Improve error message for E0659 if the source is not available

Author: FabianWolff

compiler/rustc_resolve/src/diagnostics.rs

@@ -1178,7 +1178,7 @@ impl<'a> Resolver<'a> {
 
     fn binding_description(&self, b: &NameBinding<'_>, ident: Ident, from_prelude: bool) -> String {
         let res = b.res();
-        if b.span.is_dummy() {
+        if b.span.is_dummy() || self.session.source_map().span_to_snippet(b.span).is_err() {
             // These already contain the "built-in" prefix or look bad with it.
             let add_built_in =
                 !matches!(b.res(), Res::NonMacroAttr(..) | Res::PrimTy(..) | Res::ToolMod);