Auto merge of #69555 - Centril:rollup-e53lxz4, r=Centril

Rollup of 10 pull requests

Successful merges:

 - #68989 (Update RELEASES.md for 1.42.0)
 - #69340 (instantiate_value_path: on `SelfCtor`, avoid unconstrained tyvars)
 - #69384 (parser: `token` -> `normalized_token`, `nonnormalized_token` -> `token`)
 - #69452 (typeck: use `Pattern` obligation cause more for better diagnostics)
 - #69481 (use char instead of &str for single char patterns)
 - #69522 (error_derive_forbidden_on_non_adt: be more graceful)
 - #69538 (Stabilize `boxed_slice_try_from`)
 - #69539 (late resolve, visit_fn: bail early if there's no body.)
 - #69541 (Remove unneeded calls to format!())
 - #69547 (remove redundant clones, references to operands, explicit boolean comparisons and filter(x).next() calls.)

Failed merges:

r? @ghost

RELEASES.md

@@ -1,3 +1,100 @@
+Version 1.42.0 (2020-03-12)
+==========================
+
+Language
+--------
+- [You can now use the slice pattern syntax with subslices.][67712] e.g.
+  ```rust
+  fn foo(words: &[&str]) {
+      match words {
+          ["Hello", "World", "!", ..] => println!("Hello World!"),
+          ["Foo", "Bar", ..] => println!("Baz"),
+          rest => println!("{:?}", rest),
+      }
+  }
+  ```
+- [You can now use `#[repr(transparent)]` on univariant `enum`s.][68122] Meaning
+  that you can create an enum that has the exact layout and ABI of the type
+  it contains.
+- [There are some *syntax-only* changes:][67131]
+   - `default` is syntactically allowed before items in `trait` definitions.
+   - Items in `impl`s (i.e. `const`s, `type`s, and `fn`s) may syntactically
+     leave out their bodies in favor of `;`.
+   - Bounds on associated types in `impl`s are now syntactically allowed
+     (e.g. `type Foo: Ord;`).
+   - `...` (the C-variadic type) may occur syntactically directly as the type of
+      any function parameter.
+
+  These are still rejected *semantically*, so you will likely receive an error
+  but these changes can be seen and parsed by procedural macros and
+  conditional compilation.
+
+Compiler
+--------
+- [Added tier 2\* support for `armv7a-none-eabi`.][68253]
+- [Added tier 2 support for `riscv64gc-unknown-linux-gnu`.][68339]
+- [`Option::{expect,unwrap}` and
+   `Result::{expect, expect_err, unwrap, unwrap_err}` now produce panic messages
+   pointing to the location where they were called, rather than
+   `core`'s internals. ][67887]
+
+\* Refer to Rust's [platform support page][forge-platform-support] for more
+information on Rust's tiered platform support.
+
+Libraries
+---------
+- [`iter::Empty<T>` now implements `Send` and `Sync` for any `T`.][68348]
+- [`Pin::{map_unchecked, map_unchecked_mut}` no longer require the return type
+   to implement `Sized`.][67935]
+- [`io::Cursor` now derives `PartialEq` and `Eq`.][67233]
+- [`Layout::new` is now `const`.][66254]
+- [Added Standard Library support for `riscv64gc-unknown-linux-gnu`.][66899]
+
+
+Stabilized APIs
+---------------
+- [`CondVar::wait_while`]
+- [`CondVar::wait_timeout_while`]
+- [`DebugMap::key`]
+- [`DebugMap::value`]
+- [`ManuallyDrop::take`]
+- [`matches!`]
+- [`ptr::slice_from_raw_parts_mut`]
+- [`ptr::slice_from_raw_parts`]
+
+Cargo
+-----
+- [You no longer need to include `extern crate proc_macro;` to be able to
+  `use proc_macro;` in the `2018` edition.][cargo/7700]
+
+Compatibility Notes
+-------------------
+- [`Error::description` has been deprecated, and its use will now produce a
+  warning.][66919] It's recommended to use `Display`/`to_string` instead.
+
+[68253]: https://github.com/rust-lang/rust/pull/68253/
+[68348]: https://github.com/rust-lang/rust/pull/68348/
+[67935]: https://github.com/rust-lang/rust/pull/67935/
+[68339]: https://github.com/rust-lang/rust/pull/68339/
+[68122]: https://github.com/rust-lang/rust/pull/68122/
+[67712]: https://github.com/rust-lang/rust/pull/67712/
+[67887]: https://github.com/rust-lang/rust/pull/67887/
+[67131]: https://github.com/rust-lang/rust/pull/67131/
+[67233]: https://github.com/rust-lang/rust/pull/67233/
+[66899]: https://github.com/rust-lang/rust/pull/66899/
+[66919]: https://github.com/rust-lang/rust/pull/66919/
+[66254]: https://github.com/rust-lang/rust/pull/66254/
+[cargo/7700]: https://github.com/rust-lang/cargo/pull/7700
+[`DebugMap::key`]: https://doc.rust-lang.org/stable/std/fmt/struct.DebugMap.html#method.key
+[`DebugMap::value`]: https://doc.rust-lang.org/stable/std/fmt/struct.DebugMap.html#method.value
+[`ManuallyDrop::take`]: https://doc.rust-lang.org/stable/std/mem/struct.ManuallyDrop.html#method.take
+[`matches!`]: https://doc.rust-lang.org/stable/std/macro.matches.html
+[`ptr::slice_from_raw_parts_mut`]: https://doc.rust-lang.org/stable/std/ptr/fn.slice_from_raw_parts_mut.html
+[`ptr::slice_from_raw_parts`]: https://doc.rust-lang.org/stable/std/ptr/fn.slice_from_raw_parts.html
+[`CondVar::wait_while`]: https://doc.rust-lang.org/stable/std/sync/struct.Condvar.html#method.wait_while
+[`CondVar::wait_timeout_while`]: https://doc.rust-lang.org/stable/std/sync/struct.Condvar.html#method.wait_timeout_while
+
+
 Version 1.41.1 (2020-02-27)
 ===========================
 
@@ -8,6 +105,7 @@ Version 1.41.1 (2020-02-27)
 [69225]: https://github.com/rust-lang/rust/issues/69225
 [69145]: https://github.com/rust-lang/rust/pull/69145
 
+
 Version 1.41.0 (2020-01-30)
 ===========================
 

src/liballoc/boxed.rs

@@ -825,7 +825,7 @@ impl From<Box<str>> for Box<[u8]> {
     }
 }
 
-#[unstable(feature = "boxed_slice_try_from", issue = "none")]
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]>
 where
     [T; N]: LengthAtMost32,

src/liballoc/rc.rs

@@ -1453,7 +1453,7 @@ impl<T> From<Vec<T>> for Rc<[T]> {
     }
 }
 
-#[unstable(feature = "boxed_slice_try_from", issue = "none")]
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Rc<[T]>> for Rc<[T; N]>
 where
     [T; N]: LengthAtMost32,

src/liballoc/sync.rs

@@ -2002,7 +2002,7 @@ impl<T> From<Vec<T>> for Arc<[T]> {
     }
 }
 
-#[unstable(feature = "boxed_slice_try_from", issue = "none")]
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Arc<[T]>> for Arc<[T; N]>
 where
     [T; N]: LengthAtMost32,

src/librustc/hir/map/mod.rs

@@ -153,17 +153,13 @@ pub struct Map<'hir> {
     hir_to_node_id: FxHashMap<HirId, NodeId>,
 }
 
-struct ParentHirIterator<'map, 'hir> {
+/// An iterator that walks up the ancestor tree of a given `HirId`.
+/// Constructed using `tcx.hir().parent_iter(hir_id)`.
+pub struct ParentHirIterator<'map, 'hir> {
     current_id: HirId,
     map: &'map Map<'hir>,
 }
 
-impl<'map, 'hir> ParentHirIterator<'map, 'hir> {
-    fn new(current_id: HirId, map: &'map Map<'hir>) -> Self {
-        Self { current_id, map }
-    }
-}
-
 impl<'hir> Iterator for ParentHirIterator<'_, 'hir> {
     type Item = (HirId, Node<'hir>);
 
@@ -618,6 +614,12 @@ impl<'hir> Map<'hir> {
         self.find_entry(hir_id).and_then(|x| x.parent_node()).unwrap_or(hir_id)
     }
 
+    /// Returns an iterator for the nodes in the ancestor tree of the `current_id`
+    /// until the crate root is reached. Prefer this over your own loop using `get_parent_node`.
+    pub fn parent_iter(&self, current_id: HirId) -> ParentHirIterator<'_, 'hir> {
+        ParentHirIterator { current_id, map: self }
+    }
+
     /// Checks if the node is an argument. An argument is a local variable whose
     /// immediate parent is an item or a closure.
     pub fn is_argument(&self, id: HirId) -> bool {
@@ -684,7 +686,7 @@ impl<'hir> Map<'hir> {
     /// }
     /// ```
     pub fn get_return_block(&self, id: HirId) -> Option<HirId> {
-        let mut iter = ParentHirIterator::new(id, &self).peekable();
+        let mut iter = self.parent_iter(id).peekable();
         let mut ignore_tail = false;
         if let Some(entry) = self.find_entry(id) {
             if let Node::Expr(Expr { kind: ExprKind::Ret(_), .. }) = entry.node {
@@ -731,7 +733,7 @@ impl<'hir> Map<'hir> {
     /// in the HIR which is recorded by the map and is an item, either an item
     /// in a module, trait, or impl.
     pub fn get_parent_item(&self, hir_id: HirId) -> HirId {
-        for (hir_id, node) in ParentHirIterator::new(hir_id, &self) {
+        for (hir_id, node) in self.parent_iter(hir_id) {
             match node {
                 Node::Crate
                 | Node::Item(_)
@@ -753,7 +755,7 @@ impl<'hir> Map<'hir> {
     /// Returns the `HirId` of `id`'s nearest module parent, or `id` itself if no
     /// module parent is in this map.
     pub fn get_module_parent_node(&self, hir_id: HirId) -> HirId {
-        for (hir_id, node) in ParentHirIterator::new(hir_id, &self) {
+        for (hir_id, node) in self.parent_iter(hir_id) {
             if let Node::Item(&Item { kind: ItemKind::Mod(_), .. }) = node {
                 return hir_id;
             }
@@ -767,7 +769,7 @@ impl<'hir> Map<'hir> {
     /// Used by error reporting when there's a type error in a match arm caused by the `match`
     /// expression needing to be unit.
     pub fn get_match_if_cause(&self, hir_id: HirId) -> Option<&'hir Expr<'hir>> {
-        for (_, node) in ParentHirIterator::new(hir_id, &self) {
+        for (_, node) in self.parent_iter(hir_id) {
             match node {
                 Node::Item(_) | Node::ForeignItem(_) | Node::TraitItem(_) | Node::ImplItem(_) => {
                     break;
@@ -788,7 +790,7 @@ impl<'hir> Map<'hir> {
 
     /// Returns the nearest enclosing scope. A scope is roughly an item or block.
     pub fn get_enclosing_scope(&self, hir_id: HirId) -> Option<HirId> {
-        for (hir_id, node) in ParentHirIterator::new(hir_id, &self) {
+        for (hir_id, node) in self.parent_iter(hir_id) {
             if match node {
                 Node::Item(i) => match i.kind {
                     ItemKind::Fn(..)

src/librustc_builtin_macros/asm.rs

@@ -182,7 +182,7 @@ fn parse_inline_asm<'a>(
                     };
 
                     let is_rw = output.is_some();
-                    let is_indirect = constraint_str.contains("*");
+                    let is_indirect = constraint_str.contains('*');
                     outputs.push(ast::InlineAsmOutput {
                         constraint: output.unwrap_or(constraint),
                         expr,
@@ -199,15 +199,15 @@ fn parse_inline_asm<'a>(
 
                     let constraint = parse_asm_str(&mut p)?;
 
-                    if constraint.as_str().starts_with("=") {
+                    if constraint.as_str().starts_with('=') {
                         struct_span_err!(
                             cx.parse_sess.span_diagnostic,
                             p.prev_span,
                             E0662,
                             "input operand constraint contains '='"
                         )
                         .emit();
-                    } else if constraint.as_str().starts_with("+") {
+                    } else if constraint.as_str().starts_with('+') {
                         struct_span_err!(
                             cx.parse_sess.span_diagnostic,
                             p.prev_span,
@@ -234,7 +234,7 @@ fn parse_inline_asm<'a>(
 
                     if OPTIONS.iter().any(|&opt| s == opt) {
                         cx.span_warn(p.prev_span, "expected a clobber, found an option");
-                    } else if s.as_str().starts_with("{") || s.as_str().ends_with("}") {
+                    } else if s.as_str().starts_with('{') || s.as_str().ends_with('}') {
                         struct_span_err!(
                             cx.parse_sess.span_diagnostic,
                             p.prev_span,

src/librustc_builtin_macros/format.rs

@@ -158,7 +158,7 @@ fn parse_args<'a>(
         } // accept trailing commas
         if p.token.is_ident() && p.look_ahead(1, |t| *t == token::Eq) {
             named = true;
-            let name = if let token::Ident(name, _) = p.token.kind {
+            let name = if let token::Ident(name, _) = p.normalized_token.kind {
                 p.bump();
                 name
             } else {
@@ -894,7 +894,7 @@ pub fn expand_preparsed_format_args(
     };
 
     let (is_literal, fmt_snippet) = match ecx.source_map().span_to_snippet(fmt_sp) {
-        Ok(s) => (s.starts_with("\"") || s.starts_with("r#"), Some(s)),
+        Ok(s) => (s.starts_with('"') || s.starts_with("r#"), Some(s)),
         _ => (false, None),
     };
 

src/librustc_codegen_llvm/back/lto.rs

@@ -917,7 +917,7 @@ impl ThinLTOImports {
             if line.is_empty() {
                 let importing_module = current_module.take().expect("Importing module not set");
                 imports.insert(importing_module, mem::replace(&mut current_imports, vec![]));
-            } else if line.starts_with(" ") {
+            } else if line.starts_with(' ') {
                 // Space marks an imported module
                 assert_ne!(current_module, None);
                 current_imports.push(line.trim().to_string());

src/librustc_codegen_utils/link.rs

@@ -78,7 +78,7 @@ pub fn find_crate_name(sess: Option<&Session>, attrs: &[ast::Attribute], input:
     }
     if let Input::File(ref path) = *input {
         if let Some(s) = path.file_stem().and_then(|s| s.to_str()) {
-            if s.starts_with("-") {
+            if s.starts_with('-') {
                 let msg = format!(
                     "crate names cannot start with a `-`, but \
                                    `{}` has a leading hyphen",

src/librustc_driver/args.rs

@@ -4,7 +4,7 @@ use std::fs;
 use std::io;
 
 pub fn arg_expand(arg: String) -> Result<Vec<String>, Error> {
-    if arg.starts_with("@") {
+    if arg.starts_with('@') {
         let path = &arg[1..];
         let file = match fs::read_to_string(path) {
             Ok(file) => file,

src/librustc_driver/lib.rs

@@ -521,7 +521,7 @@ fn stdout_isatty() -> bool {
 
 fn handle_explain(registry: Registry, code: &str, output: ErrorOutputType) {
     let normalised =
-        if code.starts_with("E") { code.to_string() } else { format!("E{0:0>4}", code) };
+        if code.starts_with('E') { code.to_string() } else { format!("E{0:0>4}", code) };
     match registry.find_description(&normalised) {
         Some(ref description) => {
             let mut is_in_code_block = false;
@@ -601,7 +601,7 @@ impl RustcDefaultCalls {
             });
             compiler.codegen_backend().link(&sess, Box::new(codegen_results), &outputs)
         } else {
-            sess.fatal(&format!("rlink must be a file"))
+            sess.fatal("rlink must be a file")
         }
     }
 

src/librustc_expand/expand.rs

@@ -503,13 +503,12 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
     }
 
     fn error_derive_forbidden_on_non_adt(&self, derives: &[Path], item: &Annotatable) {
-        let attr =
-            attr::find_by_name(item.attrs(), sym::derive).expect("`derive` attribute should exist");
-        let span = attr.span;
+        let attr = attr::find_by_name(item.attrs(), sym::derive);
+        let span = attr.map_or(item.span(), |attr| attr.span);
         let mut err = self
             .cx
             .struct_span_err(span, "`derive` may only be applied to structs, enums and unions");
-        if let ast::AttrStyle::Inner = attr.style {
+        if let Some(ast::Attribute { style: ast::AttrStyle::Inner, .. }) = attr {
             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
             let suggestion = format!("#[derive({})]", trait_list.join(", "));
             err.span_suggestion(
@@ -1669,10 +1668,9 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
                         }
                     }
                 } else {
-                    let mut err = self.cx.struct_span_err(
-                        it.span(),
-                        &format!("expected path to external documentation"),
-                    );
+                    let mut err = self
+                        .cx
+                        .struct_span_err(it.span(), "expected path to external documentation");
 
                     // Check if the user erroneously used `doc(include(...))` syntax.
                     let literal = it.meta_item_list().and_then(|list| {

src/librustc_expand/mbe/macro_parser.rs

@@ -753,6 +753,12 @@ pub(super) fn parse_tt(parser: &mut Cow<'_, Parser<'_>>, ms: &[TokenTree]) -> Na
 fn get_macro_name(token: &Token) -> Option<(Name, bool)> {
     match token.kind {
         token::Ident(name, is_raw) if name != kw::Underscore => Some((name, is_raw)),
+        token::Interpolated(ref nt) => match **nt {
+            token::NtIdent(ident, is_raw) if ident.name != kw::Underscore => {
+                Some((ident.name, is_raw))
+            }
+            _ => None,
+        },
         _ => None,
     }
 }
@@ -883,9 +889,8 @@ fn parse_nt_inner<'a>(p: &mut Parser<'a>, sp: Span, name: Symbol) -> PResult<'a,
         // this could be handled like a token, since it is one
         sym::ident => {
             if let Some((name, is_raw)) = get_macro_name(&p.token) {
-                let span = p.token.span;
                 p.bump();
-                token::NtIdent(Ident::new(name, span), is_raw)
+                token::NtIdent(Ident::new(name, p.normalized_prev_token.span), is_raw)
             } else {
                 let token_str = pprust::token_to_string(&p.token);
                 let msg = &format!("expected ident, found {}", &token_str);

src/librustc_expand/proc_macro_server.rs

@@ -205,7 +205,7 @@ impl ToInternal<TokenStream> for TokenTree<Group, Punct, Ident, Literal> {
             TokenTree::Literal(self::Literal {
                 lit: token::Lit { kind: token::Integer, symbol, suffix },
                 span,
-            }) if symbol.as_str().starts_with("-") => {
+            }) if symbol.as_str().starts_with('-') => {
                 let minus = BinOp(BinOpToken::Minus);
                 let symbol = Symbol::intern(&symbol.as_str()[1..]);
                 let integer = TokenKind::lit(token::Integer, symbol, suffix);
@@ -216,7 +216,7 @@ impl ToInternal<TokenStream> for TokenTree<Group, Punct, Ident, Literal> {
             TokenTree::Literal(self::Literal {
                 lit: token::Lit { kind: token::Float, symbol, suffix },
                 span,
-            }) if symbol.as_str().starts_with("-") => {
+            }) if symbol.as_str().starts_with('-') => {
                 let minus = BinOp(BinOpToken::Minus);
                 let symbol = Symbol::intern(&symbol.as_str()[1..]);
                 let float = TokenKind::lit(token::Float, symbol, suffix);

src/librustc_hir/hir.rs

@@ -1504,7 +1504,7 @@ pub fn is_range_literal(sm: &SourceMap, expr: &Expr<'_>) -> bool {
         let end_point = sm.end_point(*span);
 
         if let Ok(end_string) = sm.span_to_snippet(end_point) {
-            !(end_string.ends_with("}") || end_string.ends_with(")"))
+            !(end_string.ends_with('}') || end_string.ends_with(')'))
         } else {
             false
         }