Auto merge of rust-lang#107642 - Dylan-DPC:rollup-edcqhm5, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - rust-lang#107082 (Autotrait bounds on dyn-safe trait methods)
 - rust-lang#107427 (Add candidates for DiscriminantKind builtin)
 - rust-lang#107539 (Emit warnings on unused parens in index expressions)
 - rust-lang#107544 (Improve `TokenCursor`.)
 - rust-lang#107585 (Don't cause a cycle when formatting query description that references a FnDef)
 - rust-lang#107633 (Fix suggestion for coercing Option<&String> to Option<&str>)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_ast/src/tokenstream.rs

@@ -41,7 +41,8 @@ use std::{fmt, iter};
 /// Nothing special happens to misnamed or misplaced `SubstNt`s.
 #[derive(Debug, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
 pub enum TokenTree {
-    /// A single token.
+    /// A single token. Should never be `OpenDelim` or `CloseDelim`, because
+    /// delimiters are implicitly represented by `Delimited`.
     Token(Token, Spacing),
     /// A delimited sequence of token trees.
     Delimited(DelimSpan, Delimiter, TokenStream),
@@ -388,12 +389,12 @@ impl TokenStream {
         self.0.len()
     }
 
-    pub fn trees(&self) -> CursorRef<'_> {
-        CursorRef::new(self)
+    pub fn trees(&self) -> RefTokenTreeCursor<'_> {
+        RefTokenTreeCursor::new(self)
     }
 
-    pub fn into_trees(self) -> Cursor {
-        Cursor::new(self)
+    pub fn into_trees(self) -> TokenTreeCursor {
+        TokenTreeCursor::new(self)
     }
 
     /// Compares two `TokenStream`s, checking equality without regarding span information.
@@ -551,24 +552,25 @@ impl TokenStream {
     }
 }
 
-/// By-reference iterator over a [`TokenStream`].
+/// By-reference iterator over a [`TokenStream`], that produces `&TokenTree`
+/// items.
 #[derive(Clone)]
-pub struct CursorRef<'t> {
+pub struct RefTokenTreeCursor<'t> {
     stream: &'t TokenStream,
     index: usize,
 }
 
-impl<'t> CursorRef<'t> {
+impl<'t> RefTokenTreeCursor<'t> {
     fn new(stream: &'t TokenStream) -> Self {
-        CursorRef { stream, index: 0 }
+        RefTokenTreeCursor { stream, index: 0 }
     }
 
     pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
         self.stream.0.get(self.index + n)
     }
 }
 
-impl<'t> Iterator for CursorRef<'t> {
+impl<'t> Iterator for RefTokenTreeCursor<'t> {
     type Item = &'t TokenTree;
 
     fn next(&mut self) -> Option<&'t TokenTree> {
@@ -579,15 +581,16 @@ impl<'t> Iterator for CursorRef<'t> {
     }
 }
 
-/// Owning by-value iterator over a [`TokenStream`].
+/// Owning by-value iterator over a [`TokenStream`], that produces `TokenTree`
+/// items.
 // FIXME: Many uses of this can be replaced with by-reference iterator to avoid clones.
 #[derive(Clone)]
-pub struct Cursor {
+pub struct TokenTreeCursor {
     pub stream: TokenStream,
     index: usize,
 }
 
-impl Iterator for Cursor {
+impl Iterator for TokenTreeCursor {
     type Item = TokenTree;
 
     fn next(&mut self) -> Option<TokenTree> {
@@ -598,9 +601,9 @@ impl Iterator for Cursor {
     }
 }
 
-impl Cursor {
+impl TokenTreeCursor {
     fn new(stream: TokenStream) -> Self {
-        Cursor { stream, index: 0 }
+        TokenTreeCursor { stream, index: 0 }
     }
 
     #[inline]
@@ -614,6 +617,15 @@ impl Cursor {
     pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
         self.stream.0.get(self.index + n)
     }
+
+    // Replace the previously obtained token tree with `tts`, and rewind to
+    // just before them.
+    pub fn replace_prev_and_rewind(&mut self, tts: Vec<TokenTree>) {
+        assert!(self.index > 0);
+        self.index -= 1;
+        let stream = Lrc::make_mut(&mut self.stream.0);
+        stream.splice(self.index..self.index + 1, tts);
+    }
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]

compiler/rustc_data_structures/src/sync.rs

@@ -31,8 +31,8 @@ cfg_if! {
         pub auto trait Send {}
         pub auto trait Sync {}
 
-        impl<T: ?Sized> Send for T {}
-        impl<T: ?Sized> Sync for T {}
+        impl<T> Send for T {}
+        impl<T> Sync for T {}
 
         #[macro_export]
         macro_rules! rustc_erase_owner {

compiler/rustc_error_messages/locales/en-US/hir_typeck.ftl

@@ -61,3 +61,5 @@ hir_typeck_lang_start_incorrect_ret_ty = the return type of the `start` lang ite
 hir_typeck_help_set_edition_cargo = set `edition = "{$edition}"` in `Cargo.toml`
 hir_typeck_help_set_edition_standalone = pass `--edition {$edition}` to `rustc`
 hir_typeck_note_edition_guide = for more on editions, read https://doc.rust-lang.org/edition-guide
+
+hir_typeck_convert_to_str = try converting the passed type into a `&str`

compiler/rustc_expand/src/mbe/metavar_expr.rs

@@ -1,5 +1,5 @@
 use rustc_ast::token::{self, Delimiter};
-use rustc_ast::tokenstream::{CursorRef, TokenStream, TokenTree};
+use rustc_ast::tokenstream::{RefTokenTreeCursor, TokenStream, TokenTree};
 use rustc_ast::{LitIntType, LitKind};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Applicability, PResult};
@@ -72,7 +72,7 @@ impl MetaVarExpr {
 
 // Checks if there are any remaining tokens. For example, `${ignore(ident ... a b c ...)}`
 fn check_trailing_token<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
 ) -> PResult<'sess, ()> {
     if let Some(tt) = iter.next() {
@@ -88,7 +88,7 @@ fn check_trailing_token<'sess>(
 
 /// Parse a meta-variable `count` expression: `count(ident[, depth])`
 fn parse_count<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
     span: Span,
 ) -> PResult<'sess, MetaVarExpr> {
@@ -99,7 +99,7 @@ fn parse_count<'sess>(
 
 /// Parses the depth used by index(depth) and length(depth).
 fn parse_depth<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
     span: Span,
 ) -> PResult<'sess, usize> {
@@ -126,7 +126,7 @@ fn parse_depth<'sess>(
 
 /// Parses an generic ident
 fn parse_ident<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
     span: Span,
 ) -> PResult<'sess, Ident> {
@@ -152,7 +152,7 @@ fn parse_ident<'sess>(
 
 /// Tries to move the iterator forward returning `true` if there is a comma. If not, then the
 /// iterator is not modified and the result is `false`.
-fn try_eat_comma(iter: &mut CursorRef<'_>) -> bool {
+fn try_eat_comma(iter: &mut RefTokenTreeCursor<'_>) -> bool {
     if let Some(TokenTree::Token(token::Token { kind: token::Comma, .. }, _)) = iter.look_ahead(0) {
         let _ = iter.next();
         return true;