1 files changed, 16 insertions, 2 deletions
diff --git a/src/makefile/macro.rs b/src/makefile/macro.rs
index 5e7ea9c..65a87d1 100644
--- a/src/makefile/macro.rs
+++ b/src/makefile/macro.rs
@@ -36,7 +36,7 @@ pub trait LookupInternal: for<'a> Fn(&'a str) -> Result<String> {}
 impl<F: for<'a> Fn(&'a str) -> Result<String>> LookupInternal for F {}
 
 #[cfg(feature = "full")]
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub enum ExportConfig {
     Only(HashSet<String>),
     AllBut(HashSet<String>),
@@ -183,7 +183,21 @@ impl<'parent, 'lookup> Set<'parent, 'lookup> {
             .or_else(|| self.parent.and_then(|p| p.get(name).cloned()))
     }
 
-    pub fn extend(&mut self, other: HashMap<String, Macro>) {
+    pub fn extend(&mut self, other: HashMap<String, Macro>, other_exports: ExportConfig) {
+        match (&mut self.exported, other_exports) {
+            (ExportConfig::Only(se), ExportConfig::Only(oe)) => {
+                se.extend(oe);
+            }
+            (ExportConfig::AllBut(sne), ExportConfig::AllBut(one)) => {
+                sne.extend(one);
+            }
+            (ExportConfig::Only(se), ExportConfig::AllBut(one)) => {
+                se.extend(other.keys().cloned().filter(|name| !one.contains(name)));
+            }
+            (ExportConfig::AllBut(sne), ExportConfig::Only(oe)) => {
+                sne.extend(other.keys().cloned().filter(|name| !oe.contains(name)));
+            }
+        }
         self.data.extend(other);
     }