diagnostics: make paths to external items more visible

src/librustc/middle/cstore.rs

@@ -32,7 +32,7 @@ use mir::repr::Mir;
 use mir::mir_map::MirMap;
 use session::Session;
 use session::search_paths::PathKind;
-use util::nodemap::{FnvHashMap, NodeMap, NodeSet};
+use util::nodemap::{FnvHashMap, NodeMap, NodeSet, DefIdMap};
 use std::any::Any;
 use std::cell::RefCell;
 use std::rc::Rc;
@@ -169,6 +169,7 @@ pub trait CrateStore<'tcx> : Any {
     fn item_type(&self, tcx: &TyCtxt<'tcx>, def: DefId)
                  -> ty::TypeScheme<'tcx>;
     fn relative_item_path(&self, def: DefId) -> Vec<hir_map::PathElem>;
+    fn visible_parent_map<'a>(&'a self) -> ::std::cell::RefMut<'a, DefIdMap<DefId>>;
     fn extern_item_path(&self, def: DefId) -> Vec<hir_map::PathElem>;
     fn item_name(&self, def: DefId) -> ast::Name;
     fn item_predicates(&self, tcx: &TyCtxt<'tcx>, def: DefId)
@@ -347,6 +348,9 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
     fn item_type(&self, tcx: &TyCtxt<'tcx>, def: DefId)
                  -> ty::TypeScheme<'tcx> { unimplemented!() }
     fn relative_item_path(&self, def: DefId) -> Vec<hir_map::PathElem> { unimplemented!() }
+    fn visible_parent_map<'a>(&'a self) -> ::std::cell::RefMut<'a, DefIdMap<DefId>> {
+        unimplemented!()
+    }
     fn extern_item_path(&self, def: DefId) -> Vec<hir_map::PathElem> { unimplemented!() }
     fn item_name(&self, def: DefId) -> ast::Name { unimplemented!() }
     fn item_predicates(&self, tcx: &TyCtxt<'tcx>, def: DefId)

src/librustc/ty/item_path.rs

@@ -10,7 +10,7 @@
 
 use front::map::DefPathData;
 use middle::cstore::LOCAL_CRATE;
-use middle::def_id::DefId;
+use middle::def_id::{DefId, CRATE_DEF_INDEX};
 use ty::{self, Ty, TyCtxt};
 use syntax::ast;
 
@@ -75,9 +75,51 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
+    /// If possible, this pushes a global path resolving to `external_def_id` that is visible
+    /// from at least one local module and returns true. If the crate defining `external_def_id` is
+    /// declared with an `extern crate`, the path is guarenteed to use the `extern crate`.
+    pub fn try_push_visible_item_path<T>(&self, buffer: &mut T, external_def_id: DefId) -> bool
+        where T: ItemPathBuffer
+    {
+        let visible_parent_map = self.sess.cstore.visible_parent_map();
+
+        let (mut cur_def, mut cur_path) = (external_def_id, Vec::<ast::Name>::new());
+        loop {
+            // If `cur_def` is a direct or injected extern crate, push the path to the crate
+            // followed by the path to the item within the crate and return.
+            if cur_def.index == CRATE_DEF_INDEX {
+                match self.sess.cstore.extern_crate(cur_def.krate) {
+                    Some(extern_crate) if extern_crate.direct => {
+                        self.push_item_path(buffer, extern_crate.def_id);
+                        cur_path.iter().rev().map(|segment| buffer.push(&segment.as_str())).count();
+                        return true;
+                    }
+                    None => {
+                        buffer.push(&self.crate_name(cur_def.krate));
+                        cur_path.iter().rev().map(|segment| buffer.push(&segment.as_str())).count();
+                        return true;
+                    }
+                    _ => {},
+                }
+            }
+
+            cur_path.push(self.sess.cstore.item_name(cur_def));
+            match visible_parent_map.get(&cur_def) {
+                Some(&def) => cur_def = def,
+                None => return false,
+            };
+        }
+    }
+
     pub fn push_item_path<T>(&self, buffer: &mut T, def_id: DefId)
         where T: ItemPathBuffer
     {
+        match *buffer.root_mode() {
+            RootMode::Local if !def_id.is_local() =>
+                if self.try_push_visible_item_path(buffer, def_id) { return },
+            _ => {}
+        }
+
         let key = self.def_key(def_id);
         match key.disambiguated_data.data {
             DefPathData::CrateRoot => {

src/librustc_metadata/csearch.rs

@@ -13,17 +13,17 @@ use decoder;
 use encoder;
 use loader;
 
-use middle::cstore::{CrateStore, CrateSource, ChildItem, ExternCrate, FoundAst};
+use middle::cstore::{CrateStore, CrateSource, ChildItem, ExternCrate, FoundAst, DefLike};
 use middle::cstore::{NativeLibraryKind, LinkMeta, LinkagePreference};
 use middle::def;
 use middle::lang_items;
 use rustc::ty::{self, Ty, TyCtxt, VariantKind};
-use middle::def_id::{DefId, DefIndex};
+use middle::def_id::{DefId, DefIndex, CRATE_DEF_INDEX};
 
 use rustc::front::map as hir_map;
 use rustc::mir::repr::Mir;
 use rustc::mir::mir_map::MirMap;
-use rustc::util::nodemap::{FnvHashMap, NodeMap, NodeSet};
+use rustc::util::nodemap::{FnvHashMap, NodeMap, NodeSet, DefIdMap};
 
 use std::cell::RefCell;
 use std::rc::Rc;
@@ -544,4 +544,60 @@ impl<'tcx> CrateStore<'tcx> for cstore::CStore {
     {
         encoder::metadata_encoding_version
     }
+
+    /// Returns a map from a sufficiently visible external item (i.e. an external item that is
+    /// visible from at least one local module) to a sufficiently visible parent (considering
+    /// modules that re-export the external item to be parents).
+    fn visible_parent_map<'a>(&'a self) -> ::std::cell::RefMut<'a, DefIdMap<DefId>> {
+        let mut visible_parent_map = self.visible_parent_map.borrow_mut();
+        if !visible_parent_map.is_empty() { return visible_parent_map; }
+
+        use rustc_front::hir;
+        use rustc::middle::cstore::{CrateStore, ChildItem};
+        use std::collections::vec_deque::VecDeque;
+        use std::collections::hash_map::Entry;
+        for cnum in 1 .. self.next_crate_num() {
+            let cdata = self.get_crate_data(cnum);
+
+            match cdata.extern_crate.get() {
+                // Ignore crates without a corresponding local `extern crate` item.
+                Some(extern_crate) if !extern_crate.direct => continue,
+                _ => {},
+            }
+
+            let mut bfs_queue = &mut VecDeque::new();
+            let mut add_child = |bfs_queue: &mut VecDeque<_>, child: ChildItem, parent: DefId| {
+                let child = match child.def {
+                    DefLike::DlDef(def) if child.vis == hir::Public => def.def_id(),
+                    _ => return,
+                };
+
+                match visible_parent_map.entry(child) {
+                    Entry::Occupied(mut entry) => {
+                        // If `child` is defined in crate `cnum`, ensure
+                        // that it is mapped to a parent in `cnum`.
+                        if child.krate == cnum && entry.get().krate != cnum {
+                            entry.insert(parent);
+                        }
+                    }
+                    Entry::Vacant(entry) => {
+                        entry.insert(parent);
+                        bfs_queue.push_back(child);
+                    }
+                }
+            };
+
+            let croot = DefId { krate: cnum, index: CRATE_DEF_INDEX };
+            for child in self.crate_top_level_items(cnum) {
+                add_child(bfs_queue, child, croot);
+            }
+            while let Some(def) = bfs_queue.pop_front() {
+                for child in self.item_children(def) {
+                    add_child(bfs_queue, child, def);
+                }
+            }
+        }
+
+        visible_parent_map
+    }
 }

src/librustc_metadata/cstore.rs

@@ -22,7 +22,8 @@ use loader;
 
 use rustc::back::svh::Svh;
 use rustc::middle::cstore::{ExternCrate};
-use rustc::util::nodemap::{FnvHashMap, NodeMap, NodeSet};
+use rustc::util::nodemap::{FnvHashMap, NodeMap, NodeSet, DefIdMap};
+use rustc::middle::def_id::DefId;
 
 use std::cell::{RefCell, Ref, Cell};
 use std::rc::Rc;
@@ -92,6 +93,7 @@ pub struct CStore {
     used_link_args: RefCell<Vec<String>>,
     statically_included_foreign_items: RefCell<NodeSet>,
     pub intr: Rc<IdentInterner>,
+    pub visible_parent_map: RefCell<DefIdMap<DefId>>,
 }
 
 impl CStore {
@@ -104,6 +106,7 @@ impl CStore {
             used_link_args: RefCell::new(Vec::new()),
             intr: intr,
             statically_included_foreign_items: RefCell::new(NodeSet()),
+            visible_parent_map: RefCell::new(FnvHashMap()),
         }
     }
 

src/test/compile-fail/associated-types-unsized.rs

@@ -14,7 +14,7 @@ trait Get {
 }
 
 fn foo<T:Get>(t: T) {
-    let x = t.get(); //~ ERROR the trait `core::marker::Sized` is not implemented
+    let x = t.get(); //~ ERROR the trait `std::marker::Sized` is not implemented
 }
 
 fn main() {

src/test/compile-fail/bad-const-type.rs

@@ -10,8 +10,8 @@
 
 static i: String = 10;
 //~^ ERROR mismatched types
-//~| expected `collections::string::String`
+//~| expected `std::string::String`
 //~| found `_`
-//~| expected struct `collections::string::String`
+//~| expected struct `std::string::String`
 //~| found integral variable
 fn main() { println!("{}", i); }

src/test/compile-fail/bad-method-typaram-kind.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 fn foo<T:'static>() {
-    1.bar::<T>(); //~ ERROR `core::marker::Send` is not implemented
+    1.bar::<T>(); //~ ERROR `std::marker::Send` is not implemented
 }
 
 trait bar {

src/test/compile-fail/bad-sized.rs

@@ -12,7 +12,7 @@ trait Trait {}
 
 pub fn main() {
     let x: Vec<Trait + Sized> = Vec::new();
-    //~^ ERROR the trait `core::marker::Sized` is not implemented
-    //~| ERROR the trait `core::marker::Sized` is not implemented
-    //~| ERROR the trait `core::marker::Sized` is not implemented
+    //~^ ERROR the trait `std::marker::Sized` is not implemented
+    //~| ERROR the trait `std::marker::Sized` is not implemented
+    //~| ERROR the trait `std::marker::Sized` is not implemented
 }

src/test/compile-fail/binop-bitxor-str.rs

@@ -8,6 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:`^` cannot be applied to type `collections::string::String`
+// error-pattern:`^` cannot be applied to type `std::string::String`
 
 fn main() { let x = "a".to_string() ^ "b".to_string(); }

src/test/compile-fail/builtin-superkinds-double-superkind.rs

@@ -13,9 +13,9 @@
 
 trait Foo : Send+Sync { }
 
-impl <T: Sync+'static> Foo for (T,) { } //~ ERROR the trait `core::marker::Send` is not implemented
+impl <T: Sync+'static> Foo for (T,) { } //~ ERROR the trait `std::marker::Send` is not implemented
 
-impl <T: Send> Foo for (T,T) { } //~ ERROR the trait `core::marker::Sync` is not implemented
+impl <T: Send> Foo for (T,T) { } //~ ERROR the trait `std::marker::Sync` is not implemented
 
 impl <T: Send+Sync> Foo for (T,T,T) { } // (ok)
 

src/test/compile-fail/builtin-superkinds-in-metadata.rs

@@ -22,6 +22,6 @@ struct X<T>(T);
 impl <T:Sync> RequiresShare for X<T> { }
 
 impl <T:Sync+'static> RequiresRequiresShareAndSend for X<T> { }
-//~^ ERROR the trait `core::marker::Send` is not implemented
+//~^ ERROR the trait `std::marker::Send` is not implemented
 
 fn main() { }

src/test/compile-fail/builtin-superkinds-simple.rs

@@ -14,6 +14,6 @@
 trait Foo : Send { }
 
 impl Foo for std::rc::Rc<i8> { }
-//~^ ERROR the trait `core::marker::Send` is not implemented
+//~^ ERROR the trait `std::marker::Send` is not implemented
 
 fn main() { }

src/test/compile-fail/builtin-superkinds-typaram-not-send.rs

@@ -12,6 +12,6 @@
 
 trait Foo : Send { }
 
-impl <T: Sync+'static> Foo for T { } //~ ERROR the trait `core::marker::Send` is not implemented
+impl <T: Sync+'static> Foo for T { } //~ ERROR the trait `std::marker::Send` is not implemented
 
 fn main() { }

src/test/compile-fail/cast-rfc0401.rs

@@ -91,7 +91,7 @@ fn main()
     let _ = 42usize as *const [u8]; //~ ERROR casting
     let _ = v as *const [u8]; //~ ERROR cannot cast
     let _ = fat_v as *const Foo;
-    //~^ ERROR `core::marker::Sized` is not implemented for the type `[u8]`
+    //~^ ERROR `std::marker::Sized` is not implemented for the type `[u8]`
     //~^^ HELP run `rustc --explain E0277` to see a detailed explanation
     //~^^^ NOTE `[u8]` does not have a constant size known at compile-time
     //~^^^^ NOTE required for the cast to the object type `Foo`
@@ -106,7 +106,7 @@ fn main()
 
     let a : *const str = "hello";
     let _ = a as *const Foo;
-    //~^ ERROR `core::marker::Sized` is not implemented for the type `str`
+    //~^ ERROR `std::marker::Sized` is not implemented for the type `str`
     //~^^ HELP run `rustc --explain E0277` to see a detailed explanation
     //~^^^ NOTE `str` does not have a constant size known at compile-time
     //~^^^^ NOTE required for the cast to the object type `Foo`

src/test/compile-fail/closure-bounds-cant-promote-superkind-in-struct.rs

@@ -13,7 +13,7 @@ struct X<F> where F: FnOnce() + 'static + Send {
 }
 
 fn foo<F>(blk: F) -> X<F> where F: FnOnce() + 'static {
-    //~^ ERROR the trait `core::marker::Send` is not implemented for the type
+    //~^ ERROR the trait `std::marker::Send` is not implemented for the type
     return X { field: blk };
 }
 

src/test/compile-fail/closure-bounds-subtype.rs

@@ -21,7 +21,7 @@ fn give_any<F>(f: F) where F: FnOnce() {
 
 fn give_owned<F>(f: F) where F: FnOnce() + Send {
     take_any(f);
-    take_const_owned(f); //~ ERROR the trait `core::marker::Sync` is not implemented for the type
+    take_const_owned(f); //~ ERROR the trait `std::marker::Sync` is not implemented for the type
 }
 
 fn main() {}

src/test/compile-fail/coherence-conflicting-negative-trait-impl.rs

@@ -17,10 +17,10 @@ struct TestType<T>(::std::marker::PhantomData<T>);
 unsafe impl<T: MyTrait+'static> Send for TestType<T> {}
 
 impl<T: MyTrait> !Send for TestType<T> {}
-//~^ ERROR conflicting implementations of trait `core::marker::Send`
+//~^ ERROR conflicting implementations of trait `std::marker::Send`
 
 unsafe impl<T:'static> Send for TestType<T> {}
-//~^ ERROR error: conflicting implementations of trait `core::marker::Send`
+//~^ ERROR error: conflicting implementations of trait `std::marker::Send`
 
 impl !Send for TestType<i32> {}
 

src/test/compile-fail/deriving-no-inner-impl-error-message.rs

@@ -18,7 +18,7 @@ struct E {
 #[derive(Clone)]
 struct C {
     x: NoCloneOrEq
-    //~^ ERROR the trait `core::clone::Clone` is not implemented for the type `NoCloneOrEq`
+    //~^ ERROR the trait `std::clone::Clone` is not implemented for the type `NoCloneOrEq`
 }
 
 

src/test/compile-fail/deriving-span-Default-struct.rs

@@ -17,7 +17,7 @@ struct Error;
 
 #[derive(Default)]
 struct Struct {
-    x: Error //~ ERROR `core::default::Default` is not implemented
+    x: Error //~ ERROR `std::default::Default` is not implemented
 }
 
 fn main() {}

src/test/compile-fail/destructure-trait-ref.rs

@@ -35,7 +35,7 @@ fn main() {
     // n == m
     let &x = &1isize as &T;      //~ ERROR type `&T` cannot be dereferenced
     let &&x = &(&1isize as &T);  //~ ERROR type `&T` cannot be dereferenced
-    let box x = box 1isize as Box<T>; //~ ERROR the trait `core::marker::Sized` is not implemented
+    let box x = box 1isize as Box<T>; //~ ERROR the trait `std::marker::Sized` is not implemented
 
     // n > m
     let &&x = &1isize as &T;

src/test/compile-fail/dropck_no_diverge_on_nonregular_3.rs

@@ -39,8 +39,8 @@ enum Wrapper<T:'static> {
 }
 
 fn main() {
-    let w = //~ ERROR overflow while adding drop-check rules for core::option
+    let w = //~ ERROR overflow while adding drop-check rules for std::option
         Some(Wrapper::Simple::<u32>);
-    //~^ ERROR overflow while adding drop-check rules for core::option::Option
+    //~^ ERROR overflow while adding drop-check rules for std::option::Option
     //~| ERROR overflow while adding drop-check rules for Wrapper
 }

src/test/compile-fail/dst-bad-assign-2.rs

@@ -44,5 +44,5 @@ pub fn main() {
     // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
     let z: Box<ToBar> = Box::new(Bar1 {f: 36});
     f5.ptr = *z;
-    //~^ ERROR the trait `core::marker::Sized` is not implemented
+    //~^ ERROR the trait `std::marker::Sized` is not implemented
 }

src/test/compile-fail/dst-bad-assign.rs

@@ -49,5 +49,5 @@ pub fn main() {
     //~| found `Bar1`
     //~| expected trait ToBar
     //~| found struct `Bar1`
-    //~| ERROR the trait `core::marker::Sized` is not implemented for the type `ToBar`
+    //~| ERROR the trait `std::marker::Sized` is not implemented for the type `ToBar`
 }

src/test/compile-fail/dst-bad-deep.rs

@@ -21,5 +21,5 @@ pub fn main() {
     let f: Fat<[isize; 3]> = Fat { ptr: [5, 6, 7] };
     let g: &Fat<[isize]> = &f;
     let h: &Fat<Fat<[isize]>> = &Fat { ptr: *g };
-    //~^ ERROR the trait `core::marker::Sized` is not implemented
+    //~^ ERROR the trait `std::marker::Sized` is not implemented
 }