1 files changed, 71 insertions, 100 deletions

diff --git a/src/makefile/macro.rs b/src/makefile/macro.rs
index 27cbc14..79df339 100644
--- a/src/makefile/macro.rs
+++ b/src/makefile/macro.rs
@@ -19,11 +19,67 @@ pub(crate) trait LookupInternal: for<'a> Fn(&'a str) -> String {}
 
 impl<F: for<'a> Fn(&'a str) -> String> LookupInternal for F {}
 
-pub(crate) trait MacroSetLike: Sized {
-    fn lookup_internal(&self, name: &str) -> String;
-    fn get(&self, name: &str) -> Option<&(MacroSource, TokenString)>;
+#[derive(Clone)]
+pub(crate) struct MacroSet<'parent, 'lookup> {
+    parent: Option<&'parent MacroSet<'parent, 'lookup>>,
+    data: HashMap<String, (MacroSource, TokenString)>,
+    lookup_internal: Option<&'lookup dyn LookupInternal>,
+}
+
+impl<'parent, 'lookup> MacroSet<'parent, 'lookup> {
+    pub(crate) fn new() -> Self {
+        Self {
+            parent: None,
+            data: HashMap::new(),
+            lookup_internal: None,
+        }
+    }
+
+    pub(crate) fn add_builtins(&mut self) {
+        for (k, v) in builtins() {
+            self.data.insert(k.into(), (MacroSource::Builtin, v));
+        }
+    }
+
+    pub(crate) fn add_env(&mut self) {
+        for (k, v) in env::vars() {
+            if k != "MAKEFLAGS" && k != "SHELL" {
+                self.data
+                    .insert(k, (MacroSource::Environment, TokenString::text(v)));
+            }
+        }
+    }
+
+    fn lookup_internal(&self, name: &str) -> String {
+        if let Some(lookup) = self.lookup_internal {
+            lookup(name)
+        } else if let Some(parent) = self.parent {
+            parent.lookup_internal(name)
+        } else {
+            panic!("no lookup possible");
+        }
+    }
+
+    pub(crate) fn get(&self, name: &str) -> Option<&(MacroSource, TokenString)> {
+        self.data
+            .get(name)
+            .or_else(|| self.parent.and_then(|parent| parent.get(name)))
+    }
+
+    pub(crate) fn set(&mut self, name: String, source: MacroSource, text: TokenString) {
+        self.data.insert(name, (source, text));
+    }
+
+    pub(crate) fn is_defined(&self, name: &str) -> bool {
+        self.data.contains_key(name)
+    }
+
+    // `remove` is fine, but I think for "remove-and-return" `pop` is better
+    pub(crate) fn pop(&mut self, name: &str) -> Option<(MacroSource, TokenString)> {
+        self.data.remove(name)
+    }
 
-    fn expand(&self, text: &TokenString) -> String {
+    pub(crate) fn expand(&self, text: &TokenString) -> String {
         let mut result = String::new();
         for token in text.tokens() {
             match token {
@@ -62,112 +118,27 @@ pub(crate) trait MacroSetLike: Sized {
         result
     }
 
-    fn with_lookup<'a, 's: 'a>(
+    pub(crate) fn with_lookup<'l, 's: 'l>(
         &'s self,
-        lookup: &'a dyn LookupInternal,
-    ) -> MacroSetLikeWithLookup<'a, Self> {
-        MacroSetLikeWithLookup {
-            parent: self,
-            lookup,
-        }
-    }
-
-    fn with_overlay(&self) -> MacroSetLikeWithOverlay<Self> {
-        MacroSetLikeWithOverlay {
-            parent: self,
+        lookup: &'l dyn LookupInternal,
+    ) -> MacroSet<'s, 'l> {
+        MacroSet {
+            parent: Some(self),
             data: HashMap::new(),
+            lookup_internal: Some(lookup),
         }
     }
-}
-
-pub(crate) struct MacroSetLikeWithLookup<'a, Parent: MacroSetLike> {
-    parent: &'a Parent,
-    lookup: &'a dyn LookupInternal,
-}
-
-impl<'a, Parent: MacroSetLike> MacroSetLike for MacroSetLikeWithLookup<'a, Parent> {
-    fn lookup_internal(&self, name: &str) -> String {
-        (self.lookup)(name)
-    }
-
-    fn get(&self, name: &str) -> Option<&(MacroSource, TokenString)> {
-        self.parent.get(name)
-    }
-}
-
-pub(crate) struct MacroSetLikeWithOverlay<'a, Parent: MacroSetLike> {
-    parent: &'a Parent,
-    data: HashMap<String, (MacroSource, TokenString)>,
-}
-
-impl<'a, Parent: MacroSetLike> MacroSetLike for MacroSetLikeWithOverlay<'a, Parent> {
-    fn lookup_internal(&self, name: &str) -> String {
-        self.parent.lookup_internal(name)
-    }
-
-    fn get(&self, name: &str) -> Option<&(MacroSource, TokenString)> {
-        self.data.get(name).or_else(|| self.parent.get(name))
-    }
-}
-
-impl<'a, Parent: MacroSetLike> MacroSetLikeWithOverlay<'a, Parent> {
-    pub(crate) fn set(&mut self, name: String, text: TokenString) {
-        self.data.insert(name, (MacroSource::File, text));
-    }
-}
-
-#[derive(Clone, Debug)]
-pub(crate) struct MacroSet {
-    data: HashMap<String, (MacroSource, TokenString)>,
-}
 
-impl MacroSetLike for MacroSet {
-    fn lookup_internal(&self, _: &str) -> String {
-        panic!("can't lookup an internal macro value from a plain MacroSet");
-    }
-
-    fn get(&self, name: &str) -> Option<&(MacroSource, TokenString)> {
-        self.data.get(name)
-    }
-}
-
-impl MacroSet {
-    pub(crate) fn new() -> Self {
-        Self {
+    pub(crate) fn with_overlay<'s>(&'s self) -> MacroSet<'s, 'lookup> {
+        MacroSet {
+            parent: Some(self),
             data: HashMap::new(),
+            lookup_internal: None,
         }
     }
-
-    pub(crate) fn add_builtins(&mut self) {
-        for (k, v) in builtins() {
-            self.data.insert(k.into(), (MacroSource::Builtin, v));
-        }
-    }
-
-    pub(crate) fn add_env(&mut self) {
-        for (k, v) in env::vars() {
-            if k != "MAKEFLAGS" && k != "SHELL" {
-                self.data
-                    .insert(k, (MacroSource::Environment, TokenString::text(v)));
-            }
-        }
-    }
-
-    pub(crate) fn set(&mut self, name: String, source: MacroSource, text: TokenString) {
-        self.data.insert(name, (source, text));
-    }
-
-    pub(crate) fn is_defined(&self, name: &str) -> bool {
-        self.data.contains_key(name)
-    }
-
-    // `remove` is fine, but I think for "remove-and-return" `pop` is better
-    pub(crate) fn pop(&mut self, name: &str) -> Option<(MacroSource, TokenString)> {
-        self.data.remove(name)
-    }
 }
 
-impl fmt::Display for MacroSet {
+impl fmt::Display for MacroSet<'_, '_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let pieces = self
             .data