Add notion of lookup depth, fix bug with NULL overrides

1 files changed, 19 insertions, 1 deletions

diff --git a/build2/target b/build2/target
index af573fa..eb6154a 100644
--- a/build2/target
+++ b/build2/target
@@ -276,7 +276,10 @@ namespace build2
     // (and note that there will be no overrides).
     //
     lookup
-    operator[] (const variable&) const;
+    operator[] (const variable& var) const
+    {
+      return find (var).first;
+    }
 
     lookup
     operator[] (const string& name) const
@@ -284,6 +287,21 @@ namespace build2
       return operator[] (var_pool.find (name));
     }
 
+    // As above but also return the depth at which the value is found. The
+    // depth is calculated by adding 1 for each test performed.  So a value
+    // that is from the target will have depth 1. That from the group -- 2.
+    // From the innermost scope's target type/patter-specific variables --
+    // 3. From the innermost scope's variables -- 4. And so on.  The idea is
+    // that given two lookups from the same target, we can say which one came
+    // earlier. If no value is found, then the depth is set to ~0.
+    //
+    pair<lookup, size_t>
+    find (const variable&) const;
+
+    pair<lookup, size_t>
+    find (const string& name) const {return find (var_pool.find (name));}
+
+
     // Return a value suitable for assignment. See class scope for
     // details.
     //