fix an issue with inferring host param

Author: fee1-dead

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2126,7 +2126,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
         }
 
-        debug!("path_segs = {:?}", path_segs);
+        debug!(?path_segs);
 
         path_segs
     }

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -1349,10 +1349,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         }
                     }
                     GenericParamDefKind::Const { has_default } => {
-                        if !infer_args && has_default {
-                            tcx.const_param_default(param.def_id)
-                                .instantiate(tcx, args.unwrap())
-                                .into()
+                        // TODO: check if this is always good to be infer var
+                        let is_host = param.name == sym::host;
+                        if !infer_args && has_default && !is_host {
+                            tcx.const_param_default(param.def_id).instantiate(tcx, args.unwrap()).into()
                         } else {
                             self.fcx.var_for_def(self.span, param)
                         }

library/core/src/lib.rs

@@ -257,6 +257,9 @@
 #![feature(wasm_target_feature)]
 // tidy-alphabetical-end
 
+// TODO
+// #![cfg_attr(not(bootstrap), effects)]
+
 // allow using `core::` in intra-doc links
 #[allow(unused_extern_crates)]
 extern crate self as core;

src/tools/clippy/clippy_lints/src/derive.rs

@@ -519,7 +519,6 @@ fn param_env_for_derived_eq(tcx: TyCtxt<'_>, did: DefId, eq_trait_id: DefId) ->
             params.iter().filter(|&&(_, needs_eq)| needs_eq).map(|&(param, _)| {
                 ClauseKind::Trait(TraitPredicate {
                     trait_ref: ty::TraitRef::new(tcx, eq_trait_id, [tcx.mk_param_from_def(param)]),
-                    constness: BoundConstness::NotConst,
                     polarity: ImplPolarity::Positive,
                 })
                 .to_predicate(tcx)

tests/ui/rfcs/rfc-2632-const-trait-impl/effects/infer-host.rs

@@ -0,0 +1,13 @@
+// check-pass
+
+#![feature(const_trait_impl, effects)]
+
+// Host param needs to get infer even if there are generic params supplied
+
+pub const fn hmm<T>() -> usize {
+    1
+}
+
+pub const fn uwu(x: [u8; hmm::<()>()]) {}
+
+fn main() {}

tests/ui/rfcs/rfc-2632-const-trait-impl/effects/super-traits.rs

@@ -0,0 +1,17 @@
+// check-pass
+
+// misc tests not directly related to const traits, but encountered
+// while implementing effects
+
+#![feature(const_trait_impl, effects)]
+
+// #[const_trait]
+pub trait X<Rhs: ?Sized = Self> {}
+
+pub trait Y: X {}
+
+impl X for () {}
+
+impl Y for () {}
+
+fn main() {}