Fix Deref args when #[const_trait] is enabled

Author: compiler-errors

compiler/rustc_hir_analysis/src/autoderef.rs

@@ -109,14 +109,14 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
     pub fn new(
         infcx: &'a InferCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        body_def_id: LocalDefId,
+        body_id: LocalDefId,
         span: Span,
         base_ty: Ty<'tcx>,
     ) -> Autoderef<'a, 'tcx> {
         Autoderef {
             infcx,
             span,
-            body_id: body_def_id,
+            body_id,
             param_env,
             state: AutoderefSnapshot {
                 steps: vec![],
@@ -135,7 +135,21 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
         let tcx = self.infcx.tcx;
 
         // <ty as Deref>
-        let trait_ref = ty::TraitRef::new(tcx, tcx.lang_items().deref_trait()?, [ty]);
+        let deref_trait_def_id = tcx.lang_items().deref_trait()?;
+
+        // FIXME(effects): This is still broken, since we don't necessarily have a choice of
+        // `host = true` or `host = host` in `const` functions. This is also busted in `method_autoderef_steps`.
+        let deref_generics = self.infcx.tcx.generics_of(deref_trait_def_id);
+        let args = if let Some(host_param) = deref_generics.host_effect_index {
+            self.infcx.tcx.mk_args(&[
+                ty.into(),
+                self.infcx.var_for_def(self.span, &deref_generics.params[host_param]),
+            ])
+        } else {
+            self.infcx.tcx.mk_args(&[ty.into()])
+        };
+
+        let trait_ref = ty::TraitRef::new(tcx, deref_trait_def_id, args);
         let cause = traits::ObligationCause::misc(self.span, self.body_id);
         let obligation = traits::Obligation::new(
             tcx,
@@ -151,7 +165,7 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
         let (normalized_ty, obligations) = self.structurally_normalize(Ty::new_projection(
             tcx,
             tcx.lang_items().deref_target()?,
-            [ty],
+            trait_ref.args,
         ))?;
         debug!("overloaded_deref_ty({:?}) = ({:?}, {:?})", ty, normalized_ty, obligations);
         self.state.obligations.extend(obligations);

compiler/rustc_hir_typeck/src/autoderef.rs

@@ -20,7 +20,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         base_ty: Ty<'tcx>,
     ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
-        self.try_overloaded_place_op(span, base_ty, &[], PlaceOp::Deref)
+        let callee = self.try_overloaded_place_op(span, base_ty, &[], PlaceOp::Deref)?;
+        self.enforce_context_effects(span, callee.value.def_id, callee.value.args);
+        Some(callee)
     }
 
     /// Returns the adjustment steps.

compiler/rustc_middle/src/ty/adjustment.rs

@@ -1,5 +1,6 @@
 use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir as hir;
+use rustc_hir::def_id::LocalDefId;
 use rustc_hir::lang_items::LangItem;
 use rustc_macros::HashStable;
 use rustc_span::Span;
@@ -121,7 +122,12 @@ pub struct OverloadedDeref<'tcx> {
 
 impl<'tcx> OverloadedDeref<'tcx> {
     /// Get the zst function item type for this method call.
-    pub fn method_call(&self, tcx: TyCtxt<'tcx>, source: Ty<'tcx>) -> Ty<'tcx> {
+    pub fn method_call(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        source: Ty<'tcx>,
+        caller_def_id: LocalDefId,
+    ) -> Ty<'tcx> {
         let trait_def_id = match self.mutbl {
             hir::Mutability::Not => tcx.require_lang_item(LangItem::Deref, None),
             hir::Mutability::Mut => tcx.require_lang_item(LangItem::DerefMut, None),
@@ -132,7 +138,11 @@ impl<'tcx> OverloadedDeref<'tcx> {
             .find(|m| m.kind == ty::AssocKind::Fn)
             .unwrap()
             .def_id;
-        Ty::new_fn_def(tcx, method_def_id, [source])
+        Ty::new_fn_def(
+            tcx,
+            method_def_id,
+            tcx.with_opt_host_effect_param(caller_def_id, method_def_id, [source]),
+        )
     }
 }
 

compiler/rustc_middle/src/ty/util.rs

@@ -828,15 +828,14 @@ impl<'tcx> TyCtxt<'tcx> {
         callee_def_id: DefId,
         args: impl IntoIterator<Item: Into<ty::GenericArg<'tcx>>>,
     ) -> ty::GenericArgsRef<'tcx> {
-        let generics = self.generics_of(callee_def_id);
-        assert_eq!(generics.parent, None);
-
-        let opt_const_param = generics
-            .host_effect_index
-            .is_some()
-            .then(|| ty::GenericArg::from(self.expected_host_effect_param_for_body(caller_def_id)));
-
-        self.mk_args_from_iter(args.into_iter().map(|arg| arg.into()).chain(opt_const_param))
+        let mut args = args.into_iter();
+        ty::GenericArgs::for_item(self, callee_def_id, |param, _| {
+            if param.is_host_effect() {
+                self.expected_host_effect_param_for_body(caller_def_id).into()
+            } else {
+                args.next().unwrap().into()
+            }
+        })
     }
 }
 

compiler/rustc_mir_build/src/build/matches/test.rs

@@ -254,7 +254,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     let ref_str_ty = Ty::new_imm_ref(tcx, re_erased, tcx.types.str_);
                     let ref_str = self.temp(ref_str_ty, test.span);
                     let deref = tcx.require_lang_item(LangItem::Deref, None);
-                    let method = trait_method(tcx, deref, sym::deref, [ty]);
+                    let method = trait_method(
+                        tcx,
+                        deref,
+                        sym::deref,
+                        tcx.with_opt_host_effect_param(self.def_id, deref, [ty]),
+                    );
                     let eq_block = self.cfg.start_new_block();
                     self.cfg.push_assign(
                         block,

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -118,7 +118,7 @@ impl<'tcx> Cx<'tcx> {
             Adjust::Deref(Some(deref)) => {
                 // We don't need to do call adjust_span here since
                 // deref coercions always start with a built-in deref.
-                let call = deref.method_call(self.tcx(), expr.ty);
+                let call = deref.method_call(self.tcx(), expr.ty, self.body_owner.expect_local());
 
                 expr = Expr {
                     temp_lifetime,

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -4129,7 +4129,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
 
             // Extract `<U as Deref>::Target` assoc type and check that it is `T`
             && let Some(deref_target_did) = tcx.lang_items().deref_target()
-            && let projection = Ty::new_projection(tcx,deref_target_did, tcx.mk_args(&[ty::GenericArg::from(found_ty)]))
+            && let args = tcx.with_opt_host_effect_param(tcx.hir().enclosing_body_owner(expr.hir_id), deref_target_did, [found_ty])
+            && let projection = Ty::new_projection(tcx,deref_target_did, args)
             && let InferOk { value: deref_target, obligations } = infcx.at(&ObligationCause::dummy(), param_env).normalize(projection)
             && obligations.iter().all(|obligation| infcx.predicate_must_hold_modulo_regions(obligation))
             && infcx.can_eq(param_env, deref_target, target_ty)

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

@@ -1,4 +1,4 @@
-// check-pass
+// known-bug: unknown
 
 #![crate_type = "lib"]
 #![feature(no_core, lang_items, unboxed_closures, auto_traits, intrinsics, rustc_attrs, staged_api)]
@@ -235,7 +235,7 @@ impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b
 
 
 #[lang = "deref"]
-// #[const_trait] FIXME
+#[const_trait]
 trait Deref {
     #[lang = "deref_target"]
     type Target: ?Sized;
@@ -244,15 +244,15 @@ trait Deref {
 }
 
 
-impl<T: ?Sized> /* const */ Deref for &T {
+impl<T: ?Sized> const Deref for &T {
     type Target = T;
 
     fn deref(&self) -> &T {
         *self
     }
 }
 
-impl<T: ?Sized> /* const */ Deref for &mut T {
+impl<T: ?Sized> const Deref for &mut T {
     type Target = T;
 
     fn deref(&self) -> &T {
@@ -285,7 +285,6 @@ impl<T> Option<T> {
 
 use Option::*;
 
-/*
 const fn as_deref<T>(opt: &Option<T>) -> Option<&T::Target>
 where
     T: ~const Deref,
@@ -295,7 +294,6 @@ where
         Option::None => Option::None,
     }
 }
-*/
 
 #[const_trait]
 trait Into<T>: Sized {
@@ -400,9 +398,9 @@ impl<'a, T: ?Sized> Pin<&'a T> {
 
 
 impl<P: Deref> Pin<P> {
-    /* const */ fn as_ref(&self) -> Pin<&P::Target>
+    const fn as_ref(&self) -> Pin<&P::Target>
     where
-        P: /* ~const */ Deref,
+        P: ~const Deref,
     {
         unsafe { Pin::new_unchecked(&*self.pointer) }
     }
@@ -434,14 +432,14 @@ impl<T> Option<T> {
 }
 */
 
-impl<P: /* ~const */ Deref> /* const */ Deref for Pin<P> {
+impl<P: ~const Deref> const Deref for Pin<P> {
     type Target = P::Target;
     fn deref(&self) -> &P::Target {
         Pin::get_ref(Pin::as_ref(self))
     }
 }
 
-impl<T> /* const */ Deref for Option<T> {
+impl<T> const Deref for Option<T> {
     type Target = T;
     fn deref(&self) -> &T {
         loop {}

tests/ui/rfcs/rfc-2632-const-trait-impl/effects/minicore.stderr

@@ -0,0 +1,18 @@
+error[E0282]: type annotations needed
+  --> $DIR/minicore.rs:291:43
+   |
+LL |         Option::Some(t) => Option::Some(t.deref()),
+   |                                           ^^^^^ cannot infer type
+
+error[E0599]: no method named `deref` found for reference `&T` in the current scope
+  --> $DIR/minicore.rs:291:43
+   |
+LL |         Option::Some(t) => Option::Some(t.deref()),
+   |                                           ^^^^^ method not found in `&T`
+   |
+   = help: items from traits can only be used if the type parameter is bounded by the trait
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0282, E0599.
+For more information about an error, try `rustc --explain E0282`.