resolve/expand: Rename some things for clarity and add comments

src/librustc_resolve/macros.rs

@@ -140,11 +140,23 @@ fn resolve_imports(&mut self) {
         ImportResolver { r: self }.resolve_imports()
     }
 
-    fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: ExpnId, force: bool)
-                                -> Result<Option<Lrc<SyntaxExtension>>, Indeterminate> {
-        let inherited_parent_scope = self.invocation_parent_scopes[&invoc_id];
-        let parent_scope = *self.invocation_parent_scopes.entry(invoc.expansion_data.id)
-                                                         .or_insert(inherited_parent_scope);
+    fn resolve_macro_invocation(
+        &mut self, invoc: &Invocation, eager_expansion_root: ExpnId, force: bool
+    ) -> Result<Option<Lrc<SyntaxExtension>>, Indeterminate> {
+        let invoc_id = invoc.expansion_data.id;
+        let parent_scope = match self.invocation_parent_scopes.get(&invoc_id) {
+            Some(parent_scope) => *parent_scope,
+            None => {
+                // If there's no entry in the table, then we are resolving an eagerly expanded
+                // macro, which should inherit its parent scope from its eager expansion root -
+                // the macro that requested this eager expansion.
+                let parent_scope = *self.invocation_parent_scopes.get(&eager_expansion_root)
+                    .expect("non-eager expansion without a parent scope");
+                self.invocation_parent_scopes.insert(invoc_id, parent_scope);
+                parent_scope
+            }
+        };
+
         let (path, kind, derives, after_derive) = match invoc.kind {
             InvocationKind::Attr { ref attr, ref derives, after_derive, .. } =>
                 (&attr.path, MacroKind::Attr, self.arenas.alloc_ast_paths(derives), after_derive),
@@ -163,7 +175,7 @@ fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: ExpnId, for
                         match self.resolve_macro_path(path, Some(MacroKind::Derive),
                                                       &parent_scope, true, force) {
                             Ok((Some(ref ext), _)) if ext.is_derive_copy => {
-                                self.add_derives(invoc.expansion_data.id, SpecialDerives::COPY);
+                                self.add_derives(invoc_id, SpecialDerives::COPY);
                                 return Ok(None);
                             }
                             Err(Determinacy::Undetermined) => result = Err(Indeterminate),
@@ -180,19 +192,15 @@ fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: ExpnId, for
         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, force)?;
 
         let span = invoc.span();
-        invoc.expansion_data.id.set_expn_data(
-            ext.expn_data(parent_scope.expansion, span, fast_print_path(path))
-        );
+        invoc_id.set_expn_data(ext.expn_data(parent_scope.expansion, span, fast_print_path(path)));
 
         if let Res::Def(_, def_id) = res {
             if after_derive {
                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
             }
-            self.macro_defs.insert(invoc.expansion_data.id, def_id);
-            let normal_module_def_id =
-                self.macro_def_scope(invoc.expansion_data.id).normal_ancestor_id;
-            self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.id,
-                                                            normal_module_def_id);
+            self.macro_defs.insert(invoc_id, def_id);
+            let normal_module_def_id = self.macro_def_scope(invoc_id).normal_ancestor_id;
+            self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
         }
 
         Ok(Some(ext))

src/libsyntax/ext/base.rs

@@ -682,8 +682,9 @@ fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &A
 
     fn resolve_imports(&mut self);
 
-    fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: ExpnId, force: bool)
-                                -> Result<Option<Lrc<SyntaxExtension>>, Indeterminate>;
+    fn resolve_macro_invocation(
+        &mut self, invoc: &Invocation, eager_expansion_root: ExpnId, force: bool
+    ) -> Result<Option<Lrc<SyntaxExtension>>, Indeterminate>;
 
     fn check_unused_macros(&self);
 

src/libsyntax/ext/expand.rs

@@ -305,9 +305,11 @@ pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragm
                 continue
             };
 
-            let scope =
+            let eager_expansion_root =
                 if self.monotonic { invoc.expansion_data.id } else { orig_expansion_data.id };
-            let ext = match self.cx.resolver.resolve_macro_invocation(&invoc, scope, force) {
+            let ext = match self.cx.resolver.resolve_macro_invocation(
+                &invoc, eager_expansion_root, force
+            ) {
                 Ok(ext) => ext,
                 Err(Indeterminate) => {
                     undetermined_invocations.push(invoc);