Avoid modifying invocations in place for derive helper attributes

2 files changed, 4 insertions, 21 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 8450daa3f7c..1bc5cb93c11 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -726,7 +726,7 @@ pub trait Resolver {
     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<Attribute>, allow_derive: bool)
                               -> Option<Attribute>;
 
-    fn resolve_invoc(&mut self, invoc: &mut Invocation, scope: Mark, force: bool)
+    fn resolve_invoc(&mut self, invoc: &Invocation, scope: Mark, force: bool)
                      -> Result<Option<Lrc<SyntaxExtension>>, Determinacy>;
     fn resolve_macro(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
                      -> Result<Lrc<SyntaxExtension>, Determinacy>;
@@ -754,7 +754,7 @@ impl Resolver for DummyResolver {
     fn resolve_imports(&mut self) {}
     fn find_legacy_attr_invoc(&mut self, _attrs: &mut Vec<Attribute>, _allow_derive: bool)
                               -> Option<Attribute> { None }
-    fn resolve_invoc(&mut self, _invoc: &mut Invocation, _scope: Mark, _force: bool)
+    fn resolve_invoc(&mut self, _invoc: &Invocation, _scope: Mark, _force: bool)
                      -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
         Err(Determinacy::Determined)
     }
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 8bd30e43476..7148f3c00f2 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -252,13 +252,6 @@ impl Invocation {
             InvocationKind::Derive { ref path, .. } => path.span,
         }
     }
-
-    pub fn attr_id(&self) -> Option<ast::AttrId> {
-        match self.kind {
-            InvocationKind::Attr { attr: Some(ref attr), .. } => Some(attr.id),
-            _ => None,
-        }
-    }
 }
 
 pub struct MacroExpander<'a, 'b:'a> {
@@ -338,7 +331,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         let mut undetermined_invocations = Vec::new();
         let (mut progress, mut force) = (false, !self.monotonic);
         loop {
-            let mut invoc = if let Some(invoc) = invocations.pop() {
+            let invoc = if let Some(invoc) = invocations.pop() {
                 invoc
             } else {
                 self.resolve_imports();
@@ -350,20 +343,10 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
 
             let scope =
                 if self.monotonic { invoc.expansion_data.mark } else { orig_expansion_data.mark };
-            let attr_id_before = invoc.attr_id();
-            let ext = match self.cx.resolver.resolve_invoc(&mut invoc, scope, force) {
+            let ext = match self.cx.resolver.resolve_invoc(&invoc, scope, force) {
                 Ok(ext) => Some(ext),
                 Err(Determinacy::Determined) => None,
                 Err(Determinacy::Undetermined) => {
-                    // Sometimes attributes which we thought were invocations
-                    // end up being custom attributes for custom derives. If
-                    // that's the case our `invoc` will have changed out from
-                    // under us. If this is the case we're making progress so we
-                    // want to flag it as such, and we test this by looking if
-                    // the `attr_id()` method has been changing over time.
-                    if invoc.attr_id() != attr_id_before {
-                        progress = true;
-                    }
                     undetermined_invocations.push(invoc);
                     continue
                 }