From 67382c15f7e9176dea44c3da7f7013759c88ce33 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 21 Jan 2016 15:03:26 +0200
Subject: Add support for ==, != in eval context

---
 build2/parser.cxx | 45 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 3 deletions(-)

(limited to 'build2/parser.cxx')

diff --git a/build2/parser.cxx b/build2/parser.cxx
index b1a4414..187c47e 100644
--- a/build2/parser.cxx
+++ b/build2/parser.cxx
@@ -1134,12 +1134,51 @@ namespace build2
     mode (lexer_mode::eval);
     next (t, tt);
 
-    names_type ns (tt != type::rparen ? names (t, tt) : names_type ());
+    names_type ns;
+    eval_trailer (t, tt, ns);
+    return ns;
+  }
 
+  void parser::
+  eval_trailer (token& t, type& tt, names_type& ns)
+  {
+    // Note that names() will handle the ( == foo) case since if it gets
+    // called, it expects to see a name.
+    //
     if (tt != type::rparen)
-      fail (t) << "expected ')' instead of " << t;
+      names (t, tt, ns);
 
-    return ns;
+    switch (tt)
+    {
+    case type::equal:
+    case type::not_equal:
+      {
+        type op (tt);
+
+        // ==, != are left-associative, so get the rhs name and evaluate.
+        //
+        next (t, tt);
+        names_type rhs (names (t, tt));
+
+        bool r;
+        switch (op)
+        {
+        case type::equal:     r = ns == rhs; break;
+        case type::not_equal: r = ns != rhs; break;
+        default:              r = false;     assert (false);
+        }
+
+        ns.resize (1);
+        ns[0] = name (r ? "true" : "false");
+
+        eval_trailer (t, tt, ns);
+        break;
+      }
+    case type::rparen:
+      break;
+    default:
+      fail (t) << "expected ')' instead of " << t;
+    }
   }
 
   // Parse names inside {} and handle the following "crosses" (i.e.,
-- 
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