Enable effects for libcore

Author: fee1-dead

compiler/rustc_codegen_ssa/src/common.rs

@@ -123,7 +123,11 @@ pub fn build_langcall<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 ) -> (Bx::FnAbiOfResult, Bx::Value) {
     let tcx = bx.tcx();
     let def_id = tcx.require_lang_item(li, span);
-    let instance = ty::Instance::mono(tcx, def_id);
+    let instance = if li == LangItem::Panic {
+        ty::Instance::new(def_id, tcx.mk_args(&[tcx.consts.true_.into()]))
+    } else {
+        ty::Instance::mono(tcx, def_id)
+    };
     (bx.fn_abi_of_instance(instance, ty::List::empty()), bx.get_fn_addr(instance))
 }
 

compiler/rustc_hir_typeck/src/expr.rs

@@ -525,8 +525,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
         };
 
-        if let ty::FnDef(did, ..) = *ty.kind() {
+        if let ty::FnDef(did, callee_args) = *ty.kind() {
             let fn_sig = ty.fn_sig(tcx);
+
+            // HACK: whenever we get a FnDef in a non-const context, enforce effects to get the
+            // default `host = true` to avoid inference errors later.
+            if tcx.hir().body_const_context(self.body_id).is_none() {
+                self.enforce_context_effects(expr.hir_id, qpath.span(), did, callee_args);
+            }
             if tcx.fn_sig(did).skip_binder().abi() == RustIntrinsic
                 && tcx.item_name(did) == sym::transmute
             {

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -273,11 +273,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             //
             // This check is here because there is currently no way to express a trait bound for `FnDef` types only.
             if is_const_eval_select && (1..=2).contains(&idx) {
-                if let ty::FnDef(def_id, _) = checked_ty.kind() {
-                    if idx == 1 && !self.tcx.is_const_fn_raw(*def_id) {
-                        self.tcx
-                            .sess
-                            .emit_err(errors::ConstSelectMustBeConst { span: provided_arg.span });
+                if let ty::FnDef(def_id, args) = *checked_ty.kind() {
+                    if idx == 1 {
+                        if !self.tcx.is_const_fn_raw(def_id) {
+                            self.tcx.sess.emit_err(errors::ConstSelectMustBeConst {
+                                span: provided_arg.span,
+                            });
+                        } else {
+                            self.enforce_context_effects(
+                                provided_arg.hir_id,
+                                provided_arg.span,
+                                def_id,
+                                args,
+                            )
+                        }
                     }
                 } else {
                     self.tcx.sess.emit_err(errors::ConstSelectMustBeFn {

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -854,7 +854,7 @@ fn should_encode_span(def_kind: DefKind) -> bool {
     }
 }
 
-fn should_encode_attrs(def_kind: DefKind) -> bool {
+fn should_encode_attrs(def_kind: DefKind, def_id: DefId, tcx: TyCtxt<'_>) -> bool {
     match def_kind {
         DefKind::Mod
         | DefKind::Struct
@@ -879,8 +879,9 @@ fn should_encode_attrs(def_kind: DefKind) -> bool {
         // https://github.com/model-checking/kani and is not a performance
         // or maintenance issue for us.
         DefKind::Closure => true,
+        // encode the host param attr
+        DefKind::ConstParam => tcx.has_attr(def_id, sym::rustc_host),
         DefKind::TyParam
-        | DefKind::ConstParam
         | DefKind::Ctor(..)
         | DefKind::ExternCrate
         | DefKind::Use
@@ -1354,7 +1355,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 let def_span = tcx.def_span(local_id);
                 record!(self.tables.def_span[def_id] <- def_span);
             }
-            if should_encode_attrs(def_kind) {
+            if should_encode_attrs(def_kind, def_id, tcx) {
                 self.encode_attrs(local_id);
             }
             if should_encode_expn_that_defined(def_kind) {

compiler/rustc_monomorphize/src/collector.rs

@@ -836,9 +836,15 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
                 }
             }
             mir::TerminatorKind::Assert { ref msg, .. } => {
-                let lang_item = match &**msg {
-                    mir::AssertKind::BoundsCheck { .. } => LangItem::PanicBoundsCheck,
-                    _ => LangItem::Panic,
+                let (lang_item, has_host_effect) = match &**msg {
+                    mir::AssertKind::BoundsCheck { .. } => (LangItem::PanicBoundsCheck, false),
+                    _ => (LangItem::Panic, true),
+                };
+                let def_id = tcx.require_lang_item(lang_item, Some(source));
+                let instance = if has_host_effect {
+                    Instance::new(def_id, tcx.mk_args(&[tcx.consts.true_.into()]))
+                } else {
+                    Instance::mono(tcx, def_id)
                 };
                 push_mono_lang_item(self, lang_item);
             }

library/core/src/lib.rs

@@ -194,6 +194,7 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(not(bootstrap), feature(effects))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
 #![feature(allow_internal_unsafe)]

library/core/src/marker.rs

@@ -960,7 +960,7 @@ marker_impls! {
 #[lang = "destruct"]
 #[rustc_on_unimplemented(message = "can't drop `{Self}`", append_const_msg)]
 #[rustc_deny_explicit_impl(implement_via_object = false)]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait Destruct {}
 
 /// A marker for tuple types.

library/core/src/ops/drop.rs

@@ -202,7 +202,7 @@
 /// [nomicon]: ../../nomicon/phantom-data.html#an-exception-the-special-case-of-the-standard-library-and-its-unstable-may_dangle
 #[lang = "drop"]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait Drop {
     /// Executes the destructor for this type.
     ///

library/core/src/ops/function.rs

@@ -72,7 +72,7 @@ use crate::marker::Tuple;
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait Fn<Args: Tuple>: FnMut<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -159,7 +159,7 @@ pub trait Fn<Args: Tuple>: FnMut<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait FnMut<Args: Tuple>: FnOnce<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -238,7 +238,7 @@ pub trait FnMut<Args: Tuple>: FnOnce<Args> {
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
 #[must_use = "closures are lazy and do nothing unless called"]
-#[const_trait]
+// FIXME(effects) #[const_trait]
 pub trait FnOnce<Args: Tuple> {
     /// The returned type after the call operator is used.
     #[lang = "fn_once_output"]

tests/ui/consts/const-block-const-bound.stderr

@@ -1,11 +1,8 @@
-error[E0493]: destructor of `T` cannot be evaluated at compile-time
-  --> $DIR/const-block-const-bound.rs:8:32
+error: ~const can only be applied to `#[const_trait]` traits
+  --> $DIR/const-block-const-bound.rs:8:22
    |
 LL | const fn f<T: ~const Destruct>(x: T) {}
-   |                                ^      - value is dropped here
-   |                                |
-   |                                the destructor for this type cannot be evaluated in constant functions
+   |                      ^^^^^^^^
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0493`.