diff --git a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
index ea406e706660d..e75bc944d7ec8 100644
--- a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
+++ b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
@@ -62,8 +62,8 @@ pub(crate) fn expand(
 fn generate_handler(cx: &ExtCtxt<'_>, handler: Ident, span: Span, sig_span: Span) -> Stmt {
     let usize = cx.path_ident(span, Ident::new(sym::usize, span));
     let ty_usize = cx.ty_path(usize);
-    let size = Ident::from_str_and_span("size", span);
-    let align = Ident::from_str_and_span("align", span);
+    let size = Ident::new(sym::size, span);
+    let align = Ident::new(sym::align, span);
 
     let layout_new = cx.std_path(&[sym::alloc, sym::Layout, sym::from_size_align_unchecked]);
     let layout_new = cx.expr_path(cx.path(span, layout_new));
diff --git a/compiler/rustc_builtin_macros/src/autodiff.rs b/compiler/rustc_builtin_macros/src/autodiff.rs
index dc3bb8ab52a5d..df1b1eb60e18f 100644
--- a/compiler/rustc_builtin_macros/src/autodiff.rs
+++ b/compiler/rustc_builtin_macros/src/autodiff.rs
@@ -652,8 +652,10 @@ mod llvm_enzyme {
                 exprs = ecx.expr_call(new_decl_span, bb_call_expr, thin_vec![exprs]);
             } else {
                 let q = QSelf { ty: d_ret_ty, path_span: span, position: 0 };
-                let y =
-                    ExprKind::Path(Some(P(q)), ecx.path_ident(span, Ident::from_str("default")));
+                let y = ExprKind::Path(
+                    Some(P(q)),
+                    ecx.path_ident(span, Ident::with_dummy_span(kw::Default)),
+                );
                 let default_call_expr = ecx.expr(span, y);
                 let default_call_expr =
                     ecx.expr_call(new_decl_span, default_call_expr, thin_vec![]);
diff --git a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
index daf480a9ce472..42b7e0e06d1f3 100644
--- a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
+++ b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
@@ -56,7 +56,7 @@ pub fn inject(
     is_test_crate: bool,
     dcx: DiagCtxtHandle<'_>,
 ) {
-    let ecfg = ExpansionConfig::default("proc_macro".to_string(), features);
+    let ecfg = ExpansionConfig::default(sym::proc_macro, features);
     let mut cx = ExtCtxt::new(sess, ecfg, resolver, None);
 
     let mut collect = CollectProcMacros {
diff --git a/compiler/rustc_builtin_macros/src/standard_library_imports.rs b/compiler/rustc_builtin_macros/src/standard_library_imports.rs
index a1ee53b7ca21f..682e7c9b17ae8 100644
--- a/compiler/rustc_builtin_macros/src/standard_library_imports.rs
+++ b/compiler/rustc_builtin_macros/src/standard_library_imports.rs
@@ -36,7 +36,7 @@ pub fn inject(
     let span = DUMMY_SP.with_def_site_ctxt(expn_id.to_expn_id());
     let call_site = DUMMY_SP.with_call_site_ctxt(expn_id.to_expn_id());
 
-    let ecfg = ExpansionConfig::default("std_lib_injection".to_string(), features);
+    let ecfg = ExpansionConfig::default(sym::std_lib_injection, features);
     let cx = ExtCtxt::new(sess, ecfg, resolver, None);
 
     let ident_span = if edition >= Edition2018 { span } else { call_site };
diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
index 0bc313cbdacb4..77aafd3469a0f 100644
--- a/compiler/rustc_builtin_macros/src/test_harness.rs
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -227,7 +227,7 @@ fn generate_test_harness(
     panic_strategy: PanicStrategy,
     test_runner: Option<ast::Path>,
 ) {
-    let econfig = ExpansionConfig::default("test".to_string(), features);
+    let econfig = ExpansionConfig::default(sym::test, features);
     let ext_cx = ExtCtxt::new(sess, econfig, resolver, None);
 
     let expn_id = ext_cx.resolver.expansion_for_ast_pass(
diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
index ec0af67c0463e..714ba3bf0f4f2 100644
--- a/compiler/rustc_expand/src/errors.rs
+++ b/compiler/rustc_expand/src/errors.rs
@@ -183,12 +183,12 @@ pub(crate) struct FeatureNotAllowed {
 #[derive(Diagnostic)]
 #[diag(expand_recursion_limit_reached)]
 #[help]
-pub(crate) struct RecursionLimitReached<'a> {
+pub(crate) struct RecursionLimitReached {
     #[primary_span]
     pub span: Span,
     pub descr: String,
     pub suggested_limit: Limit,
-    pub crate_name: &'a str,
+    pub crate_name: Symbol,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 9fd524ef45cd0..37010700fab81 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -26,7 +26,7 @@ use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
 use rustc_session::parse::feature_err;
 use rustc_session::{Limit, Session};
 use rustc_span::hygiene::SyntaxContext;
-use rustc_span::{ErrorGuaranteed, FileName, Ident, LocalExpnId, Span, sym};
+use rustc_span::{ErrorGuaranteed, FileName, Ident, LocalExpnId, Span, Symbol, sym};
 use smallvec::SmallVec;
 
 use crate::base::*;
@@ -473,7 +473,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         let dir_path = file_path.parent().unwrap_or(&file_path).to_owned();
         self.cx.root_path = dir_path.clone();
         self.cx.current_expansion.module = Rc::new(ModuleData {
-            mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
+            mod_path: vec![Ident::with_dummy_span(self.cx.ecfg.crate_name)],
             file_path_stack: vec![file_path],
             dir_path,
         });
@@ -689,7 +689,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             span: expn_data.call_site,
             descr: expn_data.kind.descr(),
             suggested_limit,
-            crate_name: &self.cx.ecfg.crate_name,
+            crate_name: self.cx.ecfg.crate_name,
         });
 
         self.cx.trace_macros_diag();
@@ -2458,7 +2458,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
 }
 
 pub struct ExpansionConfig<'feat> {
-    pub crate_name: String,
+    pub crate_name: Symbol,
     pub features: &'feat Features,
     pub recursion_limit: Limit,
     pub trace_mac: bool,
@@ -2471,7 +2471,7 @@ pub struct ExpansionConfig<'feat> {
 }
 
 impl ExpansionConfig<'_> {
-    pub fn default(crate_name: String, features: &Features) -> ExpansionConfig<'_> {
+    pub fn default(crate_name: Symbol, features: &Features) -> ExpansionConfig<'_> {
         ExpansionConfig {
             crate_name,
             features,
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index fc507285860ed..233bb5cd5b858 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -22,7 +22,7 @@ use rustc_hir::{
     TyPatKind,
 };
 use rustc_span::source_map::SourceMap;
-use rustc_span::{FileName, Ident, Span, Symbol, kw};
+use rustc_span::{FileName, Ident, Span, Symbol, kw, sym};
 use {rustc_ast as ast, rustc_hir as hir};
 
 pub fn id_to_string(cx: &dyn rustc_hir::intravisit::HirTyCtxt<'_>, hir_id: HirId) -> String {
@@ -1517,7 +1517,7 @@ impl<'a> State<'a> {
                 self.bopen(ib);
 
                 // Print `let _t = $init;`:
-                let temp = Ident::from_str("_t");
+                let temp = Ident::with_dummy_span(sym::_t);
                 self.print_local(false, Some(init), None, |this| this.print_ident(temp));
                 self.word(";");
 
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 02d1ebdb31a9a..b2d7383b987a4 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -192,7 +192,7 @@ fn configure_and_expand(
         // Create the config for macro expansion
         let recursion_limit = get_recursion_limit(pre_configured_attrs, sess);
         let cfg = rustc_expand::expand::ExpansionConfig {
-            crate_name: crate_name.to_string(),
+            crate_name,
             features,
             recursion_limit,
             trace_mac: sess.opts.unstable_opts.trace_macros,
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 5ce803aa1f8a0..c6a5811237169 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -35,7 +35,7 @@ use rustc_session::lint::builtin::{
     UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES, UNUSED_ATTRIBUTES,
 };
 use rustc_session::parse::feature_err;
-use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, edition, sym};
+use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, edition, kw, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::{TyCtxtInferExt, ValuePairs};
 use rustc_trait_selection::traits::ObligationCtxt;
@@ -715,7 +715,10 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         && !matches!(other_attr.path().as_slice(), [sym::rustfmt, ..])
                     {
                         let path = other_attr.path();
-                        let path: Vec<_> = path.iter().map(|s| s.as_str()).collect();
+                        let path: Vec<_> = path
+                            .iter()
+                            .map(|s| if *s == kw::PathRoot { "" } else { s.as_str() })
+                            .collect();
                         let other_attr_name = path.join("::");
 
                         self.dcx().emit_err(errors::NakedFunctionIncompatibleAttribute {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index baadff16120f3..9924322ae9def 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -396,8 +396,7 @@ symbols! {
         __S,
         __awaitee,
         __try_var,
-        _d,
-        _e,
+        _t,
         _task_context,
         a32,
         aarch64_target_feature,
@@ -2052,6 +2051,7 @@ symbols! {
         static_recursion,
         staticlib,
         std,
+        std_lib_injection,
         std_panic,
         std_panic_2015_macro,
         std_panic_macro,
diff --git a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
index ae36bb76117d7..8f95e44bf8531 100644
--- a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
+++ b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
@@ -56,7 +56,7 @@ fn is_impl_not_trait_with_bool_out<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -
         .and_then(|trait_id| {
             cx.tcx.associated_items(trait_id).find_by_ident_and_kind(
                 cx.tcx,
-                Ident::from_str("Output"),
+                Ident::with_dummy_span(sym::Output),
                 ty::AssocTag::Type,
                 trait_id,
             )
diff --git a/src/tools/rustfmt/src/imports.rs b/src/tools/rustfmt/src/imports.rs
index b741dd9b5da54..788fed013ad29 100644
--- a/src/tools/rustfmt/src/imports.rs
+++ b/src/tools/rustfmt/src/imports.rs
@@ -184,7 +184,7 @@ impl UseSegment {
         modsep: bool,
     ) -> Option<UseSegment> {
         let name = rewrite_ident(context, path_seg.ident);
-        if name.is_empty() || name == "{{root}}" {
+        if name.is_empty() {
             return None;
         }
         let kind = match name {
diff --git a/tests/ui/asm/naked-invalid-attr.stderr b/tests/ui/asm/naked-invalid-attr.stderr
index ef389e7d921b9..6661084861eee 100644
--- a/tests/ui/asm/naked-invalid-attr.stderr
+++ b/tests/ui/asm/naked-invalid-attr.stderr
@@ -37,7 +37,7 @@ error[E0736]: attribute incompatible with `#[unsafe(naked)]`
   --> $DIR/naked-invalid-attr.rs:56:1
    |
 LL | #[::a]
-   | ^^^^^^ the `{{root}}::a` attribute is incompatible with `#[unsafe(naked)]`
+   | ^^^^^^ the `::a` attribute is incompatible with `#[unsafe(naked)]`
 ...
 LL | #[unsafe(naked)]
    | ---------------- function marked with `#[unsafe(naked)]` here