From 1ea33ab70f88fcfebf388a9a438e3c1e56fbdf0f Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 10 Jun 2020 10:01:45 +0200
Subject: Handle special variable names when spelled as $(<char>) rather than
 $<char>

---
 libbuild2/lexer.cxx  |  3 +++
 libbuild2/lexer.hxx  |  3 +++
 libbuild2/parser.cxx | 43 +++++++++++++++++++++++++++++++++++++++++--
 libbuild2/parser.hxx | 25 +++++++++++++++++++++----
 libbuild2/token.hxx  |  1 +
 5 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/libbuild2/lexer.cxx b/libbuild2/lexer.cxx
index 2f2ace4..4256422 100644
--- a/libbuild2/lexer.cxx
+++ b/libbuild2/lexer.cxx
@@ -111,6 +111,9 @@ namespace build2
       }
     case lexer_mode::eval:
       {
+        // NOTE: remember to update special() lambda in parse_names() if
+        //       adding any new single-character tokens to the eval mode.
+        //
         s1 = ":<>=!&|?, $(){}#\t\n";
         s2 = "   = &|           ";
         break;
diff --git a/libbuild2/lexer.hxx b/libbuild2/lexer.hxx
index f577828..6c2b90b 100644
--- a/libbuild2/lexer.hxx
+++ b/libbuild2/lexer.hxx
@@ -161,6 +161,9 @@ namespace build2
     lexer_mode
     mode () const {return state_.top ().mode;}
 
+    uintptr_t
+    mode_data () const {return state_.top ().data;}
+
     char
     pair_separator () const {return state_.top ().sep_pair;}
 
diff --git a/libbuild2/parser.cxx b/libbuild2/parser.cxx
index db00633..36e75a3 100644
--- a/libbuild2/parser.cxx
+++ b/libbuild2/parser.cxx
@@ -5815,7 +5815,44 @@ namespace build2
           // token is a paren or a word, we turn it on and switch to the eval
           // mode if what we get next is a paren.
           //
+          // Also sniff out the special variables string from mode data for
+          // the ad hoc $() handling below.
+          //
           mode (lexer_mode::variable);
+
+          auto special = [s = reinterpret_cast<const char*> (mode_data ())]
+            (const token& t) -> char
+          {
+            char r ('\0');
+
+            if (s != nullptr)
+            {
+              switch (t.type)
+              {
+              case type::less:           r = '<';        break;
+              case type::greater:        r = '>';        break;
+              case type::colon:          r = ':';        break;
+              case type::dollar:         r = '$';        break;
+              case type::question:       r = '?';        break;
+              case type::comma:          r = ',';        break;
+              case type::log_not:        r = '!';        break;
+              case type::lparen:         r = '(';        break;
+              case type::rparen:         r = ')';        break;
+              case type::lcbrace:        r = '{';        break;
+              case type::rcbrace:        r = '}';        break;
+              case type::lsbrace:        r = '[';        break;
+              case type::rsbrace:        r = ']';        break;
+              case type::pair_separator: r = t.value[0]; break;
+              default:                                   break;
+              }
+
+              if (r != '\0' && strchr (s, r) == nullptr)
+                r = '\0';
+            }
+
+            return r;
+          };
+
           next (t, tt);
           loc = get_location (t);
 
@@ -5838,9 +5875,11 @@ namespace build2
             // the variable name even during pre-parse. It should also be
             // faster.
             //
-            if (tt == type::word && peek () == type::rparen)
+            char c;
+            if ((tt == type::word || (c = special (t))) &&
+                peek () == type::rparen)
             {
-              name = move (t.value);
+              name = (tt == type::word ? move (t.value) : string (1, c));
               next (t, tt); // Get `)`.
             }
             else
diff --git a/libbuild2/parser.hxx b/libbuild2/parser.hxx
index 78c7d17..2db7ade 100644
--- a/libbuild2/parser.hxx
+++ b/libbuild2/parser.hxx
@@ -611,8 +611,9 @@ namespace build2
         lexer_->mode (m, ps, nullopt, d);
       else
         // As a sanity check, make sure the mode matches the next token. Note
-        // that we don't check the attributes flags or the pair separator
-        // since they can be overridden by the lexer's mode() implementation.
+        // that we don't check the attributes flags, the pair separator, or
+        // the mode data since they can be overridden by the lexer's mode()
+        // implementation.
         //
         assert (replay_i_ != replay_data_.size () &&
                 replay_data_[replay_i_].mode == m);
@@ -630,6 +631,18 @@ namespace build2
       }
     }
 
+    uintptr_t
+    mode_data () const
+    {
+      if (replay_ != replay::play)
+        return lexer_->mode_data ();
+      else
+      {
+        assert (replay_i_ != replay_data_.size ());
+        return replay_data_[replay_i_].mode_data;
+      }
+    }
+
     void
     enable_attributes ()
     {
@@ -753,8 +766,12 @@ namespace build2
     replay_token
     lexer_next ()
     {
-      lexer_mode m (lexer_->mode ()); // Get it first since it may expire.
-      return replay_token {lexer_->next (), path_, m};
+      // Get these first since the mode may expire.
+      //
+      lexer_mode m (lexer_->mode ());
+      uintptr_t d (lexer_->mode_data ());
+
+      return replay_token {lexer_->next (), path_, m, d};
     }
 
     const replay_token&
diff --git a/libbuild2/token.hxx b/libbuild2/token.hxx
index 156e428..7344ecd 100644
--- a/libbuild2/token.hxx
+++ b/libbuild2/token.hxx
@@ -206,6 +206,7 @@ namespace build2
     build2::token token;
     const path_name* file;
     lexer_mode_base mode;
+    uintptr_t       mode_data;
 
     using location_type = build2::location;
 
-- 
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