Auto merge of #53662 - kennytm:rollup, r=kennytm

Rollup of 16 pull requests

Successful merges:

 - #53311 (Window Mutex: Document that we properly initialize the SRWLock)
 - #53503 (Discourage overuse of mem::forget)
 - #53545 (Fix #50865: ICE on impl-trait returning functions reaching private items)
 - #53559 (add macro check for lint)
 - #53562 (Lament the invincibility of the Turbofish)
 - #53563 (use String::new() instead of String::from(""), "".to_string(), "".to_owned() or "".into())
 - #53592 (docs: minor stylistic changes to str/string docs)
 - #53594 (Update RELEASES.md to include clippy-preview)
 - #53600 (Fix a grammatical mistake in "expected generic arguments" errors)
 - #53614 (update nomicon and book)
 - #53617 (tidy: Stop requiring a license header)
 - #53618 (Add missing fmt examples)
 - #53636 (Prefer `.nth(n)` over `.skip(n).next()`.)
 - #53644 (Use SmallVec for SmallCStr)
 - #53664 (Remove unnecessary closure in rustc_mir/build/mod.rs)
 - #53666 (Added rustc_codegen_llvm to compiler documentation.)

src/test/run-pass-fulldeps/auxiliary/proc_macro_def.rs

@@ -19,7 +19,7 @@ use proc_macro::*;
 
 #[proc_macro_attribute]
 pub fn attr_tru(_attr: TokenStream, item: TokenStream) -> TokenStream {
-    let name = item.into_iter().skip(1).next().unwrap();
+    let name = item.into_iter().nth(1).unwrap();
     quote!(fn $name() -> bool { true })
 }
 

src/test/run-pass/command-before-exec.rs

@@ -24,7 +24,7 @@ use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
 fn main() {
-    if let Some(arg) = env::args().skip(1).next() {
+    if let Some(arg) = env::args().nth(1) {
         match &arg[..] {
             "test1" => println!("hello2"),
             "test2" => assert_eq!(env::var("FOO").unwrap(), "BAR"),

src/test/run-pass/issue-50865-private-impl-trait/auxiliary/lib.rs

@@ -0,0 +1,24 @@
+// Copyright 2018 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.
+
+#![crate_type = "lib"]
+
+pub fn bar<P>( // Error won't happen if "bar" is not generic
+    _baz: P,
+) {
+    hide_foo()();
+}
+
+fn hide_foo() -> impl Fn() { // Error won't happen if "iterate" hasn't impl Trait or has generics
+    foo
+}
+
+fn foo() { // Error won't happen if "foo" isn't used in "iterate" or has generics
+}

src/test/run-pass/issue-50865-private-impl-trait/main.rs

@@ -0,0 +1,25 @@
+// Copyright 2018 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.
+
+// aux-build:lib.rs
+
+// Regression test for #50865.
+// When using generics or specifying the type directly, this example
+// codegens `foo` internally. However, when using a private `impl Trait`
+// function which references another private item, `foo` (in this case)
+// wouldn't be codegenned until main.rs used `bar`, as with impl Trait
+// it is not cast to `fn()` automatically to satisfy e.g.
+// `fn foo() -> fn() { ... }`.
+
+extern crate lib;
+
+fn main() {
+    lib::bar(()); // Error won't happen if bar is called from same crate
+}

src/test/ui/bastion-of-the-turbofish.rs

@@ -36,6 +36,10 @@
 // My heart aches in sorrow, for I know I am defeated. Let this be a warning
 // to all those who come after. Here stands the bastion of the Turbofish.
 
+// See https://github.com/rust-lang/rust/pull/53562
+// and https://github.com/rust-lang/rfcs/pull/2527
+// for context.
+
 fn main() {
     let (oh, woe, is, me) = ("the", "Turbofish", "remains", "undefeated");
     let _: (bool, bool) = (oh<woe, is>(me));

src/test/ui/generic/generic-impl-more-params-with-defaults.stderr

@@ -2,7 +2,7 @@ error[E0244]: wrong number of type arguments: expected at most 2, found 3
   --> $DIR/generic-impl-more-params-with-defaults.rs:23:5
    |
 LL |     Vec::<isize, Heap, bool>::new();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected at most 2 type argument
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected at most 2 type arguments
 
 error: aborting due to previous error
 

src/test/ui/generic/generic-type-more-params-with-defaults.stderr

@@ -2,7 +2,7 @@ error[E0244]: wrong number of type arguments: expected at most 2, found 3
   --> $DIR/generic-type-more-params-with-defaults.rs:19:12
    |
 LL |     let _: Vec<isize, Heap, bool>;
-   |            ^^^^^^^^^^^^^^^^^^^^^^ expected at most 2 type argument
+   |            ^^^^^^^^^^^^^^^^^^^^^^ expected at most 2 type arguments
 
 error: aborting due to previous error
 

src/test/ui/lint/lints-in-foreign-macros.rs

@@ -11,7 +11,8 @@
 // aux-build:lints-in-foreign-macros.rs
 // compile-pass
 
-#![warn(unused_imports)]
+#![warn(unused_imports)] //~ missing documentation for crate [missing_docs]
+#![warn(missing_docs)]
 
 #[macro_use]
 extern crate lints_in_foreign_macros;
@@ -24,5 +25,7 @@ mod a { foo!(); }
 mod b { bar!(); }
 mod c { baz!(use std::string::ToString;); } //~ WARN: unused import
 mod d { baz2!(use std::string::ToString;); } //~ WARN: unused import
+baz!(pub fn undocumented() {}); //~ WARN: missing documentation for a function
+baz2!(pub fn undocumented2() {}); //~ WARN: missing documentation for a function
 
 fn main() {}

src/test/ui/lint/lints-in-foreign-macros.stderr

@@ -1,5 +1,5 @@
 warning: unused import: `std::string::ToString`
-  --> $DIR/lints-in-foreign-macros.rs:20:16
+  --> $DIR/lints-in-foreign-macros.rs:21:16
    |
 LL |     () => {use std::string::ToString;} //~ WARN: unused import
    |                ^^^^^^^^^^^^^^^^^^^^^
@@ -10,18 +10,48 @@ LL | mod a { foo!(); }
 note: lint level defined here
   --> $DIR/lints-in-foreign-macros.rs:14:9
    |
-LL | #![warn(unused_imports)]
+LL | #![warn(unused_imports)] //~ missing documentation for crate [missing_docs]
    |         ^^^^^^^^^^^^^^
 
 warning: unused import: `std::string::ToString`
-  --> $DIR/lints-in-foreign-macros.rs:25:18
+  --> $DIR/lints-in-foreign-macros.rs:26:18
    |
 LL | mod c { baz!(use std::string::ToString;); } //~ WARN: unused import
    |                  ^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused import: `std::string::ToString`
-  --> $DIR/lints-in-foreign-macros.rs:26:19
+  --> $DIR/lints-in-foreign-macros.rs:27:19
    |
 LL | mod d { baz2!(use std::string::ToString;); } //~ WARN: unused import
    |                   ^^^^^^^^^^^^^^^^^^^^^
 
+warning: missing documentation for crate
+  --> $DIR/lints-in-foreign-macros.rs:14:1
+   |
+LL | / #![warn(unused_imports)] //~ missing documentation for crate [missing_docs]
+LL | | #![warn(missing_docs)]
+LL | |
+LL | | #[macro_use]
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+   |
+note: lint level defined here
+  --> $DIR/lints-in-foreign-macros.rs:15:9
+   |
+LL | #![warn(missing_docs)]
+   |         ^^^^^^^^^^^^
+
+warning: missing documentation for a function
+  --> $DIR/lints-in-foreign-macros.rs:28:6
+   |
+LL | baz!(pub fn undocumented() {}); //~ WARN: missing documentation for a function
+   |      ^^^^^^^^^^^^^^^^^^^^^
+
+warning: missing documentation for a function
+  --> $DIR/lints-in-foreign-macros.rs:29:7
+   |
+LL | baz2!(pub fn undocumented2() {}); //~ WARN: missing documentation for a function
+   |       ^^^^^^^^^^^^^^^^^^^^^^
+