fix bugs with effects fallback

Author: fee1-dead

compiler/rustc_monomorphize/src/collector.rs

@@ -846,7 +846,9 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
                 } else {
                     Instance::mono(tcx, def_id)
                 };
-                push_mono_lang_item(self, lang_item);
+                if should_codegen_locally(tcx, &instance) {
+                    self.output.push(create_fn_mono_item(tcx, instance, source));
+                }
             }
             mir::TerminatorKind::UnwindTerminate(reason) => {
                 push_mono_lang_item(self, reason.lang_item());

compiler/rustc_passes/src/lang_items.rs

@@ -20,7 +20,8 @@ use rustc_hir::lang_items::{extract, GenericRequirement};
 use rustc_hir::{LangItem, LanguageItems, Target};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::cstore::ExternCrate;
-use rustc_span::{symbol::kw::Empty, Span};
+use rustc_span::symbol::kw::Empty;
+use rustc_span::{sym, Span};
 
 use rustc_middle::query::Providers;
 
@@ -157,7 +158,14 @@ impl<'tcx> LanguageItemCollector<'tcx> {
             self.tcx.hir().get_by_def_id(item_def_id)
         {
             let (actual_num, generics_span) = match kind.generics() {
-                Some(generics) => (generics.params.len(), generics.span),
+                Some(generics) => (
+                    generics
+                        .params
+                        .iter()
+                        .filter(|p| !self.tcx.has_attr(p.def_id, sym::rustc_host))
+                        .count(),
+                    generics.span,
+                ),
                 None => (0, *item_span),
             };
 

compiler/rustc_trait_selection/src/solve/canonicalize.rs

@@ -365,9 +365,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
                 // FIXME: we should fold this ty eventually
                 CanonicalVarKind::Const(ui, c.ty())
             }
-            ty::ConstKind::Infer(ty::InferConst::EffectVar(_)) => {
-                bug!("effect var has no universe")
-            }
+            ty::ConstKind::Infer(ty::InferConst::EffectVar(_)) => CanonicalVarKind::Effect,
             ty::ConstKind::Infer(ty::InferConst::Fresh(_)) => {
                 bug!("fresh var during canonicalization: {c:?}")
             }

compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs

@@ -382,6 +382,12 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for EagerResolver<'_, 'tcx> {
                     }
                 }
             }
+            ty::ConstKind::Infer(ty::InferConst::EffectVar(vid)) => {
+                match self.infcx.probe_effect_var(vid) {
+                    Some(val) => val.as_const(self.infcx.tcx).fold_with(self),
+                    None => self.infcx.tcx.consts.true_,
+                }
+            }
             _ => {
                 if c.has_infer() {
                     c.super_fold_with(self)