diff --git a/clippy_lints/src/copies.rs b/clippy_lints/src/copies.rs
index 8b79f1600aeb0..a20aa12c9ff47 100644
--- a/clippy_lints/src/copies.rs
+++ b/clippy_lints/src/copies.rs
@@ -6,7 +6,7 @@ use clippy_utils::{
 };
 use if_chain::if_chain;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{Applicability, DiagnosticBuilder};
+use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{Block, Expr, ExprKind, HirId};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
@@ -489,7 +489,7 @@ fn emit_branches_sharing_code_lint(
         add_expr_note = !cx.typeck_results().expr_ty(if_expr).is_unit();
     }
 
-    let add_optional_msgs = |diag: &mut DiagnosticBuilder<'_>| {
+    let add_optional_msgs = |diag: &mut Diagnostic| {
         if add_expr_note {
             diag.note("The end suggestion probably needs some adjustments to use the expression result correctly");
         }
diff --git a/clippy_lints/src/doc.rs b/clippy_lints/src/doc.rs
index a00361e6062ad..16173580fd461 100644
--- a/clippy_lints/src/doc.rs
+++ b/clippy_lints/src/doc.rs
@@ -628,9 +628,7 @@ fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
                 let mut parser = match maybe_new_parser_from_source_str(&sess, filename, code) {
                     Ok(p) => p,
                     Err(errs) => {
-                        for mut err in errs {
-                            err.cancel();
-                        }
+                        drop(errs);
                         return false;
                     },
                 };
@@ -668,7 +666,7 @@ fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
                             _ => {},
                         },
                         Ok(None) => break,
-                        Err(mut e) => {
+                        Err(e) => {
                             e.cancel();
                             return false;
                         },
diff --git a/clippy_lints/src/implicit_hasher.rs b/clippy_lints/src/implicit_hasher.rs
index 5e4cde553b52e..d5430a8c91750 100644
--- a/clippy_lints/src/implicit_hasher.rs
+++ b/clippy_lints/src/implicit_hasher.rs
@@ -1,7 +1,7 @@
 use std::borrow::Cow;
 use std::collections::BTreeMap;
 
-use rustc_errors::DiagnosticBuilder;
+use rustc_errors::Diagnostic;
 use rustc_hir as hir;
 use rustc_hir::intravisit::{walk_body, walk_expr, walk_inf, walk_ty, Visitor};
 use rustc_hir::{Body, Expr, ExprKind, GenericArg, Item, ItemKind, QPath, TyKind};
@@ -68,7 +68,7 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitHasher {
 
         fn suggestion<'tcx>(
             cx: &LateContext<'tcx>,
-            diag: &mut DiagnosticBuilder<'_>,
+            diag: &mut Diagnostic,
             generics_span: Span,
             generics_suggestion_span: Span,
             target: &ImplicitHasherType<'_>,
diff --git a/clippy_lints/src/inline_fn_without_body.rs b/clippy_lints/src/inline_fn_without_body.rs
index df69d3dcc5160..dd7177e0131ca 100644
--- a/clippy_lints/src/inline_fn_without_body.rs
+++ b/clippy_lints/src/inline_fn_without_body.rs
@@ -1,7 +1,7 @@
 //! checks for `#[inline]` on trait methods without bodies
 
 use clippy_utils::diagnostics::span_lint_and_then;
-use clippy_utils::sugg::DiagnosticBuilderExt;
+use clippy_utils::sugg::DiagnosticExt;
 use rustc_ast::ast::Attribute;
 use rustc_errors::Applicability;
 use rustc_hir::{TraitFn, TraitItem, TraitItemKind};
diff --git a/clippy_lints/src/needless_pass_by_value.rs b/clippy_lints/src/needless_pass_by_value.rs
index d27e1383d012b..ebfd908a6fb74 100644
--- a/clippy_lints/src/needless_pass_by_value.rs
+++ b/clippy_lints/src/needless_pass_by_value.rs
@@ -6,7 +6,7 @@ use clippy_utils::{get_trait_def_id, is_self, paths};
 use if_chain::if_chain;
 use rustc_ast::ast::Attribute;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{Applicability, DiagnosticBuilder};
+use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir::intravisit::FnKind;
 use rustc_hir::{BindingAnnotation, Body, FnDecl, GenericArg, HirId, Impl, ItemKind, Node, PatKind, QPath, TyKind};
 use rustc_hir::{HirIdMap, HirIdSet};
@@ -196,7 +196,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                     }
 
                     // Dereference suggestion
-                    let sugg = |diag: &mut DiagnosticBuilder<'_>| {
+                    let sugg = |diag: &mut Diagnostic| {
                         if let ty::Adt(def, ..) = ty.kind() {
                             if let Some(span) = cx.tcx.hir().span_if_local(def.did) {
                                 if can_type_implement_copy(cx.tcx, cx.param_env, ty, traits::ObligationCause::dummy_with_span(span)).is_ok() {
diff --git a/clippy_lints/src/new_without_default.rs b/clippy_lints/src/new_without_default.rs
index f86af7a7bb6ea..4cb79648ae36a 100644
--- a/clippy_lints/src/new_without_default.rs
+++ b/clippy_lints/src/new_without_default.rs
@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_hir_and_then;
 use clippy_utils::return_ty;
 use clippy_utils::source::snippet;
-use clippy_utils::sugg::DiagnosticBuilderExt;
+use clippy_utils::sugg::DiagnosticExt;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
diff --git a/clippy_lints/src/write.rs b/clippy_lints/src/write.rs
index 1fa6301ebd73d..a328ddda5ae7b 100644
--- a/clippy_lints/src/write.rs
+++ b/clippy_lints/src/write.rs
@@ -534,7 +534,7 @@ impl Write {
             match parser
                 .parse_expr()
                 .map(rustc_ast::ptr::P::into_inner)
-                .map_err(|mut e| e.cancel())
+                .map_err(|e| e.cancel())
             {
                 // write!(e, ...)
                 Ok(p) if parser.eat(&token::Comma) => Some(p),
@@ -563,7 +563,7 @@ impl Write {
             }
 
             let comma_span = parser.prev_token.span;
-            let token_expr = if let Ok(expr) = parser.parse_expr().map_err(|mut err| err.cancel()) {
+            let token_expr = if let Ok(expr) = parser.parse_expr().map_err(|err| err.cancel()) {
                 expr
             } else {
                 return (Some(fmtstr), None);
diff --git a/clippy_utils/src/diagnostics.rs b/clippy_utils/src/diagnostics.rs
index ca222c3d66995..a927788e6a44a 100644
--- a/clippy_utils/src/diagnostics.rs
+++ b/clippy_utils/src/diagnostics.rs
@@ -8,13 +8,13 @@
 //! Thank you!
 //! ~The `INTERNAL_METADATA_COLLECTOR` lint
 
-use rustc_errors::{Applicability, DiagnosticBuilder};
+use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir::HirId;
 use rustc_lint::{LateContext, Lint, LintContext};
 use rustc_span::source_map::{MultiSpan, Span};
 use std::env;
 
-fn docs_link(diag: &mut DiagnosticBuilder<'_>, lint: &'static Lint) {
+fn docs_link(diag: &mut Diagnostic, lint: &'static Lint) {
     if env::var("CLIPPY_DISABLE_DOCS_LINKS").is_err() {
         if let Some(lint) = lint.name_lower().strip_prefix("clippy::") {
             diag.help(&format!(
@@ -145,7 +145,7 @@ pub fn span_lint_and_then<C, S, F>(cx: &C, lint: &'static Lint, sp: S, msg: &str
 where
     C: LintContext,
     S: Into<MultiSpan>,
-    F: FnOnce(&mut DiagnosticBuilder<'_>),
+    F: FnOnce(&mut Diagnostic),
 {
     cx.struct_span_lint(lint, sp, |diag| {
         let mut diag = diag.build(msg);
@@ -169,7 +169,7 @@ pub fn span_lint_hir_and_then(
     hir_id: HirId,
     sp: impl Into<MultiSpan>,
     msg: &str,
-    f: impl FnOnce(&mut DiagnosticBuilder<'_>),
+    f: impl FnOnce(&mut Diagnostic),
 ) {
     cx.tcx.struct_span_lint_hir(lint, hir_id, sp, |diag| {
         let mut diag = diag.build(msg);
@@ -219,7 +219,7 @@ pub fn span_lint_and_sugg<'a, T: LintContext>(
 /// appear once per
 /// replacement. In human-readable format though, it only appears once before
 /// the whole suggestion.
-pub fn multispan_sugg<I>(diag: &mut DiagnosticBuilder<'_>, help_msg: &str, sugg: I)
+pub fn multispan_sugg<I>(diag: &mut Diagnostic, help_msg: &str, sugg: I)
 where
     I: IntoIterator<Item = (Span, String)>,
 {
@@ -232,7 +232,7 @@ where
 /// multiple spans. This is tracked in issue [rustfix#141](https://github.com/rust-lang/rustfix/issues/141).
 /// Suggestions with multiple spans will be silently ignored.
 pub fn multispan_sugg_with_applicability<I>(
-    diag: &mut DiagnosticBuilder<'_>,
+    diag: &mut Diagnostic,
     help_msg: &str,
     applicability: Applicability,
     sugg: I,
diff --git a/clippy_utils/src/sugg.rs b/clippy_utils/src/sugg.rs
index fa63ddff253cf..63c442e70085a 100644
--- a/clippy_utils/src/sugg.rs
+++ b/clippy_utils/src/sugg.rs
@@ -673,8 +673,8 @@ fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
         })
 }
 
-/// Convenience extension trait for `DiagnosticBuilder`.
-pub trait DiagnosticBuilderExt<T: LintContext> {
+/// Convenience extension trait for `Diagnostic`.
+pub trait DiagnosticExt<T: LintContext> {
     /// Suggests to add an attribute to an item.
     ///
     /// Correctly handles indentation of the attribute and item.
@@ -721,7 +721,7 @@ pub trait DiagnosticBuilderExt<T: LintContext> {
     fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
 }
 
-impl<T: LintContext> DiagnosticBuilderExt<T> for rustc_errors::DiagnosticBuilder<'_> {
+impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
     fn suggest_item_with_attr<D: Display + ?Sized>(
         &mut self,
         cx: &T,