comment

---tokens---
'a'           Name.Function
'//c1'        Comment.Single
'\n'          Text

' '           Text.Whitespace
'//c2'        Comment.Single
'\n'          Text.Whitespace

'label:'      Name.Function
'//c3'        Comment.Single
'\n'          Text

'a'           Name.Function
' '           Text.Whitespace
'// c4'       Comment.Single
'\n'          Text

'label:'      Name.Label
' implicit comment' Comment.Single
'\n'          Text.Whitespace