Auto merge of rust-lang#34570 - jseyfried:no_rename, r=nrc

Simplify the macro hygiene algorithm

This PR removes renaming from the hygiene algorithm and treats differently marked identifiers as unequal.

This change makes the scope of identifiers in `macro_rules!` items empty. That is, identifiers in `macro_rules!` definitions do not inherit any semantics from the `macro_rules!`'s scope.

Since `macro_rules!` macros are items, the scope of their identifiers "should" be the same as that of other items; in particular, the scope should contain only items. Since all items are unhygienic today, this would mean the scope should be empty.

However, the scope of an identifier in a `macro_rules!` statement today is the scope that the identifier would have if it replaced the `macro_rules!` (excluding anything unhygienic, i.e. locals only).

To continue to support this, this PR tracks the scope of each `macro_rules!` and uses it in `resolve` to ensure that an identifier expanded from a `macro_rules!` gets a chance to resolve to the locals in the `macro_rules!`'s scope.

This PR is a pure refactoring. After this PR,
 - `syntax::ext::expand` is much simpler.
 - We can expand macros in any order without causing problems for hygiene (needed for macro modularization).
 - We can deprecate or remove today's `macro_rules!` scope easily.
 - Expansion performance improves by 25%, post-expansion memory usage decreases by ~5%.
 - Expanding a block is no longer quadratic in the number of `let` statements (fixes rust-lang#10607).

r? @nrc

Author: bors

src/librustc_driver/driver.rs

@@ -50,7 +50,6 @@ use std::io::{self, Write};
 use std::path::{Path, PathBuf};
 use syntax::{ast, diagnostics, visit};
 use syntax::attr::{self, AttrMetaMethods};
-use syntax::fold::Folder;
 use syntax::parse::{self, PResult, token};
 use syntax::util::node_count::NodeCounter;
 use syntax;
@@ -695,6 +694,19 @@ pub fn phase_2_configure_and_expand<'a, F>(sess: &Session,
                                          sess.diagnostic())
     });
 
+    let resolver_arenas = Resolver::arenas();
+    let mut resolver = Resolver::new(sess, make_glob_map, &resolver_arenas);
+
+    let krate = time(sess.time_passes(), "assigning node ids", || resolver.assign_node_ids(krate));
+
+    if sess.opts.debugging_opts.input_stats {
+        println!("Post-expansion node count: {}", count_nodes(&krate));
+    }
+
+    if sess.opts.debugging_opts.ast_json {
+        println!("{}", json::as_json(&krate));
+    }
+
     time(time_passes,
          "checking for inline asm in case the target doesn't support it",
          || no_asm::check_crate(sess, &krate));
@@ -710,15 +722,6 @@ pub fn phase_2_configure_and_expand<'a, F>(sess: &Session,
         })
     })?;
 
-    if sess.opts.debugging_opts.input_stats {
-        println!("Post-expansion node count: {}", count_nodes(&krate));
-    }
-
-    krate = assign_node_ids(sess, krate);
-
-    let resolver_arenas = Resolver::arenas();
-    let mut resolver = Resolver::new(sess, make_glob_map, &resolver_arenas);
-
     // Collect defintions for def ids.
     time(sess.time_passes(), "collecting defs", || resolver.definitions.collect(&krate));
 
@@ -783,53 +786,6 @@ pub fn phase_2_configure_and_expand<'a, F>(sess: &Session,
     })
 }
 
-pub fn assign_node_ids(sess: &Session, krate: ast::Crate) -> ast::Crate {
-    use syntax::ptr::P;
-    use syntax::util::move_map::MoveMap;
-
-    struct NodeIdAssigner<'a> {
-        sess: &'a Session,
-    }
-
-    impl<'a> Folder for NodeIdAssigner<'a> {
-        fn new_id(&mut self, old_id: ast::NodeId) -> ast::NodeId {
-            assert_eq!(old_id, ast::DUMMY_NODE_ID);
-            self.sess.next_node_id()
-        }
-
-        fn fold_block(&mut self, block: P<ast::Block>) -> P<ast::Block> {
-            block.map(|mut block| {
-                block.id = self.new_id(block.id);
-
-                let stmt = block.stmts.pop();
-                block.stmts = block.stmts.move_flat_map(|s| self.fold_stmt(s).into_iter());
-                if let Some(ast::Stmt { node: ast::StmtKind::Expr(expr), span, .. }) = stmt {
-                    let expr = self.fold_expr(expr);
-                    block.stmts.push(ast::Stmt {
-                        id: expr.id,
-                        node: ast::StmtKind::Expr(expr),
-                        span: span,
-                    });
-                } else if let Some(stmt) = stmt {
-                    block.stmts.extend(self.fold_stmt(stmt));
-                }
-
-                block
-            })
-        }
-    }
-
-    let krate = time(sess.time_passes(),
-                     "assigning node ids",
-                     || NodeIdAssigner { sess: sess }.fold_crate(krate));
-
-    if sess.opts.debugging_opts.ast_json {
-        println!("{}", json::as_json(&krate));
-    }
-
-    krate
-}
-
 /// Run the resolution, typechecking, region checking and other
 /// miscellaneous analysis passes on the crate. Return various
 /// structures carrying the results of the analysis.

src/librustc_resolve/assign_ids.rs

@@ -0,0 +1,92 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use Resolver;
+use rustc::session::Session;
+use syntax::ast;
+use syntax::ext::mtwt;
+use syntax::fold::{self, Folder};
+use syntax::ptr::P;
+use syntax::util::move_map::MoveMap;
+use syntax::util::small_vector::SmallVector;
+
+use std::collections::HashMap;
+use std::mem;
+
+impl<'a> Resolver<'a> {
+    pub fn assign_node_ids(&mut self, krate: ast::Crate) -> ast::Crate {
+        NodeIdAssigner {
+            sess: self.session,
+            macros_at_scope: &mut self.macros_at_scope,
+        }.fold_crate(krate)
+    }
+}
+
+struct NodeIdAssigner<'a> {
+    sess: &'a Session,
+    macros_at_scope: &'a mut HashMap<ast::NodeId, Vec<ast::Mrk>>,
+}
+
+impl<'a> Folder for NodeIdAssigner<'a> {
+    fn new_id(&mut self, old_id: ast::NodeId) -> ast::NodeId {
+        assert_eq!(old_id, ast::DUMMY_NODE_ID);
+        self.sess.next_node_id()
+    }
+
+    fn fold_block(&mut self, block: P<ast::Block>) -> P<ast::Block> {
+        block.map(|mut block| {
+            block.id = self.new_id(block.id);
+
+            let stmt = block.stmts.pop();
+            let mut macros = Vec::new();
+            block.stmts = block.stmts.move_flat_map(|stmt| {
+                if let ast::StmtKind::Item(ref item) = stmt.node {
+                    if let ast::ItemKind::Mac(..) = item.node {
+                        macros.push(mtwt::outer_mark(item.ident.ctxt));
+                        return None;
+                    }
+                }
+
+                let stmt = self.fold_stmt(stmt).pop().unwrap();
+                if !macros.is_empty() {
+                    self.macros_at_scope.insert(stmt.id, mem::replace(&mut macros, Vec::new()));
+                }
+                Some(stmt)
+            });
+
+            stmt.and_then(|mut stmt| {
+                // Avoid wasting a node id on a trailing expression statement,
+                // which shares a HIR node with the expression itself.
+                if let ast::StmtKind::Expr(expr) = stmt.node {
+                    let expr = self.fold_expr(expr);
+                    stmt.id = expr.id;
+                    stmt.node = ast::StmtKind::Expr(expr);
+                    Some(stmt)
+                } else {
+                    self.fold_stmt(stmt).pop()
+                }
+            }).map(|stmt| {
+                if !macros.is_empty() {
+                    self.macros_at_scope.insert(stmt.id, mem::replace(&mut macros, Vec::new()));
+                }
+                block.stmts.push(stmt);
+            });
+
+            block
+        })
+    }
+
+    fn fold_item(&mut self, item: P<ast::Item>) -> SmallVector<P<ast::Item>> {
+        match item.node {
+            ast::ItemKind::Mac(..) => SmallVector::zero(),
+            _ => fold::noop_fold_item(item, self),
+        }
+    }
+}