Auto merge of #36166 - jonathandturner:rollup, r=jonathandturner

Rollup of 16 pull requests

- Successful merges: #35758, #35926, #36050, #36079, #36085, #36089, #36101, #36130, #36134, #36135, #36136, #36140, #36141, #36147, #36148, #36165
- Failed merges:

src/libcore/cmp.rs

@@ -383,7 +383,7 @@ impl PartialOrd for Ordering {
 /// }
 /// ```
 ///
-/// You may also find it useful to use `partial_cmp()` on your type`s fields. Here
+/// You may also find it useful to use `partial_cmp()` on your type's fields. Here
 /// is an example of `Person` types who have a floating-point `height` field that
 /// is the only field to be used for sorting:
 ///

src/libcore/iter/range.rs

@@ -263,14 +263,12 @@ impl<A: Step> ops::RangeFrom<A> {
     /// # Examples
     ///
     /// ```
-    /// # #![feature(step_by)]
-    ///
-    /// for i in (0u8..).step_by(2).take(10) {
-    ///     println!("{}", i);
+    /// #![feature(step_by)]
+    /// fn main() {
+    ///     let result: Vec<_> = (0..).step_by(2).take(5).collect();
+    ///     assert_eq!(result, vec![0, 2, 4, 6, 8]);
     /// }
     /// ```
-    ///
-    /// This prints the first ten even natural integers (0 to 18).
     #[unstable(feature = "step_by", reason = "recent addition",
                issue = "27741")]
     pub fn step_by(self, by: A) -> StepBy<A, Self> {
@@ -291,8 +289,10 @@ impl<A: Step> ops::Range<A> {
     ///
     /// ```
     /// #![feature(step_by)]
-    /// let result: Vec<_> = (0..10).step_by(2).collect();
-    /// assert_eq!(result, vec![0, 2, 4, 6, 8]);
+    /// fn main() {
+    ///     let result: Vec<_> = (0..10).step_by(2).collect();
+    ///     assert_eq!(result, vec![0, 2, 4, 6, 8]);
+    /// }
     /// ```
     #[unstable(feature = "step_by", reason = "recent addition",
                issue = "27741")]
@@ -315,20 +315,8 @@ impl<A: Step> ops::RangeInclusive<A> {
     /// ```
     /// #![feature(step_by, inclusive_range_syntax)]
     ///
-    /// for i in (0...10).step_by(2) {
-    ///     println!("{}", i);
-    /// }
-    /// ```
-    ///
-    /// This prints:
-    ///
-    /// ```text
-    /// 0
-    /// 2
-    /// 4
-    /// 6
-    /// 8
-    /// 10
+    /// let result: Vec<_> = (0...10).step_by(2).collect();
+    /// assert_eq!(result, vec![0, 2, 4, 6, 8, 10]);
     /// ```
     #[unstable(feature = "step_by", reason = "recent addition",
                issue = "27741")]

src/libcore/ops.rs

@@ -948,25 +948,55 @@ bitand_impl! { bool usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 ///
 /// # Examples
 ///
-/// A trivial implementation of `BitOr`. When `Foo | Foo` happens, it ends up
-/// calling `bitor`, and therefore, `main` prints `Bitwise Or-ing!`.
+/// In this example, the `|` operator is lifted to a trivial `Scalar` type.
 ///
 /// ```
 /// use std::ops::BitOr;
 ///
-/// struct Foo;
+/// #[derive(Debug, PartialEq)]
+/// struct Scalar(bool);
 ///
-/// impl BitOr for Foo {
-///     type Output = Foo;
+/// impl BitOr for Scalar {
+///     type Output = Self;
 ///
-///     fn bitor(self, _rhs: Foo) -> Foo {
-///         println!("Bitwise Or-ing!");
-///         self
+///     // rhs is the "right-hand side" of the expression `a | b`
+///     fn bitor(self, rhs: Self) -> Self {
+///         Scalar(self.0 | rhs.0)
+///     }
+/// }
+///
+/// fn main() {
+///     assert_eq!(Scalar(true) | Scalar(true), Scalar(true));
+///     assert_eq!(Scalar(true) | Scalar(false), Scalar(true));
+///     assert_eq!(Scalar(false) | Scalar(true), Scalar(true));
+///     assert_eq!(Scalar(false) | Scalar(false), Scalar(false));
+/// }
+/// ```
+///
+/// In this example, the `BitOr` trait is implemented for a `BooleanVector`
+/// struct.
+///
+/// ```
+/// use std::ops::BitOr;
+///
+/// #[derive(Debug, PartialEq)]
+/// struct BooleanVector(Vec<bool>);
+///
+/// impl BitOr for BooleanVector {
+///     type Output = Self;
+///
+///     fn bitor(self, BooleanVector(rhs): Self) -> Self {
+///         let BooleanVector(lhs) = self;
+///         assert_eq!(lhs.len(), rhs.len());
+///         BooleanVector(lhs.iter().zip(rhs.iter()).map(|(x, y)| *x || *y).collect())
 ///     }
 /// }
 ///
 /// fn main() {
-///     Foo | Foo;
+///     let bv1 = BooleanVector(vec![true, true, false, false]);
+///     let bv2 = BooleanVector(vec![true, false, true, false]);
+///     let expected = BooleanVector(vec![true, true, true, false]);
+///     assert_eq!(bv1 | bv2, expected);
 /// }
 /// ```
 #[lang = "bitor"]
@@ -1001,25 +1031,58 @@ bitor_impl! { bool usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 ///
 /// # Examples
 ///
-/// A trivial implementation of `BitXor`. When `Foo ^ Foo` happens, it ends up
-/// calling `bitxor`, and therefore, `main` prints `Bitwise Xor-ing!`.
+/// In this example, the `^` operator is lifted to a trivial `Scalar` type.
 ///
 /// ```
 /// use std::ops::BitXor;
 ///
-/// struct Foo;
+/// #[derive(Debug, PartialEq)]
+/// struct Scalar(bool);
 ///
-/// impl BitXor for Foo {
-///     type Output = Foo;
+/// impl BitXor for Scalar {
+///     type Output = Self;
 ///
-///     fn bitxor(self, _rhs: Foo) -> Foo {
-///         println!("Bitwise Xor-ing!");
-///         self
+///     // rhs is the "right-hand side" of the expression `a ^ b`
+///     fn bitxor(self, rhs: Self) -> Self {
+///         Scalar(self.0 ^ rhs.0)
+///     }
+/// }
+///
+/// fn main() {
+///     assert_eq!(Scalar(true) ^ Scalar(true), Scalar(false));
+///     assert_eq!(Scalar(true) ^ Scalar(false), Scalar(true));
+///     assert_eq!(Scalar(false) ^ Scalar(true), Scalar(true));
+///     assert_eq!(Scalar(false) ^ Scalar(false), Scalar(false));
+/// }
+/// ```
+///
+/// In this example, the `BitXor` trait is implemented for a `BooleanVector`
+/// struct.
+///
+/// ```
+/// use std::ops::BitXor;
+///
+/// #[derive(Debug, PartialEq)]
+/// struct BooleanVector(Vec<bool>);
+///
+/// impl BitXor for BooleanVector {
+///     type Output = Self;
+///
+///     fn bitxor(self, BooleanVector(rhs): Self) -> Self {
+///         let BooleanVector(lhs) = self;
+///         assert_eq!(lhs.len(), rhs.len());
+///         BooleanVector(lhs.iter()
+///                          .zip(rhs.iter())
+///                          .map(|(x, y)| (*x || *y) && !(*x && *y))
+///                          .collect())
 ///     }
 /// }
 ///
 /// fn main() {
-///     Foo ^ Foo;
+///     let bv1 = BooleanVector(vec![true, true, false, false]);
+///     let bv2 = BooleanVector(vec![true, false, true, false]);
+///     let expected = BooleanVector(vec![false, true, true, false]);
+///     assert_eq!(bv1 ^ bv2, expected);
 /// }
 /// ```
 #[lang = "bitxor"]

src/librustc_passes/static_recursion.rs

@@ -126,7 +126,7 @@ impl<'a, 'ast: 'a> CheckItemRecursionVisitor<'a, 'ast> {
             idstack: Vec::new(),
         }
     }
-    fn with_item_id_pushed<F>(&mut self, id: ast::NodeId, f: F)
+    fn with_item_id_pushed<F>(&mut self, id: ast::NodeId, f: F, span: Span)
         where F: Fn(&mut Self)
     {
         if self.idstack.iter().any(|&x| x == id) {
@@ -150,7 +150,9 @@ impl<'a, 'ast: 'a> CheckItemRecursionVisitor<'a, 'ast> {
                                      "recursive static");
                 }
             } else {
-                span_err!(self.sess, *self.root_span, E0265, "recursive constant");
+                struct_span_err!(self.sess, span, E0265, "recursive constant")
+                    .span_label(span, &format!("recursion not allowed in constant"))
+                    .emit();
             }
             return;
         }
@@ -203,7 +205,7 @@ impl<'a, 'ast: 'a> CheckItemRecursionVisitor<'a, 'ast> {
 
 impl<'a, 'ast: 'a> Visitor<'ast> for CheckItemRecursionVisitor<'a, 'ast> {
     fn visit_item(&mut self, it: &'ast hir::Item) {
-        self.with_item_id_pushed(it.id, |v| intravisit::walk_item(v, it));
+        self.with_item_id_pushed(it.id, |v| intravisit::walk_item(v, it), it.span);
     }
 
     fn visit_enum_def(&mut self,
@@ -233,16 +235,16 @@ impl<'a, 'ast: 'a> Visitor<'ast> for CheckItemRecursionVisitor<'a, 'ast> {
         // If `maybe_expr` is `None`, that's because no discriminant is
         // specified that affects this variant. Thus, no risk of recursion.
         if let Some(expr) = maybe_expr {
-            self.with_item_id_pushed(expr.id, |v| intravisit::walk_expr(v, expr));
+            self.with_item_id_pushed(expr.id, |v| intravisit::walk_expr(v, expr), expr.span);
         }
     }
 
     fn visit_trait_item(&mut self, ti: &'ast hir::TraitItem) {
-        self.with_item_id_pushed(ti.id, |v| intravisit::walk_trait_item(v, ti));
+        self.with_item_id_pushed(ti.id, |v| intravisit::walk_trait_item(v, ti), ti.span);
     }
 
     fn visit_impl_item(&mut self, ii: &'ast hir::ImplItem) {
-        self.with_item_id_pushed(ii.id, |v| intravisit::walk_impl_item(v, ii));
+        self.with_item_id_pushed(ii.id, |v| intravisit::walk_impl_item(v, ii), ii.span);
     }
 
     fn visit_expr(&mut self, e: &'ast hir::Expr) {

src/librustc_resolve/diagnostics.rs

@@ -1270,7 +1270,42 @@ trait Foo {}
 
 impl Foo for i32 {}
 ```
-"##
+"##,
+
+E0530: r##"
+A binding shadowed something it shouldn't.
+
+Erroneous code example:
+
+```compile_fail,E0530
+static TEST: i32 = 0;
+
+let r: (i32, i32) = (0, 0);
+match r {
+    TEST => {} // error: match bindings cannot shadow statics
+}
+```
+
+To fix this error, just change the binding's name in order to avoid shadowing
+one of the following:
+
+* struct name
+* struct/enum variant
+* static
+* const
+* associated const
+
+Fixed example:
+
+```
+static TEST: i32 = 0;
+
+let r: (i32, i32) = (0, 0);
+match r {
+    something => {} // ok!
+}
+```
+"##,
 
 }
 
@@ -1289,7 +1324,6 @@ register_diagnostics! {
 //  E0419, merged into 531
 //  E0420, merged into 532
 //  E0421, merged into 531
-    E0530, // X bindings cannot shadow Ys
     E0531, // unresolved pattern path kind `name`
     E0532, // expected pattern path kind, found another pattern path kind
 //  E0427, merged into 530

src/librustc_typeck/check/method/suggest.rs

@@ -242,6 +242,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             MethodError::Ambiguity(sources) => {
                 let mut err = struct_span_err!(self.sess(), span, E0034,
                                                "multiple applicable items in scope");
+                err.span_label(span, &format!("multiple `{}` found", item_name));
 
                 report_candidates(&mut err, sources);
                 err.emit();

src/librustc_typeck/check/mod.rs

@@ -903,14 +903,18 @@ fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 {
     let mut err = struct_span_err!(
         tcx.sess, impl_item.span, E0520,
-        "item `{}` is provided by an `impl` that specializes \
-         another, but the item in the parent `impl` is not \
-         marked `default` and so it cannot be specialized.",
+        "`{}` specializes an item from a parent `impl`, but \
+         neither that item nor the `impl` are marked `default`",
         impl_item.name);
+    err.span_label(impl_item.span, &format!("cannot specialize default item `{}`",
+                                            impl_item.name));
 
     match tcx.span_of_impl(parent_impl) {
         Ok(span) => {
-            err.span_note(span, "parent implementation is here:");
+            err.span_label(span, &"parent `impl` is here");
+            err.note(&format!("to specialize, either the parent `impl` or `{}` \
+                               in the parent `impl` must be marked `default`",
+                              impl_item.name));
         }
         Err(cname) => {
             err.note(&format!("parent implementation is in crate `{}`", cname));
@@ -1204,7 +1208,9 @@ pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, id: ast::Node
             }
             let e = fields[0].ty(tcx, substs);
             if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
-                span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous");
+                struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
+                                .span_label(sp, &format!("SIMD elements must have the same type"))
+                                .emit();
                 return;
             }
             match e.sty {

src/librustc_typeck/check/wfcheck.rs

@@ -16,7 +16,7 @@ use middle::region::{CodeExtent};
 use rustc::infer::TypeOrigin;
 use rustc::traits;
 use rustc::ty::{self, Ty, TyCtxt};
-use rustc::util::nodemap::FnvHashSet;
+use rustc::util::nodemap::{FnvHashSet, FnvHashMap};
 
 use syntax::ast;
 use syntax_pos::Span;
@@ -519,11 +519,26 @@ impl<'ccx, 'gcx> CheckTypeWellFormedVisitor<'ccx, 'gcx> {
 
 fn reject_shadowing_type_parameters(tcx: TyCtxt, span: Span, generics: &ty::Generics) {
     let parent = tcx.lookup_generics(generics.parent.unwrap());
-    let impl_params: FnvHashSet<_> = parent.types.iter().map(|tp| tp.name).collect();
+    let impl_params: FnvHashMap<_, _> = parent.types
+                                        .iter()
+                                        .map(|tp| (tp.name, tp.def_id))
+                                        .collect();
 
     for method_param in &generics.types {
-        if impl_params.contains(&method_param.name) {
-            error_194(tcx, span, method_param.name);
+        if impl_params.contains_key(&method_param.name) {
+            // Tighten up the span to focus on only the shadowing type
+            let shadow_node_id = tcx.map.as_local_node_id(method_param.def_id).unwrap();
+            let type_span = match tcx.map.opt_span(shadow_node_id) {
+                Some(osp) => osp,
+                None => span
+            };
+
+            // The expectation here is that the original trait declaration is
+            // local so it should be okay to just unwrap everything.
+            let trait_def_id = impl_params.get(&method_param.name).unwrap();
+            let trait_node_id = tcx.map.as_local_node_id(*trait_def_id).unwrap();
+            let trait_decl_span = tcx.map.opt_span(trait_node_id).unwrap();
+            error_194(tcx, type_span, trait_decl_span, method_param.name);
         }
     }
 }
@@ -630,10 +645,11 @@ fn error_392<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>, span: Span, param_name: ast::N
     err
 }
 
-fn error_194(tcx: TyCtxt, span: Span, name: ast::Name) {
+fn error_194(tcx: TyCtxt, span: Span, trait_decl_span: Span, name: ast::Name) {
     struct_span_err!(tcx.sess, span, E0194,
               "type parameter `{}` shadows another type parameter of the same name",
               name)
-        .span_label(span, &format!("`{}` shadows another type parameter", name))
+        .span_label(span, &format!("shadows another type parameter"))
+        .span_label(trait_decl_span, &format!("first `{}` declared here", name))
         .emit();
 }