Replace interning of string literals with preinterned symbols

book/src/development/common_tools_writing_lints.md

@@ -159,19 +159,21 @@ paths for Clippy can be found in [paths.rs][paths]
 To check if our type defines a method called `some_method`:
 
 ```rust
-use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::return_ty;
+use clippy_utils::ty::is_type_lang_item;
+use clippy_utils::{sym, return_ty};
 
 impl<'tcx> LateLintPass<'tcx> for MyTypeImpl {
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) {
         // Check if item is a method/function
         if let ImplItemKind::Fn(ref signature, _) = impl_item.kind
             // Check the method is named `some_method`
-            && impl_item.ident.name.as_str() == "some_method"
+            //
+            // Add `some_method` to `clippy_utils::sym` if it's not already there
+            && impl_item.ident.name == sym::some_method
             // We can also check it has a parameter `self`
             && signature.decl.implicit_self.has_implicit_self()
             // We can go further and even check if its return type is `String`
-            && is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id), sym!(string_type))
+            && is_type_lang_item(cx, return_ty(cx, impl_item.hir_id), LangItem::String)
         {
             // ...
         }

clippy_lints/src/format_impl.rs

@@ -1,13 +1,13 @@
 use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
 use clippy_utils::macros::{FormatArgsStorage, find_format_arg_expr, is_format_macro, root_macro_call_first_node};
-use clippy_utils::{get_parent_as_impl, is_diag_trait_item, path_to_local, peel_ref_operators};
+use clippy_utils::{get_parent_as_impl, is_diag_trait_item, path_to_local, peel_ref_operators, sym};
 use rustc_ast::{FormatArgsPiece, FormatTrait};
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind, Impl, ImplItem, ImplItemKind, QPath};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
+use rustc_span::Symbol;
 use rustc_span::symbol::kw;
-use rustc_span::{Symbol, sym};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -185,13 +185,13 @@ impl FormatImplExpr<'_, '_> {
                     && let trait_name = match placeholder.format_trait {
                         FormatTrait::Display => sym::Display,
                         FormatTrait::Debug => sym::Debug,
-                        FormatTrait::LowerExp => sym!(LowerExp),
-                        FormatTrait::UpperExp => sym!(UpperExp),
-                        FormatTrait::Octal => sym!(Octal),
+                        FormatTrait::LowerExp => sym::LowerExp,
+                        FormatTrait::UpperExp => sym::UpperExp,
+                        FormatTrait::Octal => sym::Octal,
                         FormatTrait::Pointer => sym::Pointer,
-                        FormatTrait::Binary => sym!(Binary),
-                        FormatTrait::LowerHex => sym!(LowerHex),
-                        FormatTrait::UpperHex => sym!(UpperHex),
+                        FormatTrait::Binary => sym::Binary,
+                        FormatTrait::LowerHex => sym::LowerHex,
+                        FormatTrait::UpperHex => sym::UpperHex,
                     }
                     && trait_name == self.format_trait_impl.name
                     && let Ok(index) = placeholder.argument.index

clippy_lints/src/indexing_slicing.rs

@@ -2,13 +2,12 @@ use clippy_config::Conf;
 use clippy_utils::consts::{ConstEvalCtxt, Constant};
 use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
 use clippy_utils::ty::{deref_chain, get_adt_inherent_method};
-use clippy_utils::{higher, is_from_proc_macro, is_in_test};
+use clippy_utils::{higher, is_from_proc_macro, is_in_test, sym};
 use rustc_ast::ast::RangeLimits;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{self, Ty};
 use rustc_session::impl_lint_pass;
-use rustc_span::sym;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -268,7 +267,7 @@ fn ty_has_applicable_get_function<'tcx>(
     index_expr: &Expr<'_>,
 ) -> bool {
     if let ty::Adt(_, _) = array_ty.kind()
-        && let Some(get_output_ty) = get_adt_inherent_method(cx, ty, sym!(get)).map(|m| {
+        && let Some(get_output_ty) = get_adt_inherent_method(cx, ty, sym::get).map(|m| {
             cx.tcx
                 .fn_sig(m.def_id)
                 .skip_binder()

clippy_lints/src/len_zero.rs

@@ -2,7 +2,7 @@ use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_the
 use clippy_utils::source::{SpanRangeExt, snippet_with_context};
 use clippy_utils::sugg::{Sugg, has_enclosing_paren};
 use clippy_utils::ty::implements_trait;
-use clippy_utils::{fulfill_or_allowed, get_item_name, get_parent_as_impl, is_trait_method, peel_ref_operators};
+use clippy_utils::{fulfill_or_allowed, get_item_name, get_parent_as_impl, is_trait_method, peel_ref_operators, sym};
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
 use rustc_hir::def::Res;
@@ -16,7 +16,6 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{self, FnSig, Ty};
 use rustc_session::declare_lint_pass;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::sym;
 use rustc_span::{Ident, Span, Symbol};
 use rustc_trait_selection::traits::supertrait_def_ids;
 
@@ -295,11 +294,9 @@ fn check_trait_items(cx: &LateContext<'_>, visited_trait: &Item<'_>, ident: Iden
     {
         let mut current_and_super_traits = DefIdSet::default();
         fill_trait_set(visited_trait.owner_id.to_def_id(), &mut current_and_super_traits, cx);
-        let is_empty = sym!(is_empty);
-
         let is_empty_method_found = current_and_super_traits
             .items()
-            .flat_map(|&i| cx.tcx.associated_items(i).filter_by_name_unhygienic(is_empty))
+            .flat_map(|&i| cx.tcx.associated_items(i).filter_by_name_unhygienic(sym::is_empty))
             .any(|i| i.is_method() && cx.tcx.fn_sig(i.def_id).skip_binder().inputs().skip_binder().len() == 1);
 
         if !is_empty_method_found {
@@ -472,12 +469,11 @@ fn check_for_is_empty(
         return;
     };
 
-    let is_empty = Symbol::intern("is_empty");
     let is_empty = cx
         .tcx
         .inherent_impls(impl_ty)
         .iter()
-        .flat_map(|&id| cx.tcx.associated_items(id).filter_by_name_unhygienic(is_empty))
+        .flat_map(|&id| cx.tcx.associated_items(id).filter_by_name_unhygienic(sym::is_empty))
         .find(|item| item.is_fn());
 
     let (msg, is_empty_span, self_kind) = match is_empty {
@@ -633,22 +629,20 @@ fn has_is_empty(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
 
     /// Checks the inherent impl's items for an `is_empty(self)` method.
     fn has_is_empty_impl(cx: &LateContext<'_>, id: DefId) -> bool {
-        let is_empty = sym!(is_empty);
         cx.tcx.inherent_impls(id).iter().any(|imp| {
             cx.tcx
                 .associated_items(*imp)
-                .filter_by_name_unhygienic(is_empty)
+                .filter_by_name_unhygienic(sym::is_empty)
                 .any(|item| is_is_empty(cx, item))
         })
     }
 
     fn ty_has_is_empty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, depth: usize) -> bool {
         match ty.kind() {
             ty::Dynamic(tt, ..) => tt.principal().is_some_and(|principal| {
-                let is_empty = sym!(is_empty);
                 cx.tcx
                     .associated_items(principal.def_id())
-                    .filter_by_name_unhygienic(is_empty)
+                    .filter_by_name_unhygienic(sym::is_empty)
                     .any(|item| is_is_empty(cx, item))
             }),
             ty::Alias(ty::Projection, proj) => has_is_empty_impl(cx, proj.def_id),

clippy_lints/src/loops/explicit_iter_loop.rs

@@ -2,6 +2,7 @@ use super::EXPLICIT_ITER_LOOP;
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::sym;
 use clippy_utils::ty::{
     implements_trait, implements_trait_with_env, is_copy, is_type_lang_item, make_normalized_projection,
     make_normalized_projection_with_regions, normalize_with_regions,
@@ -11,7 +12,6 @@ use rustc_hir::{Expr, Mutability};
 use rustc_lint::LateContext;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
 use rustc_middle::ty::{self, EarlyBinder, Ty};
-use rustc_span::sym;
 
 pub(super) fn check(
     cx: &LateContext<'_>,
@@ -119,7 +119,7 @@ fn is_ref_iterable<'tcx>(
         && let typing_env = ty::TypingEnv::non_body_analysis(cx.tcx, fn_id)
         && implements_trait_with_env(cx.tcx, typing_env, req_self_ty, trait_id, Some(fn_id), &[])
         && let Some(into_iter_ty) =
-            make_normalized_projection_with_regions(cx.tcx, typing_env, trait_id, sym!(IntoIter), [req_self_ty])
+            make_normalized_projection_with_regions(cx.tcx, typing_env, trait_id, sym::IntoIter, [req_self_ty])
         && let req_res_ty = normalize_with_regions(cx.tcx, typing_env, req_res_ty)
         && into_iter_ty == req_res_ty
     {
@@ -152,7 +152,7 @@ fn is_ref_iterable<'tcx>(
                 // Using by value won't consume anything
                 if implements_trait(cx, self_ty, trait_id, &[])
                     && let Some(ty) =
-                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym!(IntoIter), [self_ty])
+                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym::IntoIter, [self_ty])
                     && ty == res_ty
                 {
                     return Some((AdjustKind::None, self_ty));
@@ -169,7 +169,7 @@ fn is_ref_iterable<'tcx>(
                 };
                 if implements_trait(cx, self_ty, trait_id, &[])
                     && let Some(ty) =
-                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym!(IntoIter), [self_ty])
+                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym::IntoIter, [self_ty])
                     && ty == res_ty
                 {
                     return Some((AdjustKind::reborrow(mutbl), self_ty));
@@ -183,7 +183,7 @@ fn is_ref_iterable<'tcx>(
             let self_ty = Ty::new_ref(cx.tcx, cx.tcx.lifetimes.re_erased, self_ty, mutbl);
             if implements_trait(cx, self_ty, trait_id, &[])
                 && let Some(ty) =
-                    make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym!(IntoIter), [self_ty])
+                    make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym::IntoIter, [self_ty])
                 && ty == res_ty
             {
                 return Some((AdjustKind::borrow(mutbl), self_ty));
@@ -206,7 +206,7 @@ fn is_ref_iterable<'tcx>(
                     && target != self_ty
                     && implements_trait(cx, target, trait_id, &[])
                     && let Some(ty) =
-                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym!(IntoIter), [target])
+                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym::IntoIter, [target])
                     && ty == res_ty
                 {
                     Some((AdjustKind::auto_reborrow(mutbl), target))
@@ -224,7 +224,7 @@ fn is_ref_iterable<'tcx>(
                 if is_copy(cx, target)
                     && implements_trait(cx, target, trait_id, &[])
                     && let Some(ty) =
-                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym!(IntoIter), [target])
+                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym::IntoIter, [target])
                     && ty == res_ty
                 {
                     Some((AdjustKind::Deref, target))
@@ -242,7 +242,7 @@ fn is_ref_iterable<'tcx>(
                 if self_ty.is_ref()
                     && implements_trait(cx, target, trait_id, &[])
                     && let Some(ty) =
-                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym!(IntoIter), [target])
+                        make_normalized_projection(cx.tcx, cx.typing_env(), trait_id, sym::IntoIter, [target])
                     && ty == res_ty
                 {
                     Some((AdjustKind::auto_borrow(mutbl), target))

clippy_lints/src/manual_div_ceil.rs

@@ -1,8 +1,9 @@
-use clippy_utils::SpanlessEq;
+use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::sugg::{Sugg, has_enclosing_paren};
+use clippy_utils::{SpanlessEq, sym};
 use rustc_ast::{BinOpKind, LitIntType, LitKind, UnOp};
 use rustc_data_structures::packed::Pu128;
 use rustc_errors::Applicability;
@@ -11,9 +12,6 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{self};
 use rustc_session::impl_lint_pass;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Symbol;
-
-use clippy_config::Conf;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -141,8 +139,7 @@ fn check_int_ty_and_feature(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     let expr_ty = cx.typeck_results().expr_ty(expr);
     match expr_ty.peel_refs().kind() {
         ty::Uint(_) => true,
-        ty::Int(_) => cx.tcx.features().enabled(Symbol::intern("int_roundings")),
-
+        ty::Int(_) => cx.tcx.features().enabled(sym::int_roundings),
         _ => false,
     }
 }

clippy_lints/src/matches/redundant_pattern_match.rs

@@ -4,15 +4,15 @@ use clippy_utils::source::walk_span_to_context;
 use clippy_utils::sugg::{Sugg, make_unop};
 use clippy_utils::ty::{is_type_diagnostic_item, needs_ordered_drop};
 use clippy_utils::visitors::{any_temporaries_need_ordered_drop, for_each_expr_without_closures};
-use clippy_utils::{higher, is_expn_of, is_trait_method};
+use clippy_utils::{higher, is_expn_of, is_trait_method, sym};
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
 use rustc_hir::LangItem::{self, OptionNone, OptionSome, PollPending, PollReady, ResultErr, ResultOk};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{Arm, Expr, ExprKind, Node, Pat, PatExpr, PatExprKind, PatKind, QPath, UnOp};
 use rustc_lint::LateContext;
 use rustc_middle::ty::{self, GenericArgKind, Ty};
-use rustc_span::{Span, Symbol, sym};
+use rustc_span::{Span, Symbol};
 use std::fmt::Write;
 use std::ops::ControlFlow;
 
@@ -138,9 +138,9 @@ fn find_method_and_type<'tcx>(
                     Some(("is_some()", op_ty))
                 } else if Some(id) == lang_items.poll_ready_variant() {
                     Some(("is_ready()", op_ty))
-                } else if is_pat_variant(cx, check_pat, qpath, Item::Diag(sym::IpAddr, sym!(V4))) {
+                } else if is_pat_variant(cx, check_pat, qpath, Item::Diag(sym::IpAddr, sym::V4)) {
                     Some(("is_ipv4()", op_ty))
-                } else if is_pat_variant(cx, check_pat, qpath, Item::Diag(sym::IpAddr, sym!(V6))) {
+                } else if is_pat_variant(cx, check_pat, qpath, Item::Diag(sym::IpAddr, sym::V6)) {
                     Some(("is_ipv6()", op_ty))
                 } else {
                     None
@@ -345,8 +345,8 @@ fn found_good_method<'tcx>(
                         arms,
                         path_left,
                         path_right,
-                        Item::Diag(sym::IpAddr, sym!(V4)),
-                        Item::Diag(sym::IpAddr, sym!(V6)),
+                        Item::Diag(sym::IpAddr, sym::V4),
+                        Item::Diag(sym::IpAddr, sym::V6),
                         "is_ipv4()",
                         "is_ipv6()",
                     )
@@ -437,8 +437,8 @@ fn get_good_method<'tcx>(
             "None" => (Item::Lang(OptionNone), "is_none()", "is_some()"),
             "Ready" => (Item::Lang(PollReady), "is_ready()", "is_pending()"),
             "Pending" => (Item::Lang(PollPending), "is_pending()", "is_ready()"),
-            "V4" => (Item::Diag(sym::IpAddr, sym!(V4)), "is_ipv4()", "is_ipv6()"),
-            "V6" => (Item::Diag(sym::IpAddr, sym!(V6)), "is_ipv6()", "is_ipv4()"),
+            "V4" => (Item::Diag(sym::IpAddr, sym::V4), "is_ipv4()", "is_ipv6()"),
+            "V6" => (Item::Diag(sym::IpAddr, sym::V6), "is_ipv6()", "is_ipv4()"),
             _ => return None,
         };
         return find_good_method_for_matches_macro(

clippy_lints/src/methods/filter_map.rs

@@ -2,7 +2,7 @@ use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::macros::{is_panic, matching_root_macro_call, root_macro_call};
 use clippy_utils::source::{indent_of, reindent_multiline, snippet};
 use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::{SpanlessEq, higher, is_trait_method, path_to_local_id, peel_blocks};
+use clippy_utils::{SpanlessEq, higher, is_trait_method, path_to_local_id, peel_blocks, sym};
 use hir::{Body, HirId, MatchSource, Pat};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
@@ -11,7 +11,7 @@ use rustc_hir::{Closure, Expr, ExprKind, PatKind, PathSegment, QPath, UnOp};
 use rustc_lint::LateContext;
 use rustc_middle::ty::adjustment::Adjust;
 use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, sym};
+use rustc_span::symbol::{Ident, Symbol};
 
 use super::{MANUAL_FILTER_MAP, MANUAL_FIND_MAP, OPTION_FILTER_MAP, RESULT_FILTER_MAP};
 
@@ -43,10 +43,10 @@ fn is_method(cx: &LateContext<'_>, expr: &Expr<'_>, method_name: Symbol) -> bool
 }
 
 fn is_option_filter_map(cx: &LateContext<'_>, filter_arg: &Expr<'_>, map_arg: &Expr<'_>) -> bool {
-    is_method(cx, map_arg, sym::unwrap) && is_method(cx, filter_arg, sym!(is_some))
+    is_method(cx, map_arg, sym::unwrap) && is_method(cx, filter_arg, sym::is_some)
 }
 fn is_ok_filter_map(cx: &LateContext<'_>, filter_arg: &Expr<'_>, map_arg: &Expr<'_>) -> bool {
-    is_method(cx, map_arg, sym::unwrap) && is_method(cx, filter_arg, sym!(is_ok))
+    is_method(cx, map_arg, sym::unwrap) && is_method(cx, filter_arg, sym::is_ok)
 }
 
 #[derive(Debug, Copy, Clone)]
@@ -429,16 +429,15 @@ fn is_find_or_filter<'a>(
 }
 
 fn acceptable_methods(method: &PathSegment<'_>) -> bool {
-    let methods: [Symbol; 8] = [
-        sym::clone,
-        sym::as_ref,
-        sym!(copied),
-        sym!(cloned),
-        sym!(as_deref),
-        sym!(as_mut),
-        sym!(as_deref_mut),
-        sym!(to_owned),
-    ];
-
-    methods.contains(&method.ident.name)
+    matches!(
+        method.ident.name,
+        sym::clone
+            | sym::as_ref
+            | sym::copied
+            | sym::cloned
+            | sym::as_deref
+            | sym::as_mut
+            | sym::as_deref_mut
+            | sym::to_owned
+    )
 }