Auto merge of #40440 - arielb1:rollup, r=arielb1

Rollup of 13 pull requests

- Successful merges: #40146, #40299, #40315, #40319, #40344, #40345, #40367, #40372, #40373, #40385, #40400, #40404, #40431
- Failed merges:

Author: bors

src/libcore/fmt/mod.rs

@@ -529,6 +529,26 @@ pub trait Debug {
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait Display {
     /// Formats the value using the given formatter.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::fmt;
+    ///
+    /// struct Position {
+    ///     longitude: f32,
+    ///     latitude: f32,
+    /// }
+    ///
+    /// impl fmt::Display for Position {
+    ///     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    ///         write!(f, "({}, {})", self.longitude, self.latitude)
+    ///     }
+    /// }
+    ///
+    /// assert_eq!("(1.987, 2.983)".to_owned(),
+    ///            format!("{}", Position { longitude: 1.987, latitude: 2.983, }));
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     fn fmt(&self, f: &mut Formatter) -> Result;
 }
@@ -930,7 +950,6 @@ pub fn write(output: &mut Write, args: Arguments) -> Result {
 }
 
 impl<'a> Formatter<'a> {
-
     // First up is the collection of functions used to execute a format string
     // at runtime. This consumes all of the compile-time statics generated by
     // the format! syntax extension.

src/librustc/infer/README.md

@@ -152,7 +152,7 @@ course, it depends on the program.
 
 The main case which fails today that I would like to support is:
 
-```text
+```rust
 fn foo<T>(x: T, y: T) { ... }
 
 fn bar() {
@@ -168,6 +168,8 @@ because the type variable `T` is merged with the type variable for
 `X`, and thus inherits its UB/LB of `@mut int`.  This leaves no
 flexibility for `T` to later adjust to accommodate `@int`.
 
+Note: `@` and `@mut` are replaced with `Rc<T>` and `Rc<RefCell<T>>` in current Rust.
+
 ### What to do when not all bounds are present
 
 In the prior discussion we assumed that A.ub was not top and B.lb was

src/librustc/infer/region_inference/README.md

@@ -121,17 +121,19 @@ every expression, block, and pattern (patterns are considered to
 "execute" by testing the value they are applied to and creating any
 relevant bindings).  So, for example:
 
-    fn foo(x: isize, y: isize) { // -+
-    //  +------------+       //  |
-    //  |      +-----+       //  |
-    //  |  +-+ +-+ +-+       //  |
-    //  |  | | | | | |       //  |
-    //  v  v v v v v v       //  |
-        let z = x + y;       //  |
-        ...                  //  |
-    }                        // -+
-
-    fn bar() { ... }
+```rust
+fn foo(x: isize, y: isize) { // -+
+//  +------------+           //  |
+//  |      +-----+           //  |
+//  |  +-+ +-+ +-+           //  |
+//  |  | | | | | |           //  |
+//  v  v v v v v v           //  |
+    let z = x + y;           //  |
+    ...                      //  |
+}                            // -+
+
+fn bar() { ... }
+```
 
 In this example, there is a region for the fn body block as a whole,
 and then a subregion for the declaration of the local variable.
@@ -160,28 +162,32 @@ this, we get a lot of spurious errors around nested calls, in
 particular when combined with `&mut` functions. For example, a call
 like this one
 
-    self.foo(self.bar())
+```rust
+self.foo(self.bar())
+```
 
 where both `foo` and `bar` are `&mut self` functions will always yield
 an error.
 
 Here is a more involved example (which is safe) so we can see what's
 going on:
 
-    struct Foo { f: usize, g: usize }
-    ...
-    fn add(p: &mut usize, v: usize) {
-        *p += v;
-    }
-    ...
-    fn inc(p: &mut usize) -> usize {
-        *p += 1; *p
-    }
-    fn weird() {
-        let mut x: Box<Foo> = box Foo { ... };
-        'a: add(&mut (*x).f,
-                'b: inc(&mut (*x).f)) // (..)
-    }
+```rust
+struct Foo { f: usize, g: usize }
+// ...
+fn add(p: &mut usize, v: usize) {
+    *p += v;
+}
+// ...
+fn inc(p: &mut usize) -> usize {
+    *p += 1; *p
+}
+fn weird() {
+    let mut x: Box<Foo> = box Foo { /* ... */ };
+    'a: add(&mut (*x).f,
+            'b: inc(&mut (*x).f)) // (..)
+}
+```
 
 The important part is the line marked `(..)` which contains a call to
 `add()`. The first argument is a mutable borrow of the field `f`.  The
@@ -197,16 +203,18 @@ can see that this error is unnecessary. Let's examine the lifetimes
 involved with `'a` in detail. We'll break apart all the steps involved
 in a call expression:
 
-    'a: {
-        'a_arg1: let a_temp1: ... = add;
-        'a_arg2: let a_temp2: &'a mut usize = &'a mut (*x).f;
-        'a_arg3: let a_temp3: usize = {
-            let b_temp1: ... = inc;
-            let b_temp2: &'b = &'b mut (*x).f;
-            'b_call: b_temp1(b_temp2)
-        };
-        'a_call: a_temp1(a_temp2, a_temp3) // (**)
-    }
+```rust
+'a: {
+    'a_arg1: let a_temp1: ... = add;
+    'a_arg2: let a_temp2: &'a mut usize = &'a mut (*x).f;
+    'a_arg3: let a_temp3: usize = {
+        let b_temp1: ... = inc;
+        let b_temp2: &'b = &'b mut (*x).f;
+        'b_call: b_temp1(b_temp2)
+    };
+    'a_call: a_temp1(a_temp2, a_temp3) // (**)
+}
+```
 
 Here we see that the lifetime `'a` includes a number of substatements.
 In particular, there is this lifetime I've called `'a_call` that
@@ -225,19 +233,21 @@ it will not be *dereferenced* during the evaluation of the second
 argument, it can still be *invalidated* by that evaluation. Consider
 this similar but unsound example:
 
-    struct Foo { f: usize, g: usize }
-    ...
-    fn add(p: &mut usize, v: usize) {
-        *p += v;
-    }
-    ...
-    fn consume(x: Box<Foo>) -> usize {
-        x.f + x.g
-    }
-    fn weird() {
-        let mut x: Box<Foo> = box Foo { ... };
-        'a: add(&mut (*x).f, consume(x)) // (..)
-    }
+```rust
+struct Foo { f: usize, g: usize }
+// ...
+fn add(p: &mut usize, v: usize) {
+    *p += v;
+}
+// ...
+fn consume(x: Box<Foo>) -> usize {
+    x.f + x.g
+}
+fn weird() {
+    let mut x: Box<Foo> = box Foo { ... };
+    'a: add(&mut (*x).f, consume(x)) // (..)
+}
+```
 
 In this case, the second argument to `add` actually consumes `x`, thus
 invalidating the first argument.

src/librustc/infer/region_inference/graphviz.rs

@@ -91,7 +91,7 @@ pub fn maybe_print_constraints_for<'a, 'gcx, 'tcx>(
         };
 
         if output_template.is_empty() {
-            bug!("empty string provided as RUST_REGION_GRAPH");
+            panic!("empty string provided as RUST_REGION_GRAPH");
         }
 
         if output_template.contains('%') {

src/librustc/lint/context.rs

@@ -806,6 +806,12 @@ impl<'a, 'tcx> hir_visit::Visitor<'tcx> for LateContext<'a, 'tcx> {
         self.tables = old_tables;
     }
 
+    fn visit_body(&mut self, body: &'tcx hir::Body) {
+        run_lints!(self, check_body, late_passes, body);
+        hir_visit::walk_body(self, body);
+        run_lints!(self, check_body_post, late_passes, body);
+    }
+
     fn visit_item(&mut self, it: &'tcx hir::Item) {
         self.with_lint_attrs(&it.attrs, |cx| {
             run_lints!(cx, check_item, late_passes, it);

src/librustc/lint/mod.rs

@@ -133,6 +133,8 @@ pub trait LintPass {
 // FIXME: eliminate the duplication with `Visitor`. But this also
 // contains a few lint-specific methods with no equivalent in `Visitor`.
 pub trait LateLintPass<'a, 'tcx>: LintPass {
+    fn check_body(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
+    fn check_body_post(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
     fn check_name(&mut self, _: &LateContext, _: Span, _: ast::Name) { }
     fn check_crate(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }
     fn check_crate_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }

src/librustc/traits/error_reporting.rs

@@ -23,24 +23,26 @@ use super::{
     ObjectSafetyViolation,
 };
 
+use errors::DiagnosticBuilder;
 use fmt_macros::{Parser, Piece, Position};
+use hir::{intravisit, Local, Pat};
+use hir::intravisit::{Visitor, NestedVisitorMap};
+use hir::map::NodeExpr;
 use hir::def_id::DefId;
 use infer::{self, InferCtxt};
 use infer::type_variable::TypeVariableOrigin;
 use rustc::lint::builtin::EXTRA_REQUIREMENT_IN_IMPL;
+use std::fmt;
+use syntax::ast;
 use ty::{self, AdtKind, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
 use ty::error::ExpectedFound;
 use ty::fast_reject;
 use ty::fold::TypeFolder;
 use ty::subst::Subst;
 use util::nodemap::{FxHashMap, FxHashSet};
 
-use std::fmt;
-use syntax::ast;
-use hir::{intravisit, Local, Pat};
-use hir::intravisit::{Visitor, NestedVisitorMap};
 use syntax_pos::{DUMMY_SP, Span};
-use errors::DiagnosticBuilder;
+
 
 #[derive(Debug, PartialEq, Eq, Hash)]
 pub struct TraitErrorKey<'tcx> {
@@ -848,15 +850,18 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
         err.span_label(cause.span, &format!("cannot infer type for `{}`", name));
 
-        let expr = self.tcx.hir.expect_expr(cause.body_id);
-
         let mut local_visitor = FindLocalByTypeVisitor {
             infcx: &self,
             target_ty: &ty,
             found_pattern: None,
         };
 
-        local_visitor.visit_expr(expr);
+        // #40294: cause.body_id can also be a fn declaration.
+        // Currently, if it's anything other than NodeExpr, we just ignore it
+        match self.tcx.hir.find(cause.body_id) {
+            Some(NodeExpr(expr)) => local_visitor.visit_expr(expr),
+            _ => ()
+        }
 
         if let Some(pattern) = local_visitor.found_pattern {
             let pattern_span = pattern.span;

src/librustc/traits/select.rs

@@ -2461,7 +2461,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 let new_trait = tcx.mk_dynamic(
                     ty::Binder(tcx.mk_existential_predicates(iter)), r_b);
                 let InferOk { obligations, .. } =
-                    self.infcx.sub_types(false, &obligation.cause, new_trait, target)
+                    self.infcx.eq_types(false, &obligation.cause, new_trait, target)
                     .map_err(|_| Unimplemented)?;
                 self.inferred_obligations.extend(obligations);
 
@@ -2520,7 +2520,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             // [T; n] -> [T].
             (&ty::TyArray(a, _), &ty::TySlice(b)) => {
                 let InferOk { obligations, .. } =
-                    self.infcx.sub_types(false, &obligation.cause, a, b)
+                    self.infcx.eq_types(false, &obligation.cause, a, b)
                     .map_err(|_| Unimplemented)?;
                 self.inferred_obligations.extend(obligations);
             }
@@ -2583,7 +2583,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 });
                 let new_struct = tcx.mk_adt(def, tcx.mk_substs(params));
                 let InferOk { obligations, .. } =
-                    self.infcx.sub_types(false, &obligation.cause, new_struct, target)
+                    self.infcx.eq_types(false, &obligation.cause, new_struct, target)
                     .map_err(|_| Unimplemented)?;
                 self.inferred_obligations.extend(obligations);
 

src/librustc_driver/target_features.rs

@@ -25,7 +25,7 @@ const ARM_WHITELIST: &'static [&'static str] = &["neon\0", "vfp2\0", "vfp3\0", "
 const X86_WHITELIST: &'static [&'static str] = &["avx\0", "avx2\0", "bmi\0", "bmi2\0", "sse\0",
                                                  "sse2\0", "sse3\0", "sse4.1\0", "sse4.2\0",
                                                  "ssse3\0", "tbm\0", "lzcnt\0", "popcnt\0",
-                                                 "sse4a\0", "rdrnd\0", "rdseed\0"];
+                                                 "sse4a\0", "rdrnd\0", "rdseed\0", "fma\0"];
 
 /// Add `target_feature = "..."` cfgs for a variety of platform
 /// specific features (SSE, NEON etc.).

src/librustc_mir/build/expr/as_temp.rs

@@ -55,7 +55,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 (https://github.com/rust-lang/rust/issues/39283)");
         }
 
-        if temp_lifetime.is_some() {
+        if !expr_ty.is_never() && temp_lifetime.is_some() {
             this.cfg.push(block, Statement {
                 source_info: source_info,
                 kind: StatementKind::StorageLive(temp.clone())