Auto merge of #40806 - frewsxcv:rollup, r=frewsxcv

Rollup of 8 pull requests

- Successful merges: #40567, #40602, #40636, #40739, #40756, #40790, #40794, #40803
- Failed merges:

CONTRIBUTING.md

@@ -311,9 +311,13 @@ To save @bors some work, and to get small changes through more quickly, when
 the other rollup-eligible patches too, and they'll get tested and merged at
 the same time.
 
-To find documentation-related issues, sort by the [A-docs label][adocs].
+To find documentation-related issues, sort by the [T-doc label][tdoc].
 
-[adocs]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AA-docs
+[tdoc]: https://github.com/rust-lang/rust/issues?q=is%3Aopen%20is%3Aissue%20label%3AT-doc
+
+You can find documentation style guidelines in [RFC 1574][rfc1574].
+
+[rfc1574]: https://github.com/rust-lang/rfcs/blob/master/text/1574-more-api-documentation-conventions.md#appendix-a-full-conventions-text
 
 In many cases, you don't need a full `./x.py doc`. You can use `rustdoc` directly
 to check small fixes. For example, `rustdoc src/doc/reference.md` will render

src/libcollections/btree/map.rs

@@ -141,8 +141,7 @@ pub struct BTreeMap<K, V> {
 unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
     fn drop(&mut self) {
         unsafe {
-            for _ in ptr::read(self).into_iter() {
+            drop(ptr::read(self).into_iter());
-            }
         }
     }
 }

src/libcollections/slice.rs

@@ -1162,7 +1162,7 @@ impl<T> [T] {
     ///
     /// # Current implementation
     ///
-    /// The current algorithm is based on Orson Peters' [pdqsort][pattern-defeating quicksort],
+    /// The current algorithm is based on Orson Peters' [pattern-defeating quicksort][pdqsort],
     /// which is a quicksort variant designed to be very fast on certain kinds of patterns,
     /// sometimes achieving linear time. It is randomized but deterministic, and falls back to
     /// heapsort on degenerate inputs.
@@ -1199,7 +1199,7 @@ impl<T> [T] {
     ///
     /// # Current implementation
     ///
-    /// The current algorithm is based on Orson Peters' [pdqsort][pattern-defeating quicksort],
+    /// The current algorithm is based on Orson Peters' [pattern-defeating quicksort][pdqsort],
     /// which is a quicksort variant designed to be very fast on certain kinds of patterns,
     /// sometimes achieving linear time. It is randomized but deterministic, and falls back to
     /// heapsort on degenerate inputs.
@@ -1239,7 +1239,7 @@ impl<T> [T] {
     ///
     /// # Current implementation
     ///
-    /// The current algorithm is based on Orson Peters' [pdqsort][pattern-defeating quicksort],
+    /// The current algorithm is based on Orson Peters' [pattern-defeating quicksort][pdqsort],
     /// which is a quicksort variant designed to be very fast on certain kinds of patterns,
     /// sometimes achieving linear time. It is randomized but deterministic, and falls back to
     /// heapsort on degenerate inputs.

src/librustc/mir/mod.rs

@@ -983,16 +983,16 @@ impl<'tcx> Debug for Operand<'tcx> {
 }
 
 impl<'tcx> Operand<'tcx> {
-    pub fn item<'a>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
+    pub fn function_handle<'a>(
-                    def_id: DefId,
+        tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
-                    substs: &'tcx Substs<'tcx>,
+        def_id: DefId,
-                    span: Span)
+        substs: &'tcx Substs<'tcx>,
-                    -> Self
+        span: Span,
-    {
+    ) -> Self {
         Operand::Constant(Constant {
             span: span,
             ty: tcx.item_type(def_id).subst(tcx, substs),
-            literal: Literal::Item { def_id, substs }
+            literal: Literal::Value { value: ConstVal::Function(def_id, substs) },
         })
     }
 

src/librustc_mir/build/scope.rs

@@ -89,6 +89,7 @@ should go to.
 use build::{BlockAnd, BlockAndExtension, Builder, CFG};
 use rustc::middle::region::{CodeExtent, CodeExtentData};
 use rustc::middle::lang_items;
+use rustc::middle::const_val::ConstVal;
 use rustc::ty::subst::{Kind, Subst};
 use rustc::ty::{Ty, TyCtxt};
 use rustc::mir::*;
@@ -784,9 +785,8 @@ fn build_free<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
         func: Operand::Constant(Constant {
             span: data.span,
             ty: tcx.item_type(free_func).subst(tcx, substs),
-            literal: Literal::Item {
+            literal: Literal::Value {
-                def_id: free_func,
+                value: ConstVal::Function(free_func, substs),
-                substs: substs
             }
         }),
         args: vec![Operand::Consume(data.value.clone())],

src/librustc_mir/hair/cx/expr.rs

@@ -714,9 +714,8 @@ fn method_callee<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
         ty: callee.ty,
         span: expr.span,
         kind: ExprKind::Literal {
-            literal: Literal::Item {
+            literal: Literal::Value {
-                def_id: callee.def_id,
+                value: ConstVal::Function(callee.def_id, callee.substs),
-                substs: callee.substs,
             },
         },
     }
@@ -743,14 +742,24 @@ fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                      -> ExprKind<'tcx> {
     let substs = cx.tables().node_id_item_substs(expr.id)
         .unwrap_or_else(|| cx.tcx.intern_substs(&[]));
-    let def_id = match def {
+    match def {
         // A regular function, constructor function or a constant.
         Def::Fn(def_id) |
         Def::Method(def_id) |
         Def::StructCtor(def_id, CtorKind::Fn) |
-        Def::VariantCtor(def_id, CtorKind::Fn) |
+        Def::VariantCtor(def_id, CtorKind::Fn) => ExprKind::Literal {
+            literal: Literal::Value {
+                value: ConstVal::Function(def_id, substs),
+            },
+        },
+
         Def::Const(def_id) |
-        Def::AssociatedConst(def_id) => def_id,
+        Def::AssociatedConst(def_id) => ExprKind::Literal {
+            literal: Literal::Item {
+                def_id: def_id,
+                substs: substs,
+            },
+        },
 
         Def::StructCtor(def_id, CtorKind::Const) |
         Def::VariantCtor(def_id, CtorKind::Const) => {
@@ -758,7 +767,7 @@ fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                 // A unit struct/variant which is used as a value.
                 // We return a completely different ExprKind here to account for this special case.
                 ty::TyAdt(adt_def, substs) => {
-                    return ExprKind::Adt {
+                    ExprKind::Adt {
                         adt_def: adt_def,
                         variant_index: adt_def.variant_index_with_id(def_id),
                         substs: substs,
@@ -770,17 +779,11 @@ fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             }
         }
 
-        Def::Static(node_id, _) => return ExprKind::StaticRef { id: node_id },
+        Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 
-        Def::Local(..) | Def::Upvar(..) => return convert_var(cx, expr, def),
+        Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 
         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
-    };
-    ExprKind::Literal {
-        literal: Literal::Item {
-            def_id: def_id,
-            substs: substs,
-        },
     }
 }
 

src/librustc_mir/hair/cx/mod.rs

@@ -132,9 +132,8 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
                 let method_ty = self.tcx.item_type(item.def_id);
                 let method_ty = method_ty.subst(self.tcx, substs);
                 return (method_ty,
-                        Literal::Item {
+                        Literal::Value {
-                            def_id: item.def_id,
+                            value: ConstVal::Function(item.def_id, substs),
-                            substs: substs,
                         });
             }
         }

src/librustc_mir/shim.rs

@@ -12,6 +12,7 @@ use rustc::hir;
 use rustc::hir::def_id::DefId;
 use rustc::infer;
 use rustc::middle::region::ROOT_CODE_EXTENT;
+use rustc::middle::const_val::ConstVal;
 use rustc::mir::*;
 use rustc::mir::transform::MirSource;
 use rustc::ty::{self, Ty};
@@ -335,7 +336,9 @@ fn build_call_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
             Operand::Constant(Constant {
                 span: span,
                 ty: tcx.item_type(def_id).subst(tcx, param_env.free_substs),
-                literal: Literal::Item { def_id, substs: param_env.free_substs },
+                literal: Literal::Value {
+                    value: ConstVal::Function(def_id, param_env.free_substs),
+                },
             }),
             vec![rcvr]
         )

src/librustc_mir/transform/qualify_consts.rs

@@ -568,11 +568,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                 });
             }
             Operand::Constant(ref constant) => {
-                // Only functions and methods can have these types.
-                if let ty::TyFnDef(..) = constant.ty.sty {
-                    return;
-                }
-
                 if let Literal::Item { def_id, substs } = constant.literal {
                     // Don't peek inside generic (associated) constants.
                     if substs.types().next().is_some() {

src/librustc_mir/transform/type_check.rs

@@ -15,6 +15,7 @@ use rustc::infer::{self, InferCtxt, InferOk};
 use rustc::traits::{self, Reveal};
 use rustc::ty::fold::TypeFoldable;
 use rustc::ty::{self, Ty, TyCtxt, TypeVariants};
+use rustc::middle::const_val::ConstVal;
 use rustc::mir::*;
 use rustc::mir::tcx::LvalueTy;
 use rustc::mir::transform::{MirPass, MirSource, Pass};
@@ -526,7 +527,9 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
     fn is_box_free(&self, operand: &Operand<'tcx>) -> bool {
         match operand {
             &Operand::Constant(Constant {
-                literal: Literal::Item { def_id, .. }, ..
+                literal: Literal::Value {
+                    value: ConstVal::Function(def_id, _), ..
+                }, ..
             }) => {
                 Some(def_id) == self.tcx().lang_items.box_free_fn()
             }

src/librustc_mir/util/elaborate_drops.rs

@@ -525,8 +525,8 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
             }],
             terminator: Some(Terminator {
                 kind: TerminatorKind::Call {
-                    func: Operand::item(tcx, drop_fn.def_id, substs,
+                    func: Operand::function_handle(tcx, drop_fn.def_id, substs,
-                                        self.source_info.span),
+                                                   self.source_info.span),
                     args: vec![Operand::Consume(Lvalue::Local(ref_lvalue))],
                     destination: Some((unit_temp, succ)),
                     cleanup: unwind,
@@ -629,7 +629,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
         let substs = tcx.mk_substs(iter::once(Kind::from(ty)));
 
         let call = TerminatorKind::Call {
-            func: Operand::item(tcx, free_func, substs, self.source_info.span),
+            func: Operand::function_handle(tcx, free_func, substs, self.source_info.span),
             args: vec![Operand::Consume(self.lvalue.clone())],
             destination: Some((unit_temp, target)),
             cleanup: None

src/librustc_trans/mir/analyze.rs

@@ -13,7 +13,8 @@
 
 use rustc_data_structures::bitvec::BitVector;
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
-use rustc::mir::{self, Location, TerminatorKind};
+use rustc::middle::const_val::ConstVal;
+use rustc::mir::{self, Location, TerminatorKind, Literal};
 use rustc::mir::visit::{Visitor, LvalueContext};
 use rustc::mir::traversal;
 use common;
@@ -109,7 +110,9 @@ impl<'mir, 'a, 'tcx> Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'tcx> {
         match *kind {
             mir::TerminatorKind::Call {
                 func: mir::Operand::Constant(mir::Constant {
-                    literal: mir::Literal::Item { def_id, .. }, ..
+                    literal: Literal::Value {
+                        value: ConstVal::Function(def_id, _), ..
+                    }, ..
                 }),
                 ref args, ..
             } if Some(def_id) == self.cx.ccx.tcx().lang_items.box_free_fn() => {

src/librustc_trans/mir/constant.rs

@@ -101,9 +101,12 @@ impl<'tcx> Const<'tcx> {
             ConstVal::Str(ref v) => C_str_slice(ccx, v.clone()),
             ConstVal::ByteStr(ref v) => consts::addr_of(ccx, C_bytes(ccx, v), 1, "byte_str"),
             ConstVal::Struct(_) | ConstVal::Tuple(_) |
-            ConstVal::Array(..) | ConstVal::Repeat(..) |
+            ConstVal::Array(..) | ConstVal::Repeat(..) => {
+                bug!("MIR must not use `{:?}` (aggregates are expanded to MIR rvalues)", cv)
+            }
             ConstVal::Function(..) => {
-                bug!("MIR must not use `{:?}` (which refers to a local ID)", cv)
+                let llty = type_of::type_of(ccx, ty);
+                return Const::new(C_null(llty), ty);
             }
             ConstVal::Char(c) => C_integral(Type::char(ccx), c as u64, false),
         };
@@ -476,13 +479,6 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                 let ty = self.monomorphize(&constant.ty);
                 match constant.literal.clone() {
                     mir::Literal::Item { def_id, substs } => {
-                        // Shortcut for zero-sized types, including function item
-                        // types, which would not work with MirConstContext.
-                        if common::type_is_zero_size(self.ccx, ty) {
-                            let llty = type_of::type_of(self.ccx, ty);
-                            return Ok(Const::new(C_null(llty), ty));
-                        }
-
                         let substs = self.monomorphize(&substs);
                         MirConstContext::trans_def(self.ccx, def_id, substs, IndexVec::new())
                     }
@@ -924,13 +920,6 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
         let ty = self.monomorphize(&constant.ty);
         let result = match constant.literal.clone() {
             mir::Literal::Item { def_id, substs } => {
-                // Shortcut for zero-sized types, including function item
-                // types, which would not work with MirConstContext.
-                if common::type_is_zero_size(bcx.ccx, ty) {
-                    let llty = type_of::type_of(bcx.ccx, ty);
-                    return Const::new(C_null(llty), ty);
-                }
-
                 let substs = self.monomorphize(&substs);
                 MirConstContext::trans_def(bcx.ccx, def_id, substs, IndexVec::new())
             }

src/librustc_typeck/check/mod.rs

@@ -4099,6 +4099,17 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             };
 
             if self.diverges.get().always() {
+                if let ExpectHasType(ety) = expected {
+                    // Avoid forcing a type (only `!` for now) in unreachable code.
+                    // FIXME(aburka) do we need this special case? and should it be is_uninhabited?
+                    if !ety.is_never() {
+                        if let Some(ref e) = blk.expr {
+                            // Coerce the tail expression to the right type.
+                            self.demand_coerce(e, ty, ety);
+                        }
+                    }
+                }
+
                 ty = self.next_diverging_ty_var(TypeVariableOrigin::DivergingBlockExpr(blk.span));
             } else if let ExpectHasType(ety) = expected {
                 if let Some(ref e) = blk.expr {

src/librustdoc/html/render.rs

@@ -1700,6 +1700,23 @@ fn document_stability(w: &mut fmt::Formatter, cx: &Context, item: &clean::Item)
     Ok(())
 }
 
+fn name_key(name: &str) -> (&str, u64, usize) {
+    // find number at end
+    let split = name.bytes().rposition(|b| b < b'0' || b'9' < b).map_or(0, |s| s + 1);
+
+    // count leading zeroes
+    let after_zeroes =
+        name[split..].bytes().position(|b| b != b'0').map_or(name.len(), |extra| split + extra);
+
+    // sort leading zeroes last
+    let num_zeroes = after_zeroes - split;
+
+    match name[split..].parse() {
+        Ok(n) => (&name[..split], n, num_zeroes),
+        Err(_) => (name, 0, num_zeroes),
+    }
+}
+
 fn item_module(w: &mut fmt::Formatter, cx: &Context,
                item: &clean::Item, items: &[clean::Item]) -> fmt::Result {
     document(w, cx, item)?;
@@ -1744,7 +1761,9 @@ fn item_module(w: &mut fmt::Formatter, cx: &Context,
             (Some(stability::Stable), Some(stability::Unstable)) => return Ordering::Less,
             _ => {}
         }
-        i1.name.cmp(&i2.name)
+        let lhs = i1.name.as_ref().map_or("", |s| &**s);
+        let rhs = i2.name.as_ref().map_or("", |s| &**s);
+        name_key(lhs).cmp(&name_key(rhs))
     }
 
     indices.sort_by(|&i1, &i2| cmp(&items[i1], &items[i2], i1, i2));
@@ -3198,3 +3217,32 @@ fn test_unique_id() {
     reset_ids(true);
     test();
 }
+
+#[cfg(test)]
+#[test]
+fn test_name_key() {
+    assert_eq!(name_key("0"), ("", 0, 1));
+    assert_eq!(name_key("123"), ("", 123, 0));
+    assert_eq!(name_key("Fruit"), ("Fruit", 0, 0));
+    assert_eq!(name_key("Fruit0"), ("Fruit", 0, 1));
+    assert_eq!(name_key("Fruit0000"), ("Fruit", 0, 4));
+    assert_eq!(name_key("Fruit01"), ("Fruit", 1, 1));
+    assert_eq!(name_key("Fruit10"), ("Fruit", 10, 0));
+    assert_eq!(name_key("Fruit123"), ("Fruit", 123, 0));
+}
+
+#[cfg(test)]
+#[test]
+fn test_name_sorting() {
+    let names = ["Apple",
+                 "Banana",
+                 "Fruit", "Fruit0", "Fruit00",
+                 "Fruit1", "Fruit01",
+                 "Fruit2", "Fruit02",
+                 "Fruit20",
+                 "Fruit100",
+                 "Pear"];
+    let mut sorted = names.to_owned();
+    sorted.sort_by_key(|&s| name_key(s));
+    assert_eq!(names, sorted);
+}

src/libstd/collections/hash/table.rs

@@ -896,15 +896,23 @@ impl<K, V> RawTable<K, V> {
         }
     }
 
-    /// Returns an iterator that copies out each entry. Used while the table
+    /// Drops buckets in reverse order. It leaves the table in an inconsistent
-    /// is being dropped.
+    /// state and should only be used for dropping the table's remaining
-    unsafe fn rev_move_buckets(&mut self) -> RevMoveBuckets<K, V> {
+    /// entries. It's used in the implementation of Drop.
-        let raw_bucket = self.first_bucket_raw();
+    unsafe fn rev_drop_buckets(&mut self) {
-        RevMoveBuckets {
+        let first_raw = self.first_bucket_raw();
-            raw: raw_bucket.offset(self.capacity as isize),
+        let mut raw = first_raw.offset(self.capacity as isize);
-            hashes_end: raw_bucket.hash,
+        let mut elems_left = self.size;
-            elems_left: self.size,
+
-            marker: marker::PhantomData,
+        while elems_left != 0 {
+            debug_assert!(raw.hash != first_raw.hash);
+
+            raw = raw.offset(-1);
+
+            if *raw.hash != EMPTY_BUCKET {
+                elems_left -= 1;
+                ptr::drop_in_place(raw.pair as *mut (K, V));
+            }
         }
     }
 
@@ -964,43 +972,6 @@ impl<'a, K, V> Iterator for RawBuckets<'a, K, V> {
     }
 }
 
-/// An iterator that moves out buckets in reverse order. It leaves the table
-/// in an inconsistent state and should only be used for dropping
-/// the table's remaining entries. It's used in the implementation of Drop.
-struct RevMoveBuckets<'a, K, V> {
-    raw: RawBucket<K, V>,
-    hashes_end: *mut HashUint,
-    elems_left: usize,
-
-    // As above, `&'a (K,V)` would seem better, but we often use
-    // 'static for the lifetime, and this is not a publicly exposed
-    // type.
-    marker: marker::PhantomData<&'a ()>,
-}
-
-impl<'a, K, V> Iterator for RevMoveBuckets<'a, K, V> {
-    type Item = (K, V);
-
-    fn next(&mut self) -> Option<(K, V)> {
-        if self.elems_left == 0 {
-            return None;
-        }
-
-        loop {
-            debug_assert!(self.raw.hash != self.hashes_end);
-
-            unsafe {
-                self.raw = self.raw.offset(-1);
-
-                if *self.raw.hash != EMPTY_BUCKET {
-                    self.elems_left -= 1;
-                    return Some(ptr::read(self.raw.pair));
-                }
-            }
-        }
-    }
-}
-
 /// Iterator over shared references to entries in a table.
 pub struct Iter<'a, K: 'a, V: 'a> {
     iter: RawBuckets<'a, K, V>,
@@ -1227,7 +1198,7 @@ unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for RawTable<K, V> {
         unsafe {
             if needs_drop::<(K, V)>() {
                 // avoid linear runtime for types that don't need drop
-                for _ in self.rev_move_buckets() {}
+                self.rev_drop_buckets();
             }
         }
 

src/libstd/process.rs

@@ -437,7 +437,10 @@ impl Command {
     /// # Examples
     ///
     /// Basic usage:
+    ///
     /// ```no_run
+    /// #![feature(command_envs)]
+    ///
     /// use std::process::{Command, Stdio};
     /// use std::env;
     /// use std::collections::HashMap;

src/test/compile-fail/issue-10176.rs

@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-fn g() {
-    &panic!()
-}
-
 fn f() -> isize {
     (return 1, return 2)
+//~^ ERROR mismatched types
+//~| expected type `isize`
+//~| found type `(_, _)`
+//~| expected isize, found tuple
 }
 
 fn main() {}

src/test/compile-fail/issue-5500.rs

@@ -0,0 +1,17 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    &panic!()
+    //~^ ERROR mismatched types
+    //~| expected type `()`
+    //~| found type `&_`
+    //~| expected (), found reference
+}

src/test/run-pass/issue-15763.rs

@@ -8,8 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![allow(unused_features)]
+#![allow(unknown_features)]
-#![allow(unreachable_code)]
 #![feature(box_syntax)]
 
 #[derive(PartialEq, Debug)]
@@ -29,14 +28,14 @@ struct Foo {
 }
 
 fn foo() -> Result<Foo, isize> {
-    return Ok::<Foo, isize>(Foo {
+    return Ok(Foo {
         x: Bar { x: 22 },
         a: return Err(32)
     });
 }
 
 fn baz() -> Result<Foo, isize> {
-    Ok::<Foo, isize>(Foo {
+    Ok(Foo {
         x: Bar { x: 22 },
         a: return Err(32)
     })

src/test/run-pass/issue-39984.rs

@@ -0,0 +1,21 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Regression test for issue #39984.
+//
+// The key here is that the error type of the `Ok` call ought to be
+// constrained to `String`, even though it is dead-code.
+
+fn main() {}
+
+fn t() -> Result<(), String> {
+    return Err("".into());
+    Ok(())
+}

src/test/run-pass/project-defer-unification.rs

@@ -11,8 +11,6 @@
 // A regression test extracted from image-0.3.11. The point of
 // failure was in `index_colors` below.
 
-#![allow(unused)]
-
 use std::ops::{Deref, DerefMut};
 
 #[derive(Copy, Clone)]
@@ -94,7 +92,7 @@ pub fn index_colors<Pix>(image: &ImageBuffer<Pix, Vec<u8>>)
                          -> ImageBuffer<Luma<u8>, Vec<u8>>
 where Pix: Pixel<Subpixel=u8> + 'static,
 {
-    let mut indices: ImageBuffer<Luma<u8>, Vec<u8>> = loop { };
+    let mut indices: ImageBuffer<_,Vec<_>> = loop { };
     for (pixel, idx) in image.pixels().zip(indices.pixels_mut()) {
         // failured occurred here ^^ because we were requiring that we
         // could project Pixel or Subpixel from `T_indices` (type of