Auto merge of rust-lang#94453 - matthiaskrgr:rollup-xv9y98j, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - rust-lang#92399 (fix typo in btree/vec doc: Self -> self)
 - rust-lang#92823 (Tweak diagnostics)
 - rust-lang#94248 (Fix ICE when passing block to while-loop condition)
 - rust-lang#94414 (Fix ICE when using Box<T, A> with large A)
 - rust-lang#94445 (4 - Make more use of `let_chains`)
 - rust-lang#94449 (Add long explanation for E0726)

Failed merges:

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

Author: bors

Diff for: compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -453,7 +453,18 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         };
         for elem in place_ref.projection[base..].iter() {
             cg_base = match elem.clone() {
-                mir::ProjectionElem::Deref => bx.load_operand(cg_base).deref(bx.cx()),
+                mir::ProjectionElem::Deref => {
+                    // custom allocators can change box's abi, making it unable to be derefed directly
+                    if cg_base.layout.ty.is_box()
+                        && matches!(cg_base.layout.abi, Abi::Aggregate { .. } | Abi::Uninhabited)
+                    {
+                        let ptr = cg_base.project_field(bx, 0).project_field(bx, 0);
+
+                        bx.load_operand(ptr).deref(bx.cx())
+                    } else {
+                        bx.load_operand(cg_base).deref(bx.cx())
+                    }
+                }
                 mir::ProjectionElem::Field(ref field, _) => {
                     cg_base.project_field(bx, field.index())
                 }

Diff for: compiler/rustc_error_codes/src/error_codes.rs

@@ -429,6 +429,7 @@ E0720: include_str!("./error_codes/E0720.md"),
 E0722: include_str!("./error_codes/E0722.md"),
 E0724: include_str!("./error_codes/E0724.md"),
 E0725: include_str!("./error_codes/E0725.md"),
+E0726: include_str!("./error_codes/E0726.md"),
 E0727: include_str!("./error_codes/E0727.md"),
 E0728: include_str!("./error_codes/E0728.md"),
 E0729: include_str!("./error_codes/E0729.md"),
@@ -641,6 +642,5 @@ E0787: include_str!("./error_codes/E0787.md"),
     E0717, // rustc_promotable without stability attribute
 //  E0721, // `await` keyword
 //  E0723, // unstable feature in `const` context
-    E0726, // non-explicit (not `'_`) elided lifetime in unsupported position
 //  E0738, // Removed; errored on `#[track_caller] fn`s in `extern "Rust" { ... }`.
 }

Diff for: compiler/rustc_error_codes/src/error_codes/E0726.md

@@ -0,0 +1,46 @@
+An argument lifetime was elided in an async function.
+
+Erroneous code example:
+
+When a struct or a type is bound/declared with a lifetime it is important for
+the Rust compiler to know, on usage, the lifespan of the type. When the
+lifetime is not explicitly mentioned and the Rust Compiler cannot determine
+the lifetime of your type, the following error occurs.
+
+```compile_fail,E0726
+use futures::executor::block_on;
+struct Content<'a> {
+    title: &'a str,
+    body: &'a str,
+}
+async fn create(content: Content) { // error: implicit elided
+                                    // lifetime not allowed here
+    println!("title: {}", content.title);
+    println!("body: {}", content.body);
+}
+let content = Content { title: "Rust", body: "is great!" };
+let future = create(content);
+block_on(future);
+```
+
+Specify desired lifetime of parameter `content` or indicate the anonymous
+lifetime like `content: Content<'_>`. The anonymous lifetime tells the Rust
+compiler that `content` is only needed until create function is done with
+it's execution.
+
+The `implicit elision` meaning the omission of suggested lifetime that is
+`pub async fn create<'a>(content: Content<'a>) {}` is not allowed here as
+lifetime of the `content` can differ from current context:
+
+```ignore (needs futures dependency)
+async fn create(content: Content<'_>) { // ok!
+    println!("title: {}", content.title);
+    println!("body: {}", content.body);
+}
+```
+
+Know more about lifetime elision in this [chapter][lifetime-elision] and a
+chapter on lifetimes can be found [here][lifetimes].
+
+[lifetime-elision]: https://doc.rust-lang.org/book/ch10-03-lifetime-syntax.html#lifetime-elision
+[lifetimes]: https://doc.rust-lang.org/rust-by-example/scope/lifetime.html

Diff for: compiler/rustc_expand/src/expand.rs

@@ -20,7 +20,7 @@ use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Applicability, PResult};
 use rustc_feature::Features;
 use rustc_parse::parser::{
-    AttemptLocalParseRecovery, ForceCollect, Parser, RecoverColon, RecoverComma,
+    AttemptLocalParseRecovery, CommaRecoveryMode, ForceCollect, Parser, RecoverColon, RecoverComma,
 };
 use rustc_parse::validate_attr;
 use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
@@ -911,6 +911,7 @@ pub fn parse_ast_fragment<'a>(
             None,
             RecoverComma::No,
             RecoverColon::Yes,
+            CommaRecoveryMode::LikelyTuple,
         )?),
         AstFragmentKind::Crate => AstFragment::Crate(this.parse_crate_mod()?),
         AstFragmentKind::Arms

Diff for: compiler/rustc_parse/src/lexer/tokentrees.rs

@@ -282,14 +282,13 @@ struct TokenStreamBuilder {
 
 impl TokenStreamBuilder {
     fn push(&mut self, (tree, joint): TreeAndSpacing) {
-        if let Some((TokenTree::Token(prev_token), Joint)) = self.buf.last() {
-            if let TokenTree::Token(token) = &tree {
-                if let Some(glued) = prev_token.glue(token) {
-                    self.buf.pop();
-                    self.buf.push((TokenTree::Token(glued), joint));
-                    return;
-                }
-            }
+        if let Some((TokenTree::Token(prev_token), Joint)) = self.buf.last()
+            && let TokenTree::Token(token) = &tree
+            && let Some(glued) = prev_token.glue(token)
+        {
+            self.buf.pop();
+            self.buf.push((TokenTree::Token(glued), joint));
+            return;
         }
         self.buf.push((tree, joint))
     }

Diff for: compiler/rustc_parse/src/lib.rs

@@ -1,9 +1,10 @@
 //! The main parser interface.
 
 #![feature(array_windows)]
+#![feature(box_patterns)]
 #![feature(crate_visibility_modifier)]
 #![feature(if_let_guard)]
-#![feature(box_patterns)]
+#![feature(let_chains)]
 #![feature(let_else)]
 #![recursion_limit = "256"]
 

Diff for: compiler/rustc_parse/src/parser/diagnostics.rs

@@ -1,8 +1,8 @@
 use super::pat::Expected;
 use super::ty::{AllowPlus, IsAsCast};
 use super::{
-    BlockMode, Parser, PathStyle, RecoverColon, RecoverComma, Restrictions, SemiColonMode, SeqSep,
-    TokenExpectType, TokenType,
+    BlockMode, CommaRecoveryMode, Parser, PathStyle, RecoverColon, RecoverComma, Restrictions,
+    SemiColonMode, SeqSep, TokenExpectType, TokenType,
 };
 
 use rustc_ast as ast;
@@ -732,43 +732,42 @@ impl<'a> Parser<'a> {
         mut e: DiagnosticBuilder<'a, ErrorReported>,
         expr: &mut P<Expr>,
     ) -> PResult<'a, ()> {
-        if let ExprKind::Binary(binop, _, _) = &expr.kind {
-            if let ast::BinOpKind::Lt = binop.node {
-                if self.eat(&token::Comma) {
-                    let x = self.parse_seq_to_before_end(
-                        &token::Gt,
-                        SeqSep::trailing_allowed(token::Comma),
-                        |p| p.parse_generic_arg(None),
-                    );
-                    match x {
-                        Ok((_, _, false)) => {
-                            if self.eat(&token::Gt) {
-                                e.span_suggestion_verbose(
-                                    binop.span.shrink_to_lo(),
-                                    TURBOFISH_SUGGESTION_STR,
-                                    "::".to_string(),
-                                    Applicability::MaybeIncorrect,
-                                )
-                                .emit();
-                                match self.parse_expr() {
-                                    Ok(_) => {
-                                        *expr =
-                                            self.mk_expr_err(expr.span.to(self.prev_token.span));
-                                        return Ok(());
-                                    }
-                                    Err(err) => {
-                                        *expr = self.mk_expr_err(expr.span);
-                                        err.cancel();
-                                    }
-                                }
+        if let ExprKind::Binary(binop, _, _) = &expr.kind
+            && let ast::BinOpKind::Lt = binop.node
+            && self.eat(&token::Comma)
+        {
+            let x = self.parse_seq_to_before_end(
+                &token::Gt,
+                SeqSep::trailing_allowed(token::Comma),
+                |p| p.parse_generic_arg(None),
+            );
+            match x {
+                Ok((_, _, false)) => {
+                    if self.eat(&token::Gt) {
+                        e.span_suggestion_verbose(
+                            binop.span.shrink_to_lo(),
+                            TURBOFISH_SUGGESTION_STR,
+                            "::".to_string(),
+                            Applicability::MaybeIncorrect,
+                        )
+                        .emit();
+                        match self.parse_expr() {
+                            Ok(_) => {
+                                *expr =
+                                    self.mk_expr_err(expr.span.to(self.prev_token.span));
+                                return Ok(());
+                            }
+                            Err(err) => {
+                                *expr = self.mk_expr_err(expr.span);
+                                err.cancel();
                             }
                         }
-                        Err(err) => {
-                            err.cancel();
-                        }
-                        _ => {}
                     }
                 }
+                Err(err) => {
+                    err.cancel();
+                }
+                _ => {}
             }
         }
         Err(e)
@@ -784,12 +783,13 @@ impl<'a> Parser<'a> {
         outer_op: &Spanned<AssocOp>,
     ) -> bool /* advanced the cursor */ {
         if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
-            if let ExprKind::Field(_, ident) = l1.kind {
-                if ident.as_str().parse::<i32>().is_err() && !matches!(r1.kind, ExprKind::Lit(_)) {
-                    // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
-                    // suggestion being the only one to apply is high.
-                    return false;
-                }
+            if let ExprKind::Field(_, ident) = l1.kind
+                && ident.as_str().parse::<i32>().is_err()
+                && !matches!(r1.kind, ExprKind::Lit(_))
+            {
+                // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
+                // suggestion being the only one to apply is high.
+                return false;
             }
             let mut enclose = |left: Span, right: Span| {
                 err.multipart_suggestion(
@@ -2245,12 +2245,32 @@ impl<'a> Parser<'a> {
         first_pat
     }
 
+    crate fn maybe_recover_unexpected_block_label(&mut self) -> bool {
+        let Some(label) = self.eat_label().filter(|_| {
+            self.eat(&token::Colon) && self.token.kind == token::OpenDelim(token::Brace)
+        }) else {
+            return false;
+        };
+        let span = label.ident.span.to(self.prev_token.span);
+        let mut err = self.struct_span_err(span, "block label not supported here");
+        err.span_label(span, "not supported here");
+        err.tool_only_span_suggestion(
+            label.ident.span.until(self.token.span),
+            "remove this block label",
+            String::new(),
+            Applicability::MachineApplicable,
+        );
+        err.emit();
+        true
+    }
+
     /// Some special error handling for the "top-level" patterns in a match arm,
     /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
     crate fn maybe_recover_unexpected_comma(
         &mut self,
         lo: Span,
         rc: RecoverComma,
+        rt: CommaRecoveryMode,
     ) -> PResult<'a, ()> {
         if rc == RecoverComma::No || self.token != token::Comma {
             return Ok(());
@@ -2270,20 +2290,25 @@ impl<'a> Parser<'a> {
         let seq_span = lo.to(self.prev_token.span);
         let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
         if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
-            const MSG: &str = "try adding parentheses to match on a tuple...";
-
-            err.span_suggestion(
-                seq_span,
-                MSG,
-                format!("({})", seq_snippet),
-                Applicability::MachineApplicable,
-            );
-            err.span_suggestion(
-                seq_span,
-                "...or a vertical bar to match on multiple alternatives",
-                seq_snippet.replace(',', " |"),
+            err.multipart_suggestion(
+                &format!(
+                    "try adding parentheses to match on a tuple{}",
+                    if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
+                ),
+                vec![
+                    (seq_span.shrink_to_lo(), "(".to_string()),
+                    (seq_span.shrink_to_hi(), ")".to_string()),
+                ],
                 Applicability::MachineApplicable,
             );
+            if let CommaRecoveryMode::EitherTupleOrPipe = rt {
+                err.span_suggestion(
+                    seq_span,
+                    "...or a vertical bar to match on multiple alternatives",
+                    seq_snippet.replace(',', " |"),
+                    Applicability::MachineApplicable,
+                );
+            }
         }
         Err(err)
     }