Auto merge of #32439 - jseyfried:visible_suggestions, r=nrc

diagnostics: make paths to external items more visible

This PR changes the reported path for an external item so that it is visible from at least one local module (i.e. it does not use any inaccessible external modules) if possible. If the external item's crate was declared with an `extern crate`, the path is guarenteed to use the `extern crate`.

Fixes #23224, fixes #23355, fixes #26635, fixes #27165.

r? @nrc

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
 }