Check the invariant for principal inside the method

src/librustc_codegen_llvm/debuginfo/metadata.rs

@@ -435,12 +435,7 @@ fn trait_pointer_metadata(
     // But it does not describe the trait's methods.
 
     let containing_scope = match trait_type.sty {
-        ty::Dynamic(ref data, ..) => if let Some(principal) = data.principal() {
-            let def_id = principal.def_id();
-            Some(get_namespace_for_item(cx, def_id))
-        } else {
-            NO_SCOPE_METADATA
-        },
+        ty::Dynamic(ref data, ..) => Some(get_namespace_for_item(cx, data.principal().def_id())),
         _ => {
             bug!("debuginfo: Unexpected trait-object type in \
                   trait_pointer_metadata(): {:?}",