---

yaml
---
r: 179789
b: refs/heads/tmp
c: d9393c2
h: refs/heads/master
i:
  179787: b852d5d
v: v3

Author: pnkfelix

[refs]

@@ -34,4 +34,4 @@ refs/heads/building: 126db549b038c84269a1e4fe46f051b2c15d6970
 refs/heads/beta: 44a287e6eb22ec3c2a687fc156813577464017f7
 refs/heads/windistfix: 7608dbad651f02e837ed05eef3d74a6662a6e928
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
-refs/heads/tmp: 7fcc330ea3a5cbe9b861edf05b74d332b53a64b0
+refs/heads/tmp: d9393c21d788347a993108021e8395d0ff992d03

branches/tmp/src/doc/grammar.md

@@ -157,7 +157,7 @@ token : simple_token | ident | literal | symbol | whitespace token ;
 
 |          |          |          |          |        |
 |----------|----------|----------|----------|--------|
-| abstract | alignof  | as       | become   | box    |
+| abstract | alignof  | as       | be       | box    |
 | break    | const    | continue | crate    | do     |
 | else     | enum     | extern   | false    | final  |
 | fn       | for      | if       | impl     | in     |

branches/tmp/src/doc/reference.md

@@ -189,7 +189,7 @@ grammar as double-quoted strings. Other tokens have exact rules given.
 
 |          |          |          |          |         |
 |----------|----------|----------|----------|---------|
-| abstract | alignof  | as       | become   | box     |
+| abstract | alignof  | as       | be       | box     |
 | break    | const    | continue | crate    | do      |
 | else     | enum     | extern   | false    | final   |
 | fn       | for      | if       | impl     | in      |
@@ -2014,11 +2014,6 @@ type int8_t = i8;
 - `no_start` - disable linking to the `native` crate, which specifies the
   "start" language item.
 - `no_std` - disable linking to the `std` crate.
-- `plugin` — load a list of named crates as compiler plugins, e.g.
-             `#![plugin(foo, bar)]`. Optional arguments for each plugin,
-             i.e. `#![plugin(foo(... args ...))]`, are provided to the plugin's
-             registrar function.  The `plugin` feature gate is required to use
-             this attribute.
 
 ### Module-only attributes
 
@@ -2087,7 +2082,7 @@ On `struct`s:
   remove any padding between fields (note that this is very fragile and may
   break platforms which require aligned access).
 
-### Macro-related attributes
+### Macro- and plugin-related attributes
 
 - `macro_use` on a `mod` — macros defined in this module will be visible in the
   module's parent, after this module has been included.
@@ -2102,8 +2097,13 @@ On `struct`s:
 
 - `macro_export` - export a macro for cross-crate usage.
 
-- `no_link` on an `extern crate` — even if we load this crate for macros, don't
-  link it into the output.
+- `plugin` on an `extern crate` — load this crate as a [compiler
+  plugin][plugin].  The `plugin` feature gate is required.  Any arguments to
+  the attribute, e.g. `#[plugin=...]` or `#[plugin(...)]`, are provided to the
+  plugin.
+
+- `no_link` on an `extern crate` — even if we load this crate for macros or
+  compiler plugins, don't link it into the output.
 
 See the [macros section of the
 book](book/macros.html#scoping-and-macro-import/export) for more information on

branches/tmp/src/doc/trpl/compound-data-types.md

@@ -72,20 +72,6 @@ if x == y {
 
 This will print `no`, because some of the values aren't equal.
 
-Note that the order of the values is considered when checking for equality,
-so the following example will also print `no`.
-
-```rust
-let x = (1, 2, 3);
-let y = (2, 1, 3);
-
-if x == y {
-    println!("yes");
-} else {
-    println!("no");
-}
-```
-
 One other use of tuples is to return multiple values from a function:
 
 ```rust

branches/tmp/src/doc/trpl/plugins.md

@@ -30,14 +30,14 @@ information.
 extend the compiler's behavior with new syntax extensions, lint checks, etc.
 
 A plugin is a dynamic library crate with a designated *registrar* function that
-registers extensions with `rustc`. Other crates can load these extensions using
-the crate attribute `#![plugin(...)]`.  See the
+registers extensions with `rustc`. Other crates can use these extensions by
+loading the plugin crate with `#[plugin] extern crate`. See the
 [`rustc::plugin`](../rustc/plugin/index.html) documentation for more about the
 mechanics of defining and loading a plugin.
 
-If present, arguments passed as `#![plugin(foo(... args ...))]` are not
-interpreted by rustc itself.  They are provided to the plugin through the
-`Registry`'s [`args` method](../rustc/plugin/registry/struct.Registry.html#method.args).
+Arguments passed as `#[plugin=...]` or `#[plugin(...)]` are not interpreted by
+rustc itself.  They are provided to the plugin through the `Registry`'s [`args`
+method](../rustc/plugin/registry/struct.Registry.html#method.args).
 
 # Syntax extensions
 
@@ -110,7 +110,8 @@ Then we can use `rn!()` like any other macro:
 
 ```ignore
 #![feature(plugin)]
-#![plugin(roman_numerals)]
+
+#[plugin] extern crate roman_numerals;
 
 fn main() {
     assert_eq!(rn!(MMXV), 2015);
@@ -218,7 +219,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
 Then code like
 
 ```ignore
-#![plugin(lint_plugin_test)]
+#[plugin] extern crate lint_plugin_test;
 
 fn lintme() { }
 ```

branches/tmp/src/libcollections/str.rs

@@ -80,7 +80,7 @@ pub use core::str::{Lines, LinesAny, MatchIndices, SplitStr, CharRange};
 pub use core::str::{Split, SplitTerminator};
 pub use core::str::{SplitN, RSplitN};
 pub use core::str::{from_utf8, CharEq, Chars, CharIndices, Bytes};
-pub use core::str::{from_utf8_unchecked, from_c_str, ParseBoolError};
+pub use core::str::{from_utf8_unchecked, from_c_str};
 pub use unicode::str::{Words, Graphemes, GraphemeIndices};
 
 /*

branches/tmp/src/librustc/diagnostics.rs

@@ -126,8 +126,7 @@ register_diagnostics! {
     E0312, // lifetime of reference outlives lifetime of borrowed content
     E0313, // lifetime of borrowed pointer outlives lifetime of captured variable
     E0314, // closure outlives stack frame
-    E0315, // cannot invoke closure outside of its lifetime
-    E0316 // nested quantification of lifetimes
+    E0315 // cannot invoke closure outside of its lifetime
 }
 
 __build_diagnostic_array! { DIAGNOSTICS }

branches/tmp/src/librustc/metadata/creader.rs

@@ -26,7 +26,7 @@ use syntax::ast;
 use syntax::abi;
 use syntax::attr;
 use syntax::attr::AttrMetaMethods;
-use syntax::codemap::{Span, mk_sp};
+use syntax::codemap::{COMMAND_LINE_SP, Span, mk_sp};
 use syntax::parse;
 use syntax::parse::token::InternedString;
 use syntax::parse::token;
@@ -457,13 +457,13 @@ impl<'a> CrateReader<'a> {
             CrateOrString::Krate(c) => {
                 (self.extract_crate_info(c).unwrap(), c.span)
             }
-            CrateOrString::Str(sp, s) => {
+            CrateOrString::Str(s) => {
                 (CrateInfo {
                      name: s.to_string(),
                      ident: s.to_string(),
                      id: ast::DUMMY_NODE_ID,
                      should_link: true,
-                 }, sp)
+                 }, COMMAND_LINE_SP)
             }
         };
         let target_triple = &self.sess.opts.target_triple[];
@@ -531,7 +531,7 @@ impl<'a> CrateReader<'a> {
 #[derive(Copy)]
 pub enum CrateOrString<'a> {
     Krate(&'a ast::Item),
-    Str(Span, &'a str)
+    Str(&'a str)
 }
 
 impl<'a> PluginMetadata<'a> {

branches/tmp/src/librustc/middle/infer/error_reporting.rs

@@ -1076,8 +1076,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
                         trait_ref: ast::TraitRef {
                             path: new_path,
                             ref_id: tr.ref_id,
-                        },
-                        span: poly_tr.span,
+                        }
                     }, modifier)
                 }
             }

branches/tmp/src/librustc/middle/resolve_lifetime.rs

@@ -45,31 +45,15 @@ pub enum DefRegion {
                   /* lifetime decl */ ast::NodeId),
 }
 
-// Maps the id of each lifetime reference to the lifetime decl
-// that it corresponds to.
+// maps the id of each lifetime reference to the lifetime decl
+// that it corresponds to
 pub type NamedRegionMap = NodeMap<DefRegion>;
 
 struct LifetimeContext<'a> {
     sess: &'a Session,
     named_region_map: &'a mut NamedRegionMap,
     scope: Scope<'a>,
     def_map: &'a DefMap,
-    // Deep breath. Our representation for poly trait refs contains a single
-    // binder and thus we only allow a single level of quantification. However,
-    // the syntax of Rust permits quantification in two places, e.g., `T: for <'a> Foo<'a>`
-    // and `for <'a, 'b> &'b T: Foo<'a>`. In order to get the de Bruijn indices
-    // correct when representing these constraints, we should only introduce one
-    // scope. However, we want to support both locations for the quantifier and
-    // during lifetime resolution we want precise information (so we can't
-    // desugar in an earlier phase).
-
-    // SO, if we encounter a quantifier at the outer scope, we set
-    // trait_ref_hack to true (and introduce a scope), and then if we encounter
-    // a quantifier at the inner scope, we error. If trait_ref_hack is false,
-    // then we introduce the scope at the inner quantifier.
-
-    // I'm sorry.
-    trait_ref_hack: bool,
 }
 
 enum ScopeChain<'a> {
@@ -96,7 +80,6 @@ pub fn krate(sess: &Session, krate: &ast::Crate, def_map: &DefMap) -> NamedRegio
         named_region_map: &mut named_region_map,
         scope: &ROOT_SCOPE,
         def_map: def_map,
-        trait_ref_hack: false,
     }, krate);
     sess.abort_if_errors();
     named_region_map
@@ -215,22 +198,9 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
             match predicate {
                 &ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{ ref bounded_ty,
                                                                                ref bounds,
-                                                                               ref bound_lifetimes,
                                                                                .. }) => {
-                    if bound_lifetimes.len() > 0 {
-                        self.trait_ref_hack = true;
-                        let result = self.with(LateScope(bound_lifetimes, self.scope),
-                                               |old_scope, this| {
-                            this.check_lifetime_defs(old_scope, bound_lifetimes);
-                            this.visit_ty(&**bounded_ty);
-                            visit::walk_ty_param_bounds_helper(this, bounds);
-                        });
-                        self.trait_ref_hack = false;
-                        result
-                    } else {
-                        self.visit_ty(&**bounded_ty);
-                        visit::walk_ty_param_bounds_helper(self, bounds);
-                    }
+                    self.visit_ty(&**bounded_ty);
+                    visit::walk_ty_param_bounds_helper(self, bounds);
                 }
                 &ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{ref lifetime,
                                                                                 ref bounds,
@@ -252,27 +222,18 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
         }
     }
 
-    fn visit_poly_trait_ref(&mut self,
-                            trait_ref: &ast::PolyTraitRef,
+    fn visit_poly_trait_ref(&mut self, trait_ref:
+                            &ast::PolyTraitRef,
                             _modifier: &ast::TraitBoundModifier) {
         debug!("visit_poly_trait_ref trait_ref={:?}", trait_ref);
 
-        if !self.trait_ref_hack || trait_ref.bound_lifetimes.len() > 0 {
-            if self.trait_ref_hack {
-                println!("{:?}", trait_ref.span);
-                span_err!(self.sess, trait_ref.span, E0316,
-                          "nested quantification of lifetimes");
+        self.with(LateScope(&trait_ref.bound_lifetimes, self.scope), |old_scope, this| {
+            this.check_lifetime_defs(old_scope, &trait_ref.bound_lifetimes);
+            for lifetime in &trait_ref.bound_lifetimes {
+                this.visit_lifetime_def(lifetime);
             }
-            self.with(LateScope(&trait_ref.bound_lifetimes, self.scope), |old_scope, this| {
-                this.check_lifetime_defs(old_scope, &trait_ref.bound_lifetimes);
-                for lifetime in &trait_ref.bound_lifetimes {
-                    this.visit_lifetime_def(lifetime);
-                }
-                this.visit_trait_ref(&trait_ref.trait_ref)
-            })
-        } else {
-            self.visit_trait_ref(&trait_ref.trait_ref)
-        }
+            this.visit_trait_ref(&trait_ref.trait_ref)
+        })
     }
 
     fn visit_trait_ref(&mut self, trait_ref: &ast::TraitRef) {
@@ -290,7 +251,6 @@ impl<'a> LifetimeContext<'a> {
             named_region_map: *named_region_map,
             scope: &wrap_scope,
             def_map: self.def_map,
-            trait_ref_hack: self.trait_ref_hack,
         };
         debug!("entering scope {:?}", this.scope);
         f(self.scope, &mut this);

branches/tmp/src/librustc/middle/traits/doc.rs

@@ -434,11 +434,87 @@ attached to the `ParameterEnvironment` and the global cache attached
 to the `tcx`. We use the local cache whenever the result might depend
 on the where clauses that are in scope. The determination of which
 cache to use is done by the method `pick_candidate_cache` in
-`select.rs`. At the moment, we use a very simple, conservative rule:
-if there are any where-clauses in scope, then we use the local cache.
-We used to try and draw finer-grained distinctions, but that led to a
-serious of annoying and weird bugs like #22019 and #18290. This simple
-rule seems to be pretty clearly safe and also still retains a very
-high hit rate (~95% when compiling rustc).
+`select.rs`.
+
+There are two cases where we currently use the local cache. The
+current rules are probably more conservative than necessary.
+
+### Trait references that involve parameter types
+
+The most obvious case where you need the local environment is
+when the trait reference includes parameter types. For example,
+consider the following function:
+
+    impl<T> Vec<T> {
+        fn foo(x: T)
+            where T : Foo
+        { ... }
+
+        fn bar(x: T)
+        { ... }
+    }
+
+If there is an obligation `T : Foo`, or `int : Bar<T>`, or whatever,
+clearly the results from `foo` and `bar` are potentially different,
+since the set of where clauses in scope are different.
+
+### Trait references with unbound variables when where clauses are in scope
+
+There is another less obvious interaction which involves unbound variables
+where *only* where clauses are in scope (no impls). This manifested as
+issue #18209 (`run-pass/trait-cache-issue-18209.rs`). Consider
+this snippet:
+
+```
+pub trait Foo {
+    fn load_from() -> Box<Self>;
+    fn load() -> Box<Self> {
+        Foo::load_from()
+    }
+}
+```
+
+The default method will incur an obligation `$0 : Foo` from the call
+to `load_from`. If there are no impls, this can be eagerly resolved to
+`VtableParam(Self : Foo)` and cached. Because the trait reference
+doesn't involve any parameters types (only the resolution does), this
+result was stored in the global cache, causing later calls to
+`Foo::load_from()` to get nonsense.
+
+To fix this, we always use the local cache if there are unbound
+variables and where clauses in scope. This is more conservative than
+necessary as far as I can tell. However, it still seems to be a simple
+rule and I observe ~99% hit rate on rustc, so it doesn't seem to hurt
+us in particular.
+
+Here is an example of the kind of subtle case that I would be worried
+about with a more complex rule (although this particular case works
+out ok). Imagine the trait reference doesn't directly reference a
+where clause, but the where clause plays a role in the winnowing
+phase. Something like this:
+
+```
+pub trait Foo<T> { ... }
+pub trait Bar { ... }
+impl<U,T:Bar> Foo<U> for T { ... } // Impl A
+impl Foo<char> for uint { ... }    // Impl B
+```
+
+Now, in some function, we have no where clauses in scope, and we have
+an obligation `$1 : Foo<$0>`. We might then conclude that `$0=char`
+and `$1=uint`: this is because for impl A to apply, `uint:Bar` would
+have to hold, and we know it does not or else the coherence check
+would have failed.  So we might enter into our global cache: `$1 :
+Foo<$0> => Impl B`.  Then we come along in a different scope, where a
+generic type `A` is around with the bound `A:Bar`. Now suddenly the
+impl is viable.
+
+The flaw in this imaginary DOOMSDAY SCENARIO is that we would not
+currently conclude that `$1 : Foo<$0>` implies that `$0 == uint` and
+`$1 == char`, even though it is true that (absent type parameters)
+there is no other type the user could enter. However, it is not
+*completely* implausible that we *could* draw this conclusion in the
+future; we wouldn't have to guess types, in particular, we could be
+led by the impls.
 
 */