Tighten up attribute recognition during parsing

Now it should be possible to use `[]` for wildcard patterns, for example:

  foo = foo.[hit]xx

Note that a leading bracket expression will still be recognized as attributes
and escaping or quoting it will inhibit pattern matching. To resolve this case
we need to specify an empty attribute list:

  foo = [] [abc]-foo.cxx

1 files changed, 7 insertions, 2 deletions

diff --git a/libbuild2/token.hxx b/libbuild2/token.hxx
index 2370f8d..e420aa8 100644
--- a/libbuild2/token.hxx
+++ b/libbuild2/token.hxx
@@ -14,7 +14,8 @@
 
 namespace build2
 {
-  // Extendable/inheritable enum-like class.
+
+  // Token type.
   //
   // A line consists of a sequence of words separated by separators and
   // terminated with the newline. If whitespace is a separator, then it is
@@ -22,6 +23,8 @@ namespace build2
   //
   struct token_type
   {
+    // Extendable/inheritable enum-like class.
+    //
     enum
     {
       // NOTE: remember to update token_printer()!
@@ -145,10 +148,12 @@ namespace build2
   inline ostream&
   operator<< (ostream& o, const token& t) {t.printer (o, t, true); return o;}
 
-  // Extendable/inheritable enum-like class.
+  // Context-dependent lexing (see lexer_mode for details).
   //
   struct lexer_mode_base
   {
+    // Extendable/inheritable enum-like class.
+    //
     enum { value_next };
 
     using value_type = uint16_t;