Merge from rustc

11 files changed, 89 insertions, 42 deletions

diff --git a/src/doc/reference b/src/doc/reference
-Subproject e95ebdfee02514d93f79ec92ae310a804e87f01
+Subproject 46435cd4eba11b66acaa42c01da5c80ad88aee4
diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
-Subproject 6f69823c28ae8d929d6c815181c73d3e99ef16d
+Subproject 0d7964d5b22cf920237ef1282d869564b4883b8
diff --git a/src/doc/rustc-dev-guide/book.toml b/src/doc/rustc-dev-guide/book.toml
index eb2f6806b96..b84b1e7548a 100644
--- a/src/doc/rustc-dev-guide/book.toml
+++ b/src/doc/rustc-dev-guide/book.toml
@@ -1,6 +1,6 @@
 [book]
 title = "Rust Compiler Development Guide"
-author = "The Rust Project Developers"
+authors = ["The Rust Project Developers"]
 description = "A guide to developing the Rust compiler (rustc)"
 
 [build]
diff --git a/src/doc/rustc-dev-guide/rust-version b/src/doc/rustc-dev-guide/rust-version
index d7c20d8ce62..a6f29510879 100644
--- a/src/doc/rustc-dev-guide/rust-version
+++ b/src/doc/rustc-dev-guide/rust-version
@@ -1 +1 @@
-ae9173d7dd4a31806c950c90dcc331f1508b4d17
+25a615bf829b9f6d6f22da537e3851043f92e5f2
diff --git a/src/doc/rustc-dev-guide/src/backend/libs-and-metadata.md b/src/doc/rustc-dev-guide/src/backend/libs-and-metadata.md
index 556b3fdf8f8..513df1650c3 100644
--- a/src/doc/rustc-dev-guide/src/backend/libs-and-metadata.md
+++ b/src/doc/rustc-dev-guide/src/backend/libs-and-metadata.md
@@ -110,7 +110,7 @@ See [`compute_hir_hash`] for where the hash is actually computed.
 
 [SVH]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_data_structures/svh/struct.Svh.html
 [incremental compilation]: ../queries/incremental-compilation.md
-[`compute_hir_hash`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast_lowering/struct.LoweringContext.html#method.compute_hir_hash
+[`compute_hir_hash`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast_lowering/fn.compute_hir_hash.html
 
 ### Stable Crate Id
 
diff --git a/src/doc/rustc-dev-guide/src/rustdoc.md b/src/doc/rustc-dev-guide/src/rustdoc.md
index 320dc9d5825..e36d6a388a9 100644
--- a/src/doc/rustc-dev-guide/src/rustdoc.md
+++ b/src/doc/rustc-dev-guide/src/rustdoc.md
@@ -90,7 +90,9 @@ does is call the `main()` that's in this crate's `lib.rs`, though.)
   are in `tests/rustdoc-gui`. These use a [NodeJS tool called
   browser-UI-test](https://github.com/GuillaumeGomez/browser-UI-test/) that uses
   puppeteer to run tests in a headless browser and check rendering and
-  interactivity.
+  interactivity.  For information on how to write this form of test,
+  see [`tests/rustdoc-gui/README.md`][rustdoc-gui-readme]
+  as well as [the description of the `.goml` format][goml-script]
 * Additionally, JavaScript type annotations are written using [TypeScript-flavored JSDoc]
   comments and an external d.ts file. The code itself is plain, valid JavaScript; we only
   use tsc as a linter.
@@ -100,6 +102,8 @@ does is call the `main()` that's in this crate's `lib.rs`, though.)
   [These tests have several extra directives available to them](./rustdoc-internals/rustdoc-test-suite.md).
 
 [TypeScript-flavored JSDoc]: https://www.typescriptlang.org/docs/handbook/jsdoc-supported-types.html
+[rustdoc-gui-readme]: https://github.com/rust-lang/rust/blob/master/tests/rustdoc-gui/README.md
+[goml-script]: https://github.com/GuillaumeGomez/browser-UI-test/blob/master/goml-script.md
 
 ## Constraints
 
diff --git a/src/doc/rustc-dev-guide/src/solve/opaque-types.md b/src/doc/rustc-dev-guide/src/solve/opaque-types.md
index 672aab77080..509c34a4d3a 100644
--- a/src/doc/rustc-dev-guide/src/solve/opaque-types.md
+++ b/src/doc/rustc-dev-guide/src/solve/opaque-types.md
@@ -33,7 +33,7 @@ For opaque types in the defining scope and in the implicit-negative coherence mo
 always done in two steps. Outside of the defining scope `normalizes-to` for opaques always
 returns `Err(NoSolution)`.
 
-We start by trying to to assign the expected type as a hidden type.
+We start by trying to assign the expected type as a hidden type.
 
 In the implicit-negative coherence mode, this currently always results in ambiguity without
 interacting with the opaque types storage. We could instead add allow 'defining' all opaque types,
diff --git a/src/doc/rustc-dev-guide/src/tests/directives.md b/src/doc/rustc-dev-guide/src/tests/directives.md
index 81aa35f1a46..8e4a710178e 100644
--- a/src/doc/rustc-dev-guide/src/tests/directives.md
+++ b/src/doc/rustc-dev-guide/src/tests/directives.md
@@ -6,7 +6,8 @@
 FIXME(jieyouxu) completely revise this chapter.
 -->
 
-Directives are special comments that tell compiletest how to build and interpret a test. They must appear before the Rust source in the test. They may also appear in `rmake.rs` [run-make tests](compiletest.md#run-make-tests).
+Directives are special comments that tell compiletest how to build and interpret a test.
+They may also appear in `rmake.rs` [run-make tests](compiletest.md#run-make-tests).
 
 They are normally put after the short comment that explains the point of this
 test. Compiletest test suites use `//@` to signal that a comment is a directive.
diff --git a/src/doc/rustc-dev-guide/src/tests/ui.md b/src/doc/rustc-dev-guide/src/tests/ui.md
index 407862d48af..e862a07cae0 100644
--- a/src/doc/rustc-dev-guide/src/tests/ui.md
+++ b/src/doc/rustc-dev-guide/src/tests/ui.md
@@ -335,8 +335,9 @@ But for strict testing, try to use the `ERROR` annotation as much as possible,
 including `//~?` annotations for diagnostics without span.
 For compile time diagnostics `error-pattern` should very rarely be necessary.
 
-Per-line annotations (`//~`) are still checked in tests using `error-pattern`,
-to opt out of these checks in exceptional cases use `//@ compile-flags: --error-format=human`.
+Per-line annotations (`//~`) are still checked in tests using `error-pattern`.
+To opt out of these checks, use `//@ compile-flags: --error-format=human`.
+Do that only in exceptional cases.
 
 ### Error levels
 
diff --git a/src/doc/style-guide/src/expressions.md b/src/doc/style-guide/src/expressions.md
index 12037b5992e..031e59d86e1 100644
--- a/src/doc/style-guide/src/expressions.md
+++ b/src/doc/style-guide/src/expressions.md
@@ -521,8 +521,11 @@ self.pre_comment.as_ref().map_or(
 
 ## Control flow expressions
 
-This section covers `if`, `if let`, `loop`, `while`, `while let`, and `for`
-expressions.
+This section covers `for` and `loop` expressions, as well as `if` and `while`
+expressions with their sub-expression variants. This includes those with a
+single `let` sub-expression (i.e. `if let` and `while let`)
+as well as "let-chains": those with one or more `let` sub-expressions and
+one or more bool-type conditions (i.e.  `if a && let Some(b) = c`).
 
 Put the keyword, any initial clauses, and the opening brace of the block all on
 a single line, if they fit. Apply the usual rules for [block
@@ -548,10 +551,11 @@ if let ... {
 }
 ```
 
-If the control line needs to be broken, prefer to break before the `=` in `*
-let` expressions and before `in` in a `for` expression; block-indent the
-following line. If the control line is broken for any reason, put the opening
-brace on its own line, not indented. Examples:
+If the control line needs to be broken, then prefer breaking after the `=` for any
+`let` sub-expression in an `if` or `while` expression that does not fit,
+and before `in` in a `for` expression; the following line should be block indented.
+If the control line is broken for any reason, then the opening brace should be on its
+own line and not indented. Examples:
 
 ```rust
 while let Some(foo)
@@ -572,6 +576,68 @@ if a_long_expression
 {
     ...
 }
+
+if let Some(a) = b
+    && another_long_expression
+    && a_third_long_expression
+{
+    // ...
+}
+
+if let Some(relatively_long_thing)
+    = a_long_expression
+    && another_long_expression
+    && a_third_long_expression
+{
+    // ...
+}
+
+if some_expr
+    && another_long_expression
+    && let Some(relatively_long_thing) =
+        a_long_long_long_long_long_long_really_reallllllllllyyyyyyy_long_expression
+    && a_third_long_expression
+{
+    // ...
+}
+```
+
+A let-chain control line is allowed to be formatted on a single line provided
+it only consists of two clauses, with the first, left-hand side operand being a literal or an
+`ident` (which can optionally be preceded by any number of unary prefix operators),
+and the second, right-hand side operand being a single-line `let` clause. Otherwise,
+the control line must be broken and formatted according to the above rules. For example:
+
+```rust
+if a && let Some(b) = foo() {
+    // ...
+}
+
+if true && let Some(b) = foo() {
+    // ...
+}
+
+let operator = if !from_hir_call && let Some(p) = parent {
+    // ...
+};
+
+if let Some(b) = foo()
+    && a
+{
+    // ..
+}
+
+if foo()
+    && let Some(b) = bar
+{
+    // ...
+}
+
+if gen_pos != GenericArgPosition::Type
+    && let Some(b) = gen_args.bindings.first()
+{
+    // ..
+}
 ```
 
 Where the initial clause spans multiple lines and ends with one or more closing
diff --git a/src/doc/unstable-book/src/language-features/intrinsics.md b/src/doc/unstable-book/src/language-features/intrinsics.md
index 975b400447e..9e59dd88998 100644
--- a/src/doc/unstable-book/src/language-features/intrinsics.md
+++ b/src/doc/unstable-book/src/language-features/intrinsics.md
@@ -52,9 +52,9 @@ with any regular function.
 Various intrinsics have native MIR operations that they correspond to. Instead of requiring
 backends to implement both the intrinsic and the MIR operation, the `lower_intrinsics` pass
 will convert the calls to the MIR operation. Backends do not need to know about these intrinsics
-at all. These intrinsics only make sense without a body, and can either be declared as a "rust-intrinsic"
-or as a `#[rustc_intrinsic]`. The body is never used, as calls to the intrinsic do not exist
-anymore after MIR analyses.
+at all. These intrinsics only make sense without a body, and can be declared as a `#[rustc_intrinsic]`.
+The body is never used as the lowering pass implements support for all backends, so we never have to
+use the fallback logic.
 
 ## Intrinsics without fallback logic
 
@@ -70,28 +70,3 @@ These are written without a body:
 #[rustc_intrinsic]
 pub fn abort() -> !;
 ```
-
-### Legacy extern ABI based intrinsics
-
-*This style is deprecated, always prefer the above form.*
-
-These are imported as if they were FFI functions, with the special
-`rust-intrinsic` ABI. For example, if one was in a freestanding
-context, but wished to be able to `transmute` between types, and
-perform efficient pointer arithmetic, one would import those functions
-via a declaration like
-
-```rust
-#![feature(intrinsics)]
-#![allow(internal_features)]
-# fn main() {}
-
-extern "rust-intrinsic" {
-    fn transmute<T, U>(x: T) -> U;
-
-    fn arith_offset<T>(dst: *const T, offset: isize) -> *const T;
-}
-```
-
-As with any other FFI functions, these are by default always `unsafe` to call.
-You can add `#[rustc_safe_intrinsic]` to the intrinsic to make it safe to call.