From 9ca783f9fab41eac40b96313749533ea5c965426 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 28 Jun 2018 11:04:24 +0200
Subject: Add prerequisite variable visibility specification/enforcement

---
 build2/scope.cxx | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'build2/scope.cxx')

diff --git a/build2/scope.cxx b/build2/scope.cxx
index ff004b5..dc08925 100644
--- a/build2/scope.cxx
+++ b/build2/scope.cxx
@@ -23,6 +23,9 @@ namespace build2
 
     size_t d (0);
 
+    if (var.visibility == variable_visibility::prereq)
+      return make_pair (lookup (), d);
+
     // Process target type/pattern-specific prepend/append values.
     //
     auto pre_app = [&var] (lookup& l,
@@ -164,6 +167,8 @@ namespace build2
       case variable_visibility::normal:
         s = s->parent_scope ();
         break;
+      case variable_visibility::prereq:
+        assert (false);
       }
     }
 
@@ -247,6 +252,7 @@ namespace build2
       case variable_visibility::normal:
         break;
       case variable_visibility::target:
+      case variable_visibility::prereq:
         assert (false);
       }
 
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