Use a symbol for `ExpansionConfig::crate_name`.

This avoids some symbol interning and `to_string` conversions.

3 files changed, 3 insertions, 3 deletions

diff --git a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
index daf480a9ce4..42b7e0e06d1 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 a1ee53b7ca2..682e7c9b17a 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 0bc313cbdac..77aafd3469a 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(