Auto merge of #40346 - jseyfried:path_and_tokenstream_attr, r=nrc

`TokenStream`-based attributes, paths in attribute and derive macro invocations

This PR
 - refactors `Attribute` to use  `Path` and `TokenStream` instead of `MetaItem`.
 - supports macro invocation paths for attribute procedural macros.
   - e.g. `#[::foo::attr_macro] struct S;`, `#[cfg_attr(all(), foo::attr_macro)] struct S;`
 - supports macro invocation paths for derive procedural macros.
   - e.g. `#[derive(foo::Bar, super::Baz)] struct S;`
 - supports arbitrary tokens as arguments to attribute procedural macros.
   - e.g. `#[foo::attr_macro arbitrary + tokens] struct S;`
 - supports using arbitrary tokens in "inert attributes" with derive procedural macros.
   - e.g. `#[derive(Foo)] struct S(#[inert arbitrary + tokens] i32);`
where `#[proc_macro_derive(Foo, attributes(inert))]`

r? @nrc

3 files changed, 12 insertions, 10 deletions

diff --git a/src/libsyntax_ext/deriving/custom.rs b/src/libsyntax_ext/deriving/custom.rs
index a7e2d82bb97..b01ef65e5fe 100644
--- a/src/libsyntax_ext/deriving/custom.rs
+++ b/src/libsyntax_ext/deriving/custom.rs
@@ -23,9 +23,11 @@ struct MarkAttrs<'a>(&'a [ast::Name]);
 
 impl<'a> Visitor<'a> for MarkAttrs<'a> {
     fn visit_attribute(&mut self, attr: &Attribute) {
-        if self.0.contains(&attr.name()) {
-            mark_used(attr);
-            mark_known(attr);
+        if let Some(name) = attr.name() {
+            if self.0.contains(&name) {
+                mark_used(attr);
+                mark_known(attr);
+            }
         }
     }
 
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index fe492bd7fc8..48e7ff0d243 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -439,7 +439,7 @@ impl<'a> TraitDef<'a> {
                 attrs.extend(item.attrs
                     .iter()
                     .filter(|a| {
-                        match &*a.name().as_str() {
+                        a.name().is_some() && match &*a.name().unwrap().as_str() {
                             "allow" | "warn" | "deny" | "forbid" | "stable" | "unstable" => true,
                             _ => false,
                         }
diff --git a/src/libsyntax_ext/proc_macro_registrar.rs b/src/libsyntax_ext/proc_macro_registrar.rs
index 5adaf470f23..2d815b3f1bb 100644
--- a/src/libsyntax_ext/proc_macro_registrar.rs
+++ b/src/libsyntax_ext/proc_macro_registrar.rs
@@ -248,7 +248,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
     fn visit_item(&mut self, item: &'a ast::Item) {
         if let ast::ItemKind::MacroDef(..) = item.node {
             if self.is_proc_macro_crate &&
-               item.attrs.iter().any(|attr| attr.name() == "macro_export") {
+               item.attrs.iter().any(|attr| attr.path == "macro_export") {
                 let msg =
                     "cannot export macro_rules! macros from a `proc-macro` crate type currently";
                 self.handler.span_err(item.span, msg);
@@ -270,12 +270,12 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
         for attr in &item.attrs {
             if is_proc_macro_attr(&attr) {
                 if let Some(prev_attr) = found_attr {
-                    let msg = if attr.name() == prev_attr.name() {
+                    let msg = if attr.path == prev_attr.path {
                         format!("Only one `#[{}]` attribute is allowed on any given function",
-                                attr.name())
+                                attr.path)
                     } else {
                         format!("`#[{}]` and `#[{}]` attributes cannot both be applied \
-                                to the same function", attr.name(), prev_attr.name())
+                                to the same function", attr.path, prev_attr.path)
                     };
 
                     self.handler.struct_span_err(attr.span(), &msg)
@@ -299,7 +299,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
 
         if !is_fn {
             let msg = format!("the `#[{}]` attribute may only be used on bare functions",
-                              attr.name());
+                              attr.path);
 
             self.handler.span_err(attr.span(), &msg);
             return;
@@ -311,7 +311,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
 
         if !self.is_proc_macro_crate {
             let msg = format!("the `#[{}]` attribute is only usable with crates of the \
-                              `proc-macro` crate type", attr.name());
+                              `proc-macro` crate type", attr.path);
 
             self.handler.span_err(attr.span(), &msg);
             return;