Rollup merge of rust-lang#72707 - matthewjasper:rustc_min_spec, r=oli-obk

Use min_specialization in the remaining rustc crates

This adds a lot of `transmute` calls to replace the unsound uses of specialization.
It's ugly, but at least it's honest about what's going on.

cc rust-lang#71420, @RalfJung

Author: RalfJung

src/librustc_arena/lib.rs

@@ -602,7 +602,7 @@ macro_rules! which_arena_for_type {
 
 #[macro_export]
 macro_rules! declare_arena {
-    ([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
+    ([], [$($a:tt $name:ident: $ty:ty, $gen_ty:ty;)*], $tcx:lifetime) => {
         #[derive(Default)]
         pub struct Arena<$tcx> {
             pub dropless: $crate::DroplessArena,
@@ -611,17 +611,17 @@ macro_rules! declare_arena {
         }
 
         #[marker]
-        pub trait ArenaAllocatable {}
+        pub trait ArenaAllocatable<'tcx> {}
 
-        impl<T: Copy> ArenaAllocatable for T {}
+        impl<'tcx, T: Copy> ArenaAllocatable<'tcx> for T {}
 
-        unsafe trait ArenaField<'tcx>: Sized {
+        unsafe trait ArenaField<'tcx>: Sized + ArenaAllocatable<'tcx> {
             /// Returns a specific arena to allocate from.
             /// If `None` is returned, the `DropArena` will be used.
             fn arena<'a>(arena: &'a Arena<'tcx>) -> Option<&'a $crate::TypedArena<Self>>;
         }
 
-        unsafe impl<'tcx, T> ArenaField<'tcx> for T {
+        unsafe impl<'tcx, T: ArenaAllocatable<'tcx>> ArenaField<'tcx> for T {
             #[inline]
             default fn arena<'a>(_: &'a Arena<'tcx>) -> Option<&'a $crate::TypedArena<Self>> {
                 panic!()
@@ -630,18 +630,27 @@ macro_rules! declare_arena {
 
         $(
             #[allow(unused_lifetimes)]
-            impl<$tcx> ArenaAllocatable for $ty {}
-            unsafe impl<$tcx> ArenaField<$tcx> for $ty {
+            impl<$tcx> ArenaAllocatable<$tcx> for $ty {}
+            unsafe impl<$tcx, '_x, '_y, '_z, '_w> ArenaField<$tcx> for $gen_ty where Self: ArenaAllocatable<$tcx> {
                 #[inline]
                 fn arena<'a>(_arena: &'a Arena<$tcx>) -> Option<&'a $crate::TypedArena<Self>> {
-                    $crate::which_arena_for_type!($a[&_arena.$name])
+                    // SAFETY: We only implement `ArenaAllocatable<$tcx>` for
+                    // `$ty`, so `$ty` and Self are the same type
+                    unsafe {
+                        ::std::mem::transmute::<
+                            Option<&'a $crate::TypedArena<$ty>>,
+                            Option<&'a $crate::TypedArena<Self>>,
+                        >(
+                            $crate::which_arena_for_type!($a[&_arena.$name])
+                        )
+                    }
                 }
             }
         )*
 
         impl<'tcx> Arena<'tcx> {
             #[inline]
-            pub fn alloc<T: ArenaAllocatable>(&self, value: T) -> &mut T {
+            pub fn alloc<T: ArenaAllocatable<'tcx>>(&self, value: T) -> &mut T {
                 if !::std::mem::needs_drop::<T>() {
                     return self.dropless.alloc(value);
                 }
@@ -659,7 +668,7 @@ macro_rules! declare_arena {
                 self.dropless.alloc_slice(value)
             }
 
-            pub fn alloc_from_iter<'a, T: ArenaAllocatable>(
+            pub fn alloc_from_iter<'a, T: ArenaAllocatable<'tcx>>(
                 &'a self,
                 iter: impl ::std::iter::IntoIterator<Item = T>,
             ) -> &'a mut [T] {

src/librustc_ast_lowering/lib.rs

@@ -33,7 +33,7 @@
 #![feature(array_value_iter)]
 #![feature(crate_visibility_modifier)]
 #![feature(marker_trait_attr)]
-#![feature(specialization)] // FIXME: min_specialization does not work
+#![feature(min_specialization)]
 #![feature(or_patterns)]
 #![recursion_limit = "256"]
 

src/librustc_hir/arena.rs

@@ -12,41 +12,41 @@ macro_rules! arena_types {
     ($macro:path, $args:tt, $tcx:lifetime) => (
         $macro!($args, [
             // HIR types
-            [few] hir_krate: rustc_hir::Crate<$tcx>,
-            [] arm: rustc_hir::Arm<$tcx>,
-            [] asm_operand: rustc_hir::InlineAsmOperand<$tcx>,
-            [] asm_template: rustc_ast::ast::InlineAsmTemplatePiece,
-            [] attribute: rustc_ast::ast::Attribute,
-            [] block: rustc_hir::Block<$tcx>,
-            [] bare_fn_ty: rustc_hir::BareFnTy<$tcx>,
-            [few] global_asm: rustc_hir::GlobalAsm,
-            [] generic_arg: rustc_hir::GenericArg<$tcx>,
-            [] generic_args: rustc_hir::GenericArgs<$tcx>,
-            [] generic_bound: rustc_hir::GenericBound<$tcx>,
-            [] generic_param: rustc_hir::GenericParam<$tcx>,
-            [] expr: rustc_hir::Expr<$tcx>,
-            [] field: rustc_hir::Field<$tcx>,
-            [] field_pat: rustc_hir::FieldPat<$tcx>,
-            [] fn_decl: rustc_hir::FnDecl<$tcx>,
-            [] foreign_item: rustc_hir::ForeignItem<$tcx>,
-            [] impl_item_ref: rustc_hir::ImplItemRef<$tcx>,
-            [few] inline_asm: rustc_hir::InlineAsm<$tcx>,
-            [few] llvm_inline_asm: rustc_hir::LlvmInlineAsm<$tcx>,
-            [] local: rustc_hir::Local<$tcx>,
-            [few] macro_def: rustc_hir::MacroDef<$tcx>,
-            [] param: rustc_hir::Param<$tcx>,
-            [] pat: rustc_hir::Pat<$tcx>,
-            [] path: rustc_hir::Path<$tcx>,
-            [] path_segment: rustc_hir::PathSegment<$tcx>,
-            [] poly_trait_ref: rustc_hir::PolyTraitRef<$tcx>,
-            [] qpath: rustc_hir::QPath<$tcx>,
-            [] stmt: rustc_hir::Stmt<$tcx>,
-            [] struct_field: rustc_hir::StructField<$tcx>,
-            [] trait_item_ref: rustc_hir::TraitItemRef,
-            [] ty: rustc_hir::Ty<$tcx>,
-            [] type_binding: rustc_hir::TypeBinding<$tcx>,
-            [] variant: rustc_hir::Variant<$tcx>,
-            [] where_predicate: rustc_hir::WherePredicate<$tcx>,
+            [few] hir_krate: rustc_hir::Crate<$tcx>, rustc_hir::Crate<'_x>;
+            [] arm: rustc_hir::Arm<$tcx>, rustc_hir::Arm<'_x>;
+            [] asm_operand: rustc_hir::InlineAsmOperand<$tcx>, rustc_hir::InlineAsmOperand<'_x>;
+            [] asm_template: rustc_ast::ast::InlineAsmTemplatePiece, rustc_ast::ast::InlineAsmTemplatePiece;
+            [] attribute: rustc_ast::ast::Attribute, rustc_ast::ast::Attribute;
+            [] block: rustc_hir::Block<$tcx>, rustc_hir::Block<'_x>;
+            [] bare_fn_ty: rustc_hir::BareFnTy<$tcx>, rustc_hir::BareFnTy<'_x>;
+            [few] global_asm: rustc_hir::GlobalAsm, rustc_hir::GlobalAsm;
+            [] generic_arg: rustc_hir::GenericArg<$tcx>, rustc_hir::GenericArg<'_x>;
+            [] generic_args: rustc_hir::GenericArgs<$tcx>, rustc_hir::GenericArgs<'_x>;
+            [] generic_bound: rustc_hir::GenericBound<$tcx>, rustc_hir::GenericBound<'_x>;
+            [] generic_param: rustc_hir::GenericParam<$tcx>, rustc_hir::GenericParam<'_x>;
+            [] expr: rustc_hir::Expr<$tcx>, rustc_hir::Expr<'_x>;
+            [] field: rustc_hir::Field<$tcx>, rustc_hir::Field<'_x>;
+            [] field_pat: rustc_hir::FieldPat<$tcx>, rustc_hir::FieldPat<'_x>;
+            [] fn_decl: rustc_hir::FnDecl<$tcx>, rustc_hir::FnDecl<'_x>;
+            [] foreign_item: rustc_hir::ForeignItem<$tcx>, rustc_hir::ForeignItem<'_x>;
+            [] impl_item_ref: rustc_hir::ImplItemRef<$tcx>, rustc_hir::ImplItemRef<'_x>;
+            [few] inline_asm: rustc_hir::InlineAsm<$tcx>, rustc_hir::InlineAsm<'_x>;
+            [few] llvm_inline_asm: rustc_hir::LlvmInlineAsm<$tcx>, rustc_hir::LlvmInlineAsm<'_x>;
+            [] local: rustc_hir::Local<$tcx>, rustc_hir::Local<'_x>;
+            [few] macro_def: rustc_hir::MacroDef<$tcx>, rustc_hir::MacroDef<'_x>;
+            [] param: rustc_hir::Param<$tcx>, rustc_hir::Param<'_x>;
+            [] pat: rustc_hir::Pat<$tcx>, rustc_hir::Pat<'_x>;
+            [] path: rustc_hir::Path<$tcx>, rustc_hir::Path<'_x>;
+            [] path_segment: rustc_hir::PathSegment<$tcx>, rustc_hir::PathSegment<'_x>;
+            [] poly_trait_ref: rustc_hir::PolyTraitRef<$tcx>, rustc_hir::PolyTraitRef<'_x>;
+            [] qpath: rustc_hir::QPath<$tcx>, rustc_hir::QPath<'_x>;
+            [] stmt: rustc_hir::Stmt<$tcx>, rustc_hir::Stmt<'_x>;
+            [] struct_field: rustc_hir::StructField<$tcx>, rustc_hir::StructField<'_x>;
+            [] trait_item_ref: rustc_hir::TraitItemRef, rustc_hir::TraitItemRef;
+            [] ty: rustc_hir::Ty<$tcx>, rustc_hir::Ty<'_x>;
+            [] type_binding: rustc_hir::TypeBinding<$tcx>, rustc_hir::TypeBinding<'_x>;
+            [] variant: rustc_hir::Variant<$tcx>, rustc_hir::Variant<'_x>;
+            [] where_predicate: rustc_hir::WherePredicate<$tcx>, rustc_hir::WherePredicate<'_x>;
         ], $tcx);
     )
 }

src/librustc_infer/infer/canonical/query_response.rs

@@ -56,7 +56,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
     ) -> Fallible<CanonicalizedQueryResponse<'tcx, T>>
     where
         T: Debug + TypeFoldable<'tcx>,
-        Canonical<'tcx, QueryResponse<'tcx, T>>: ArenaAllocatable,
+        Canonical<'tcx, QueryResponse<'tcx, T>>: ArenaAllocatable<'tcx>,
     {
         let query_response = self.make_query_response(inference_vars, answer, fulfill_cx)?;
         let canonical_result = self.canonicalize_response(&query_response);

src/librustc_macros/src/query.rs

@@ -433,7 +433,7 @@ pub fn rustc_queries(input: TokenStream) -> TokenStream {
 
                 try_load_from_on_disk_cache_stream.extend(quote! {
                     ::rustc_middle::dep_graph::DepKind::#name => {
-                        if <#arg as DepNodeParams<TyCtxt<'_>>>::CAN_RECONSTRUCT_QUERY_KEY {
+                        if <#arg as DepNodeParams<TyCtxt<'_>>>::can_reconstruct_query_key() {
                             debug_assert!($tcx.dep_graph
                                             .node_color($dep_node)
                                             .map(|c| c.is_green())
@@ -490,7 +490,7 @@ pub fn rustc_queries(input: TokenStream) -> TokenStream {
             // Add a match arm to force the query given the dep node
             dep_node_force_stream.extend(quote! {
                 ::rustc_middle::dep_graph::DepKind::#name => {
-                    if <#arg as DepNodeParams<TyCtxt<'_>>>::CAN_RECONSTRUCT_QUERY_KEY {
+                    if <#arg as DepNodeParams<TyCtxt<'_>>>::can_reconstruct_query_key() {
                         if let Some(key) = <#arg as DepNodeParams<TyCtxt<'_>>>::recover($tcx, $dep_node) {
                             force_query::<crate::ty::query::queries::#name<'_>, _>(
                                 $tcx,

src/librustc_metadata/lib.rs

@@ -7,7 +7,7 @@
 #![feature(nll)]
 #![feature(or_patterns)]
 #![feature(proc_macro_internals)]
-#![feature(specialization)] // FIXME: min_specialization ICEs
+#![feature(min_specialization)]
 #![feature(stmt_expr_attributes)]
 #![recursion_limit = "256"]
 

src/librustc_metadata/rmeta/decoder.rs

@@ -30,7 +30,7 @@ use rustc_middle::mir::{self, interpret, Body, Promoted};
 use rustc_middle::ty::codec::TyDecoder;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::util::common::record_time;
-use rustc_serialize::{opaque, Decodable, Decoder, SpecializedDecoder};
+use rustc_serialize::{opaque, Decodable, Decoder, SpecializedDecoder, UseSpecializedDecodable};
 use rustc_session::Session;
 use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{sym, Ident, Symbol};
@@ -218,15 +218,15 @@ impl<'a, 'tcx> Metadata<'a, 'tcx> for (&'a CrateMetadataRef<'a>, TyCtxt<'tcx>) {
     }
 }
 
-impl<'a, 'tcx, T: Decodable> Lazy<T> {
+impl<'a, 'tcx, T: Decodable> Lazy<T, ()> {
     fn decode<M: Metadata<'a, 'tcx>>(self, metadata: M) -> T {
         let mut dcx = metadata.decoder(self.position.get());
         dcx.lazy_state = LazyState::NodeStart(self.position);
         T::decode(&mut dcx).unwrap()
     }
 }
 
-impl<'a: 'x, 'tcx: 'x, 'x, T: Decodable> Lazy<[T]> {
+impl<'a: 'x, 'tcx: 'x, 'x, T: Decodable> Lazy<[T], usize> {
     fn decode<M: Metadata<'a, 'tcx>>(
         self,
         metadata: M,
@@ -321,20 +321,20 @@ impl<'a, 'tcx> TyDecoder<'tcx> for DecodeContext<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx, T> SpecializedDecoder<Lazy<T>> for DecodeContext<'a, 'tcx> {
+impl<'a, 'tcx, T> SpecializedDecoder<Lazy<T, ()>> for DecodeContext<'a, 'tcx> {
     fn specialized_decode(&mut self) -> Result<Lazy<T>, Self::Error> {
         self.read_lazy_with_meta(())
     }
 }
 
-impl<'a, 'tcx, T> SpecializedDecoder<Lazy<[T]>> for DecodeContext<'a, 'tcx> {
+impl<'a, 'tcx, T> SpecializedDecoder<Lazy<[T], usize>> for DecodeContext<'a, 'tcx> {
     fn specialized_decode(&mut self) -> Result<Lazy<[T]>, Self::Error> {
         let len = self.read_usize()?;
         if len == 0 { Ok(Lazy::empty()) } else { self.read_lazy_with_meta(len) }
     }
 }
 
-impl<'a, 'tcx, I: Idx, T> SpecializedDecoder<Lazy<Table<I, T>>> for DecodeContext<'a, 'tcx>
+impl<'a, 'tcx, I: Idx, T> SpecializedDecoder<Lazy<Table<I, T>, usize>> for DecodeContext<'a, 'tcx>
 where
     Option<T>: FixedSizeEncoding,
 {
@@ -515,8 +515,9 @@ impl<'a, 'tcx> SpecializedDecoder<Fingerprint> for DecodeContext<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx, T: Decodable> SpecializedDecoder<mir::ClearCrossCrate<T>>
-    for DecodeContext<'a, 'tcx>
+impl<'a, 'tcx, T> SpecializedDecoder<mir::ClearCrossCrate<T>> for DecodeContext<'a, 'tcx>
+where
+    mir::ClearCrossCrate<T>: UseSpecializedDecodable,
 {
     #[inline]
     fn specialized_decode(&mut self) -> Result<mir::ClearCrossCrate<T>, Self::Error> {

src/librustc_metadata/rmeta/encoder.rs

@@ -27,7 +27,7 @@ use rustc_middle::mir::{self, interpret};
 use rustc_middle::traits::specialization_graph;
 use rustc_middle::ty::codec::{self as ty_codec, TyEncoder};
 use rustc_middle::ty::{self, SymbolName, Ty, TyCtxt};
-use rustc_serialize::{opaque, Encodable, Encoder, SpecializedEncoder};
+use rustc_serialize::{opaque, Encodable, Encoder, SpecializedEncoder, UseSpecializedEncodable};
 use rustc_session::config::CrateType;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
@@ -93,13 +93,13 @@ impl<'tcx> Encoder for EncodeContext<'tcx> {
     }
 }
 
-impl<'tcx, T> SpecializedEncoder<Lazy<T>> for EncodeContext<'tcx> {
+impl<'tcx, T> SpecializedEncoder<Lazy<T, ()>> for EncodeContext<'tcx> {
     fn specialized_encode(&mut self, lazy: &Lazy<T>) -> Result<(), Self::Error> {
         self.emit_lazy_distance(*lazy)
     }
 }
 
-impl<'tcx, T> SpecializedEncoder<Lazy<[T]>> for EncodeContext<'tcx> {
+impl<'tcx, T> SpecializedEncoder<Lazy<[T], usize>> for EncodeContext<'tcx> {
     fn specialized_encode(&mut self, lazy: &Lazy<[T]>) -> Result<(), Self::Error> {
         self.emit_usize(lazy.meta)?;
         if lazy.meta == 0 {
@@ -109,7 +109,7 @@ impl<'tcx, T> SpecializedEncoder<Lazy<[T]>> for EncodeContext<'tcx> {
     }
 }
 
-impl<'tcx, I: Idx, T> SpecializedEncoder<Lazy<Table<I, T>>> for EncodeContext<'tcx>
+impl<'tcx, I: Idx, T> SpecializedEncoder<Lazy<Table<I, T>, usize>> for EncodeContext<'tcx>
 where
     Option<T>: FixedSizeEncoding,
 {
@@ -228,8 +228,13 @@ impl<'tcx> SpecializedEncoder<LocalDefId> for EncodeContext<'tcx> {
     }
 }
 
-impl<'tcx> SpecializedEncoder<Ty<'tcx>> for EncodeContext<'tcx> {
-    fn specialized_encode(&mut self, ty: &Ty<'tcx>) -> Result<(), Self::Error> {
+impl<'a, 'b, 'tcx> SpecializedEncoder<&'a ty::TyS<'b>> for EncodeContext<'tcx>
+where
+    &'a ty::TyS<'b>: UseSpecializedEncodable,
+{
+    fn specialized_encode(&mut self, ty: &&'a ty::TyS<'b>) -> Result<(), Self::Error> {
+        debug_assert!(self.tcx.lift(ty).is_some());
+        let ty = unsafe { std::mem::transmute::<&&'a ty::TyS<'b>, &&'tcx ty::TyS<'tcx>>(ty) };
         ty_codec::encode_with_shorthand(self, ty, |ecx| &mut ecx.type_shorthands)
     }
 }
@@ -251,12 +256,19 @@ impl<'tcx> SpecializedEncoder<interpret::AllocId> for EncodeContext<'tcx> {
     }
 }
 
-impl<'tcx> SpecializedEncoder<&'tcx [(ty::Predicate<'tcx>, Span)]> for EncodeContext<'tcx> {
+impl<'a, 'b, 'tcx> SpecializedEncoder<&'a [(ty::Predicate<'b>, Span)]> for EncodeContext<'tcx> {
     fn specialized_encode(
         &mut self,
-        predicates: &&'tcx [(ty::Predicate<'tcx>, Span)],
+        predicates: &&'a [(ty::Predicate<'b>, Span)],
     ) -> Result<(), Self::Error> {
-        ty_codec::encode_spanned_predicates(self, predicates, |ecx| &mut ecx.predicate_shorthands)
+        debug_assert!(self.tcx.lift(*predicates).is_some());
+        let predicates = unsafe {
+            std::mem::transmute::<
+                &&'a [(ty::Predicate<'b>, Span)],
+                &&'tcx [(ty::Predicate<'tcx>, Span)],
+            >(predicates)
+        };
+        ty_codec::encode_spanned_predicates(self, &predicates, |ecx| &mut ecx.predicate_shorthands)
     }
 }
 
@@ -266,7 +278,10 @@ impl<'tcx> SpecializedEncoder<Fingerprint> for EncodeContext<'tcx> {
     }
 }
 
-impl<'tcx, T: Encodable> SpecializedEncoder<mir::ClearCrossCrate<T>> for EncodeContext<'tcx> {
+impl<'tcx, T> SpecializedEncoder<mir::ClearCrossCrate<T>> for EncodeContext<'tcx>
+where
+    mir::ClearCrossCrate<T>: UseSpecializedEncodable,
+{
     fn specialized_encode(&mut self, _: &mir::ClearCrossCrate<T>) -> Result<(), Self::Error> {
         Ok(())
     }