Rollup of 7 pull requests

Successful merges:

 - #70998 (Suggest `-> impl Trait` and `-> Box<dyn Trait>` on fn that doesn't return)
 - #71236 (Remove unused rustc_serialize::hex module)
 - #71366 (Use assoc int consts3)
 - #71372 (Fix #! (shebang) stripping account space issue)
 - #71384 (Fix stage0.txt version number comment)
 - #71390 (Fix incorrect description of E0690)
 - #71399 (Clean up E0554 explanation)

Failed merges:

r? @ghost

Clean up E0554 explanation

r? @Dylan-DPC

Fix incorrect description of E0690

r? @steveklabnik

Fix stage0.txt version number comment

r? @Mark-Simulacrum

Fix #! (shebang) stripping account space issue

 #70528

Use assoc int consts3

Define module level int consts with associated constants instead of `min_value()` and `max_value()`. So the code become consistent with what the docs recommend etc. Seems natural.

Also remove the last usages of the int module constants from this repo (except src/test/ directory which I have still not really done anything in). Some places were missed in the previous PRs because the code uses `crate::<IntTy>` to reach the constants.

This is a continuation of #70857

r? @dtolnay

Remove unused rustc_serialize::hex module

* Remove unused `rustc_serialize::hex` module
* Cleanup `Cargo.toml`

Suggest `-> impl Trait` and `-> Box<dyn Trait>` on fn that doesn't return

During development, a function could have a return type set that is a
bare trait object by accident. We already suggest using either a boxed
trait object or `impl Trait` if the return paths will allow it. We now
do so too when there are *no* return paths or they all resolve to `!`.
We still don't handle cases where the trait object is *not* the entirety
of the return type gracefully.

Closes #38376.

Update cargo, rls

## cargo

17 commits in ebda5065ee8a1e46801380abcbac21a25bc7e755..8751eb3010d4cdb5329b5a6bd2b6d765c95b0dca
2020-04-16 14:28:43 +0000 to 2020-04-21 18:04:35 +0000
- Uplift windows gnu DLL import libraries. (rust-lang/cargo#8141)
- Add windows-gnu CI and fix tests (rust-lang/cargo#8139)
- Several updates to token/index handling. (rust-lang/cargo#7973)
- Add `resolver` opt-in for new feature resolver. (rust-lang/cargo#8129)
- Improve error message when running `cargo install .` (rust-lang/cargo#8137)
- fix mem replace unused (rust-lang/cargo#8138)
- Change `-Cembed-bitcode=no` use to `-Cbitcode-in-rlib=no`. (rust-lang/cargo#8134)
- Refactor BuildContext (rust-lang/cargo#8068)
- Rename allows_underscores to allows_dashes. (rust-lang/cargo#8135)
- Fixed a needless borrow. (rust-lang/cargo#8130)
- Add link to changelog in the Cargo book. (rust-lang/cargo#8126)
- Fix target for doc test cross compilation (rust-lang/cargo#8094)
- Add note about .cargo/config support. (rust-lang/cargo#8125)
- Fix pdb uplift when executable has dashes. (rust-lang/cargo#8123)
- Hint upgrading for future edition keys (rust-lang/cargo#8122)
- Use some fs shorthand functions. (rust-lang/cargo#8124)
- Update documentation to mention "config.toml" instead of "config" (rust-lang/cargo#8121)

## rls

1 commits in 2659cbf14bfb0929a16d7ce9b6858d0bb286ede7..7de2a1f299f8744ffe109139f9f1fdf28bfec909
2020-04-14 22:07:24 +0200 to 2020-04-19 22:41:55 +0000
- Update cargo (rust-lang-nursery/rls#1663)

Make Box<dyn FnOnce> respect self alignment

Closes #68304

r? @EddyB @nikomatsakis

attempt to recover perf by removing `exports_all_green`

attempt to recover perf by removing `exports_all_green` flag.

cc #71248

(My hypothesis is that my use of this flag was an overly conservative generalization of PR #67020.)

Rollup of 4 pull requests

Successful merges:

 - #69362 (Stabilize most common subset of alloc_layout_extras)
 - #71174 (Check that main/start is not async)
 - #71285 (MIR: use HirId instead of NodeId to avoid cycles while inlining)
 - #71346 (Do not build tools if user do not want them)

Failed merges:

r? @ghost

Do not build tools if user do not want them

Fixes https://github.com/rust-lang/rust/issues/71307

MIR: use HirId instead of NodeId to avoid cycles while inlining

I wanted to see if I could limit the number of uses of `NodeId` when `HirId` is available and I saw that some of the MIR `Inliner` code could use `Span` instead of `NodeId`, not unlike in https://github.com/rust-lang/rust/pull/71197.

~If I'm understanding the reason for not calling `optimized_mir` in incremental builds here correctly, this change could also allow us to do so.~

This change could affect performance, so if this approach makes sense, a perf run is probably a good idea.

Check that main/start is not async

* Add new error code E0752
* Add span to hir::IsAsync::Yes
* Emit an error if main or the start function is marked as async
* Add two regression tests

This PR fixes #68523.

Stabilize most common subset of alloc_layout_extras

Tracking issue: https://github.com/rust-lang/rust/issues/55724

Specifically, this stabilizes:

```rust
pub fn Layout::align_to(&self, align: usize) -> Result<Layout, LayoutErr>;
pub fn Layout::pad_to_align(&self) -> Layout;
pub fn Layout::extend(&self, next: Layout) -> Result<(Layout, usize), LayoutErr>;
pub fn Layout::array<T>(n: usize) -> Result<Layout, LayoutErr>;
```

Methods that are tracked by #55724 but are not stabilized here:

```rust
pub fn Layout::padding_needed_for(&self, align: usize) -> usize;
pub fn Layout::repeat(&self, n: usize) -> Result<(Layout, usize), LayoutErr>;
pub fn Layout::repeat_packed(&self, n: usize) -> Result<Layout, LayoutErr>;
pub fn Layout::extend_packed(&self, next: Layout) -> Result<Layout, LayoutErr>;
```

Combined, these stabilized functions allow code to construct and manipulate `repr(C)` layouts while letting the standard library handle correctness in the face of edge cases. For example use cases, consider the usage in [hashbrown](https://github.com/Amanieu/hashbrown/blob/2f2af1d/src/raw/mod.rs#L143), [crossbeam-skiplist](https://github.com/crossbeam-rs/crossbeam-skiplist/blob/master/src/base.rs#L99), [pointer-utils/slice-dst](https://github.com/CAD97/pointer-utils/blob/92aeefeed9399f28d1b1654b63f8dcbe1242d8d4/crates/slice-dst/src/layout_polyfill.rs), and of course the standard library itself.

Providing a higher-level API such as `Layout::repr_c<const N: usize>(fields: [Layout; N]) -> Result<(Layout, [usize; N]), LayoutErr>` is blocked on const generics, which are a ways off. Providing an API that doesn't provide offsets would be quite suboptimal, as the reason for calculating the layout like this rather than `Layout::new` is to get the field offsets.

The primary issue with the current API is having to call `.pad_to_align()` to match the layout of a `repr(C)` struct. However, I think this is not just a (failing? limitation?) of the API, but rather intrinsic complexity. While all Rust-defined types have size==stride, and probably will for the foreseeable future, there is no inherent reason why this is a limitation of all allocations. As such, the `Layout` manipulation APIs shouldn't impose this limitation, and instead the higher level api of `repr_c` (or just plain old using `Layout::new`) can make keeping it simple.

cc @matklad r? @rust-lang/libs

Rollup of 5 pull requests

Successful merges:

 - #71250 (Replace big JS dict with JSON parsing)
 - #71270 (Fix `has_no_input_arg` check and rename it to `has_only_self_parameter`)
 - #71284 (fix -Zast-json to output correct JSON form)
 - #71328 (Stabilize PathBuf capacity methods)
 - #71334 (Update pattern docs.)

Failed merges:

r? @ghost

When the return type is `!Sized` we look for all the returned
expressions in the body to fetch their types and provide a reasonable
suggestion. The tail expression of the body is normally evaluated after
checking whether the return type is `Sized`. Changing the order of the
evaluation produces undesirable knock down effects, so we detect the
specific case that newcomers are likely to encounter ,returning a single
bare trait object, and only in that case we evaluate the tail
expression's type so that the suggestion will be accurate.

Co-Authored-By: NAmanieu d'Antras <amanieu@gmail.com>

During development, a function could have a return type set that is a
bare trait object by accident. We already suggest using either a boxed
trait object or `impl Trait` if the return paths will allow it. We now
do so too when there are *no* return paths or they all resolve to `!`.
We still don't handle cases where the trait object is *not* the entirety
of the return type gracefully.

Update pattern docs.

A few changes to help clarify string pattern usage:

* Add some examples and stability information in the `pattern` module.
* Fixes the links at https://doc.rust-lang.org/std/str/pattern/ because intra-doc-links don't work with re-exported modules (#65983 I think?).
* Consistently use the same phrasing for `str` methods taking a pattern.
    * Also mention that array of `char` is also accepted.

When `Pattern` is stabilized, the phrasing in the `str` methods can be updated to be more general to reflect the exact behavior. I'm reluctant to do this now because the stability story for `Pattern` is uncertain. It may perhaps look something like:

> The pattern can be any type that implements the [`Pattern`] trait. Notable examples are `&str`, [`char`], arrays of [`char`], or functions or closures that determines if a character matches. Additional libraries might provide more complex patterns like regular expressions.

This is complicated because methods like `trim_matches` have bounds, which for example don't support `str`, so those methods may need more elaboration.

Stabilize PathBuf capacity methods

Closes https://github.com/rust-lang/rust/issues/58234.

Stabilization FCP finished in https://github.com/rust-lang/rust/issues/58234#issuecomment-616048777.

fix -Zast-json to output correct JSON form

fixes #71086 (Reverts some of the changes made in #70215)

JSON output (from an empty library) after fix has something for **"id"** field
```shell
lonelyjoe@lonelyjoe-desktop:~/workspace/empty_lib/src$ rustc lib.rs -Zast-json
```
```json
{
   "module":{
      "inner":{
         "lo":0,
         "hi":94
      },
      "items":[
         {
            "attrs":[
               {
                  "kind":{
                     "variant":"Normal",
                     "fields":[
                        {
                           "path":{
                              "span":{
                                 "lo":0,
                                 "hi":0
                              },
                              "segments":[
                                 {
                                    "ident":{
                                       "name":"prelude_import",
                                       "span":{
                                          "lo":0,
                                          "hi":0
                                       }
                                    },
                                    "id":3,
                                    "args":null
                                 }
                              ]
                           },
                           "args":"Empty"
                        }
                     ]
                  },
                  "id":null,
                  "style":"Outer",
                  "span":{
                     "lo":0,
                     "hi":0
                  }
               }
            ],
            "id":4,
            "span":{
               "lo":0,
               "hi":0
            },
            "vis":{
               "node":"Inherited",
               "span":{
                  "lo":0,
                  "hi":0
               }
            },
            "ident":{
               "name":"",
               "span":{
                  "lo":0,
                  "hi":0
               }
            },
            "kind":{
               "variant":"Use",
               "fields":[
                  {
                     "prefix":{
                        "span":{
                           "lo":0,
                           "hi":0
                        },
                        "segments":[
                           {
                              "ident":{
                                 "name":"{{root}}",
                                 "span":{
                                    "lo":0,
                                    "hi":0
                                 }
                              },
                              "id":5,
                              "args":null
                           },
                           {
                              "ident":{
                                 "name":"std",
                                 "span":{
                                    "lo":0,
                                    "hi":0
                                 }
                              },
                              "id":6,
                              "args":null
                           },
                           {
                              "ident":{
                                 "name":"prelude",
                                 "span":{
                                    "lo":0,
                                    "hi":0
                                 }
                              },
                              "id":7,
                              "args":null
                           },
                           {
                              "ident":{
                                 "name":"v1",
                                 "span":{
                                    "lo":0,
                                    "hi":0
                                 }
                              },
                              "id":8,
                              "args":null
                           }
                        ]
                     },
                     "kind":"Glob",
                     "span":{
                        "lo":0,
                        "hi":0
                     }
                  }
               ]
            },
            "tokens":null
         },
         {
            "attrs":[
               {
                  "kind":{
                     "variant":"Normal",
                     "fields":[
                        {
                           "path":{
                              "span":{
                                 "lo":0,
                                 "hi":0
                              },
                              "segments":[
                                 {
                                    "ident":{
                                       "name":"macro_use",
                                       "span":{
                                          "lo":0,
                                          "hi":0
                                       }
                                    },
                                    "id":9,
                                    "args":null
                                 }
                              ]
                           },
                           "args":"Empty"
                        }
                     ]
                  },
                  "id":null,
                  "style":"Outer",
                  "span":{
                     "lo":0,
                     "hi":0
                  }
               }
            ],
            "id":10,
            "span":{
               "lo":0,
               "hi":0
            },
            "vis":{
               "node":"Inherited",
               "span":{
                  "lo":0,
                  "hi":0
               }
            },
            "ident":{
               "name":"std",
               "span":{
                  "lo":0,
                  "hi":0
               }
            },
            "kind":{
               "variant":"ExternCrate",
               "fields":[
                  null
               ]
            },
            "tokens":null
         }
      ],
      "inline":true
   },
   "attrs":[

   ],
   "span":{
      "lo":0,
      "hi":94
   },
   "proc_macros":[

   ]
}
```

Fix `has_no_input_arg` check and rename it to `has_only_self_parameter`
Signed-off-by: NRustin-Liu <rustin.liu@gmail.com>

Fixes https://github.com/rust-lang/rust/pull/70643#discussion_r401571789.

Replace big JS dict with JSON parsing

Part of #56545.

@ollie27 suggested that using JSON instead of a JS dict might be faster, so I decided to test it. And the results far exceeded whatever expectations I had...

I used https://github.com/adamgreig/stm32ral for my tests. If you want to build it locally:

```bash
$ cargo doc --features doc --open
```

But I strongly recommend to do it with this PR. Some numbers:

 * Loading a page with the JSON search-index: less than 1 second
 * Loading a page with the JS search-index: crashed after 30 seconds

I think the results are clear enough...

r? @ollie27

cc @rust-lang/rustdoc