Rollup of 5 pull requests

Cargo.lock

@@ -3595,6 +3595,7 @@ dependencies = [
  "rustc_data_structures",
  "rustc_errors",
  "rustc_feature",
+ "rustc_macros",
  "rustc_parse",
  "rustc_session",
  "rustc_span",

compiler/rustc_ast_passes/Cargo.toml

@@ -11,6 +11,7 @@ rustc_attr = { path = "../rustc_attr" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
+rustc_macros = { path = "../rustc_macros" }
 rustc_parse = { path = "../rustc_parse" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }

compiler/rustc_ast_passes/src/errors.rs

@@ -0,0 +1,248 @@
+//! Errors emitted by ast_passes.
+
+use rustc_errors::{fluent, AddSubdiagnostic, Applicability, Diagnostic};
+use rustc_macros::{SessionDiagnostic, SessionSubdiagnostic};
+use rustc_span::{Span, Symbol};
+
+use crate::ast_validation::ForbiddenLetReason;
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::forbidden_let)]
+#[note]
+pub struct ForbiddenLet {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub(crate) reason: ForbiddenLetReason,
+}
+
+impl AddSubdiagnostic for ForbiddenLetReason {
+    fn add_to_diagnostic(self, diag: &mut Diagnostic) {
+        match self {
+            Self::GenericForbidden => {}
+            Self::NotSupportedOr(span) => {
+                diag.span_note(span, fluent::ast_passes::not_supported_or);
+            }
+            Self::NotSupportedParentheses(span) => {
+                diag.span_note(span, fluent::ast_passes::not_supported_parentheses);
+            }
+        }
+    }
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::forbidden_assoc_constraint)]
+pub struct ForbiddenAssocConstraint {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::keyword_lifetime)]
+pub struct KeywordLifetime {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::invalid_label)]
+pub struct InvalidLabel {
+    #[primary_span]
+    pub span: Span,
+    pub name: Symbol,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::invalid_visibility, code = "E0449")]
+pub struct InvalidVisibility {
+    #[primary_span]
+    pub span: Span,
+    #[label(ast_passes::implied)]
+    pub implied: Option<Span>,
+    #[subdiagnostic]
+    pub note: Option<InvalidVisibilityNote>,
+}
+
+#[derive(SessionSubdiagnostic)]
+pub enum InvalidVisibilityNote {
+    #[note(ast_passes::individual_impl_items)]
+    IndividualImplItems,
+    #[note(ast_passes::individual_foreign_items)]
+    IndividualForeignItems,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::trait_fn_async, code = "E0706")]
+#[note]
+#[note(ast_passes::note2)]
+pub struct TraitFnAsync {
+    #[primary_span]
+    pub fn_span: Span,
+    #[label]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::trait_fn_const, code = "E0379")]
+pub struct TraitFnConst {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::forbidden_lifetime_bound)]
+pub struct ForbiddenLifetimeBound {
+    #[primary_span]
+    pub spans: Vec<Span>,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::forbidden_non_lifetime_param)]
+pub struct ForbiddenNonLifetimeParam {
+    #[primary_span]
+    pub spans: Vec<Span>,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::fn_param_too_many)]
+pub struct FnParamTooMany {
+    #[primary_span]
+    pub span: Span,
+    pub max_num_args: usize,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::fn_param_c_var_args_only)]
+pub struct FnParamCVarArgsOnly {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::fn_param_c_var_args_not_last)]
+pub struct FnParamCVarArgsNotLast {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::fn_param_doc_comment)]
+pub struct FnParamDocComment {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::fn_param_forbidden_attr)]
+pub struct FnParamForbiddenAttr {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::fn_param_forbidden_self)]
+#[note]
+pub struct FnParamForbiddenSelf {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::forbidden_default)]
+pub struct ForbiddenDefault {
+    #[primary_span]
+    pub span: Span,
+    #[label]
+    pub def_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::assoc_const_without_body)]
+pub struct AssocConstWithoutBody {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(code = " = <expr>;", applicability = "has-placeholders")]
+    pub replace_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::assoc_fn_without_body)]
+pub struct AssocFnWithoutBody {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(code = " {{ <body> }}", applicability = "has-placeholders")]
+    pub replace_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::assoc_type_without_body)]
+pub struct AssocTypeWithoutBody {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(code = " = <type>;", applicability = "has-placeholders")]
+    pub replace_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::const_without_body)]
+pub struct ConstWithoutBody {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(code = " = <expr>;", applicability = "has-placeholders")]
+    pub replace_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::static_without_body)]
+pub struct StaticWithoutBody {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(code = " = <expr>;", applicability = "has-placeholders")]
+    pub replace_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::ty_alias_without_body)]
+pub struct TyAliasWithoutBody {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(code = " = <type>;", applicability = "has-placeholders")]
+    pub replace_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(ast_passes::fn_without_body)]
+pub struct FnWithoutBody {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(code = " {{ <body> }}", applicability = "has-placeholders")]
+    pub replace_span: Span,
+    #[subdiagnostic]
+    pub extern_block_suggestion: Option<ExternBlockSuggestion>,
+}
+
+pub struct ExternBlockSuggestion {
+    pub start_span: Span,
+    pub end_span: Span,
+    pub abi: Option<Symbol>,
+}
+
+impl AddSubdiagnostic for ExternBlockSuggestion {
+    fn add_to_diagnostic(self, diag: &mut Diagnostic) {
+        let start_suggestion = if let Some(abi) = self.abi {
+            format!("extern \"{}\" {{", abi)
+        } else {
+            "extern {".to_owned()
+        };
+        let end_suggestion = " }".to_owned();
+
+        diag.multipart_suggestion(
+            fluent::ast_passes::extern_block_suggestion,
+            vec![(self.start_span, start_suggestion), (self.end_span, end_suggestion)],
+            Applicability::MaybeIncorrect,
+        );
+    }
+}

compiler/rustc_ast_passes/src/lib.rs

@@ -12,6 +12,7 @@
 #![recursion_limit = "256"]
 
 pub mod ast_validation;
+mod errors;
 pub mod feature_gate;
 pub mod node_count;
 pub mod show_span;

compiler/rustc_builtin_macros/src/format.rs

@@ -1176,7 +1176,7 @@ fn create_lints_for_named_arguments_used_positionally(cx: &mut Context<'_, '_>)
 
         cx.ecx.buffered_early_lint.push(BufferedEarlyLint {
             span: MultiSpan::from_span(named_arg.positional_named_arg_span),
-            msg: msg.clone(),
+            msg: msg.into(),
             node_id: ast::CRATE_NODE_ID,
             lint_id: LintId::of(&NAMED_ARGUMENTS_USED_POSITIONALLY),
             diagnostic: BuiltinLintDiagnostics::NamedArgumentUsedPositionally {

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

@@ -0,0 +1,93 @@
+ast_passes_forbidden_let =
+    `let` expressions are not supported here
+    .note = only supported directly in conditions of `if` and `while` expressions
+    .not_supported_or = `||` operators are not supported in let chain expressions
+    .not_supported_parentheses = `let`s wrapped in parentheses are not supported in a context with let chains
+
+ast_passes_deprecated_where_clause_location =
+    where clause not allowed here
+
+ast_passes_forbidden_assoc_constraint =
+    associated type bounds are not allowed within structs, enums, or unions
+
+ast_passes_keyword_lifetime =
+    lifetimes cannot use keyword names
+
+ast_passes_invalid_label =
+    invalid label name `{$name}`
+
+ast_passes_invalid_visibility =
+    unnecessary visibility qualifier
+    .implied = `pub` not permitted here because it's implied
+    .individual_impl_items = place qualifiers on individual impl items instead
+    .individual_foreign_items = place qualifiers on individual foreign items instead
+
+ast_passes_trait_fn_async =
+    functions in traits cannot be declared `async`
+    .label = `async` because of this
+    .note = `async` trait functions are not currently supported
+    .note2 = consider using the `async-trait` crate: https://crates.io/crates/async-trait
+
+ast_passes_trait_fn_const =
+    functions in traits cannot be declared const
+    .label = functions in traits cannot be const
+
+ast_passes_forbidden_lifetime_bound =
+    lifetime bounds cannot be used in this context
+
+ast_passes_forbidden_non_lifetime_param =
+    only lifetime parameters can be used in this context
+
+ast_passes_fn_param_too_many =
+    function can not have more than {$max_num_args} arguments
+
+ast_passes_fn_param_c_var_args_only =
+    C-variadic function must be declared with at least one named argument
+
+ast_passes_fn_param_c_var_args_not_last =
+    `...` must be the last argument of a C-variadic function
+
+ast_passes_fn_param_doc_comment =
+    documentation comments cannot be applied to function parameters
+    .label = doc comments are not allowed here
+
+ast_passes_fn_param_forbidden_attr =
+    allow, cfg, cfg_attr, deny, expect, forbid, and warn are the only allowed built-in attributes in function parameters
+
+ast_passes_fn_param_forbidden_self =
+    `self` parameter is only allowed in associated functions
+    .label = not semantically valid as function parameter
+    .note = associated functions are those in `impl` or `trait` definitions
+
+ast_passes_forbidden_default =
+    `default` is only allowed on items in trait impls
+    .label = `default` because of this
+
+ast_passes_assoc_const_without_body =
+    associated constant in `impl` without body
+    .suggestion = provide a definition for the constant
+
+ast_passes_assoc_fn_without_body =
+    associated function in `impl` without body
+    .suggestion = provide a definition for the function
+
+ast_passes_assoc_type_without_body =
+    associated type in `impl` without body
+    .suggestion = provide a definition for the type
+
+ast_passes_const_without_body =
+    free constant item without body
+    .suggestion = provide a definition for the constant
+
+ast_passes_static_without_body =
+    free static item without body
+    .suggestion = provide a definition for the static
+
+ast_passes_ty_alias_without_body =
+    free type alias without body
+    .suggestion = provide a definition for the type
+
+ast_passes_fn_without_body =
+    free function without a body
+    .suggestion = provide a definition for the function
+    .extern_block_suggestion = if you meant to declare an externally defined function, use an `extern` block

compiler/rustc_error_messages/src/lib.rs

@@ -32,6 +32,7 @@ pub use unic_langid::{langid, LanguageIdentifier};
 
 // Generates `DEFAULT_LOCALE_RESOURCES` static and `fluent_generated` module.
 fluent_messages! {
+    ast_passes => "../locales/en-US/ast_passes.ftl",
     borrowck => "../locales/en-US/borrowck.ftl",
     builtin_macros => "../locales/en-US/builtin_macros.ftl",
     const_eval => "../locales/en-US/const_eval.ftl",

compiler/rustc_lint/src/early.rs

@@ -45,7 +45,7 @@ impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
                 lint_id.lint,
                 Some(span),
                 |lint| {
-                    lint.build(&msg).emit();
+                    lint.build(msg).emit();
                 },
                 diagnostic,
             );

compiler/rustc_lint_defs/src/lib.rs

@@ -9,7 +9,7 @@ pub use self::Level::*;
 use rustc_ast::node_id::{NodeId, NodeMap};
 use rustc_ast::{AttrId, Attribute};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
-use rustc_error_messages::MultiSpan;
+use rustc_error_messages::{DiagnosticMessage, MultiSpan};
 use rustc_hir::HashStableContext;
 use rustc_hir::HirId;
 use rustc_span::edition::Edition;
@@ -491,7 +491,7 @@ pub struct BufferedEarlyLint {
     pub span: MultiSpan,
 
     /// The lint message.
-    pub msg: String,
+    pub msg: DiagnosticMessage,
 
     /// The `NodeId` of the AST node that generated the lint.
     pub node_id: NodeId,
@@ -520,11 +520,11 @@ impl LintBuffer {
         lint: &'static Lint,
         node_id: NodeId,
         span: MultiSpan,
-        msg: &str,
+        msg: impl Into<DiagnosticMessage>,
         diagnostic: BuiltinLintDiagnostics,
     ) {
         let lint_id = LintId::of(lint);
-        let msg = msg.to_string();
+        let msg = msg.into();
         self.add_early_lint(BufferedEarlyLint { lint_id, node_id, span, msg, diagnostic });
     }
 
@@ -537,7 +537,7 @@ impl LintBuffer {
         lint: &'static Lint,
         id: NodeId,
         sp: impl Into<MultiSpan>,
-        msg: &str,
+        msg: impl Into<DiagnosticMessage>,
     ) {
         self.add_lint(lint, id, sp.into(), msg, BuiltinLintDiagnostics::Normal)
     }
@@ -547,7 +547,7 @@ impl LintBuffer {
         lint: &'static Lint,
         id: NodeId,
         sp: impl Into<MultiSpan>,
-        msg: &str,
+        msg: impl Into<DiagnosticMessage>,
         diagnostic: BuiltinLintDiagnostics,
     ) {
         self.add_lint(lint, id, sp.into(), msg, diagnostic)

compiler/rustc_macros/src/diagnostics/utils.rs

@@ -235,35 +235,40 @@ pub(crate) trait HasFieldMap {
         // the referenced fields. Leaves `it` sitting on the closing brace of the format string, so
         // the next call to `it.next()` retrieves the next character.
         while let Some(c) = it.next() {
-            if c == '{' && *it.peek().unwrap_or(&'\0') != '{' {
-                let mut eat_argument = || -> Option<String> {
-                    let mut result = String::new();
-                    // Format specifiers look like:
-                    //
-                    //   format   := '{' [ argument ] [ ':' format_spec ] '}' .
-                    //
-                    // Therefore, we only need to eat until ':' or '}' to find the argument.
-                    while let Some(c) = it.next() {
-                        result.push(c);
-                        let next = *it.peek().unwrap_or(&'\0');
-                        if next == '}' {
-                            break;
-                        } else if next == ':' {
-                            // Eat the ':' character.
-                            assert_eq!(it.next().unwrap(), ':');
-                            break;
-                        }
-                    }
-                    // Eat until (and including) the matching '}'
-                    while it.next()? != '}' {
-                        continue;
+            if c != '{' {
+                continue;
+            }
+            if *it.peek().unwrap_or(&'\0') == '{' {
+                assert_eq!(it.next().unwrap(), '{');
+                continue;
+            }
+            let mut eat_argument = || -> Option<String> {
+                let mut result = String::new();
+                // Format specifiers look like:
+                //
+                //   format   := '{' [ argument ] [ ':' format_spec ] '}' .
+                //
+                // Therefore, we only need to eat until ':' or '}' to find the argument.
+                while let Some(c) = it.next() {
+                    result.push(c);
+                    let next = *it.peek().unwrap_or(&'\0');
+                    if next == '}' {
+                        break;
+                    } else if next == ':' {
+                        // Eat the ':' character.
+                        assert_eq!(it.next().unwrap(), ':');
+                        break;
                     }
-                    Some(result)
-                };
-
-                if let Some(referenced_field) = eat_argument() {
-                    referenced_fields.insert(referenced_field);
                 }
+                // Eat until (and including) the matching '}'
+                while it.next()? != '}' {
+                    continue;
+                }
+                Some(result)
+            };
+
+            if let Some(referenced_field) = eat_argument() {
+                referenced_fields.insert(referenced_field);
             }
         }
 

compiler/rustc_parse/src/parser/ty.rs

@@ -640,7 +640,13 @@ impl<'a> Parser<'a> {
         let mut bounds = Vec::new();
         let mut negative_bounds = Vec::new();
 
-        while self.can_begin_bound() || self.token.is_keyword(kw::Dyn) {
+        while self.can_begin_bound()
+            // Continue even if we find a keyword.
+            // This is necessary for error recover on, for example, `impl fn()`.
+            //
+            // The only keyword that can go after generic bounds is `where`, so stop if it's it.
+            || (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))
+        {
             if self.token.is_keyword(kw::Dyn) {
                 // Account for `&dyn Trait + dyn Other`.
                 self.struct_span_err(self.token.span, "invalid `dyn` keyword")
@@ -803,6 +809,20 @@ impl<'a> Parser<'a> {
             self.expect_keyword(kw::Const)?;
             let span = tilde.to(self.prev_token.span);
             self.sess.gated_spans.gate(sym::const_trait_impl, span);
+            Some(span)
+        } else if self.eat_keyword(kw::Const) {
+            let span = self.prev_token.span;
+            self.sess.gated_spans.gate(sym::const_trait_impl, span);
+
+            self.struct_span_err(span, "const bounds must start with `~`")
+                .span_suggestion(
+                    span.shrink_to_lo(),
+                    "add `~`",
+                    "~",
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+
             Some(span)
         } else {
             None

compiler/rustc_session/src/parse.rs

@@ -360,6 +360,17 @@ impl ParseSess {
         self.create_warning(warning).emit()
     }
 
+    pub fn create_fatal<'a>(
+        &'a self,
+        fatal: impl SessionDiagnostic<'a, !>,
+    ) -> DiagnosticBuilder<'a, !> {
+        fatal.into_diagnostic(self)
+    }
+
+    pub fn emit_fatal<'a>(&'a self, fatal: impl SessionDiagnostic<'a, !>) -> ! {
+        self.create_fatal(fatal).emit()
+    }
+
     #[rustc_lint_diagnostics]
     pub fn struct_err(
         &self,
@@ -373,6 +384,11 @@ impl ParseSess {
         self.span_diagnostic.struct_warn(msg)
     }
 
+    #[rustc_lint_diagnostics]
+    pub fn struct_fatal(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, !> {
+        self.span_diagnostic.struct_fatal(msg)
+    }
+
     #[rustc_lint_diagnostics]
     pub fn struct_diagnostic<G: EmissionGuarantee>(
         &self,

compiler/rustc_session/src/session.rs

@@ -482,6 +482,15 @@ impl Session {
     pub fn emit_warning<'a>(&'a self, warning: impl SessionDiagnostic<'a, ()>) {
         self.parse_sess.emit_warning(warning)
     }
+    pub fn create_fatal<'a>(
+        &'a self,
+        fatal: impl SessionDiagnostic<'a, !>,
+    ) -> DiagnosticBuilder<'a, !> {
+        self.parse_sess.create_fatal(fatal)
+    }
+    pub fn emit_fatal<'a>(&'a self, fatal: impl SessionDiagnostic<'a, !>) -> ! {
+        self.parse_sess.emit_fatal(fatal)
+    }
     #[inline]
     pub fn err_count(&self) -> usize {
         self.diagnostic().err_count()

compiler/rustc_trait_selection/src/traits/project.rs

@@ -554,6 +554,18 @@ impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> {
                     .flatten()
                     .unwrap_or_else(|| ty::Term::Ty(ty.super_fold_with(self)))
                 };
+                // For cases like #95134 we would like to catch overflows early
+                // otherwise they slip away away and cause ICE.
+                let recursion_limit = self.tcx().recursion_limit();
+                if !recursion_limit.value_within_limit(self.depth) {
+                    let obligation = Obligation::with_depth(
+                        self.cause.clone(),
+                        recursion_limit.0,
+                        self.param_env,
+                        ty,
+                    );
+                    self.selcx.infcx().report_overflow_error(&obligation, true);
+                }
                 debug!(
                     ?self.depth,
                     ?ty,

library/alloc/src/boxed.rs

@@ -1,4 +1,4 @@
-//! A pointer type for heap allocation.
+//! The `Box<T>` type for heap allocation.
 //!
 //! [`Box<T>`], casually referred to as a 'box', provides the simplest form of
 //! heap allocation in Rust. Boxes provide ownership for this allocation, and

library/alloc/src/slice.rs

@@ -1,82 +1,12 @@
-//! A dynamically-sized view into a contiguous sequence, `[T]`.
+//! Utilities for the slice primitive type.
 //!
 //! *[See also the slice primitive type](slice).*
 //!
-//! Slices are a view into a block of memory represented as a pointer and a
-//! length.
+//! Most of the structs in this module are iterator types which can only be created
+//! using a certain function. For example, `slice.iter()` yields an [`Iter`].
 //!
-//! ```
-//! // slicing a Vec
-//! let vec = vec![1, 2, 3];
-//! let int_slice = &vec[..];
-//! // coercing an array to a slice
-//! let str_slice: &[&str] = &["one", "two", "three"];
-//! ```
-//!
-//! Slices are either mutable or shared. The shared slice type is `&[T]`,
-//! while the mutable slice type is `&mut [T]`, where `T` represents the element
-//! type. For example, you can mutate the block of memory that a mutable slice
-//! points to:
-//!
-//! ```
-//! let x = &mut [1, 2, 3];
-//! x[1] = 7;
-//! assert_eq!(x, &[1, 7, 3]);
-//! ```
-//!
-//! Here are some of the things this module contains:
-//!
-//! ## Structs
-//!
-//! There are several structs that are useful for slices, such as [`Iter`], which
-//! represents iteration over a slice.
-//!
-//! ## Trait Implementations
-//!
-//! There are several implementations of common traits for slices. Some examples
-//! include:
-//!
-//! * [`Clone`]
-//! * [`Eq`], [`Ord`] - for slices whose element type are [`Eq`] or [`Ord`].
-//! * [`Hash`] - for slices whose element type is [`Hash`].
-//!
-//! ## Iteration
-//!
-//! The slices implement `IntoIterator`. The iterator yields references to the
-//! slice elements.
-//!
-//! ```
-//! let numbers = &[0, 1, 2];
-//! for n in numbers {
-//!     println!("{n} is a number!");
-//! }
-//! ```
-//!
-//! The mutable slice yields mutable references to the elements:
-//!
-//! ```
-//! let mut scores = [7, 8, 9];
-//! for score in &mut scores[..] {
-//!     *score += 1;
-//! }
-//! ```
-//!
-//! This iterator yields mutable references to the slice's elements, so while
-//! the element type of the slice is `i32`, the element type of the iterator is
-//! `&mut i32`.
-//!
-//! * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default
-//!   iterators.
-//! * Further methods that return iterators are [`.split`], [`.splitn`],
-//!   [`.chunks`], [`.windows`] and more.
-//!
-//! [`Hash`]: core::hash::Hash
-//! [`.iter`]: slice::iter
-//! [`.iter_mut`]: slice::iter_mut
-//! [`.split`]: slice::split
-//! [`.splitn`]: slice::splitn
-//! [`.chunks`]: slice::chunks
-//! [`.windows`]: slice::windows
+//! A few functions are provided to create a slice from a value reference
+//! or from a raw pointer.
 #![stable(feature = "rust1", since = "1.0.0")]
 // Many of the usings in this module are only used in the test configuration.
 // It's cleaner to just turn off the unused_imports warning than to fix them.

library/alloc/src/str.rs

@@ -1,26 +1,6 @@
-//! Unicode string slices.
+//! Utilities for the `str` primitive type.
 //!
 //! *[See also the `str` primitive type](str).*
-//!
-//! The `&str` type is one of the two main string types, the other being `String`.
-//! Unlike its `String` counterpart, its contents are borrowed.
-//!
-//! # Basic Usage
-//!
-//! A basic string declaration of `&str` type:
-//!
-//! ```
-//! let hello_world = "Hello, World!";
-//! ```
-//!
-//! Here we have declared a string literal, also known as a string slice.
-//! String literals have a static lifetime, which means the string `hello_world`
-//! is guaranteed to be valid for the duration of the entire program.
-//! We can explicitly specify `hello_world`'s lifetime as well:
-//!
-//! ```
-//! let hello_world: &'static str = "Hello, world!";
-//! ```
 
 #![stable(feature = "rust1", since = "1.0.0")]
 // Many of the usings in this module are only used in the test configuration.

library/alloc/tests/vec.rs

@@ -293,6 +293,22 @@ fn test_retain() {
     assert_eq!(vec, [2, 4]);
 }
 
+#[test]
+fn test_retain_predicate_order() {
+    for to_keep in [true, false] {
+        let mut number_of_executions = 0;
+        let mut vec = vec![1, 2, 3, 4];
+        let mut next_expected = 1;
+        vec.retain(|&x| {
+            assert_eq!(next_expected, x);
+            next_expected += 1;
+            number_of_executions += 1;
+            to_keep
+        });
+        assert_eq!(number_of_executions, 4);
+    }
+}
+
 #[test]
 fn test_retain_pred_panic_with_hole() {
     let v = (0..5).map(Rc::new).collect::<Vec<_>>();
@@ -354,6 +370,35 @@ fn test_retain_drop_panic() {
     assert!(v.iter().all(|r| Rc::strong_count(r) == 1));
 }
 
+#[test]
+fn test_retain_maybeuninits() {
+    // This test aimed to be run under miri.
+    use core::mem::MaybeUninit;
+    let mut vec: Vec<_> = [1i32, 2, 3, 4].map(|v| MaybeUninit::new(vec![v])).into();
+    vec.retain(|x| {
+        // SAFETY: Retain must visit every element of Vec in original order and exactly once.
+        // Our values is initialized at creation of Vec.
+        let v = unsafe { x.assume_init_ref()[0] };
+        if v & 1 == 0 {
+            return true;
+        }
+        // SAFETY: Value is initialized.
+        // Value wouldn't be dropped by `Vec::retain`
+        // because `MaybeUninit` doesn't drop content.
+        drop(unsafe { x.assume_init_read() });
+        false
+    });
+    let vec: Vec<i32> = vec
+        .into_iter()
+        .map(|x| unsafe {
+            // SAFETY: All values dropped in retain predicate must be removed by `Vec::retain`.
+            // Remaining values are initialized.
+            x.assume_init()[0]
+        })
+        .collect();
+    assert_eq!(vec, [2, 4]);
+}
+
 #[test]
 fn test_dedup() {
     fn case(a: Vec<i32>, b: Vec<i32>) {

library/core/src/any.rs

@@ -1,7 +1,4 @@
-//! This module contains the `Any` trait, which enables dynamic typing
-//! of any `'static` type through runtime reflection. It also contains the
-//! `Provider` trait and accompanying API, which enable trait objects to provide
-//! data based on typed requests, an alternate form of runtime reflection.
+//! Utilities for dynamic typing or type reflection.
 //!
 //! # `Any` and `TypeId`
 //!

library/core/src/array/mod.rs

@@ -1,4 +1,4 @@
-//! Helper functions and types for fixed-length arrays.
+//! Utilities for the array primitive type.
 //!
 //! *[See also the array primitive type](array).*
 

library/core/src/borrow.rs

@@ -1,4 +1,4 @@
-//! A module for working with borrowed data.
+//! Utilities for working with borrowed data.
 
 #![stable(feature = "rust1", since = "1.0.0")]
 

library/core/src/char/mod.rs

@@ -1,4 +1,6 @@
-//! A character type.
+//! Utilities for the `char` primitive type.
+//!
+//! *[See also the `char` primitive type](primitive@char).*
 //!
 //! The `char` type represents a single character. More specifically, since
 //! 'character' isn't a well-defined concept in Unicode, `char` is a '[Unicode

library/core/src/cmp.rs

@@ -1,6 +1,6 @@
-//! Functionality for ordering and comparison.
+//! Utilities for comparing and ordering values.
 //!
-//! This module contains various tools for ordering and comparing values. In
+//! This module contains various tools for comparing and ordering values. In
 //! summary:
 //!
 //! * [`Eq`] and [`PartialEq`] are traits that allow you to define total and

library/core/src/default.rs

@@ -1,4 +1,4 @@
-//! The `Default` trait for types which may have meaningful default values.
+//! The `Default` trait for types with a default value.
 
 #![stable(feature = "rust1", since = "1.0.0")]
 

library/core/src/num/f32.rs

@@ -1,4 +1,4 @@
-//! Constants specific to the `f32` single-precision floating point type.
+//! Constants for the `f32` single-precision floating point type.
 //!
 //! *[See also the `f32` primitive type][f32].*
 //!

library/core/src/num/f64.rs

@@ -1,4 +1,4 @@
-//! Constants specific to the `f64` double-precision floating point type.
+//! Constants for the `f64` double-precision floating point type.
 //!
 //! *[See also the `f64` primitive type][f64].*
 //!

library/core/src/primitive_docs.rs

@@ -801,11 +801,53 @@ mod prim_array {}
 /// assert_eq!(2 * pointer_size, std::mem::size_of::<Box<[u8]>>());
 /// assert_eq!(2 * pointer_size, std::mem::size_of::<Rc<[u8]>>());
 /// ```
+///
+/// ## Trait Implementations
+///
+/// Some traits are implemented for slices if the element type implements
+/// that trait. This includes [`Eq`], [`Hash`] and [`Ord`].
+///
+/// ## Iteration
+///
+/// The slices implement `IntoIterator`. The iterator yields references to the
+/// slice elements.
+///
+/// ```
+/// let numbers: &[i32] = &[0, 1, 2];
+/// for n in numbers {
+///     println!("{n} is a number!");
+/// }
+/// ```
+///
+/// The mutable slice yields mutable references to the elements:
+///
+/// ```
+/// let mut scores: &mut [i32] = &mut [7, 8, 9];
+/// for score in scores {
+///     *score += 1;
+/// }
+/// ```
+///
+/// This iterator yields mutable references to the slice's elements, so while
+/// the element type of the slice is `i32`, the element type of the iterator is
+/// `&mut i32`.
+///
+/// * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default
+///   iterators.
+/// * Further methods that return iterators are [`.split`], [`.splitn`],
+///   [`.chunks`], [`.windows`] and more.
+///
+/// [`Hash`]: core::hash::Hash
+/// [`.iter`]: slice::iter
+/// [`.iter_mut`]: slice::iter_mut
+/// [`.split`]: slice::split
+/// [`.splitn`]: slice::splitn
+/// [`.chunks`]: slice::chunks
+/// [`.windows`]: slice::windows
 #[stable(feature = "rust1", since = "1.0.0")]
 mod prim_slice {}
 
 #[doc(primitive = "str")]
-//
 /// String slices.
 ///
 /// *[See also the `std::str` module](crate::str).*
@@ -816,19 +858,22 @@ mod prim_slice {}
 ///
 /// String slices are always valid UTF-8.
 ///
-/// # Examples
+/// # Basic Usage
 ///
 /// String literals are string slices:
 ///
 /// ```
-/// let hello = "Hello, world!";
-///
-/// // with an explicit type annotation
-/// let hello: &'static str = "Hello, world!";
+/// let hello_world = "Hello, World!";
 /// ```
 ///
-/// They are `'static` because they're stored directly in the final binary, and
-/// so will be valid for the `'static` duration.
+/// Here we have declared a string slice initialized with a string literal.
+/// String literals have a static lifetime, which means the string `hello_world`
+/// is guaranteed to be valid for the duration of the entire program.
+/// We can explicitly specify `hello_world`'s lifetime as well:
+///
+/// ```
+/// let hello_world: &'static str = "Hello, world!";
+/// ```
 ///
 /// # Representation
 ///

library/std/src/error.rs

@@ -1,4 +1,4 @@
-//! Interfaces for working with Errors.
+//! The `Error` trait provides common functionality for errors.
 //!
 //! # Error Handling In Rust
 //!

library/std/src/f32.rs

@@ -1,4 +1,4 @@
-//! Constants specific to the `f32` single-precision floating point type.
+//! Constants for the `f32` single-precision floating point type.
 //!
 //! *[See also the `f32` primitive type](primitive@f32).*
 //!

library/std/src/f64.rs

@@ -1,4 +1,4 @@
-//! Constants specific to the `f64` double-precision floating point type.
+//! Constants for the `f64` double-precision floating point type.
 //!
 //! *[See also the `f64` primitive type](primitive@f64).*
 //!

library/std/src/primitive_docs.rs

@@ -801,11 +801,53 @@ mod prim_array {}
 /// assert_eq!(2 * pointer_size, std::mem::size_of::<Box<[u8]>>());
 /// assert_eq!(2 * pointer_size, std::mem::size_of::<Rc<[u8]>>());
 /// ```
+///
+/// ## Trait Implementations
+///
+/// Some traits are implemented for slices if the element type implements
+/// that trait. This includes [`Eq`], [`Hash`] and [`Ord`].
+///
+/// ## Iteration
+///
+/// The slices implement `IntoIterator`. The iterator yields references to the
+/// slice elements.
+///
+/// ```
+/// let numbers: &[i32] = &[0, 1, 2];
+/// for n in numbers {
+///     println!("{n} is a number!");
+/// }
+/// ```
+///
+/// The mutable slice yields mutable references to the elements:
+///
+/// ```
+/// let mut scores: &mut [i32] = &mut [7, 8, 9];
+/// for score in scores {
+///     *score += 1;
+/// }
+/// ```
+///
+/// This iterator yields mutable references to the slice's elements, so while
+/// the element type of the slice is `i32`, the element type of the iterator is
+/// `&mut i32`.
+///
+/// * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default
+///   iterators.
+/// * Further methods that return iterators are [`.split`], [`.splitn`],
+///   [`.chunks`], [`.windows`] and more.
+///
+/// [`Hash`]: core::hash::Hash
+/// [`.iter`]: slice::iter
+/// [`.iter_mut`]: slice::iter_mut
+/// [`.split`]: slice::split
+/// [`.splitn`]: slice::splitn
+/// [`.chunks`]: slice::chunks
+/// [`.windows`]: slice::windows
 #[stable(feature = "rust1", since = "1.0.0")]
 mod prim_slice {}
 
 #[doc(primitive = "str")]
-//
 /// String slices.
 ///
 /// *[See also the `std::str` module](crate::str).*
@@ -816,19 +858,22 @@ mod prim_slice {}
 ///
 /// String slices are always valid UTF-8.
 ///
-/// # Examples
+/// # Basic Usage
 ///
 /// String literals are string slices:
 ///
 /// ```
-/// let hello = "Hello, world!";
-///
-/// // with an explicit type annotation
-/// let hello: &'static str = "Hello, world!";
+/// let hello_world = "Hello, World!";
 /// ```
 ///
-/// They are `'static` because they're stored directly in the final binary, and
-/// so will be valid for the `'static` duration.
+/// Here we have declared a string slice initialized with a string literal.
+/// String literals have a static lifetime, which means the string `hello_world`
+/// is guaranteed to be valid for the duration of the entire program.
+/// We can explicitly specify `hello_world`'s lifetime as well:
+///
+/// ```
+/// let hello_world: &'static str = "Hello, world!";
+/// ```
 ///
 /// # Representation
 ///

src/test/ui/issues/issue-23122-2.stderr

@@ -1,15 +1,10 @@
-error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next: Sized`
+error[E0275]: overflow evaluating the requirement `<T as Next>::Next`
   --> $DIR/issue-23122-2.rs:10:17
    |
 LL |     type Next = <GetNext<T::Next> as Next>::Next;
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_23122_2`)
-note: required for `GetNext<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next>` to implement `Next`
-  --> $DIR/issue-23122-2.rs:9:15
-   |
-LL | impl<T: Next> Next for GetNext<T> {
-   |               ^^^^     ^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/kw-in-trait-bounds.rs

@@ -0,0 +1,47 @@
+// edition:2018
+
+fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
+//~^ ERROR expected identifier, found keyword `fn`
+//~| ERROR expected identifier, found keyword `fn`
+//~| ERROR expected identifier, found keyword `fn`
+//~| ERROR cannot find trait `r#fn` in this scope
+//~| ERROR cannot find trait `r#fn` in this scope
+//~| ERROR cannot find trait `r#fn` in this scope
+//~| HELP  a trait with a similar name exists
+//~| HELP  a trait with a similar name exists
+//~| HELP  a trait with a similar name exists
+//~| HELP  escape `fn` to use it as an identifier
+//~| HELP  escape `fn` to use it as an identifier
+//~| HELP  escape `fn` to use it as an identifier
+where
+G: fn(),
+    //~^ ERROR expected identifier, found keyword `fn`
+    //~| ERROR cannot find trait `r#fn` in this scope
+    //~| HELP  a trait with a similar name exists
+    //~| HELP  escape `fn` to use it as an identifier
+{}
+
+fn _g<A: struct, B>(_: impl struct, _: &dyn struct)
+//~^ ERROR expected identifier, found keyword `struct`
+//~| ERROR expected identifier, found keyword `struct`
+//~| ERROR expected identifier, found keyword `struct`
+//~| ERROR cannot find trait `r#struct` in this scope
+//~| ERROR cannot find trait `r#struct` in this scope
+//~| ERROR cannot find trait `r#struct` in this scope
+//~| HELP  a trait with a similar name exists
+//~| HELP  a trait with a similar name exists
+//~| HELP  a trait with a similar name exists
+//~| HELP  escape `struct` to use it as an identifier
+//~| HELP  escape `struct` to use it as an identifier
+//~| HELP  escape `struct` to use it as an identifier
+where
+    B: struct,
+    //~^ ERROR expected identifier, found keyword `struct`
+    //~| ERROR cannot find trait `r#struct` in this scope
+    //~| HELP  a trait with a similar name exists
+    //~| HELP  escape `struct` to use it as an identifier
+{}
+
+trait Struct {}
+
+fn main() {}

src/test/ui/parser/kw-in-trait-bounds.stderr

@@ -0,0 +1,171 @@
+error: expected identifier, found keyword `fn`
+  --> $DIR/kw-in-trait-bounds.rs:3:10
+   |
+LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
+   |          ^^ expected identifier, found keyword
+   |
+help: escape `fn` to use it as an identifier
+   |
+LL | fn _f<F: r#fn(), G>(_: impl fn(), _: &dyn fn())
+   |          ++
+
+error: expected identifier, found keyword `fn`
+  --> $DIR/kw-in-trait-bounds.rs:3:27
+   |
+LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
+   |                           ^^ expected identifier, found keyword
+   |
+help: escape `fn` to use it as an identifier
+   |
+LL | fn _f<F: fn(), G>(_: impl r#fn(), _: &dyn fn())
+   |                           ++
+
+error: expected identifier, found keyword `fn`
+  --> $DIR/kw-in-trait-bounds.rs:3:41
+   |
+LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
+   |                                         ^^ expected identifier, found keyword
+   |
+help: escape `fn` to use it as an identifier
+   |
+LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn r#fn())
+   |                                         ++
+
+error: expected identifier, found keyword `fn`
+  --> $DIR/kw-in-trait-bounds.rs:17:4
+   |
+LL | G: fn(),
+   |    ^^ expected identifier, found keyword
+   |
+help: escape `fn` to use it as an identifier
+   |
+LL | G: r#fn(),
+   |    ++
+
+error: expected identifier, found keyword `struct`
+  --> $DIR/kw-in-trait-bounds.rs:24:10
+   |
+LL | fn _g<A: struct, B>(_: impl struct, _: &dyn struct)
+   |          ^^^^^^ expected identifier, found keyword
+   |
+help: escape `struct` to use it as an identifier
+   |
+LL | fn _g<A: r#struct, B>(_: impl struct, _: &dyn struct)
+   |          ++
+
+error: expected identifier, found keyword `struct`
+  --> $DIR/kw-in-trait-bounds.rs:24:29
+   |
+LL | fn _g<A: struct, B>(_: impl struct, _: &dyn struct)
+   |                             ^^^^^^ expected identifier, found keyword
+   |
+help: escape `struct` to use it as an identifier
+   |
+LL | fn _g<A: struct, B>(_: impl r#struct, _: &dyn struct)
+   |                             ++
+
+error: expected identifier, found keyword `struct`
+  --> $DIR/kw-in-trait-bounds.rs:24:45
+   |
+LL | fn _g<A: struct, B>(_: impl struct, _: &dyn struct)
+   |                                             ^^^^^^ expected identifier, found keyword
+   |
+help: escape `struct` to use it as an identifier
+   |
+LL | fn _g<A: struct, B>(_: impl struct, _: &dyn r#struct)
+   |                                             ++
+
+error: expected identifier, found keyword `struct`
+  --> $DIR/kw-in-trait-bounds.rs:38:8
+   |
+LL |     B: struct,
+   |        ^^^^^^ expected identifier, found keyword
+   |
+help: escape `struct` to use it as an identifier
+   |
+LL |     B: r#struct,
+   |        ++
+
+error[E0405]: cannot find trait `r#fn` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:3:10
+   |
+LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
+   |          ^^ help: a trait with a similar name exists (notice the capitalization): `Fn`
+   |
+  ::: $SRC_DIR/core/src/ops/function.rs:LL:COL
+   |
+LL | pub trait Fn<Args>: FnMut<Args> {
+   | ------------------------------- similarly named trait `Fn` defined here
+
+error[E0405]: cannot find trait `r#fn` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:17:4
+   |
+LL | G: fn(),
+   |    ^^ help: a trait with a similar name exists (notice the capitalization): `Fn`
+   |
+  ::: $SRC_DIR/core/src/ops/function.rs:LL:COL
+   |
+LL | pub trait Fn<Args>: FnMut<Args> {
+   | ------------------------------- similarly named trait `Fn` defined here
+
+error[E0405]: cannot find trait `r#fn` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:3:27
+   |
+LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
+   |                           ^^ help: a trait with a similar name exists (notice the capitalization): `Fn`
+   |
+  ::: $SRC_DIR/core/src/ops/function.rs:LL:COL
+   |
+LL | pub trait Fn<Args>: FnMut<Args> {
+   | ------------------------------- similarly named trait `Fn` defined here
+
+error[E0405]: cannot find trait `r#fn` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:3:41
+   |
+LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
+   |                                         ^^ help: a trait with a similar name exists (notice the capitalization): `Fn`
+   |
+  ::: $SRC_DIR/core/src/ops/function.rs:LL:COL
+   |
+LL | pub trait Fn<Args>: FnMut<Args> {
+   | ------------------------------- similarly named trait `Fn` defined here
+
+error[E0405]: cannot find trait `r#struct` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:24:10
+   |
+LL | fn _g<A: struct, B>(_: impl struct, _: &dyn struct)
+   |          ^^^^^^ help: a trait with a similar name exists (notice the capitalization): `Struct`
+...
+LL | trait Struct {}
+   | ------------ similarly named trait `Struct` defined here
+
+error[E0405]: cannot find trait `r#struct` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:38:8
+   |
+LL |     B: struct,
+   |        ^^^^^^ help: a trait with a similar name exists (notice the capitalization): `Struct`
+...
+LL | trait Struct {}
+   | ------------ similarly named trait `Struct` defined here
+
+error[E0405]: cannot find trait `r#struct` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:24:29
+   |
+LL | fn _g<A: struct, B>(_: impl struct, _: &dyn struct)
+   |                             ^^^^^^ help: a trait with a similar name exists (notice the capitalization): `Struct`
+...
+LL | trait Struct {}
+   | ------------ similarly named trait `Struct` defined here
+
+error[E0405]: cannot find trait `r#struct` in this scope
+  --> $DIR/kw-in-trait-bounds.rs:24:45
+   |
+LL | fn _g<A: struct, B>(_: impl struct, _: &dyn struct)
+   |                                             ^^^^^^ help: a trait with a similar name exists (notice the capitalization): `Struct`
+...
+LL | trait Struct {}
+   | ------------ similarly named trait `Struct` defined here
+
+error: aborting due to 16 previous errors
+
+For more information about this error, try `rustc --explain E0405`.

src/test/ui/recursion/issue-83150.stderr

@@ -9,9 +9,11 @@ LL |     func(&mut iter.map(|x| x + 1))
    = note: `#[warn(unconditional_recursion)]` on by default
    = help: a `loop` may express intention better if this is on purpose
 
-error[E0275]: overflow evaluating the requirement `Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut std::ops::Range<u8>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>: Iterator`
+error[E0275]: overflow evaluating the requirement `<std::ops::Range<u8> as Iterator>::Item`
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_83150`)
+   = note: required for `Map<&mut std::ops::Range<u8>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>` to implement `Iterator`
+   = note: 64 redundant requirements hidden
    = note: required for `&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut std::ops::Range<u8>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>, [closure@$DIR/issue-83150.rs:11:24: 11:27]>` to implement `Iterator`
 
 error: aborting due to previous error; 1 warning emitted

src/test/ui/recursion/issue-95134.rs

@@ -0,0 +1,28 @@
+// build-fail
+// compile-flags: -Copt-level=0
+//~^^ ERROR overflow evaluating the requirement
+
+pub fn encode_num<Writer: ExampleWriter>(n: u32, mut writer: Writer) -> Result<(), Writer::Error> {
+    if n > 15 {
+        encode_num(n / 16, &mut writer)?;
+    }
+    Ok(())
+}
+
+pub trait ExampleWriter {
+    type Error;
+}
+
+impl<'a, T: ExampleWriter> ExampleWriter for &'a mut T {
+    type Error = T::Error;
+}
+
+struct EmptyWriter;
+
+impl ExampleWriter for EmptyWriter {
+    type Error = ();
+}
+
+fn main() {
+    encode_num(69, &mut EmptyWriter).unwrap();
+}

src/test/ui/recursion/issue-95134.stderr

@@ -0,0 +1,7 @@
+error[E0275]: overflow evaluating the requirement `<EmptyWriter as ExampleWriter>::Error`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_95134`)
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0275`.

src/test/ui/rfc-2632-const-trait-impl/without-tilde.rs

@@ -3,4 +3,4 @@
 #![feature(const_trait_impl)]
 
 struct S<T: const Tr>;
-//~^ ERROR expected one of `!`, `(`, `,`, `=`, `>`, `?`, `for`, `~`, lifetime, or path
+//~^ ERROR const bounds must start with `~`

src/test/ui/rfc-2632-const-trait-impl/without-tilde.stderr

@@ -1,8 +1,10 @@
-error: expected one of `!`, `(`, `,`, `=`, `>`, `?`, `for`, `~`, lifetime, or path, found keyword `const`
+error: const bounds must start with `~`
   --> $DIR/without-tilde.rs:5:13
    |
 LL | struct S<T: const Tr>;
-   |             ^^^^^ expected one of 10 possible tokens
+   |             -^^^^
+   |             |
+   |             help: add `~`: `~`
 
 error: aborting due to previous error