Auto merge of #51969 - pietroalbini:rollup, r=pietroalbini

Rollup of 7 pull requests

Successful merges:

 - #51511 (Stabilize Iterator::flatten in 1.29, fixes #48213.)
 - #51853 (Fix some doc links)
 - #51890 (Fix inconsequential typo in GlobalAlloc doc example)
 - #51920 (use literal span for concrete type suggestion)
 - #51921 (improve the error message when `#[panic_implementation]` is missing)
 - #51922 (rename the llvm-tools component to llvm-tools-preview and tweak its image)
 - #51961 (Fix typo in /src/librustc_resolve/lib.rs)

Failed merges:

r? @ghost

src/test/compile-fail/panic-implementation-missing.rs

@@ -0,0 +1,18 @@
+// 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.
+
+// error-pattern: `#[panic_implementation]` function required, but not found
+
+#![feature(lang_items)]
+#![no_main]
+#![no_std]
+
+#[lang = "eh_personality"]
+fn eh() {}

src/test/compile-fail/weak-lang-item.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // aux-build:weak-lang-items.rs
-// error-pattern: language item required, but not found: `panic_impl`
+// error-pattern: `#[panic_implementation]` function required, but not found
 // error-pattern: language item required, but not found: `eh_personality`
 // ignore-wasm32-bare compiled with panic=abort, personality not required
 

src/test/ui/issue-51874.rs

@@ -0,0 +1,13 @@
+// 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.
+
+fn main() {
+    let a = (1.0).pow(1.0); //~ ERROR can't call method `pow` on ambiguous numeric type
+}

src/test/ui/issue-51874.stderr

@@ -0,0 +1,13 @@
+error[E0689]: can't call method `pow` on ambiguous numeric type `{float}`
+  --> $DIR/issue-51874.rs:12:19
+   |
+LL |     let a = (1.0).pow(1.0); //~ ERROR can't call method `pow` on ambiguous numeric type
+   |                   ^^^
+help: you must specify a concrete type for this numeric value, like `f32`
+   |
+LL |     let a = (1.0_f32).pow(1.0); //~ ERROR can't call method `pow` on ambiguous numeric type
+   |              ^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0689`.