Add support for undetermined macro invocations.

src/librustc_resolve/macros.rs

@@ -17,7 +17,7 @@
 use std::rc::Rc;
 use syntax::ast;
 use syntax::errors::DiagnosticBuilder;
-use syntax::ext::base::{self, MultiModifier, MultiDecorator, MultiItemModifier};
+use syntax::ext::base::{self, Determinacy, MultiModifier, MultiDecorator, MultiItemModifier};
 use syntax::ext::base::{NormalTT, SyntaxExtension};
 use syntax::ext::expand::{Expansion, Invocation, InvocationKind};
 use syntax::ext::hygiene::Mark;
@@ -173,7 +173,8 @@ fn find_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>) -> Option<ast::At
         None
     }
 
-    fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation) -> Option<Rc<SyntaxExtension>> {
+    fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation, _force: bool)
+                     -> Result<Rc<SyntaxExtension>, Determinacy> {
         let (name, span) = match invoc.kind {
             InvocationKind::Bang { ref mac, .. } => {
                 let path = &mac.node.path;
@@ -181,7 +182,7 @@ fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation) -> Option<Rc<Syntax
                    !path.segments[0].parameters.is_empty() {
                     self.session.span_err(path.span,
                                           "expected macro name without module separators");
-                    return None;
+                    return Err(Determinacy::Determined);
                 }
                 (path.segments[0].identifier.name, path.span)
             }
@@ -192,12 +193,12 @@ fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation) -> Option<Rc<Syntax
         if let LegacyScope::Expansion(parent) = invocation.legacy_scope.get() {
             invocation.legacy_scope.set(LegacyScope::simplify_expansion(parent));
         }
-        self.resolve_macro_name(invocation.legacy_scope.get(), name, true).or_else(|| {
+        self.resolve_macro_name(invocation.legacy_scope.get(), name, true).ok_or_else(|| {
             let mut err =
                 self.session.struct_span_err(span, &format!("macro undefined: '{}!'", name));
             self.suggest_macro_name(&name.as_str(), &mut err);
             err.emit();
-            None
+            Determinacy::Determined
         })
     }
 

src/librustc_resolve/resolve_imports.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use self::Determinacy::*;
 use self::ImportDirectiveSubclass::*;
 
 use Module;
@@ -26,6 +25,7 @@
 use rustc::hir::def::*;
 
 use syntax::ast::{NodeId, Name};
+use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax_pos::Span;
 
@@ -37,12 +37,6 @@ pub fn resolve_imports(&mut self) {
     }
 }
 
-#[derive(Copy, Clone, Debug)]
-pub enum Determinacy {
-    Determined,
-    Undetermined,
-}
-
 /// Contains data for specific types of import directives.
 #[derive(Clone, Debug)]
 pub enum ImportDirectiveSubclass<'a> {

src/libsyntax/ext/base.rs

@@ -522,10 +522,17 @@ pub trait Resolver {
     fn add_expansions_at_stmt(&mut self, id: ast::NodeId, macros: Vec<Mark>);
 
     fn find_attr_invoc(&mut self, attrs: &mut Vec<Attribute>) -> Option<Attribute>;
-    fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation) -> Option<Rc<SyntaxExtension>>;
+    fn resolve_invoc(&mut self, scope: Mark, invoc: &Invocation, force: bool)
+                     -> Result<Rc<SyntaxExtension>, Determinacy>;
     fn resolve_derive_mode(&mut self, ident: ast::Ident) -> Option<Rc<MultiItemModifier>>;
 }
 
+#[derive(Copy, Clone, Debug)]
+pub enum Determinacy {
+    Determined,
+    Undetermined,
+}
+
 pub struct DummyResolver;
 
 impl Resolver for DummyResolver {
@@ -539,8 +546,9 @@ fn add_expansions_at_stmt(&mut self, _id: ast::NodeId, _macros: Vec<Mark>) {}
 
     fn find_attr_invoc(&mut self, _attrs: &mut Vec<Attribute>) -> Option<Attribute> { None }
     fn resolve_derive_mode(&mut self, _ident: ast::Ident) -> Option<Rc<MultiItemModifier>> { None }
-    fn resolve_invoc(&mut self, _scope: Mark, _invoc: &Invocation) -> Option<Rc<SyntaxExtension>> {
-        None
+    fn resolve_invoc(&mut self, _scope: Mark, _invoc: &Invocation, _force: bool)
+                     -> Result<Rc<SyntaxExtension>, Determinacy> {
+        Err(Determinacy::Determined)
     }
 }
 

src/libsyntax/ext/expand.rs

@@ -225,13 +225,36 @@ fn expand(&mut self, expansion: Expansion) -> Expansion {
         invocations.reverse();
 
         let mut expansions = Vec::new();
-        while let Some(invoc) = invocations.pop() {
+        let mut undetermined_invocations = Vec::new();
+        let (mut progress, mut force) = (false, !self.monotonic);
+        loop {
+            let invoc = if let Some(invoc) = invocations.pop() {
+                invoc
+            } else if undetermined_invocations.is_empty() {
+                break
+            } else {
+                invocations = mem::replace(&mut undetermined_invocations, Vec::new());
+                force = !mem::replace(&mut progress, false);
+                continue
+            };
+
+            let scope =
+                if self.monotonic { invoc.expansion_data.mark } else { orig_expansion_data.mark };
+            let ext = match self.cx.resolver.resolve_invoc(scope, &invoc, force) {
+                Ok(ext) => Some(ext),
+                Err(Determinacy::Determined) => None,
+                Err(Determinacy::Undetermined) => {
+                    undetermined_invocations.push(invoc);
+                    continue
+                }
+            };
+
+            progress = true;
             let ExpansionData { depth, mark, .. } = invoc.expansion_data;
             self.cx.current_expansion = invoc.expansion_data.clone();
 
-            let scope = if self.monotonic { mark } else { orig_expansion_data.mark };
             self.cx.current_expansion.mark = scope;
-            let expansion = match self.cx.resolver.resolve_invoc(scope, &invoc) {
+            let expansion = match ext {
                 Some(ext) => self.expand_invoc(invoc, ext),
                 None => invoc.expansion_kind.dummy(invoc.span()),
             };