Rollup merge of #122588 - klensy:imported_source_file, r=michaelwoerister

less useless filter calls in imported_source_file

This reduces calls to `filter` greatly, giving 0.3% instructions win on some tests.

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1590,6 +1590,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             })
         }
 
+        let try_to_translate_virtual_to_real = |name: &mut rustc_span::FileName| {
             // Translate the virtual `/rustc/$hash` prefix back to a real directory
             // that should hold actual sources, where possible.
             //
@@ -1600,7 +1601,6 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
                 filter(sess, sess.opts.unstable_opts.simulate_remapped_rust_src_base.as_deref()),
             ];
 
-        let try_to_translate_virtual_to_real = |name: &mut rustc_span::FileName| {
             debug!(
                 "try_to_translate_virtual_to_real(name={:?}): \
                  virtual_rust_source_base_dir={:?}, real_rust_source_base_dir={:?}",