Make enter_trace_span take a closure for better optimization

Author: Stypox

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -636,7 +636,7 @@ pub trait Machine<'tcx>: Sized {
     /// return `span.entered()`. Also see [crate::enter_trace_span].
     #[must_use]
     #[inline(always)]
-    fn enter_trace_span(_span: tracing::Span) -> impl EnteredTraceSpan {
+    fn enter_trace_span(_span: impl FnOnce() -> tracing::Span) -> impl EnteredTraceSpan {
         ()
     }
 }

compiler/rustc_const_eval/src/interpret/util.rs

@@ -60,6 +60,6 @@ impl EnteredTraceSpan for tracing::span::EnteredSpan {}
 #[macro_export]
 macro_rules! enter_trace_span {
     ($machine:ident, $($tt:tt)*) => {
-        $machine::enter_trace_span(tracing::info_span!($($tt)*))
+        $machine::enter_trace_span(|| tracing::info_span!($($tt)*))
     }
 }