Add comment and remove obsolete special case

compiler/rustc_middle/src/mir/visit.rs

@@ -1018,6 +1018,7 @@ macro_rules! visit_place_fns {
 
             if !place.projection.is_empty() {
                 if context.is_use() {
+                    // ^ Only change the context if it is a real use, not a "use" in debuginfo.
                     context = if context.is_mutating_use() {
                         PlaceContext::MutatingUse(MutatingUseContext::Projection)
                     } else {