diff --git a/compiler/rustc_apfloat/src/lib.rs b/compiler/rustc_apfloat/src/lib.rs
index cfc3d5b15a6ec..dde368e7b924f 100644
--- a/compiler/rustc_apfloat/src/lib.rs
+++ b/compiler/rustc_apfloat/src/lib.rs
@@ -33,6 +33,8 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![no_std]
 #![forbid(unsafe_code)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate alloc;
diff --git a/compiler/rustc_arena/src/lib.rs b/compiler/rustc_arena/src/lib.rs
index 6529f11100d2d..98faacdc1fb59 100644
--- a/compiler/rustc_arena/src/lib.rs
+++ b/compiler/rustc_arena/src/lib.rs
@@ -19,6 +19,8 @@
 #![feature(rustc_attrs)]
 #![cfg_attr(test, feature(test))]
 #![feature(strict_provenance)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 use smallvec::SmallVec;
 
diff --git a/compiler/rustc_ast/src/lib.rs b/compiler/rustc_ast/src/lib.rs
index 528fc4816e928..2426a0cb7dd10 100644
--- a/compiler/rustc_ast/src/lib.rs
+++ b/compiler/rustc_ast/src/lib.rs
@@ -19,6 +19,8 @@
 #![feature(slice_internals)]
 #![feature(stmt_expr_attributes)]
 #![recursion_limit = "256"]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate rustc_macros;
diff --git a/compiler/rustc_ast_pretty/src/lib.rs b/compiler/rustc_ast_pretty/src/lib.rs
index 79178830bf949..bf094af5f7bb0 100644
--- a/compiler/rustc_ast_pretty/src/lib.rs
+++ b/compiler/rustc_ast_pretty/src/lib.rs
@@ -1,3 +1,5 @@
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(associated_type_bounds)]
 #![feature(box_patterns)]
 #![feature(with_negative_coherence)]
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 098e8de9420fb..683084cf09d44 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -1086,14 +1086,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             ),
                         );
                     }
-                    if is_option_or_result && maybe_reinitialized_locations_is_empty {
-                        err.span_suggestion_verbose(
-                            fn_call_span.shrink_to_lo(),
-                            "consider calling `.as_ref()` to borrow the type's contents",
-                            "as_ref().",
-                            Applicability::MachineApplicable,
-                        );
-                    }
                     // Avoid pointing to the same function in multiple different
                     // error messages.
                     if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) {
@@ -1102,6 +1094,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             &format!("this function takes ownership of the receiver `self`, which moves {}", place_name)
                         );
                     }
+                    if is_option_or_result && maybe_reinitialized_locations_is_empty {
+                        err.span_label(
+                            var_span,
+                            "help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents",
+                        );
+                    }
                 }
                 // Other desugarings takes &self, which cannot cause a move
                 _ => {}
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
index 3380226164460..c9cfc1f3f469c 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
@@ -1,6 +1,7 @@
 //! Concrete error types for all operations which may be invalid in a certain const context.
 
 use hir::def_id::LocalDefId;
+use hir::ConstContext;
 use rustc_errors::{
     error_code, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed,
 };
@@ -331,6 +332,10 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
             ccx.const_kind(),
         ));
 
+        if let ConstContext::Static(_) = ccx.const_kind() {
+            err.note("consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell");
+        }
+
         err
     }
 }
diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index 265f45b72d1bf..c8b09cffe0136 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -28,6 +28,8 @@
 #![feature(vec_into_raw_parts)]
 #![allow(rustc::default_hash_types)]
 #![allow(rustc::potential_query_instability)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate tracing;
diff --git a/compiler/rustc_error_codes/src/lib.rs b/compiler/rustc_error_codes/src/lib.rs
index f2432f6165353..bd424dd9d0685 100644
--- a/compiler/rustc_error_codes/src/lib.rs
+++ b/compiler/rustc_error_codes/src/lib.rs
@@ -1,4 +1,6 @@
 #![deny(rustdoc::invalid_codeblock_attributes)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 //! This library is used to gather all error codes into one place,
 //! the goal being to make their maintenance easier.
 
diff --git a/compiler/rustc_error_messages/locales/en-US/parser.ftl b/compiler/rustc_error_messages/locales/en-US/parser.ftl
index 7e58375361835..2d378013dd053 100644
--- a/compiler/rustc_error_messages/locales/en-US/parser.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/parser.ftl
@@ -32,3 +32,12 @@ parser_incorrect_use_of_await =
 parser_in_in_typo =
     expected iterable, found keyword `in`
     .suggestion = remove the duplicated `in`
+
+parser_invalid_variable_declaration =
+    invalid variable declaration
+
+parser_switch_mut_let_order =
+    switch the order of `mut` and `let`
+parser_missing_let_before_mut = missing keyword
+parser_use_let_not_auto = write `let` instead of `auto` to introduce a new variable
+parser_use_let_not_var = write `let` instead of `var` to introduce a new variable
diff --git a/compiler/rustc_error_messages/locales/en-US/typeck.ftl b/compiler/rustc_error_messages/locales/en-US/typeck.ftl
index 22b32ff838e59..272731d9914cc 100644
--- a/compiler/rustc_error_messages/locales/en-US/typeck.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/typeck.ftl
@@ -131,3 +131,5 @@ typeck_unused_extern_crate =
 typeck_extern_crate_not_idiomatic =
     `extern crate` is not idiomatic in the new edition
     .suggestion = convert it to a `{$msg_code}`
+
+typeck_expected_used_symbol = expected `used`, `used(compiler)` or `used(linker)`
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index 6ae4dab3a35eb..ee978f04be2a5 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -1,6 +1,8 @@
 #![feature(once_cell)]
 #![feature(rustc_attrs)]
 #![feature(type_alias_impl_trait)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 use fluent_bundle::FluentResource;
 use fluent_syntax::parser::ParserError;
diff --git a/compiler/rustc_feature/src/lib.rs b/compiler/rustc_feature/src/lib.rs
index efb83052768bc..e44c9291f8483 100644
--- a/compiler/rustc_feature/src/lib.rs
+++ b/compiler/rustc_feature/src/lib.rs
@@ -12,6 +12,8 @@
 //! symbol to the `accepted` or `removed` modules respectively.
 
 #![feature(once_cell)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 mod accepted;
 mod active;
diff --git a/compiler/rustc_fs_util/src/lib.rs b/compiler/rustc_fs_util/src/lib.rs
index 87e97c746ef56..63998bb6b00cf 100644
--- a/compiler/rustc_fs_util/src/lib.rs
+++ b/compiler/rustc_fs_util/src/lib.rs
@@ -1,3 +1,6 @@
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
+
 use std::ffi::CString;
 use std::fs;
 use std::io;
diff --git a/compiler/rustc_graphviz/src/lib.rs b/compiler/rustc_graphviz/src/lib.rs
index 6eaff5c2f746f..3c1bb5532661a 100644
--- a/compiler/rustc_graphviz/src/lib.rs
+++ b/compiler/rustc_graphviz/src/lib.rs
@@ -273,6 +273,8 @@
     html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
     test(attr(allow(unused_variables), deny(warnings)))
 )]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 use LabelText::*;
 
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index 0f9e6fa7b9895..7097f998bebda 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -11,6 +11,8 @@
 #![feature(never_type)]
 #![feature(rustc_attrs)]
 #![recursion_limit = "256"]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate rustc_macros;
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index 0f754dddbec84..42663da8a3f9c 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -1,4 +1,6 @@
 #![recursion_limit = "256"]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 use rustc_ast as ast;
 use rustc_ast::util::parser::{self, AssocOp, Fixity};
diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs
index 33c3c536f119b..aa34673de81d7 100644
--- a/compiler/rustc_index/src/lib.rs
+++ b/compiler/rustc_index/src/lib.rs
@@ -1,3 +1,5 @@
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(allow_internal_unstable)]
 #![feature(bench_black_box)]
 #![feature(extend_one)]
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index 3c7dac2bfd816..6993245c605ae 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -2079,7 +2079,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                             diag.span_suggestion(
                                 span,
                                 *msg,
-                                format!("{}.as_ref()", snippet),
+                                // HACK: fix issue# 100605, suggesting convert from &Option<T> to Option<&T>, remove the extra `&`
+                                format!("{}.as_ref()", snippet.trim_start_matches('&')),
                                 Applicability::MachineApplicable,
                             );
                         }
diff --git a/compiler/rustc_lexer/src/lib.rs b/compiler/rustc_lexer/src/lib.rs
index 6d311af9007b1..178366f7d8045 100644
--- a/compiler/rustc_lexer/src/lib.rs
+++ b/compiler/rustc_lexer/src/lib.rs
@@ -18,6 +18,8 @@
 //! lexeme types.
 //!
 //! [`rustc_parse::lexer`]: ../rustc_parse/lexer/index.html
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 // We want to be able to build this crate with a stable compiler, so no
 // `#![feature]` attributes should be added.
 
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
index 6acbe97a7a118..a826f599e9cd5 100644
--- a/compiler/rustc_lint_defs/src/lib.rs
+++ b/compiler/rustc_lint_defs/src/lib.rs
@@ -1,4 +1,6 @@
 #![feature(min_specialization)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate rustc_macros;
diff --git a/compiler/rustc_llvm/src/lib.rs b/compiler/rustc_llvm/src/lib.rs
index 8eade02a408bc..8542dcf5bf0fe 100644
--- a/compiler/rustc_llvm/src/lib.rs
+++ b/compiler/rustc_llvm/src/lib.rs
@@ -1,3 +1,5 @@
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 
 // NOTE: This crate only exists to allow linking on mingw targets.
diff --git a/compiler/rustc_log/src/lib.rs b/compiler/rustc_log/src/lib.rs
index f2ec80b0c1b63..458f5e87baeac 100644
--- a/compiler/rustc_log/src/lib.rs
+++ b/compiler/rustc_log/src/lib.rs
@@ -38,6 +38,9 @@
 //! debugging, you can make changes inside those crates and quickly run main.rs
 //! to read the debug logs.
 
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
+
 use std::env::{self, VarError};
 use std::fmt::{self, Display};
 use std::io;
diff --git a/compiler/rustc_macros/src/lib.rs b/compiler/rustc_macros/src/lib.rs
index 2f9c13cf817ee..e01d035767ba6 100644
--- a/compiler/rustc_macros/src/lib.rs
+++ b/compiler/rustc_macros/src/lib.rs
@@ -4,6 +4,8 @@
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_span)]
 #![allow(rustc::default_hash_types)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 #![recursion_limit = "128"]
 
 use synstructure::decl_derive;
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 93e70e9abdaca..744ec7e611402 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -334,6 +334,35 @@ struct InInTypo {
     sugg_span: Span,
 }
 
+#[derive(SessionDiagnostic)]
+#[error(parser::invalid_variable_declaration)]
+pub struct InvalidVariableDeclaration {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub sub: InvalidVariableDeclarationSub,
+}
+
+#[derive(SessionSubdiagnostic)]
+pub enum InvalidVariableDeclarationSub {
+    #[suggestion(
+        parser::switch_mut_let_order,
+        applicability = "maybe-incorrect",
+        code = "let mut"
+    )]
+    SwitchMutLetOrder(#[primary_span] Span),
+    #[suggestion(
+        parser::missing_let_before_mut,
+        applicability = "machine-applicable",
+        code = "let mut"
+    )]
+    MissingLet(#[primary_span] Span),
+    #[suggestion(parser::use_let_not_auto, applicability = "machine-applicable", code = "let")]
+    UseLetNotAuto(#[primary_span] Span),
+    #[suggestion(parser::use_let_not_var, applicability = "machine-applicable", code = "let")]
+    UseLetNotVar(#[primary_span] Span),
+}
+
 // SnapshotParser is used to create a snapshot of the parser
 // without causing duplicate errors being emitted when the `Parser`
 // is dropped.
@@ -611,6 +640,15 @@ impl<'a> Parser<'a> {
                     appl,
                 );
             }
+
+            if ["def", "fun", "func", "function"].contains(&symbol.as_str()) {
+                err.span_suggestion_short(
+                    self.prev_token.span,
+                    &format!("write `fn` instead of `{symbol}` to declare a function"),
+                    "fn",
+                    appl,
+                );
+            }
         }
 
         // Add suggestion for a missing closing angle bracket if '>' is included in expected_tokens
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index cac39f8f25fb8..875636bdc2879 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -1,5 +1,7 @@
 use super::attr::DEFAULT_INNER_ATTR_FORBIDDEN;
-use super::diagnostics::{AttemptLocalParseRecovery, Error};
+use super::diagnostics::{
+    AttemptLocalParseRecovery, Error, InvalidVariableDeclaration, InvalidVariableDeclarationSub,
+};
 use super::expr::LhsExpr;
 use super::pat::RecoverComma;
 use super::path::PathStyle;
@@ -58,28 +60,22 @@ impl<'a> Parser<'a> {
         if self.token.is_keyword(kw::Mut) && self.is_keyword_ahead(1, &[kw::Let]) {
             self.bump();
             let mut_let_span = lo.to(self.token.span);
-            self.struct_span_err(mut_let_span, "invalid variable declaration")
-                .span_suggestion(
-                    mut_let_span,
-                    "switch the order of `mut` and `let`",
-                    "let mut",
-                    Applicability::MaybeIncorrect,
-                )
-                .emit();
+            self.sess.emit_err(InvalidVariableDeclaration {
+                span: mut_let_span,
+                sub: InvalidVariableDeclarationSub::SwitchMutLetOrder(mut_let_span),
+            });
         }
 
         Ok(Some(if self.token.is_keyword(kw::Let) {
             self.parse_local_mk(lo, attrs, capture_semi, force_collect)?
         } else if self.is_kw_followed_by_ident(kw::Mut) {
-            self.recover_stmt_local(lo, attrs, "missing keyword", "let mut")?
+            self.recover_stmt_local(lo, attrs, InvalidVariableDeclarationSub::MissingLet)?
         } else if self.is_kw_followed_by_ident(kw::Auto) {
             self.bump(); // `auto`
-            let msg = "write `let` instead of `auto` to introduce a new variable";
-            self.recover_stmt_local(lo, attrs, msg, "let")?
+            self.recover_stmt_local(lo, attrs, InvalidVariableDeclarationSub::UseLetNotAuto)?
         } else if self.is_kw_followed_by_ident(sym::var) {
             self.bump(); // `var`
-            let msg = "write `let` instead of `var` to introduce a new variable";
-            self.recover_stmt_local(lo, attrs, msg, "let")?
+            self.recover_stmt_local(lo, attrs, InvalidVariableDeclarationSub::UseLetNotVar)?
         } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() {
             // We have avoided contextual keywords like `union`, items with `crate` visibility,
             // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
@@ -217,13 +213,10 @@ impl<'a> Parser<'a> {
         &mut self,
         lo: Span,
         attrs: AttrWrapper,
-        msg: &str,
-        sugg: &str,
+        subdiagnostic: fn(Span) -> InvalidVariableDeclarationSub,
     ) -> PResult<'a, Stmt> {
         let stmt = self.recover_local_after_let(lo, attrs)?;
-        self.struct_span_err(lo, "invalid variable declaration")
-            .span_suggestion(lo, msg, sugg, Applicability::MachineApplicable)
-            .emit();
+        self.sess.emit_err(InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });
         Ok(stmt)
     }
 
diff --git a/compiler/rustc_parse_format/src/lib.rs b/compiler/rustc_parse_format/src/lib.rs
index 4890fade50faf..e4842d2afb705 100644
--- a/compiler/rustc_parse_format/src/lib.rs
+++ b/compiler/rustc_parse_format/src/lib.rs
@@ -9,6 +9,8 @@
     html_playground_url = "https://play.rust-lang.org/",
     test(attr(deny(warnings)))
 )]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 // We want to be able to build this crate with a stable compiler, so no
 // `#![feature]` attributes should be added.
 
diff --git a/compiler/rustc_query_impl/src/lib.rs b/compiler/rustc_query_impl/src/lib.rs
index eda61df7700d7..df187ea0c94d8 100644
--- a/compiler/rustc_query_impl/src/lib.rs
+++ b/compiler/rustc_query_impl/src/lib.rs
@@ -7,6 +7,8 @@
 #![feature(rustc_attrs)]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate rustc_macros;
diff --git a/compiler/rustc_serialize/src/lib.rs b/compiler/rustc_serialize/src/lib.rs
index e606f427335b7..079d44bac685b 100644
--- a/compiler/rustc_serialize/src/lib.rs
+++ b/compiler/rustc_serialize/src/lib.rs
@@ -18,6 +18,8 @@ Core encoding and decoding interfaces.
 #![feature(new_uninit)]
 #![cfg_attr(test, feature(test))]
 #![allow(rustc::internal)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 pub use self::serialize::{Decodable, Decoder, Encodable, Encoder};
 
diff --git a/compiler/rustc_smir/src/lib.rs b/compiler/rustc_smir/src/lib.rs
index 5c7aaf35b9032..3e93c6bba977f 100644
--- a/compiler/rustc_smir/src/lib.rs
+++ b/compiler/rustc_smir/src/lib.rs
@@ -11,6 +11,8 @@
     test(attr(allow(unused_variables), deny(warnings)))
 )]
 #![cfg_attr(not(feature = "default"), feature(rustc_private))]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 pub mod mir;
 
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 8d26cd6bee334..d14e28e85be1a 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -20,6 +20,8 @@
 #![feature(negative_impls)]
 #![feature(min_specialization)]
 #![feature(rustc_attrs)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate rustc_macros;
diff --git a/compiler/rustc_target/src/lib.rs b/compiler/rustc_target/src/lib.rs
index 59dbea7053447..9c9e297849ed5 100644
--- a/compiler/rustc_target/src/lib.rs
+++ b/compiler/rustc_target/src/lib.rs
@@ -16,6 +16,8 @@
 #![feature(never_type)]
 #![feature(rustc_attrs)]
 #![feature(step_trait)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 use std::iter::FromIterator;
 use std::path::{Path, PathBuf};
diff --git a/compiler/rustc_traits/src/lib.rs b/compiler/rustc_traits/src/lib.rs
index 2bea164c05114..318e76c79f18b 100644
--- a/compiler/rustc_traits/src/lib.rs
+++ b/compiler/rustc_traits/src/lib.rs
@@ -1,6 +1,8 @@
 //! New recursive solver modeled on Chalk's recursive solver. Most of
 //! the guts are broken up into modules; see the comments in those modules.
 
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(let_else)]
 #![recursion_limit = "256"]
 
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index e7c5ecc60ec78..970b39dc845af 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -2836,12 +2836,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
                 }
                 Some(_) => {
-                    tcx.sess
-                        .struct_span_err(
-                            attr.span,
-                            "expected `used`, `used(compiler)` or `used(linker)`",
-                        )
-                        .emit();
+                    tcx.sess.emit_err(errors::ExpectedUsedSymbol { span: attr.span });
                 }
                 None => {
                     // Unfortunately, unconditionally using `llvm.used` causes
diff --git a/compiler/rustc_typeck/src/errors.rs b/compiler/rustc_typeck/src/errors.rs
index 76599721e586f..8b1cb8d1c939a 100644
--- a/compiler/rustc_typeck/src/errors.rs
+++ b/compiler/rustc_typeck/src/errors.rs
@@ -340,3 +340,10 @@ pub struct ExternCrateNotIdiomatic {
     pub msg_code: String,
     pub suggestion_code: String,
 }
+
+#[derive(SessionDiagnostic)]
+#[error(typeck::expected_used_symbol)]
+pub struct ExpectedUsedSymbol {
+    #[primary_span]
+    pub span: Span,
+}
diff --git a/library/std/src/sys/sgx/abi/usercalls/alloc.rs b/library/std/src/sys/sgx/abi/usercalls/alloc.rs
index 66fa1efbf103f..34634da44de67 100644
--- a/library/std/src/sys/sgx/abi/usercalls/alloc.rs
+++ b/library/std/src/sys/sgx/abi/usercalls/alloc.rs
@@ -305,6 +305,34 @@ where
     }
 }
 
+// Split a memory region ptr..ptr + len into three parts:
+//   +--------+
+//   | small0 | Chunk smaller than 8 bytes
+//   +--------+
+//   |   big  | Chunk 8-byte aligned, and size a multiple of 8 bytes
+//   +--------+
+//   | small1 | Chunk smaller than 8 bytes
+//   +--------+
+fn region_as_aligned_chunks(ptr: *const u8, len: usize) -> (usize, usize, usize) {
+    let small0_size = if ptr as usize % 8 == 0 { 0 } else { 8 - ptr as usize % 8 };
+    let small1_size = (len - small0_size as usize) % 8;
+    let big_size = len - small0_size as usize - small1_size as usize;
+
+    (small0_size, big_size, small1_size)
+}
+
+unsafe fn copy_quadwords(src: *const u8, dst: *mut u8, len: usize) {
+    unsafe {
+        asm!(
+            "rep movsq (%rsi), (%rdi)",
+            inout("rcx") len / 8 => _,
+            inout("rdi") dst => _,
+            inout("rsi") src => _,
+            options(att_syntax, nostack, preserves_flags)
+        );
+    }
+}
+
 /// Copies `len` bytes of data from enclave pointer `src` to userspace `dst`
 ///
 /// This function mitigates stale data vulnerabilities by ensuring all writes to untrusted memory are either:
@@ -343,17 +371,6 @@ pub(crate) unsafe fn copy_to_userspace(src: *const u8, dst: *mut u8, len: usize)
         }
     }
 
-    unsafe fn copy_aligned_quadwords_to_userspace(src: *const u8, dst: *mut u8, len: usize) {
-        unsafe {
-            asm!(
-                "rep movsq (%rsi), (%rdi)",
-                inout("rcx") len / 8 => _,
-                inout("rdi") dst => _,
-                inout("rsi") src => _,
-                options(att_syntax, nostack, preserves_flags)
-            );
-        }
-    }
     assert!(!src.is_null());
     assert!(!dst.is_null());
     assert!(is_enclave_range(src, len));
@@ -370,7 +387,7 @@ pub(crate) unsafe fn copy_to_userspace(src: *const u8, dst: *mut u8, len: usize)
     } else if len % 8 == 0 && dst as usize % 8 == 0 {
         // Copying 8-byte aligned quadwords: copy quad word per quad word
         unsafe {
-            copy_aligned_quadwords_to_userspace(src, dst, len);
+            copy_quadwords(src, dst, len);
         }
     } else {
         // Split copies into three parts:
@@ -381,20 +398,16 @@ pub(crate) unsafe fn copy_to_userspace(src: *const u8, dst: *mut u8, len: usize)
         //   +--------+
         //   | small1 | Chunk smaller than 8 bytes
         //   +--------+
+        let (small0_size, big_size, small1_size) = region_as_aligned_chunks(dst, len);
 
         unsafe {
             // Copy small0
-            let small0_size = (8 - dst as usize % 8) as u8;
-            let small0_src = src;
-            let small0_dst = dst;
-            copy_bytewise_to_userspace(small0_src as _, small0_dst, small0_size as _);
+            copy_bytewise_to_userspace(src, dst, small0_size as _);
 
             // Copy big
-            let small1_size = ((len - small0_size as usize) % 8) as u8;
-            let big_size = len - small0_size as usize - small1_size as usize;
             let big_src = src.offset(small0_size as _);
             let big_dst = dst.offset(small0_size as _);
-            copy_aligned_quadwords_to_userspace(big_src as _, big_dst, big_size);
+            copy_quadwords(big_src as _, big_dst, big_size);
 
             // Copy small1
             let small1_src = src.offset(big_size as isize + small0_size as isize);
@@ -404,6 +417,106 @@ pub(crate) unsafe fn copy_to_userspace(src: *const u8, dst: *mut u8, len: usize)
     }
 }
 
+/// Copies `len` bytes of data from userspace pointer `src` to enclave pointer `dst`
+///
+/// This function mitigates AEPIC leak vulnerabilities by ensuring all reads from untrusted memory are 8-byte aligned
+///
+/// # Panics
+/// This function panics if:
+///
+/// * The `src` pointer is null
+/// * The `dst` pointer is null
+/// * The `src` memory range is not in user memory
+/// * The `dst` memory range is not in enclave memory
+///
+/// # References
+///  - https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00657.html
+///  - https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/advisory-guidance/stale-data-read-from-xapic.html
+pub(crate) unsafe fn copy_from_userspace(src: *const u8, dst: *mut u8, len: usize) {
+    // Copies memory region `src..src + len` to the enclave at `dst`. The source memory region
+    // is:
+    //  - strictly less than 8 bytes in size and may be
+    //  - located at a misaligned memory location
+    fn copy_misaligned_chunk_to_enclave(src: *const u8, dst: *mut u8, len: usize) {
+        let mut tmp_buff = [0u8; 16];
+
+        unsafe {
+            // Compute an aligned memory region to read from
+            // +--------+ <-- aligned_src + aligned_len (8B-aligned)
+            // |  pad1  |
+            // +--------+ <-- src + len (misaligned)
+            // |        |
+            // |        |
+            // |        |
+            // +--------+ <-- src (misaligned)
+            // |  pad0  |
+            // +--------+ <-- aligned_src (8B-aligned)
+            let pad0_size = src as usize % 8;
+            let aligned_src = src.sub(pad0_size);
+
+            let pad1_size = 8 - (src.add(len) as usize % 8);
+            let aligned_len = pad0_size + len + pad1_size;
+
+            debug_assert!(len < 8);
+            debug_assert_eq!(aligned_src as usize % 8, 0);
+            debug_assert_eq!(aligned_len % 8, 0);
+            debug_assert!(aligned_len <= 16);
+
+            // Copy the aligned buffer to a temporary buffer
+            // Note: copying from a slightly different memory location is a bit odd. In this case it
+            // can't lead to page faults or inadvertent copying from the enclave as we only ensured
+            // that the `src` pointer is aligned at an 8 byte boundary. As pages are 4096 bytes
+            // aligned, `aligned_src` must be on the same page as `src`. A similar argument can be made
+            // for `src + len`
+            copy_quadwords(aligned_src as _, tmp_buff.as_mut_ptr(), aligned_len);
+
+            // Copy the correct parts of the temporary buffer to the destination
+            ptr::copy(tmp_buff.as_ptr().add(pad0_size), dst, len);
+        }
+    }
+
+    assert!(!src.is_null());
+    assert!(!dst.is_null());
+    assert!(is_user_range(src, len));
+    assert!(is_enclave_range(dst, len));
+    assert!(!(src as usize).overflowing_add(len + 8).1);
+    assert!(!(dst as usize).overflowing_add(len + 8).1);
+
+    if len < 8 {
+        copy_misaligned_chunk_to_enclave(src, dst, len);
+    } else if len % 8 == 0 && src as usize % 8 == 0 {
+        // Copying 8-byte aligned quadwords: copy quad word per quad word
+        unsafe {
+            copy_quadwords(src, dst, len);
+        }
+    } else {
+        // Split copies into three parts:
+        //   +--------+
+        //   | small0 | Chunk smaller than 8 bytes
+        //   +--------+
+        //   |   big  | Chunk 8-byte aligned, and size a multiple of 8 bytes
+        //   +--------+
+        //   | small1 | Chunk smaller than 8 bytes
+        //   +--------+
+        let (small0_size, big_size, small1_size) = region_as_aligned_chunks(dst, len);
+
+        unsafe {
+            // Copy small0
+            copy_misaligned_chunk_to_enclave(src, dst, small0_size);
+
+            // Copy big
+            let big_src = src.add(small0_size);
+            let big_dst = dst.add(small0_size);
+            copy_quadwords(big_src, big_dst, big_size);
+
+            // Copy small1
+            let small1_src = src.add(big_size + small0_size);
+            let small1_dst = dst.add(big_size + small0_size);
+            copy_misaligned_chunk_to_enclave(small1_src, small1_dst, small1_size);
+        }
+    }
+}
+
 #[unstable(feature = "sgx_platform", issue = "56975")]
 impl<T: ?Sized> UserRef<T>
 where
@@ -468,7 +581,7 @@ where
     pub fn copy_to_enclave(&self, dest: &mut T) {
         unsafe {
             assert_eq!(mem::size_of_val(dest), mem::size_of_val(&*self.0.get()));
-            ptr::copy(
+            copy_from_userspace(
                 self.0.get() as *const T as *const u8,
                 dest as *mut T as *mut u8,
                 mem::size_of_val(dest),
@@ -494,7 +607,11 @@ where
 {
     /// Copies the value from user memory into enclave memory.
     pub fn to_enclave(&self) -> T {
-        unsafe { ptr::read(self.0.get()) }
+        unsafe {
+            let mut data: T = mem::MaybeUninit::uninit().assume_init();
+            copy_from_userspace(self.0.get() as _, &mut data as *mut T as _, mem::size_of::<T>());
+            data
+        }
     }
 }
 
diff --git a/library/std/src/sys/sgx/abi/usercalls/tests.rs b/library/std/src/sys/sgx/abi/usercalls/tests.rs
index cbf7d7d54f7a2..4320f0bccd199 100644
--- a/library/std/src/sys/sgx/abi/usercalls/tests.rs
+++ b/library/std/src/sys/sgx/abi/usercalls/tests.rs
@@ -1,8 +1,8 @@
-use super::alloc::copy_to_userspace;
 use super::alloc::User;
+use super::alloc::{copy_from_userspace, copy_to_userspace};
 
 #[test]
-fn test_copy_function() {
+fn test_copy_to_userspace_function() {
     let mut src = [0u8; 100];
     let mut dst = User::<[u8]>::uninitialized(100);
 
@@ -28,3 +28,29 @@ fn test_copy_function() {
         }
     }
 }
+
+#[test]
+fn test_copy_from_userspace_function() {
+    let mut dst = [0u8; 100];
+    let mut src = User::<[u8]>::uninitialized(100);
+
+    src.copy_from_enclave(&[0u8; 100]);
+
+    for size in 0..48 {
+        // For all possible alignment
+        for offset in 0..8 {
+            // overwrite complete dst
+            dst = [0u8; 100];
+
+            // Copy src[0..size] to dst + offset
+            unsafe { copy_from_userspace(src.as_ptr().offset(offset), dst.as_mut_ptr(), size) };
+
+            // Verify copy
+            for byte in 0..size {
+                unsafe {
+                    assert_eq!(dst[byte as usize], *src.as_ptr().offset(offset + byte as isize));
+                }
+            }
+        }
+    }
+}
diff --git a/library/std/src/sys/windows/mod.rs b/library/std/src/sys/windows/mod.rs
index b3f6d2d0aaed4..a9846a484880b 100644
--- a/library/std/src/sys/windows/mod.rs
+++ b/library/std/src/sys/windows/mod.rs
@@ -2,6 +2,7 @@
 
 use crate::ffi::{CStr, OsStr, OsString};
 use crate::io::ErrorKind;
+use crate::mem::MaybeUninit;
 use crate::os::windows::ffi::{OsStrExt, OsStringExt};
 use crate::path::PathBuf;
 use crate::time::Duration;
@@ -204,8 +205,8 @@ where
     // This initial size also works around `GetFullPathNameW` returning
     // incorrect size hints for some short paths:
     // https://github.com/dylni/normpath/issues/5
-    let mut stack_buf = [0u16; 512];
-    let mut heap_buf = Vec::new();
+    let mut stack_buf: [MaybeUninit<u16>; 512] = MaybeUninit::uninit_array();
+    let mut heap_buf: Vec<MaybeUninit<u16>> = Vec::new();
     unsafe {
         let mut n = stack_buf.len();
         loop {
@@ -214,6 +215,11 @@ where
             } else {
                 let extra = n - heap_buf.len();
                 heap_buf.reserve(extra);
+                // We used `reserve` and not `reserve_exact`, so in theory we
+                // may have gotten more than requested. If so, we'd like to use
+                // it... so long as we won't cause overflow.
+                n = heap_buf.capacity().min(c::DWORD::MAX as usize);
+                // Safety: MaybeUninit<u16> does not need initialization
                 heap_buf.set_len(n);
                 &mut heap_buf[..]
             };
@@ -228,13 +234,13 @@ where
             // error" is still 0 then we interpret it as a 0 length buffer and
             // not an actual error.
             c::SetLastError(0);
-            let k = match f1(buf.as_mut_ptr(), n as c::DWORD) {
+            let k = match f1(buf.as_mut_ptr().cast::<u16>(), n as c::DWORD) {
                 0 if c::GetLastError() == 0 => 0,
                 0 => return Err(crate::io::Error::last_os_error()),
                 n => n,
             } as usize;
             if k == n && c::GetLastError() == c::ERROR_INSUFFICIENT_BUFFER {
-                n *= 2;
+                n = n.saturating_mul(2).min(c::DWORD::MAX as usize);
             } else if k > n {
                 n = k;
             } else if k == n {
@@ -244,7 +250,9 @@ where
                 // Therefore k never equals n.
                 unreachable!();
             } else {
-                return Ok(f2(&buf[..k]));
+                // Safety: First `k` values are initialized.
+                let slice: &[u16] = MaybeUninit::slice_assume_init_ref(&buf[..k]);
+                return Ok(f2(slice));
             }
         }
     }
diff --git a/src/test/ui/borrowck/issue-64453.stderr b/src/test/ui/borrowck/issue-64453.stderr
index 1f8a1acb89f50..245c3a40e0506 100644
--- a/src/test/ui/borrowck/issue-64453.stderr
+++ b/src/test/ui/borrowck/issue-64453.stderr
@@ -14,6 +14,7 @@ LL | static settings_dir: String = format!("");
    |                               ^^^^^^^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
    = note: this error originates in the macro `format` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0507]: cannot move out of static item `settings_dir`
diff --git a/src/test/ui/borrowck/suggest-as-ref-on-mut-closure.stderr b/src/test/ui/borrowck/suggest-as-ref-on-mut-closure.stderr
index af26169c80681..b1af090aec2b0 100644
--- a/src/test/ui/borrowck/suggest-as-ref-on-mut-closure.stderr
+++ b/src/test/ui/borrowck/suggest-as-ref-on-mut-closure.stderr
@@ -5,6 +5,7 @@ LL |     cb.map(|cb| cb());
    |     ^^^--------------
    |     |  |
    |     |  `*cb` moved due to this method call
+   |     help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
    |     move occurs because `*cb` has type `Option<&mut dyn FnMut()>`, which does not implement the `Copy` trait
    |
 note: this function takes ownership of the receiver `self`, which moves `*cb`
@@ -12,10 +13,6 @@ note: this function takes ownership of the receiver `self`, which moves `*cb`
    |
 LL |     pub const fn map<U, F>(self, f: F) -> Option<U>
    |                            ^^^^
-help: consider calling `.as_ref()` to borrow the type's contents
-   |
-LL |     cb.as_ref().map(|cb| cb());
-   |        +++++++++
 
 error[E0596]: cannot borrow `*cb` as mutable, as it is behind a `&` reference
   --> $DIR/suggest-as-ref-on-mut-closure.rs:12:26
diff --git a/src/test/ui/check-static-values-constraints.stderr b/src/test/ui/check-static-values-constraints.stderr
index b28cf0d6bd0f5..3c193ca34acce 100644
--- a/src/test/ui/check-static-values-constraints.stderr
+++ b/src/test/ui/check-static-values-constraints.stderr
@@ -22,6 +22,7 @@ LL |     field2: SafeEnum::Variant4("str".to_string())
    |                                      ^^^^^^^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error[E0010]: allocations are not allowed in statics
   --> $DIR/check-static-values-constraints.rs:94:5
diff --git a/src/test/ui/consts/issue-32829-2.stderr b/src/test/ui/consts/issue-32829-2.stderr
index b94bdc0e3df11..0fec3581873eb 100644
--- a/src/test/ui/consts/issue-32829-2.stderr
+++ b/src/test/ui/consts/issue-32829-2.stderr
@@ -13,6 +13,7 @@ LL |         invalid();
    |         ^^^^^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error[E0015]: cannot call non-const fn `invalid` in statics
   --> $DIR/issue-32829-2.rs:54:9
@@ -21,6 +22,7 @@ LL |         invalid();
    |         ^^^^^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/consts/mir_check_nonconst.stderr b/src/test/ui/consts/mir_check_nonconst.stderr
index 2bac995eebf09..1e0652722ff2d 100644
--- a/src/test/ui/consts/mir_check_nonconst.stderr
+++ b/src/test/ui/consts/mir_check_nonconst.stderr
@@ -5,6 +5,7 @@ LL | static foo: Foo = bar();
    |                   ^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-100605.rs b/src/test/ui/issues/issue-100605.rs
new file mode 100644
index 0000000000000..917a45c15bbc8
--- /dev/null
+++ b/src/test/ui/issues/issue-100605.rs
@@ -0,0 +1,9 @@
+fn takes_option(_arg: Option<&String>) {}
+
+fn main() {
+    takes_option(&None); //~ ERROR 4:18: 4:23: mismatched types [E0308]
+
+    let x = String::from("x");
+    let res = Some(x);
+    takes_option(&res); //~ ERROR 8:18: 8:22: mismatched types [E0308]
+}
diff --git a/src/test/ui/issues/issue-100605.stderr b/src/test/ui/issues/issue-100605.stderr
new file mode 100644
index 0000000000000..886e3cd6bb794
--- /dev/null
+++ b/src/test/ui/issues/issue-100605.stderr
@@ -0,0 +1,46 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-100605.rs:4:18
+   |
+LL |     takes_option(&None);
+   |     ------------ ^^^^^ expected enum `Option`, found `&Option<_>`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note:   expected enum `Option<&String>`
+           found reference `&Option<_>`
+note: function defined here
+  --> $DIR/issue-100605.rs:1:4
+   |
+LL | fn takes_option(_arg: Option<&String>) {}
+   |    ^^^^^^^^^^^^ ---------------------
+help: you can convert from `&Option<T>` to `Option<&T>` using `.as_ref()`
+   |
+LL |     takes_option(None.as_ref());
+   |                  ~~~~~~~~~~~~~
+help: consider removing the borrow
+   |
+LL -     takes_option(&None);
+LL +     takes_option(None);
+   |
+
+error[E0308]: mismatched types
+  --> $DIR/issue-100605.rs:8:18
+   |
+LL |     takes_option(&res);
+   |     ------------ ^^^^
+   |     |            |
+   |     |            expected enum `Option`, found `&Option<String>`
+   |     |            help: you can convert from `&Option<T>` to `Option<&T>` using `.as_ref()`: `res.as_ref()`
+   |     arguments to this function are incorrect
+   |
+   = note:   expected enum `Option<&String>`
+           found reference `&Option<String>`
+note: function defined here
+  --> $DIR/issue-100605.rs:1:4
+   |
+LL | fn takes_option(_arg: Option<&String>) {}
+   |    ^^^^^^^^^^^^ ---------------------
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/issues/issue-16538.mir.stderr b/src/test/ui/issues/issue-16538.mir.stderr
index 7dab7de761970..e320df4b7ad8f 100644
--- a/src/test/ui/issues/issue-16538.mir.stderr
+++ b/src/test/ui/issues/issue-16538.mir.stderr
@@ -5,6 +5,7 @@ LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error[E0133]: use of extern static is unsafe and requires unsafe function or block
   --> $DIR/issue-16538.rs:14:30
diff --git a/src/test/ui/issues/issue-16538.thir.stderr b/src/test/ui/issues/issue-16538.thir.stderr
index a18b0197d879a..4a862869274f8 100644
--- a/src/test/ui/issues/issue-16538.thir.stderr
+++ b/src/test/ui/issues/issue-16538.thir.stderr
@@ -21,6 +21,7 @@ LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/issues/issue-25901.stderr b/src/test/ui/issues/issue-25901.stderr
index e933745c44e87..c6c80e41cf67e 100644
--- a/src/test/ui/issues/issue-25901.stderr
+++ b/src/test/ui/issues/issue-25901.stderr
@@ -16,6 +16,7 @@ note: impl defined here, but it is not `const`
 LL | impl Deref for A {
    | ^^^^^^^^^^^^^^^^
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/fn-defined-using-def.rs b/src/test/ui/parser/fn-defined-using-def.rs
new file mode 100644
index 0000000000000..21da34c47c9fd
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-def.rs
@@ -0,0 +1,10 @@
+// Check what happens when `def` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+def foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `def` to declare a function
+
+fn main() {}
diff --git a/src/test/ui/parser/fn-defined-using-def.stderr b/src/test/ui/parser/fn-defined-using-def.stderr
new file mode 100644
index 0000000000000..f34329012a02f
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-def.stderr
@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-def.rs:6:5
+   |
+LL | def foo() {}
+   | --- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `def` to declare a function
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/parser/fn-defined-using-fun.rs b/src/test/ui/parser/fn-defined-using-fun.rs
new file mode 100644
index 0000000000000..4f74605043e19
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-fun.rs
@@ -0,0 +1,10 @@
+// Check what happens when `fun` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+fun foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `fun` to declare a function
+
+fn main() {}
diff --git a/src/test/ui/parser/fn-defined-using-fun.stderr b/src/test/ui/parser/fn-defined-using-fun.stderr
new file mode 100644
index 0000000000000..2f6cfff350c90
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-fun.stderr
@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-fun.rs:6:5
+   |
+LL | fun foo() {}
+   | --- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `fun` to declare a function
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/parser/fn-defined-using-func.rs b/src/test/ui/parser/fn-defined-using-func.rs
new file mode 100644
index 0000000000000..2dce96fdce078
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-func.rs
@@ -0,0 +1,10 @@
+// Check what happens when `func` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+func foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `func` to declare a function
+
+fn main() {}
diff --git a/src/test/ui/parser/fn-defined-using-func.stderr b/src/test/ui/parser/fn-defined-using-func.stderr
new file mode 100644
index 0000000000000..355741e8949a9
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-func.stderr
@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-func.rs:6:6
+   |
+LL | func foo() {}
+   | ---- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `func` to declare a function
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/parser/fn-defined-using-function.rs b/src/test/ui/parser/fn-defined-using-function.rs
new file mode 100644
index 0000000000000..fd8782728e2b9
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-function.rs
@@ -0,0 +1,10 @@
+// Check what happens when `function` is used to define a function, instead of `fn`
+// edition:2021
+
+#![allow(dead_code)]
+
+function foo() {}
+//~^ ERROR expected one of `!` or `::`, found `foo`
+//~^^ HELP write `fn` instead of `function` to declare a function
+
+fn main() {}
diff --git a/src/test/ui/parser/fn-defined-using-function.stderr b/src/test/ui/parser/fn-defined-using-function.stderr
new file mode 100644
index 0000000000000..43c33a2cdd7e8
--- /dev/null
+++ b/src/test/ui/parser/fn-defined-using-function.stderr
@@ -0,0 +1,10 @@
+error: expected one of `!` or `::`, found `foo`
+  --> $DIR/fn-defined-using-function.rs:6:10
+   |
+LL | function foo() {}
+   | -------- ^^^ expected one of `!` or `::`
+   | |
+   | help: write `fn` instead of `function` to declare a function
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/static/static-vec-repeat-not-constant.stderr b/src/test/ui/static/static-vec-repeat-not-constant.stderr
index 84fc638a973cb..dec0123184d70 100644
--- a/src/test/ui/static/static-vec-repeat-not-constant.stderr
+++ b/src/test/ui/static/static-vec-repeat-not-constant.stderr
@@ -5,6 +5,7 @@ LL | static a: [isize; 2] = [foo(); 2];
    |                         ^^^^^
    |
    = note: calls in statics are limited to constant functions, tuple structs and tuple variants
+   = note: consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/as-ref-2.fixed b/src/test/ui/suggestions/as-ref-2.fixed
deleted file mode 100644
index 13bbb233f3986..0000000000000
--- a/src/test/ui/suggestions/as-ref-2.fixed
+++ /dev/null
@@ -1,13 +0,0 @@
-// run-rustfix
-
-struct Struct;
-
-fn bar(_: &Struct) -> Struct {
-    Struct
-}
-
-fn main() {
-    let foo = Some(Struct);
-    let _x: Option<Struct> = foo.as_ref().map(|s| bar(&s));
-    let _y = foo; //~ERROR use of moved value: `foo`
-}
diff --git a/src/test/ui/suggestions/as-ref-2.rs b/src/test/ui/suggestions/as-ref-2.rs
index 74d61cdd95f8d..b22f409b44a93 100644
--- a/src/test/ui/suggestions/as-ref-2.rs
+++ b/src/test/ui/suggestions/as-ref-2.rs
@@ -1,5 +1,3 @@
-// run-rustfix
-
 struct Struct;
 
 fn bar(_: &Struct) -> Struct {
diff --git a/src/test/ui/suggestions/as-ref-2.stderr b/src/test/ui/suggestions/as-ref-2.stderr
index 3c9d0f72abe0c..e15e45d86b992 100644
--- a/src/test/ui/suggestions/as-ref-2.stderr
+++ b/src/test/ui/suggestions/as-ref-2.stderr
@@ -1,10 +1,12 @@
 error[E0382]: use of moved value: `foo`
-  --> $DIR/as-ref-2.rs:12:14
+  --> $DIR/as-ref-2.rs:10:14
    |
 LL |     let foo = Some(Struct);
    |         --- move occurs because `foo` has type `Option<Struct>`, which does not implement the `Copy` trait
 LL |     let _x: Option<Struct> = foo.map(|s| bar(&s));
-   |                                  ---------------- `foo` moved due to this method call
+   |                              --- ---------------- `foo` moved due to this method call
+   |                              |
+   |                              help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
 LL |     let _y = foo;
    |              ^^^ value used here after move
    |
@@ -13,10 +15,6 @@ note: this function takes ownership of the receiver `self`, which moves `foo`
    |
 LL |     pub const fn map<U, F>(self, f: F) -> Option<U>
    |                            ^^^^
-help: consider calling `.as_ref()` to borrow the type's contents
-   |
-LL |     let _x: Option<Struct> = foo.as_ref().map(|s| bar(&s));
-   |                                  +++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/option-content-move.fixed b/src/test/ui/suggestions/option-content-move.fixed
deleted file mode 100644
index ba16bcc8a336d..0000000000000
--- a/src/test/ui/suggestions/option-content-move.fixed
+++ /dev/null
@@ -1,39 +0,0 @@
-//run-rustfix
-
-pub struct LipogramCorpora {
-    selections: Vec<(char, Option<String>)>,
-}
-
-impl LipogramCorpora {
-    pub fn validate_all(&mut self) -> Result<(), char> {
-        for selection in &self.selections {
-            if selection.1.is_some() {
-                if selection.1.as_ref().unwrap().contains(selection.0) {
-                //~^ ERROR cannot move out of `selection.1`
-                    return Err(selection.0);
-                }
-            }
-        }
-        Ok(())
-    }
-}
-
-pub struct LipogramCorpora2 {
-    selections: Vec<(char, Result<String, String>)>,
-}
-
-impl LipogramCorpora2 {
-    pub fn validate_all(&mut self) -> Result<(), char> {
-        for selection in &self.selections {
-            if selection.1.is_ok() {
-                if selection.1.as_ref().unwrap().contains(selection.0) {
-                //~^ ERROR cannot move out of `selection.1`
-                    return Err(selection.0);
-                }
-            }
-        }
-        Ok(())
-    }
-}
-
-fn main() {}
diff --git a/src/test/ui/suggestions/option-content-move.rs b/src/test/ui/suggestions/option-content-move.rs
index ef38f114eca55..46c895b95f536 100644
--- a/src/test/ui/suggestions/option-content-move.rs
+++ b/src/test/ui/suggestions/option-content-move.rs
@@ -1,5 +1,3 @@
-//run-rustfix
-
 pub struct LipogramCorpora {
     selections: Vec<(char, Option<String>)>,
 }
diff --git a/src/test/ui/suggestions/option-content-move.stderr b/src/test/ui/suggestions/option-content-move.stderr
index fccfbe1d744c2..a6f1ebc975fd5 100644
--- a/src/test/ui/suggestions/option-content-move.stderr
+++ b/src/test/ui/suggestions/option-content-move.stderr
@@ -1,9 +1,10 @@
 error[E0507]: cannot move out of `selection.1` which is behind a shared reference
-  --> $DIR/option-content-move.rs:11:20
+  --> $DIR/option-content-move.rs:9:20
    |
 LL |                 if selection.1.unwrap().contains(selection.0) {
    |                    ^^^^^^^^^^^ -------- `selection.1` moved due to this method call
    |                    |
+   |                    help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
    |                    move occurs because `selection.1` has type `Option<String>`, which does not implement the `Copy` trait
    |
 note: this function takes ownership of the receiver `self`, which moves `selection.1`
@@ -11,17 +12,14 @@ note: this function takes ownership of the receiver `self`, which moves `selecti
    |
 LL |     pub const fn unwrap(self) -> T {
    |                         ^^^^
-help: consider calling `.as_ref()` to borrow the type's contents
-   |
-LL |                 if selection.1.as_ref().unwrap().contains(selection.0) {
-   |                                +++++++++
 
 error[E0507]: cannot move out of `selection.1` which is behind a shared reference
-  --> $DIR/option-content-move.rs:29:20
+  --> $DIR/option-content-move.rs:27:20
    |
 LL |                 if selection.1.unwrap().contains(selection.0) {
    |                    ^^^^^^^^^^^ -------- `selection.1` moved due to this method call
    |                    |
+   |                    help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
    |                    move occurs because `selection.1` has type `Result<String, String>`, which does not implement the `Copy` trait
    |
 note: this function takes ownership of the receiver `self`, which moves `selection.1`
@@ -29,10 +27,6 @@ note: this function takes ownership of the receiver `self`, which moves `selecti
    |
 LL |     pub fn unwrap(self) -> T
    |                   ^^^^
-help: consider calling `.as_ref()` to borrow the type's contents
-   |
-LL |                 if selection.1.as_ref().unwrap().contains(selection.0) {
-   |                                +++++++++
 
 error: aborting due to 2 previous errors
 
diff --git a/triagebot.toml b/triagebot.toml
index b7532e016b68e..4d3f748195b80 100644
--- a/triagebot.toml
+++ b/triagebot.toml
@@ -129,6 +129,7 @@ trigger_files = [
 
     # Internal tooling
     "src/etc/htmldocck.py",
+    "src/etc/check_missing_items.py",
     "src/tools/jsondocck",
     "src/tools/rustdoc-gui",
     "src/tools/rustdoc-js",
@@ -138,6 +139,15 @@ exclude_labels = [
     "T-*",
 ]
 
+[autolabel."A-rustdoc-json"]
+trigger_files = [
+    "src/etc/check_missing_items.py",
+    "src/librustdoc/json/",
+    "src/rustdoc-json-types",
+    "src/test/rustdoc-json",
+    "src/tools/jsondocck",
+]
+
 [autolabel."T-compiler"]
 trigger_files = [
     # Source code