Rm diagnostic item, use lang item

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -464,7 +464,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     ref_cnt += 1;
                 }
                 if let ty::Adt(adt, _) = peeled.kind()
-                    && self.tcx.is_diagnostic_item(sym::String, adt.did())
+                    && Some(adt.did()) == self.tcx.lang_items().string()
                 {
                     err.span_suggestion_verbose(
                         expr.span.shrink_to_hi(),

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -926,10 +926,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 ty.is_str()
                                     || matches!(
                                         ty.kind(),
-                                        ty::Adt(adt, _) if self.tcx.is_diagnostic_item(sym::String, adt.did())
+                                        ty::Adt(adt, _) if Some(adt.did()) == self.tcx.lang_items().string()
                                     )
                             }
-                            ty::Adt(adt, _) => self.tcx.is_diagnostic_item(sym::String, adt.did()),
+                            ty::Adt(adt, _) => Some(adt.did()) == self.tcx.lang_items().string(),
                             _ => false,
                         };
                         if is_string_or_ref_str && item_name.name == sym::iter {

compiler/rustc_hir_typeck/src/op.rs

@@ -556,9 +556,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let rm_borrow_msg = "remove the borrow to obtain an owned `String`";
         let to_owned_msg = "create an owned `String` from a string reference";
 
+        let string_type = self.tcx.lang_items().string();
         let is_std_string = |ty: Ty<'tcx>| {
-            ty.ty_adt_def()
-                .map_or(false, |ty_def| self.tcx.is_diagnostic_item(sym::String, ty_def.did()))
+            ty.ty_adt_def().map_or(false, |ty_def| Some(ty_def.did()) == string_type)
         };
 
         match (lhs_ty.kind(), rhs_ty.kind()) {

compiler/rustc_lint/src/non_fmt_panic.rs

@@ -148,7 +148,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
                 ty::Ref(_, r, _) if *r.kind() == ty::Str,
             ) || matches!(
                 ty.ty_adt_def(),
-                Some(ty_def) if cx.tcx.is_diagnostic_item(sym::String, ty_def.did()),
+                Some(ty_def) if Some(ty_def.did()) == cx.tcx.lang_items().string(),
             );
 
             let infcx = cx.tcx.infer_ctxt().build();

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -1732,7 +1732,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 ty::Bool => Some(0),
                 ty::Char => Some(1),
                 ty::Str => Some(2),
-                ty::Adt(def, _) if tcx.is_diagnostic_item(sym::String, def.did()) => Some(2),
+                ty::Adt(def, _) if Some(def.did()) == tcx.lang_items().string() => Some(2),
                 ty::Int(..)
                 | ty::Uint(..)
                 | ty::Float(..)

library/alloc/src/string.rs

@@ -362,9 +362,8 @@ use crate::vec::Vec;
 /// [`Deref`]: core::ops::Deref "ops::Deref"
 /// [`as_str()`]: String::as_str
 #[derive(PartialOrd, Eq, Ord)]
-#[cfg_attr(not(test), rustc_diagnostic_item = "String")]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg_attr(not(bootstrap), lang = "String")]
+#[cfg_attr(all(not(bootstrap), not(test)), lang = "String")]
 pub struct String {
     vec: Vec<u8>,
 }

src/tools/clippy/clippy_lints/src/format.rs

@@ -73,7 +73,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessFormat {
                 if format_args.format_string.parts == [kw::Empty];
                 if arg.format.is_default();
                 if match cx.typeck_results().expr_ty(value).peel_refs().kind() {
-                    ty::Adt(adt, _) => cx.tcx.is_diagnostic_item(sym::String, adt.did()),
+                    ty::Adt(adt, _) => Some(adt.did()) == cx.tcx.lang_items().string(),
                     ty::Str => true,
                     _ => false,
                 };

src/tools/clippy/clippy_lints/src/format_push_string.rs

@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use clippy_utils::{match_def_path, paths, peel_hir_expr_refs};
-use rustc_hir::{BinOpKind, Expr, ExprKind};
+use rustc_hir::{BinOpKind, Expr, ExprKind, LangItem};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::sym;
@@ -41,7 +41,7 @@ declare_clippy_lint! {
 declare_lint_pass!(FormatPushString => [FORMAT_PUSH_STRING]);
 
 fn is_string(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
-    is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(e).peel_refs(), sym::String)
+    is_type_lang_item(cx, cx.typeck_results().expr_ty(e).peel_refs(), LangItem::String)
 }
 fn is_format(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
     if let Some(macro_def_id) = e.span.ctxt().outer_expn_data().macro_def_id {

src/tools/clippy/clippy_lints/src/from_str_radix_10.rs

@@ -1,10 +1,10 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::is_integer_literal;
 use clippy_utils::sugg::Sugg;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::{def, Expr, ExprKind, PrimTy, QPath, TyKind};
+use rustc_hir::{def, Expr, ExprKind, LangItem, PrimTy, QPath, TyKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::Ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -98,5 +98,5 @@ impl<'tcx> LateLintPass<'tcx> for FromStrRadix10 {
 
 /// Checks if a Ty is `String` or `&str`
 fn is_ty_stringish(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
-    is_type_diagnostic_item(cx, ty, sym::String) || is_type_diagnostic_item(cx, ty, sym::str)
+    is_type_lang_item(cx, ty, LangItem::String) || is_type_diagnostic_item(cx, ty, sym::str)
 }

src/tools/clippy/clippy_lints/src/inherent_to_string.rs

@@ -1,8 +1,8 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
+use clippy_utils::ty::{implements_trait, is_type_lang_item};
 use clippy_utils::{return_ty, trait_ref_of_method};
 use if_chain::if_chain;
-use rustc_hir::{GenericParamKind, ImplItem, ImplItemKind};
+use rustc_hir::{GenericParamKind, ImplItem, ImplItemKind, LangItem};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::sym;
@@ -105,7 +105,7 @@ impl<'tcx> LateLintPass<'tcx> for InherentToString {
             if impl_item.generics.params.iter().all(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }));
 
             // Check if return type is String
-            if is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id()), sym::String);
+            if is_type_lang_item(cx, return_ty(cx, impl_item.hir_id()), LangItem::String);
 
             // Filters instances of to_string which are required by a trait
             if trait_ref_of_method(cx, impl_item.owner_id.def_id).is_none();

src/tools/clippy/clippy_lints/src/manual_retain.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
 use clippy_utils::{get_parent_expr, match_def_path, paths, SpanlessEq};
 use clippy_utils::{meets_msrv, msrvs};
 use rustc_errors::Applicability;
@@ -140,7 +140,7 @@ fn check_to_owned(
         && let Some(chars_expr_def_id) = cx.typeck_results().type_dependent_def_id(chars_expr.hir_id)
         && match_def_path(cx, chars_expr_def_id, &paths::STR_CHARS)
         && let ty = cx.typeck_results().expr_ty(str_expr).peel_refs()
-        && is_type_diagnostic_item(cx, ty, sym::String)
+        && is_type_lang_item(cx, ty, hir::LangItem::String)
         && SpanlessEq::new(cx).eq_expr(left_expr, str_expr) {
         suggest(cx, parent_expr, left_expr, filter_expr);
     }

src/tools/clippy/clippy_lints/src/manual_string_new.rs

@@ -44,7 +44,7 @@ impl LateLintPass<'_> for ManualStringNew {
         let ty = cx.typeck_results().expr_ty(expr);
         match ty.kind() {
             ty::Adt(adt_def, _) if adt_def.is_struct() => {
-                if !cx.tcx.is_diagnostic_item(sym::String, adt_def.did()) {
+                if cx.tcx.lang_items().string() != Some(adt_def.did()) {
                     return;
                 }
             },

src/tools/clippy/clippy_lints/src/matches/match_str_case_mismatch.rs

@@ -1,13 +1,13 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::{walk_expr, Visitor};
-use rustc_hir::{Arm, Expr, ExprKind, PatKind};
+use rustc_hir::{Arm, Expr, ExprKind, LangItem, PatKind};
 use rustc_lint::LateContext;
 use rustc_middle::ty;
 use rustc_span::symbol::Symbol;
-use rustc_span::{sym, Span};
+use rustc_span::Span;
 
 use super::MATCH_STR_CASE_MISMATCH;
 
@@ -59,7 +59,7 @@ impl<'a, 'tcx> MatchExprVisitor<'a, 'tcx> {
         if let Some(case_method) = get_case_method(segment_ident) {
             let ty = self.cx.typeck_results().expr_ty(receiver).peel_refs();
 
-            if is_type_diagnostic_item(self.cx, ty, sym::String) || ty.kind() == &ty::Str {
+            if is_type_lang_item(self.cx, ty, LangItem::String) || ty.kind() == &ty::Str {
                 self.case_method = Some(case_method);
                 return true;
             }

src/tools/clippy/clippy_lints/src/methods/bytes_count_to_len.rs

@@ -1,11 +1,10 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
-use rustc_span::sym;
 
 use super::BYTES_COUNT_TO_LEN;
 
@@ -20,7 +19,7 @@ pub(super) fn check<'tcx>(
         if let Some(impl_id) = cx.tcx.impl_of_method(bytes_id);
         if cx.tcx.type_of(impl_id).is_str();
         let ty = cx.typeck_results().expr_ty(bytes_recv).peel_refs();
-        if ty.is_str() || is_type_diagnostic_item(cx, ty, sym::String);
+        if ty.is_str() || is_type_lang_item(cx, ty, hir::LangItem::String);
         then {
             let mut applicability = Applicability::MachineApplicable;
             span_lint_and_sugg(

src/tools/clippy/clippy_lints/src/methods/bytes_nth.rs

@@ -1,18 +1,17 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use rustc_errors::Applicability;
-use rustc_hir::Expr;
+use rustc_hir::{Expr, LangItem};
 use rustc_lint::LateContext;
-use rustc_span::sym;
 
 use super::BYTES_NTH;
 
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, recv: &'tcx Expr<'tcx>, n_arg: &'tcx Expr<'tcx>) {
     let ty = cx.typeck_results().expr_ty(recv).peel_refs();
     let caller_type = if ty.is_str() {
         "str"
-    } else if is_type_diagnostic_item(cx, ty, sym::String) {
+    } else if is_type_lang_item(cx, ty, LangItem::String) {
         "String"
     } else {
         return;

src/tools/clippy/clippy_lints/src/methods/case_sensitive_file_extension_comparisons.rs

@@ -1,10 +1,10 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use if_chain::if_chain;
 use rustc_ast::ast::LitKind;
-use rustc_hir::{Expr, ExprKind};
+use rustc_hir::{Expr, ExprKind, LangItem};
 use rustc_lint::LateContext;
-use rustc_span::{source_map::Spanned, symbol::sym, Span};
+use rustc_span::{source_map::Spanned, Span};
 
 use super::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS;
 
@@ -26,7 +26,7 @@ pub(super) fn check<'tcx>(
         if ext_str.chars().skip(1).all(|c| c.is_uppercase() || c.is_ascii_digit())
             || ext_str.chars().skip(1).all(|c| c.is_lowercase() || c.is_ascii_digit());
         let recv_ty = cx.typeck_results().expr_ty(recv).peel_refs();
-        if recv_ty.is_str() || is_type_diagnostic_item(cx, recv_ty, sym::String);
+        if recv_ty.is_str() || is_type_lang_item(cx, recv_ty, LangItem::String);
         then {
             span_lint_and_help(
                 cx,

src/tools/clippy/clippy_lints/src/methods/expect_fun_call.rs

@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::macros::{root_macro_call_first_node, FormatArgsExpn};
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
@@ -33,7 +33,7 @@ pub(super) fn check<'tcx>(
                     if (method_name.ident.name == sym::as_str || method_name.ident.name == sym::as_ref) && {
                         let arg_type = cx.typeck_results().expr_ty(receiver);
                         let base_type = arg_type.peel_refs();
-                        *base_type.kind() == ty::Str || is_type_diagnostic_item(cx, base_type, sym::String)
+                        *base_type.kind() == ty::Str || is_type_lang_item(cx, base_type, hir::LangItem::String)
                     } {
                         receiver
                     } else {
@@ -50,7 +50,7 @@ pub(super) fn check<'tcx>(
     // converted to string.
     fn requires_to_string(cx: &LateContext<'_>, arg: &hir::Expr<'_>) -> bool {
         let arg_ty = cx.typeck_results().expr_ty(arg);
-        if is_type_diagnostic_item(cx, arg_ty, sym::String) {
+        if is_type_lang_item(cx, arg_ty, hir::LangItem::String) {
             return false;
         }
         if let ty::Ref(_, ty, ..) = arg_ty.kind() {

src/tools/clippy/clippy_lints/src/methods/inefficient_to_string.rs

@@ -1,13 +1,13 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::{is_type_diagnostic_item, walk_ptrs_ty_depth};
+use clippy_utils::ty::{is_type_lang_item, walk_ptrs_ty_depth};
 use clippy_utils::{match_def_path, paths};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
 use rustc_middle::ty::{self, Ty};
-use rustc_span::symbol::{sym, Symbol};
+use rustc_span::symbol::{Symbol, sym};
 
 use super::INEFFICIENT_TO_STRING;
 
@@ -60,7 +60,7 @@ fn specializes_tostring(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
         return true;
     }
 
-    if is_type_diagnostic_item(cx, ty, sym::String) {
+    if is_type_lang_item(cx, ty, hir::LangItem::String) {
         return true;
     }
 

src/tools/clippy/clippy_lints/src/methods/manual_str_repeat.rs

@@ -36,14 +36,14 @@ fn parse_repeat_arg(cx: &LateContext<'_>, e: &Expr<'_>) -> Option<RepeatKind> {
         }
     } else {
         let ty = cx.typeck_results().expr_ty(e);
-        if is_type_diagnostic_item(cx, ty, sym::String)
+        if is_type_lang_item(cx, ty, LangItem::String)
             || (is_type_lang_item(cx, ty, LangItem::OwnedBox) && get_ty_param(ty).map_or(false, Ty::is_str))
             || (is_type_diagnostic_item(cx, ty, sym::Cow) && get_ty_param(ty).map_or(false, Ty::is_str))
         {
             Some(RepeatKind::String)
         } else {
             let ty = ty.peel_refs();
-            (ty.is_str() || is_type_diagnostic_item(cx, ty, sym::String)).then_some(RepeatKind::String)
+            (ty.is_str() || is_type_lang_item(cx, ty, LangItem::String)).then_some(RepeatKind::String)
         }
     }
 }
@@ -58,7 +58,7 @@ pub(super) fn check(
     if_chain! {
         if let ExprKind::Call(repeat_fn, [repeat_arg]) = take_self_arg.kind;
         if is_path_diagnostic_item(cx, repeat_fn, sym::iter_repeat);
-        if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(collect_expr), sym::String);
+        if is_type_lang_item(cx, cx.typeck_results().expr_ty(collect_expr), LangItem::String);
         if let Some(collect_id) = cx.typeck_results().type_dependent_def_id(collect_expr.hir_id);
         if let Some(take_id) = cx.typeck_results().type_dependent_def_id(take_expr.hir_id);
         if let Some(iter_trait_id) = cx.tcx.get_diagnostic_item(sym::Iterator);

src/tools/clippy/clippy_lints/src/methods/no_effect_replace.rs

@@ -1,11 +1,10 @@
 use clippy_utils::diagnostics::span_lint;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use clippy_utils::SpanlessEq;
 use if_chain::if_chain;
 use rustc_ast::LitKind;
-use rustc_hir::ExprKind;
+use rustc_hir::{ExprKind, LangItem};
 use rustc_lint::LateContext;
-use rustc_span::sym;
 
 use super::NO_EFFECT_REPLACE;
 
@@ -16,7 +15,7 @@ pub(super) fn check<'tcx>(
     arg2: &'tcx rustc_hir::Expr<'_>,
 ) {
     let ty = cx.typeck_results().expr_ty(expr).peel_refs();
-    if !(ty.is_str() || is_type_diagnostic_item(cx, ty, sym::String)) {
+    if !(ty.is_str() || is_type_lang_item(cx, ty, LangItem::String)) {
         return;
     }
 

src/tools/clippy/clippy_lints/src/methods/repeat_once.rs

@@ -1,11 +1,10 @@
 use clippy_utils::consts::{constant_context, Constant};
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use rustc_errors::Applicability;
-use rustc_hir::Expr;
+use rustc_hir::{Expr, LangItem};
 use rustc_lint::LateContext;
-use rustc_span::sym;
 
 use super::REPEAT_ONCE;
 
@@ -37,7 +36,7 @@ pub(super) fn check<'tcx>(
                 format!("{}.to_vec()", snippet(cx, recv.span, r#""...""#)),
                 Applicability::MachineApplicable,
             );
-        } else if is_type_diagnostic_item(cx, ty, sym::String) {
+        } else if is_type_lang_item(cx, ty, LangItem::String) {
             span_lint_and_sugg(
                 cx,
                 REPEAT_ONCE,

src/tools/clippy/clippy_lints/src/methods/search_is_some.rs

@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg};
 use clippy_utils::source::{snippet, snippet_with_applicability};
 use clippy_utils::sugg::deref_closure_args;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::ty::is_type_lang_item;
 use clippy_utils::{is_trait_method, strip_pat_refs};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
@@ -105,7 +105,7 @@ pub(super) fn check<'tcx>(
     else if search_method == "find" {
         let is_string_or_str_slice = |e| {
             let self_ty = cx.typeck_results().expr_ty(e).peel_refs();
-            if is_type_diagnostic_item(cx, self_ty, sym::String) {
+            if is_type_lang_item(cx, self_ty, hir::LangItem::String) {
                 true
             } else {
                 *self_ty.kind() == ty::Str