Move magic traits queries to rustc::traits::drop.

7 files changed, 211 insertions, 203 deletions

diff --git a/src/librustc/traits/drop.rs b/src/librustc/traits/drop.rs
new file mode 100644
index 00000000000..08c3a77bf3a
--- /dev/null
+++ b/src/librustc/traits/drop.rs
@@ -0,0 +1,202 @@
+//! Miscellaneous type-system utilities that are too small to deserve their own modules.
+
+use crate::middle::lang_items;
+use crate::traits::{self, ObligationCause};
+use crate::ty::util::NeedsDrop;
+use crate::ty::{self, Ty, TyCtxt, TypeFoldable};
+
+use rustc_hir as hir;
+use rustc_span::DUMMY_SP;
+
+#[derive(Clone)]
+pub enum CopyImplementationError<'tcx> {
+    InfrigingFields(Vec<&'tcx ty::FieldDef>),
+    NotAnAdt,
+    HasDestructor,
+}
+
+pub fn can_type_implement_copy(
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    self_type: Ty<'tcx>,
+) -> Result<(), CopyImplementationError<'tcx>> {
+    // FIXME: (@jroesch) float this code up
+    tcx.infer_ctxt().enter(|infcx| {
+        let (adt, substs) = match self_type.kind {
+            // These types used to have a builtin impl.
+            // Now libcore provides that impl.
+            ty::Uint(_)
+            | ty::Int(_)
+            | ty::Bool
+            | ty::Float(_)
+            | ty::Char
+            | ty::RawPtr(..)
+            | ty::Never
+            | ty::Ref(_, _, hir::Mutability::Not) => return Ok(()),
+
+            ty::Adt(adt, substs) => (adt, substs),
+
+            _ => return Err(CopyImplementationError::NotAnAdt),
+        };
+
+        let mut infringing = Vec::new();
+        for variant in &adt.variants {
+            for field in &variant.fields {
+                let ty = field.ty(tcx, substs);
+                if ty.references_error() {
+                    continue;
+                }
+                let span = tcx.def_span(field.did);
+                let cause = ObligationCause { span, ..ObligationCause::dummy() };
+                let ctx = traits::FulfillmentContext::new();
+                match traits::fully_normalize(&infcx, ctx, cause, param_env, &ty) {
+                    Ok(ty) => {
+                        if !infcx.type_is_copy_modulo_regions(param_env, ty, span) {
+                            infringing.push(field);
+                        }
+                    }
+                    Err(errors) => {
+                        infcx.report_fulfillment_errors(&errors, None, false);
+                    }
+                };
+            }
+        }
+        if !infringing.is_empty() {
+            return Err(CopyImplementationError::InfrigingFields(infringing));
+        }
+        if adt.has_dtor(tcx) {
+            return Err(CopyImplementationError::HasDestructor);
+        }
+
+        Ok(())
+    })
+}
+
+fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
+    is_item_raw(tcx, query, lang_items::CopyTraitLangItem)
+}
+
+fn is_sized_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
+    is_item_raw(tcx, query, lang_items::SizedTraitLangItem)
+}
+
+fn is_freeze_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
+    is_item_raw(tcx, query, lang_items::FreezeTraitLangItem)
+}
+
+fn is_item_raw<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
+    item: lang_items::LangItem,
+) -> bool {
+    let (param_env, ty) = query.into_parts();
+    let trait_def_id = tcx.require_lang_item(item, None);
+    tcx.infer_ctxt().enter(|infcx| {
+        traits::type_known_to_meet_bound_modulo_regions(
+            &infcx,
+            param_env,
+            ty,
+            trait_def_id,
+            DUMMY_SP,
+        )
+    })
+}
+
+fn needs_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> NeedsDrop {
+    let (param_env, ty) = query.into_parts();
+
+    let needs_drop = |ty: Ty<'tcx>| -> bool { tcx.needs_drop_raw(param_env.and(ty)).0 };
+
+    assert!(!ty.needs_infer());
+
+    NeedsDrop(match ty.kind {
+        // Fast-path for primitive types
+        ty::Infer(ty::FreshIntTy(_))
+        | ty::Infer(ty::FreshFloatTy(_))
+        | ty::Bool
+        | ty::Int(_)
+        | ty::Uint(_)
+        | ty::Float(_)
+        | ty::Never
+        | ty::FnDef(..)
+        | ty::FnPtr(_)
+        | ty::Char
+        | ty::GeneratorWitness(..)
+        | ty::RawPtr(_)
+        | ty::Ref(..)
+        | ty::Str => false,
+
+        // Foreign types can never have destructors
+        ty::Foreign(..) => false,
+
+        // `ManuallyDrop` doesn't have a destructor regardless of field types.
+        ty::Adt(def, _) if Some(def.did) == tcx.lang_items().manually_drop() => false,
+
+        // Issue #22536: We first query `is_copy_modulo_regions`.  It sees a
+        // normalized version of the type, and therefore will definitely
+        // know whether the type implements Copy (and thus needs no
+        // cleanup/drop/zeroing) ...
+        _ if ty.is_copy_modulo_regions(tcx, param_env, DUMMY_SP) => false,
+
+        // ... (issue #22536 continued) but as an optimization, still use
+        // prior logic of asking for the structural "may drop".
+
+        // FIXME(#22815): Note that this is a conservative heuristic;
+        // it may report that the type "may drop" when actual type does
+        // not actually have a destructor associated with it. But since
+        // the type absolutely did not have the `Copy` bound attached
+        // (see above), it is sound to treat it as having a destructor.
+
+        // User destructors are the only way to have concrete drop types.
+        ty::Adt(def, _) if def.has_dtor(tcx) => true,
+
+        // Can refer to a type which may drop.
+        // FIXME(eddyb) check this against a ParamEnv.
+        ty::Dynamic(..)
+        | ty::Projection(..)
+        | ty::Param(_)
+        | ty::Bound(..)
+        | ty::Placeholder(..)
+        | ty::Opaque(..)
+        | ty::Infer(_)
+        | ty::Error => true,
+
+        ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
+
+        // Zero-length arrays never contain anything to drop.
+        ty::Array(_, len) if len.try_eval_usize(tcx, param_env) == Some(0) => false,
+
+        // Structural recursion.
+        ty::Array(ty, _) | ty::Slice(ty) => needs_drop(ty),
+
+        ty::Closure(def_id, ref substs) => {
+            substs.as_closure().upvar_tys(def_id, tcx).any(needs_drop)
+        }
+
+        // Pessimistically assume that all generators will require destructors
+        // as we don't know if a destructor is a noop or not until after the MIR
+        // state transformation pass
+        ty::Generator(..) => true,
+
+        ty::Tuple(..) => ty.tuple_fields().any(needs_drop),
+
+        // unions don't have destructors because of the child types,
+        // only if they manually implement `Drop` (handled above).
+        ty::Adt(def, _) if def.is_union() => false,
+
+        ty::Adt(def, substs) => def
+            .variants
+            .iter()
+            .any(|variant| variant.fields.iter().any(|field| needs_drop(field.ty(tcx, substs)))),
+    })
+}
+
+pub fn provide(providers: &mut ty::query::Providers<'_>) {
+    *providers = ty::query::Providers {
+        is_copy_raw,
+        is_sized_raw,
+        is_freeze_raw,
+        needs_drop_raw,
+        ..*providers
+    };
+}
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 3c49d1b6f36..11473dc2a3a 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -7,6 +7,7 @@ pub mod auto_trait;
 mod chalk_fulfill;
 pub mod codegen;
 mod coherence;
+pub mod drop;
 mod engine;
 pub mod error_reporting;
 mod fulfill;
@@ -1243,6 +1244,7 @@ impl<'tcx> TraitObligation<'tcx> {
 }
 
 pub fn provide(providers: &mut ty::query::Providers<'_>) {
+    drop::provide(providers);
     *providers = ty::query::Providers {
         is_object_safe: object_safety::is_object_safe_provider,
         specialization_graph_of: specialize::specialization_graph_provider,
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 5457516a6a2..7cca12308e6 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -3318,7 +3318,6 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
     context::provide(providers);
     erase_regions::provide(providers);
     layout::provide(providers);
-    util::provide(providers);
     constness::provide(providers);
     *providers = ty::query::Providers {
         asyncness,
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index ee99176dc47..aa93f35661a 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -2,9 +2,7 @@
 
 use crate::hir::map::DefPathData;
 use crate::ich::NodeIdHashingMode;
-use crate::middle::lang_items;
 use crate::mir::interpret::{sign_extend, truncate};
-use crate::traits::{self, ObligationCause};
 use crate::ty::layout::{Integer, IntegerExt};
 use crate::ty::query::TyCtxtAt;
 use crate::ty::subst::{GenericArgKind, InternalSubsts, Subst, SubstsRef};
@@ -18,7 +16,7 @@ use rustc_hir::def_id::DefId;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_macros::HashStable;
-use rustc_span::{Span, DUMMY_SP};
+use rustc_span::Span;
 use std::{cmp, fmt};
 use syntax::ast;
 use syntax::attr::{self, SignedInt, UnsignedInt};
@@ -122,13 +120,6 @@ impl IntTypeExt for attr::IntType {
     }
 }
 
-#[derive(Clone)]
-pub enum CopyImplementationError<'tcx> {
-    InfrigingFields(Vec<&'tcx ty::FieldDef>),
-    NotAnAdt,
-    HasDestructor,
-}
-
 /// Describes whether a type is representable. For types that are not
 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
 /// distinguish between types that are recursive with themselves and types that
@@ -144,65 +135,6 @@ pub enum Representability {
     SelfRecursive(Vec<Span>),
 }
 
-impl<'tcx> ty::ParamEnv<'tcx> {
-    pub fn can_type_implement_copy(
-        self,
-        tcx: TyCtxt<'tcx>,
-        self_type: Ty<'tcx>,
-    ) -> Result<(), CopyImplementationError<'tcx>> {
-        // FIXME: (@jroesch) float this code up
-        tcx.infer_ctxt().enter(|infcx| {
-            let (adt, substs) = match self_type.kind {
-                // These types used to have a builtin impl.
-                // Now libcore provides that impl.
-                ty::Uint(_)
-                | ty::Int(_)
-                | ty::Bool
-                | ty::Float(_)
-                | ty::Char
-                | ty::RawPtr(..)
-                | ty::Never
-                | ty::Ref(_, _, hir::Mutability::Not) => return Ok(()),
-
-                ty::Adt(adt, substs) => (adt, substs),
-
-                _ => return Err(CopyImplementationError::NotAnAdt),
-            };
-
-            let mut infringing = Vec::new();
-            for variant in &adt.variants {
-                for field in &variant.fields {
-                    let ty = field.ty(tcx, substs);
-                    if ty.references_error() {
-                        continue;
-                    }
-                    let span = tcx.def_span(field.did);
-                    let cause = ObligationCause { span, ..ObligationCause::dummy() };
-                    let ctx = traits::FulfillmentContext::new();
-                    match traits::fully_normalize(&infcx, ctx, cause, self, &ty) {
-                        Ok(ty) => {
-                            if !infcx.type_is_copy_modulo_regions(self, ty, span) {
-                                infringing.push(field);
-                            }
-                        }
-                        Err(errors) => {
-                            infcx.report_fulfillment_errors(&errors, None, false);
-                        }
-                    };
-                }
-            }
-            if !infringing.is_empty() {
-                return Err(CopyImplementationError::InfrigingFields(infringing));
-            }
-            if adt.has_dtor(tcx) {
-                return Err(CopyImplementationError::HasDestructor);
-            }
-
-            Ok(())
-        })
-    }
-}
-
 impl<'tcx> TyCtxt<'tcx> {
     /// Creates a hash of the type `Ty` which will be the same no matter what crate
     /// context it's calculated within. This is used by the `type_id` intrinsic.
@@ -942,128 +874,9 @@ impl<'tcx> ty::TyS<'tcx> {
     }
 }
 
-fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
-    is_item_raw(tcx, query, lang_items::CopyTraitLangItem)
-}
-
-fn is_sized_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
-    is_item_raw(tcx, query, lang_items::SizedTraitLangItem)
-}
-
-fn is_freeze_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
-    is_item_raw(tcx, query, lang_items::FreezeTraitLangItem)
-}
-
-fn is_item_raw<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
-    item: lang_items::LangItem,
-) -> bool {
-    let (param_env, ty) = query.into_parts();
-    let trait_def_id = tcx.require_lang_item(item, None);
-    tcx.infer_ctxt().enter(|infcx| {
-        traits::type_known_to_meet_bound_modulo_regions(
-            &infcx,
-            param_env,
-            ty,
-            trait_def_id,
-            DUMMY_SP,
-        )
-    })
-}
-
 #[derive(Clone, HashStable)]
 pub struct NeedsDrop(pub bool);
 
-fn needs_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> NeedsDrop {
-    let (param_env, ty) = query.into_parts();
-
-    let needs_drop = |ty: Ty<'tcx>| -> bool { tcx.needs_drop_raw(param_env.and(ty)).0 };
-
-    assert!(!ty.needs_infer());
-
-    NeedsDrop(match ty.kind {
-        // Fast-path for primitive types
-        ty::Infer(ty::FreshIntTy(_))
-        | ty::Infer(ty::FreshFloatTy(_))
-        | ty::Bool
-        | ty::Int(_)
-        | ty::Uint(_)
-        | ty::Float(_)
-        | ty::Never
-        | ty::FnDef(..)
-        | ty::FnPtr(_)
-        | ty::Char
-        | ty::GeneratorWitness(..)
-        | ty::RawPtr(_)
-        | ty::Ref(..)
-        | ty::Str => false,
-
-        // Foreign types can never have destructors
-        ty::Foreign(..) => false,
-
-        // `ManuallyDrop` doesn't have a destructor regardless of field types.
-        ty::Adt(def, _) if Some(def.did) == tcx.lang_items().manually_drop() => false,
-
-        // Issue #22536: We first query `is_copy_modulo_regions`.  It sees a
-        // normalized version of the type, and therefore will definitely
-        // know whether the type implements Copy (and thus needs no
-        // cleanup/drop/zeroing) ...
-        _ if ty.is_copy_modulo_regions(tcx, param_env, DUMMY_SP) => false,
-
-        // ... (issue #22536 continued) but as an optimization, still use
-        // prior logic of asking for the structural "may drop".
-
-        // FIXME(#22815): Note that this is a conservative heuristic;
-        // it may report that the type "may drop" when actual type does
-        // not actually have a destructor associated with it. But since
-        // the type absolutely did not have the `Copy` bound attached
-        // (see above), it is sound to treat it as having a destructor.
-
-        // User destructors are the only way to have concrete drop types.
-        ty::Adt(def, _) if def.has_dtor(tcx) => true,
-
-        // Can refer to a type which may drop.
-        // FIXME(eddyb) check this against a ParamEnv.
-        ty::Dynamic(..)
-        | ty::Projection(..)
-        | ty::Param(_)
-        | ty::Bound(..)
-        | ty::Placeholder(..)
-        | ty::Opaque(..)
-        | ty::Infer(_)
-        | ty::Error => true,
-
-        ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
-
-        // Zero-length arrays never contain anything to drop.
-        ty::Array(_, len) if len.try_eval_usize(tcx, param_env) == Some(0) => false,
-
-        // Structural recursion.
-        ty::Array(ty, _) | ty::Slice(ty) => needs_drop(ty),
-
-        ty::Closure(def_id, ref substs) => {
-            substs.as_closure().upvar_tys(def_id, tcx).any(needs_drop)
-        }
-
-        // Pessimistically assume that all generators will require destructors
-        // as we don't know if a destructor is a noop or not until after the MIR
-        // state transformation pass
-        ty::Generator(..) => true,
-
-        ty::Tuple(..) => ty.tuple_fields().any(needs_drop),
-
-        // unions don't have destructors because of the child types,
-        // only if they manually implement `Drop` (handled above).
-        ty::Adt(def, _) if def.is_union() => false,
-
-        ty::Adt(def, substs) => def
-            .variants
-            .iter()
-            .any(|variant| variant.fields.iter().any(|field| needs_drop(field.ty(tcx, substs)))),
-    })
-}
-
 pub enum ExplicitSelf<'tcx> {
     ByValue,
     ByReference(ty::Region<'tcx>, hir::Mutability),
@@ -1112,13 +925,3 @@ impl<'tcx> ExplicitSelf<'tcx> {
         }
     }
 }
-
-pub fn provide(providers: &mut ty::query::Providers<'_>) {
-    *providers = ty::query::Providers {
-        is_copy_raw,
-        is_sized_raw,
-        is_freeze_raw,
-        needs_drop_raw,
-        ..*providers
-    };
-}
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 59b87afe216..e251e6d6aea 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -27,6 +27,7 @@ use lint::{EarlyContext, EarlyLintPass, LateLintPass, LintPass};
 use lint::{LateContext, LintArray, LintContext};
 use rustc::lint;
 use rustc::lint::FutureIncompatibleInfo;
+use rustc::traits::drop::can_type_implement_copy;
 use rustc::ty::{self, layout::VariantIdx, Ty, TyCtxt};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_feature::Stability;
@@ -555,7 +556,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingCopyImplementations {
         if ty.is_copy_modulo_regions(cx.tcx, param_env, item.span) {
             return;
         }
-        if param_env.can_type_implement_copy(cx.tcx, ty).is_ok() {
+        if can_type_implement_copy(cx.tcx, param_env, ty).is_ok() {
             cx.span_lint(
                 MISSING_COPY_IMPLEMENTATIONS,
                 item.span,
diff --git a/src/librustc_passes/stability.rs b/src/librustc_passes/stability.rs
index 4c5b57791c5..35ef7ec148f 100644
--- a/src/librustc_passes/stability.rs
+++ b/src/librustc_passes/stability.rs
@@ -6,6 +6,7 @@ use rustc::lint;
 use rustc::middle::privacy::AccessLevels;
 use rustc::middle::stability::{DeprecationEntry, Index};
 use rustc::session::Session;
+use rustc::traits::drop::can_type_implement_copy;
 use rustc::ty::query::Providers;
 use rustc::ty::TyCtxt;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -488,7 +489,7 @@ impl Visitor<'tcx> for Checker<'tcx> {
                     .emit();
                 } else {
                     let param_env = self.tcx.param_env(def_id);
-                    if !param_env.can_type_implement_copy(self.tcx, ty).is_ok() {
+                    if !can_type_implement_copy(self.tcx, param_env, ty).is_ok() {
                         feature_err(
                             &self.tcx.sess.parse_sess,
                             sym::untagged_unions,
diff --git a/src/librustc_typeck/coherence/builtin.rs b/src/librustc_typeck/coherence/builtin.rs
index 5a80b762f74..1bb512e350a 100644
--- a/src/librustc_typeck/coherence/builtin.rs
+++ b/src/librustc_typeck/coherence/builtin.rs
@@ -7,10 +7,10 @@ use rustc::middle::lang_items::UnsizeTraitLangItem;
 use rustc::middle::region;
 
 use rustc::infer;
+use rustc::traits::drop::{can_type_implement_copy, CopyImplementationError};
 use rustc::traits::predicate_for_trait_def;
 use rustc::traits::{self, ObligationCause, TraitEngine};
 use rustc::ty::adjustment::CoerceUnsizedInfo;
-use rustc::ty::util::CopyImplementationError;
 use rustc::ty::TypeFoldable;
 use rustc::ty::{self, Ty, TyCtxt};
 
@@ -92,7 +92,7 @@ fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: DefId) {
 
     debug!("visit_implementation_of_copy: self_type={:?} (free)", self_type);
 
-    match param_env.can_type_implement_copy(tcx, self_type) {
+    match can_type_implement_copy(tcx, param_env, self_type) {
         Ok(()) => {}
         Err(CopyImplementationError::InfrigingFields(fields)) => {
             let item = tcx.hir().expect_item(impl_hir_id);