Use visible_crates rather than crates for solving and diagnostics

For places where we don't want stdlib-private crates to be accessible,
use `.visible_crates()` rather than `.crates()`. The current effect is
that items in stdlib-private crates will no longer show up in
diagnostics related to trait selection.

Fixes: rust-lang#135232

compiler/rustc_middle/src/ty/context.rs

@@ -2080,7 +2080,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     pub fn all_traits(self) -> impl Iterator<Item = DefId> + 'tcx {
         iter::once(LOCAL_CRATE)
-            .chain(self.crates(()).iter().copied())
+            .chain(self.visible_crates(()).iter().copied())
             .flat_map(move |cnum| self.traits(cnum).iter().copied())
     }
 

compiler/rustc_passes/src/diagnostic_items.rs

@@ -80,7 +80,7 @@ fn all_diagnostic_items(tcx: TyCtxt<'_>, (): ()) -> DiagnosticItems {
     let mut items = DiagnosticItems::default();
 
     // Collect diagnostic items in other crates.
-    for &cnum in tcx.crates(()).iter().chain(std::iter::once(&LOCAL_CRATE)) {
+    for &cnum in tcx.visible_crates(()).iter().chain(std::iter::once(&LOCAL_CRATE)) {
         for (&name, &def_id) in &tcx.diagnostic_items(cnum).name_to_id {
             collect_item(tcx, &mut items, name, def_id);
         }