Currently, rustc uses a heuristic to determine if a range expression is
not a literal based on whether the expression looks like a function call
or struct initialization. This fails for range literals whose
lower/upper bounds are the results of function calls. A possibly-better
heuristic is to check if the expression contains `..`, required in range
literals.

Of course, this is also not perfect; for example, if the range
expression is a struct which includes some text with `..` this will
fail, but in general I believe it is a better heuristic.

A better alternative altogether is to add the `QPath::LangItem` enum
variant suggested in rust-lang#60607. I would be happy to do this as a precursor
to this patch if someone is able to provide general suggestions on how
usages of `QPath` need to be changed later in the compiler with the
`LangItem` variant.

Closes rust-lang#73553

In the following example, an inaccessible path is suggested via
`use foo::bar::X;` whereas an accessible public exported path can
be suggested instead.

```
mod foo {
    mod bar {
        pub struct X;
    }
    pub use self::bar::X;
}

fn main() { X; }
```

This fixes the issue.

…r=nikomatsakis

Remove unused crate imports in 2018 edition crates

Closes rust-lang#73570

Change heuristic for determining range literal

Currently, rustc uses a heuristic to determine if a range expression is
not a literal based on whether the expression looks like a function call
or struct initialization. This fails for range literals whose
lower/upper bounds are the results of function calls. A possibly-better
heuristic is to check if the expression contains `..`, required in range
literals.

Of course, this is also not perfect; for example, if the range
expression is a struct which includes some text with `..` this will
fail, but in general I believe it is a better heuristic.

A better alternative altogether is to add the `QPath::LangItem` enum
variant suggested in rust-lang#60607. I would be happy to do this as a precursor
to this patch if someone is able to provide general suggestions on how
usages of `QPath` need to be changed later in the compiler with the
`LangItem` variant.

Closes rust-lang#73553

Add some regression tests

Closes rust-lang#44861
Closes rust-lang#51506
Closes rust-lang#59435
Closes rust-lang#69840

…ons, r=petrochenkov

Add re-exports to use suggestions

In the following example, an inaccessible path is suggested via `use foo::bar::X;` whereas an accessible public exported path can be suggested instead.

```rust
mod foo {
    mod bar {
        pub struct X;
    }
    pub use self::bar::X;
}

fn main() { X; }
```

This fixes the issue.

Update BTreeMap::new() doc

Updates the documentation according to [this comment](https://github.com/rust-lang/rust/pull/72876/files/0c5c644c91edf6ed949cfa5ffc524f43369df604#r433232581) on rust-lang#72876

Update books

## reference

5 commits in 5d40ba5c2515caffa7790cda621239dc21ef5a72..04d5d5d7ba624b6f5016298451f3a63d557f3260
2020-06-06 20:25:36 -0700 to 2020-06-16 15:08:05 -0700
- Mention `feature="foo"` is a Cargo convention. (rust-lang/reference#833)
- fix out of date info on type aliases (rust-lang/reference#831)
- Fix an invalid variable name in the loop example (rust-lang/reference#832)
- Fix note about using proc_macro with Cargo. (rust-lang/reference#815)
- Add a link to the definition of Pattern_White_Space. (rust-lang/reference#824)

## book

7 commits in 30cd9dfe71c446de63826bb4472627af45acc9db..4e7c00bece1544d409312ec93467beb62b5bd0cb
2020-06-07 23:07:19 -0500 to 2020-06-19 09:39:12 -0400
- Link to the reference file that exists
- Link to the reference
- Clean up discussion around advanced lifetime stuff (rust-lang/book#2351)
- Reword Chapter 6 page 2, match (rust-lang/book#2374)
- Clarify some package/crate distinctions in chapter 14 (rust-lang/book#2373)
- Not mandatory with cargo 1.41.0-nightly (rust-lang/book#2368)
- Use same naming for Rhs as libcore/ops (rust-lang/book#2371)

## rust-by-example

4 commits in 7aa82129aa23e7e181efbeb8da03a2a897ef6afc..6f94ccb48da6fa4ed0031290f21411cf789f7d5e
2020-05-25 14:54:26 -0300 to 2020-06-20 17:51:30 -0300
- Update to mdbook 0.3.7 (rust-lang/rust-by-example#1352)
- Update fn.md (rust-lang/rust-by-example#1351)
- Fixed typo in formatted print (rust-lang/rust-by-example#1350)
- This explanation incorrectly inverts the meaning of SuperTrait (rust-lang/rust-by-example#1349)

## embedded-book

5 commits in 5555a97f04ad7974ac6fb8fb47c267c4274adf4a..616962ad0dd80f34d8b802da038d0aed9dd691bb
2020-05-25 18:00:51 +0000 to 2020-06-23 16:03:45 +0000
- Update RTFM name to RTIC, fixed links, updated singletons.md example.  (rust-embedded/book#254)
- Note on how to rebuild if memory.x is changed  (rust-embedded/book#253)
- Ease the readers into the Discovery book  (rust-embedded/book#250)
- Provide a note on 'extern crate' usage in edition 2018 syntax of Rust  (rust-embedded/book#248)
- Fix Typos and Improve Readability  (rust-embedded/book#245)