Rollup of 12 pull requests

.mailmap

@@ -29,6 +29,7 @@ Ariel Ben-Yehuda <[email protected]> Ariel Ben-Yehuda <[email protected]>
 Ariel Ben-Yehuda <[email protected]> arielb1 <[email protected]>
 Austin Seipp <[email protected]> <[email protected]>
 Aydin Kim <[email protected]> aydin.kim <[email protected]>
+Bastian Kauschke <[email protected]>
 Barosl Lee <[email protected]> Barosl LEE <[email protected]>
 Ben Alpert <[email protected]> <[email protected]>
 Ben Sago <[email protected]> Ben S <[email protected]>

src/liballoc/borrow.rs

@@ -135,7 +135,7 @@ impl<T> ToOwned for T
 /// Another example showing how to keep `Cow` in a struct:
 ///
 /// ```
-/// use std::borrow::{Cow, ToOwned};
+/// use std::borrow::Cow;
 ///
 /// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
 ///     values: Cow<'a, [X]>,

src/libcore/cell.rs

@@ -1186,7 +1186,6 @@ impl<'b, T: ?Sized> Ref<'b, T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(refcell_map_split)]
     /// use std::cell::{Ref, RefCell};
     ///
     /// let cell = RefCell::new([1, 2, 3, 4]);
@@ -1195,7 +1194,7 @@ impl<'b, T: ?Sized> Ref<'b, T> {
     /// assert_eq!(*begin, [1, 2]);
     /// assert_eq!(*end, [3, 4]);
     /// ```
-    #[unstable(feature = "refcell_map_split", issue = "51476")]
+    #[stable(feature = "refcell_map_split", since = "1.35.0")]
     #[inline]
     pub fn map_split<U: ?Sized, V: ?Sized, F>(orig: Ref<'b, T>, f: F) -> (Ref<'b, U>, Ref<'b, V>)
         where F: FnOnce(&T) -> (&U, &V)
@@ -1268,7 +1267,6 @@ impl<'b, T: ?Sized> RefMut<'b, T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(refcell_map_split)]
     /// use std::cell::{RefCell, RefMut};
     ///
     /// let cell = RefCell::new([1, 2, 3, 4]);
@@ -1279,7 +1277,7 @@ impl<'b, T: ?Sized> RefMut<'b, T> {
     /// begin.copy_from_slice(&[4, 3]);
     /// end.copy_from_slice(&[2, 1]);
     /// ```
-    #[unstable(feature = "refcell_map_split", issue = "51476")]
+    #[stable(feature = "refcell_map_split", since = "1.35.0")]
     #[inline]
     pub fn map_split<U: ?Sized, V: ?Sized, F>(
         orig: RefMut<'b, T>, f: F
@@ -1423,7 +1421,6 @@ impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
 ///
 /// ```
 /// use std::cell::UnsafeCell;
-/// use std::marker::Sync;
 ///
 /// # #[allow(dead_code)]
 /// struct NotThreadSafe<T> {

src/libcore/macros.rs

@@ -559,6 +559,65 @@ macro_rules! unimplemented {
     ($($arg:tt)+) => (panic!("not yet implemented: {}", format_args!($($arg)*)));
 }
 
+/// A standardized placeholder for marking unfinished code.
+///
+/// This can be useful if you are prototyping and are just looking to have your
+/// code typecheck. `todo!` works exactly like `unimplemented!`, there only
+/// difference between the two macros is the name.
+///
+/// # Panics
+///
+/// This will always [panic!](macro.panic.html)
+///
+/// # Examples
+///
+/// Here's an example of some in-progress code. We have a trait `Foo`:
+///
+/// ```
+/// trait Foo {
+///     fn bar(&self);
+///     fn baz(&self);
+/// }
+/// ```
+///
+/// We want to implement `Foo` on one of our types, but we also want to work on
+/// just `bar()` first. In order for our code to compile, we need to implement
+/// `baz()`, so we can use `todo!`:
+///
+/// ```
+/// #![feature(todo_macro)]
+///
+/// # trait Foo {
+/// #     fn bar(&self);
+/// #     fn baz(&self);
+/// # }
+/// struct MyStruct;
+///
+/// impl Foo for MyStruct {
+///     fn bar(&self) {
+///         // implementation goes here
+///     }
+///
+///     fn baz(&self) {
+///         // let's not worry about implementing baz() for now
+///         todo!();
+///     }
+/// }
+///
+/// fn main() {
+///     let s = MyStruct;
+///     s.bar();
+///
+///     // we aren't even using baz() yet, so this is fine.
+/// }
+/// ```
+#[macro_export]
+#[unstable(feature = "todo_macro", issue = "59277")]
+macro_rules! todo {
+    () => (panic!("not yet implemented"));
+    ($($arg:tt)+) => (panic!("not yet implemented: {}", format_args!($($arg)*)));
+}
+
 /// A macro to create an array of [`MaybeUninit`]
 ///
 /// This macro constructs an uninitialized array of the type `[MaybeUninit<K>; N]`.

src/libcore/pin.rs

@@ -109,7 +109,7 @@
 //! assert_eq!(still_unmoved.slice, NonNull::from(&still_unmoved.data));
 //!
 //! // Since our type doesn't implement Unpin, this will fail to compile:
-//! // let new_unmoved = Unmovable::new("world".to_string());
+//! // let mut new_unmoved = Unmovable::new("world".to_string());
 //! // std::mem::swap(&mut *still_unmoved, &mut *new_unmoved);
 //! ```
 //!

src/libcore/tests/lib.rs

@@ -16,7 +16,6 @@
 #![feature(pattern)]
 #![feature(range_is_empty)]
 #![feature(raw)]
-#![feature(refcell_map_split)]
 #![feature(refcell_replace_swap)]
 #![feature(slice_patterns)]
 #![feature(sort_internals)]

src/librustc/lint/builtin.rs

@@ -482,6 +482,7 @@ pub enum BuiltinLintDiagnostics {
     UnknownCrateTypes(Span, String, String),
     UnusedImports(String, Vec<(Span, String)>),
     NestedImplTrait { outer_impl_trait_span: Span, inner_impl_trait_span: Span },
+    RedundantImport(Vec<(Span, bool)>, ast::Ident),
 }
 
 impl BuiltinLintDiagnostics {
@@ -578,6 +579,15 @@ impl BuiltinLintDiagnostics {
                 db.span_label(outer_impl_trait_span, "outer `impl Trait`");
                 db.span_label(inner_impl_trait_span, "nested `impl Trait` here");
             }
+            BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
+                for (span, is_imported) in spans {
+                    let introduced = if is_imported { "imported" } else { "defined" };
+                    db.span_label(
+                        span,
+                        format!("the item `{}` is already {} here", ident, introduced)
+                    );
+                }
+            }
         }
     }
 }

src/librustc/ty/query/on_disk_cache.rs

@@ -778,7 +778,6 @@ impl<'enc, 'a, 'tcx, E> CacheEncoder<'enc, 'a, 'tcx, E>
                                                  value: &V)
                                                  -> Result<(), E::Error>
     {
-        use crate::ty::codec::TyEncoder;
         let start_pos = self.position();
 
         tag.encode(self)?;

src/librustc_codegen_llvm/context.rs

@@ -377,7 +377,6 @@ impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     // Returns a Value of the "eh_unwind_resume" lang item if one is defined,
     // otherwise declares it as an external function.
     fn eh_unwind_resume(&self) -> &'ll Value {
-        use crate::attributes;
         let unwresume = &self.eh_unwind_resume;
         if let Some(llfn) = unwresume.get() {
             return llfn;

src/librustc_codegen_ssa/mir/rvalue.rs

@@ -750,7 +750,6 @@ fn cast_int_to_float<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
         // All inputs greater or equal to (f32::MAX + 0.5 ULP) are rounded to infinity,
         // and for everything else LLVM's uitofp works just fine.
         use rustc_apfloat::ieee::Single;
-        use rustc_apfloat::Float;
         const MAX_F32_PLUS_HALF_ULP: u128 = ((1 << (Single::PRECISION + 1)) - 1)
                                             << (Single::MAX_EXP - Single::PRECISION as i16);
         let max = bx.cx().const_uint_big(int_ty, MAX_F32_PLUS_HALF_ULP);

src/librustc_errors/lib.rs

@@ -155,7 +155,7 @@ impl CodeSuggestion {
     /// Returns the assembled code suggestions and whether they should be shown with an underline.
     pub fn splice_lines(&self, cm: &SourceMapperDyn)
                         -> Vec<(String, Vec<SubstitutionPart>)> {
-        use syntax_pos::{CharPos, Loc, Pos};
+        use syntax_pos::{CharPos, Pos};
 
         fn push_trailing(buf: &mut String,
                          line_opt: Option<&Cow<'_, str>>,

src/librustc_interface/profile/mod.rs

@@ -61,7 +61,6 @@ fn total_duration(traces: &[trace::Rec]) -> Duration {
 fn profile_queries_thread(r: Receiver<ProfileQueriesMsg>) {
     use self::trace::*;
     use std::fs::File;
-    use std::time::{Instant};
 
     let mut profq_msgs: Vec<ProfileQueriesMsg> = vec![];
     let mut frame: StackFrame = StackFrame { parse_st: ParseState::Clear, traces: vec![] };

src/librustc_mir/hair/pattern/mod.rs

@@ -427,7 +427,6 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
 
                 let mut kind = match (lo, hi) {
                     (PatternKind::Constant { value: lo }, PatternKind::Constant { value: hi }) => {
-                        use std::cmp::Ordering;
                         let cmp = compare_const_vals(
                             self.tcx,
                             lo,

src/librustc_mir/interpret/operator.rs

@@ -331,8 +331,6 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         val: ImmTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx, Scalar<M::PointerTag>> {
         use rustc::mir::UnOp::*;
-        use rustc_apfloat::ieee::{Single, Double};
-        use rustc_apfloat::Float;
 
         let layout = val.layout;
         let val = val.to_scalar()?;

src/librustc_resolve/lib.rs

@@ -1733,7 +1733,6 @@ impl<'a> Resolver<'a> {
     /// just that an error occurred.
     pub fn resolve_str_path_error(&mut self, span: Span, path_str: &str, is_value: bool)
         -> Result<hir::Path, ()> {
-        use std::iter;
         let mut errored = false;
 
         let path = if path_str.starts_with("::") {

src/librustc_resolve/resolve_imports.rs

@@ -7,14 +7,19 @@ use crate::{NameBinding, NameBindingKind, ToNameBinding, PathResult, PrivacyErro
 use crate::{Resolver, Segment};
 use crate::{names_to_string, module_to_string};
 use crate::{resolve_error, ResolutionError, Suggestion};
+use crate::ModuleKind;
 use crate::macros::ParentScope;
 
 use errors::Applicability;
 
 use rustc_data_structures::ptr_key::PtrKey;
 use rustc::ty;
 use rustc::lint::builtin::BuiltinLintDiagnostics;
-use rustc::lint::builtin::{DUPLICATE_MACRO_EXPORTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE};
+use rustc::lint::builtin::{
+    DUPLICATE_MACRO_EXPORTS,
+    PUB_USE_OF_PRIVATE_EXTERN_CRATE,
+    UNUSED_IMPORTS,
+};
 use rustc::hir::def_id::{CrateNum, DefId};
 use rustc::hir::def::*;
 use rustc::session::DiagnosticMessageId;
@@ -1230,10 +1235,97 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
             import[ns] = Some(PathResolution::new(def));
         });
 
+        self.check_for_redundant_imports(
+            ident,
+            directive,
+            source_bindings,
+            target_bindings,
+            target,
+        );
+
         debug!("(resolving single import) successfully resolved import");
         None
     }
 
+    fn check_for_redundant_imports(
+        &mut self,
+        ident: Ident,
+        directive: &'b ImportDirective<'b>,
+        source_bindings: &PerNS<Cell<Result<&'b NameBinding<'b>, Determinacy>>>,
+        target_bindings: &PerNS<Cell<Option<&'b NameBinding<'b>>>>,
+        target: Ident,
+    ) {
+        // Skip if the import was produced by a macro.
+        if directive.parent_scope.expansion != Mark::root() {
+            return;
+        }
+
+        // Skip if we are inside a named module (in contrast to an anonymous
+        // module defined by a block).
+        if let ModuleKind::Def(_, _) = directive.parent_scope.module.kind {
+            return;
+        }
+
+        let mut is_redundant = PerNS {
+            value_ns: None,
+            type_ns: None,
+            macro_ns: None,
+        };
+
+        let mut redundant_span = PerNS {
+            value_ns: None,
+            type_ns: None,
+            macro_ns: None,
+        };
+
+        self.per_ns(|this, ns| if let Some(binding) = source_bindings[ns].get().ok() {
+            if binding.def() == Def::Err {
+                return;
+            }
+
+            let orig_blacklisted_binding = mem::replace(
+                &mut this.blacklisted_binding,
+                target_bindings[ns].get()
+            );
+
+            match this.early_resolve_ident_in_lexical_scope(
+                target,
+                ScopeSet::Import(ns),
+                &directive.parent_scope,
+                false,
+                false,
+                directive.span,
+            ) {
+                Ok(other_binding) => {
+                    is_redundant[ns] = Some(
+                        binding.def() == other_binding.def()
+                        && !other_binding.is_ambiguity()
+                    );
+                    redundant_span[ns] =
+                        Some((other_binding.span, other_binding.is_import()));
+                }
+                Err(_) => is_redundant[ns] = Some(false)
+            }
+
+            this.blacklisted_binding = orig_blacklisted_binding;
+        });
+
+        if !is_redundant.is_empty() &&
+            is_redundant.present_items().all(|is_redundant| is_redundant)
+        {
+            self.session.buffer_lint_with_diagnostic(
+                UNUSED_IMPORTS,
+                directive.id,
+                directive.span,
+                &format!("the item `{}` is imported redundantly", ident),
+                BuiltinLintDiagnostics::RedundantImport(
+                    redundant_span.present_items().collect(),
+                    ident,
+                ),
+            );
+        }
+    }
+
     fn resolve_glob_import(&mut self, directive: &'b ImportDirective<'b>) {
         let module = match directive.imported_module.get().unwrap() {
             ModuleOrUniformRoot::Module(module) => module,

src/librustc_traits/lowering/environment.rs

@@ -190,7 +190,7 @@ crate fn environment<'a, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     def_id: DefId
 ) -> Environment<'tcx> {
-    use super::{Lower, IntoFromEnvGoal};
+    use super::IntoFromEnvGoal;
     use rustc::hir::{Node, TraitItemKind, ImplItemKind, ItemKind, ForeignItemKind};
 
     debug!("environment(def_id = {:?})", def_id);

src/librustc_typeck/check/wfcheck.rs

@@ -420,9 +420,6 @@ fn check_where_clauses<'a, 'gcx, 'fcx, 'tcx>(
     def_id: DefId,
     return_ty: Option<Ty<'tcx>>,
 ) {
-    use ty::subst::Subst;
-    use rustc::ty::TypeFoldable;
-
     let predicates = fcx.tcx.predicates_of(def_id);
 
     let generics = tcx.generics_of(def_id);
@@ -1010,8 +1007,6 @@ fn check_false_global_bounds<'a, 'gcx, 'tcx>(
     span: Span,
     id: hir::HirId)
 {
-    use rustc::ty::TypeFoldable;
-
     let empty_env = ty::ParamEnv::empty();
 
     let def_id = fcx.tcx.hir().local_def_id_from_hir_id(id);