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Diffstat (limited to 'compiler/rustc_middle/src/ty/util.rs')
| -rw-r--r-- | compiler/rustc_middle/src/ty/util.rs | 1168 |
1 files changed, 1168 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs new file mode 100644 index 00000000000..63d4dcca080 --- /dev/null +++ b/compiler/rustc_middle/src/ty/util.rs @@ -0,0 +1,1168 @@ +//! Miscellaneous type-system utilities that are too small to deserve their own modules. + +use crate::ich::NodeIdHashingMode; +use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags; +use crate::mir::interpret::{sign_extend, truncate}; +use crate::ty::fold::TypeFolder; +use crate::ty::layout::IntegerExt; +use crate::ty::query::TyCtxtAt; +use crate::ty::subst::{GenericArgKind, InternalSubsts, Subst, SubstsRef}; +use crate::ty::TyKind::*; +use crate::ty::{self, DefIdTree, GenericParamDefKind, List, Ty, TyCtxt, TypeFoldable}; +use rustc_apfloat::Float as _; +use rustc_ast as ast; +use rustc_attr::{self as attr, SignedInt, UnsignedInt}; +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; +use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; +use rustc_errors::ErrorReported; +use rustc_hir as hir; +use rustc_hir::def::DefKind; +use rustc_hir::def_id::DefId; +use rustc_macros::HashStable; +use rustc_span::Span; +use rustc_target::abi::{Integer, Size, TargetDataLayout}; +use smallvec::SmallVec; +use std::{cmp, fmt}; + +#[derive(Copy, Clone, Debug)] +pub struct Discr<'tcx> { + /// Bit representation of the discriminant (e.g., `-128i8` is `0xFF_u128`). + pub val: u128, + pub ty: Ty<'tcx>, +} + +impl<'tcx> fmt::Display for Discr<'tcx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + match self.ty.kind { + ty::Int(ity) => { + let size = ty::tls::with(|tcx| Integer::from_attr(&tcx, SignedInt(ity)).size()); + let x = self.val; + // sign extend the raw representation to be an i128 + let x = sign_extend(x, size) as i128; + write!(fmt, "{}", x) + } + _ => write!(fmt, "{}", self.val), + } + } +} + +fn signed_min(size: Size) -> i128 { + sign_extend(1_u128 << (size.bits() - 1), size) as i128 +} + +fn signed_max(size: Size) -> i128 { + i128::MAX >> (128 - size.bits()) +} + +fn unsigned_max(size: Size) -> u128 { + u128::MAX >> (128 - size.bits()) +} + +fn int_size_and_signed<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (Size, bool) { + let (int, signed) = match ty.kind { + Int(ity) => (Integer::from_attr(&tcx, SignedInt(ity)), true), + Uint(uty) => (Integer::from_attr(&tcx, UnsignedInt(uty)), false), + _ => bug!("non integer discriminant"), + }; + (int.size(), signed) +} + +impl<'tcx> Discr<'tcx> { + /// Adds `1` to the value and wraps around if the maximum for the type is reached. + pub fn wrap_incr(self, tcx: TyCtxt<'tcx>) -> Self { + self.checked_add(tcx, 1).0 + } + pub fn checked_add(self, tcx: TyCtxt<'tcx>, n: u128) -> (Self, bool) { + let (size, signed) = int_size_and_signed(tcx, self.ty); + let (val, oflo) = if signed { + let min = signed_min(size); + let max = signed_max(size); + let val = sign_extend(self.val, size) as i128; + assert!(n < (i128::MAX as u128)); + let n = n as i128; + let oflo = val > max - n; + let val = if oflo { min + (n - (max - val) - 1) } else { val + n }; + // zero the upper bits + let val = val as u128; + let val = truncate(val, size); + (val, oflo) + } else { + let max = unsigned_max(size); + let val = self.val; + let oflo = val > max - n; + let val = if oflo { n - (max - val) - 1 } else { val + n }; + (val, oflo) + }; + (Self { val, ty: self.ty }, oflo) + } +} + +pub trait IntTypeExt { + fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>; + fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>>; + fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx>; +} + +impl IntTypeExt for attr::IntType { + fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { + match *self { + SignedInt(ast::IntTy::I8) => tcx.types.i8, + SignedInt(ast::IntTy::I16) => tcx.types.i16, + SignedInt(ast::IntTy::I32) => tcx.types.i32, + SignedInt(ast::IntTy::I64) => tcx.types.i64, + SignedInt(ast::IntTy::I128) => tcx.types.i128, + SignedInt(ast::IntTy::Isize) => tcx.types.isize, + UnsignedInt(ast::UintTy::U8) => tcx.types.u8, + UnsignedInt(ast::UintTy::U16) => tcx.types.u16, + UnsignedInt(ast::UintTy::U32) => tcx.types.u32, + UnsignedInt(ast::UintTy::U64) => tcx.types.u64, + UnsignedInt(ast::UintTy::U128) => tcx.types.u128, + UnsignedInt(ast::UintTy::Usize) => tcx.types.usize, + } + } + + fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx> { + Discr { val: 0, ty: self.to_ty(tcx) } + } + + fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>> { + if let Some(val) = val { + assert_eq!(self.to_ty(tcx), val.ty); + let (new, oflo) = val.checked_add(tcx, 1); + if oflo { None } else { Some(new) } + } else { + Some(self.initial_discriminant(tcx)) + } + } +} + +/// 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 +/// contain a different recursive type. These cases can therefore be treated +/// differently when reporting errors. +/// +/// The ordering of the cases is significant. They are sorted so that cmp::max +/// will keep the "more erroneous" of two values. +#[derive(Clone, PartialOrd, Ord, Eq, PartialEq, Debug)] +pub enum Representability { + Representable, + ContainsRecursive, + SelfRecursive(Vec<Span>), +} + +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. + pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 { + let mut hasher = StableHasher::new(); + let mut hcx = self.create_stable_hashing_context(); + + // We want the type_id be independent of the types free regions, so we + // erase them. The erase_regions() call will also anonymize bound + // regions, which is desirable too. + let ty = self.erase_regions(&ty); + + hcx.while_hashing_spans(false, |hcx| { + hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| { + ty.hash_stable(hcx, &mut hasher); + }); + }); + hasher.finish() + } +} + +impl<'tcx> TyCtxt<'tcx> { + pub fn has_error_field(self, ty: Ty<'tcx>) -> bool { + if let ty::Adt(def, substs) = ty.kind { + for field in def.all_fields() { + let field_ty = field.ty(self, substs); + if let Error(_) = field_ty.kind { + return true; + } + } + } + false + } + + /// Attempts to returns the deeply last field of nested structures, but + /// does not apply any normalization in its search. Returns the same type + /// if input `ty` is not a structure at all. + pub fn struct_tail_without_normalization(self, ty: Ty<'tcx>) -> Ty<'tcx> { + let tcx = self; + tcx.struct_tail_with_normalize(ty, |ty| ty) + } + + /// Returns the deeply last field of nested structures, or the same type if + /// not a structure at all. Corresponds to the only possible unsized field, + /// and its type can be used to determine unsizing strategy. + /// + /// Should only be called if `ty` has no inference variables and does not + /// need its lifetimes preserved (e.g. as part of codegen); otherwise + /// normalization attempt may cause compiler bugs. + pub fn struct_tail_erasing_lifetimes( + self, + ty: Ty<'tcx>, + param_env: ty::ParamEnv<'tcx>, + ) -> Ty<'tcx> { + let tcx = self; + tcx.struct_tail_with_normalize(ty, |ty| tcx.normalize_erasing_regions(param_env, ty)) + } + + /// Returns the deeply last field of nested structures, or the same type if + /// not a structure at all. Corresponds to the only possible unsized field, + /// and its type can be used to determine unsizing strategy. + /// + /// This is parameterized over the normalization strategy (i.e. how to + /// handle `<T as Trait>::Assoc` and `impl Trait`); pass the identity + /// function to indicate no normalization should take place. + /// + /// See also `struct_tail_erasing_lifetimes`, which is suitable for use + /// during codegen. + pub fn struct_tail_with_normalize( + self, + mut ty: Ty<'tcx>, + normalize: impl Fn(Ty<'tcx>) -> Ty<'tcx>, + ) -> Ty<'tcx> { + loop { + match ty.kind { + ty::Adt(def, substs) => { + if !def.is_struct() { + break; + } + match def.non_enum_variant().fields.last() { + Some(f) => ty = f.ty(self, substs), + None => break, + } + } + + ty::Tuple(tys) => { + if let Some((&last_ty, _)) = tys.split_last() { + ty = last_ty.expect_ty(); + } else { + break; + } + } + + ty::Projection(_) | ty::Opaque(..) => { + let normalized = normalize(ty); + if ty == normalized { + return ty; + } else { + ty = normalized; + } + } + + _ => { + break; + } + } + } + ty + } + + /// Same as applying `struct_tail` on `source` and `target`, but only + /// keeps going as long as the two types are instances of the same + /// structure definitions. + /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`, + /// whereas struct_tail produces `T`, and `Trait`, respectively. + /// + /// Should only be called if the types have no inference variables and do + /// not need their lifetimes preserved (e.g., as part of codegen); otherwise, + /// normalization attempt may cause compiler bugs. + pub fn struct_lockstep_tails_erasing_lifetimes( + self, + source: Ty<'tcx>, + target: Ty<'tcx>, + param_env: ty::ParamEnv<'tcx>, + ) -> (Ty<'tcx>, Ty<'tcx>) { + let tcx = self; + tcx.struct_lockstep_tails_with_normalize(source, target, |ty| { + tcx.normalize_erasing_regions(param_env, ty) + }) + } + + /// Same as applying `struct_tail` on `source` and `target`, but only + /// keeps going as long as the two types are instances of the same + /// structure definitions. + /// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`, + /// whereas struct_tail produces `T`, and `Trait`, respectively. + /// + /// See also `struct_lockstep_tails_erasing_lifetimes`, which is suitable for use + /// during codegen. + pub fn struct_lockstep_tails_with_normalize( + self, + source: Ty<'tcx>, + target: Ty<'tcx>, + normalize: impl Fn(Ty<'tcx>) -> Ty<'tcx>, + ) -> (Ty<'tcx>, Ty<'tcx>) { + let (mut a, mut b) = (source, target); + loop { + match (&a.kind, &b.kind) { + (&Adt(a_def, a_substs), &Adt(b_def, b_substs)) + if a_def == b_def && a_def.is_struct() => + { + if let Some(f) = a_def.non_enum_variant().fields.last() { + a = f.ty(self, a_substs); + b = f.ty(self, b_substs); + } else { + break; + } + } + (&Tuple(a_tys), &Tuple(b_tys)) if a_tys.len() == b_tys.len() => { + if let Some(a_last) = a_tys.last() { + a = a_last.expect_ty(); + b = b_tys.last().unwrap().expect_ty(); + } else { + break; + } + } + (ty::Projection(_) | ty::Opaque(..), _) + | (_, ty::Projection(_) | ty::Opaque(..)) => { + // If either side is a projection, attempt to + // progress via normalization. (Should be safe to + // apply to both sides as normalization is + // idempotent.) + let a_norm = normalize(a); + let b_norm = normalize(b); + if a == a_norm && b == b_norm { + break; + } else { + a = a_norm; + b = b_norm; + } + } + + _ => break, + } + } + (a, b) + } + + /// Calculate the destructor of a given type. + pub fn calculate_dtor( + self, + adt_did: DefId, + validate: &mut dyn FnMut(Self, DefId) -> Result<(), ErrorReported>, + ) -> Option<ty::Destructor> { + let drop_trait = self.lang_items().drop_trait()?; + self.ensure().coherent_trait(drop_trait); + + let mut dtor_did = None; + let ty = self.type_of(adt_did); + self.for_each_relevant_impl(drop_trait, ty, |impl_did| { + if let Some(item) = self.associated_items(impl_did).in_definition_order().next() { + if validate(self, impl_did).is_ok() { + dtor_did = Some(item.def_id); + } + } + }); + + Some(ty::Destructor { did: dtor_did? }) + } + + /// Returns the set of types that are required to be alive in + /// order to run the destructor of `def` (see RFCs 769 and + /// 1238). + /// + /// Note that this returns only the constraints for the + /// destructor of `def` itself. For the destructors of the + /// contents, you need `adt_dtorck_constraint`. + pub fn destructor_constraints(self, def: &'tcx ty::AdtDef) -> Vec<ty::subst::GenericArg<'tcx>> { + let dtor = match def.destructor(self) { + None => { + debug!("destructor_constraints({:?}) - no dtor", def.did); + return vec![]; + } + Some(dtor) => dtor.did, + }; + + let impl_def_id = self.associated_item(dtor).container.id(); + let impl_generics = self.generics_of(impl_def_id); + + // We have a destructor - all the parameters that are not + // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute) + // must be live. + + // We need to return the list of parameters from the ADTs + // generics/substs that correspond to impure parameters on the + // impl's generics. This is a bit ugly, but conceptually simple: + // + // Suppose our ADT looks like the following + // + // struct S<X, Y, Z>(X, Y, Z); + // + // and the impl is + // + // impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0> + // + // We want to return the parameters (X, Y). For that, we match + // up the item-substs <X, Y, Z> with the substs on the impl ADT, + // <P1, P2, P0>, and then look up which of the impl substs refer to + // parameters marked as pure. + + let impl_substs = match self.type_of(impl_def_id).kind { + ty::Adt(def_, substs) if def_ == def => substs, + _ => bug!(), + }; + + let item_substs = match self.type_of(def.did).kind { + ty::Adt(def_, substs) if def_ == def => substs, + _ => bug!(), + }; + + let result = item_substs + .iter() + .zip(impl_substs.iter()) + .filter(|&(_, k)| { + match k.unpack() { + GenericArgKind::Lifetime(&ty::RegionKind::ReEarlyBound(ref ebr)) => { + !impl_generics.region_param(ebr, self).pure_wrt_drop + } + GenericArgKind::Type(&ty::TyS { kind: ty::Param(ref pt), .. }) => { + !impl_generics.type_param(pt, self).pure_wrt_drop + } + GenericArgKind::Const(&ty::Const { + val: ty::ConstKind::Param(ref pc), .. + }) => !impl_generics.const_param(pc, self).pure_wrt_drop, + GenericArgKind::Lifetime(_) + | GenericArgKind::Type(_) + | GenericArgKind::Const(_) => { + // Not a type, const or region param: this should be reported + // as an error. + false + } + } + }) + .map(|(item_param, _)| item_param) + .collect(); + debug!("destructor_constraint({:?}) = {:?}", def.did, result); + result + } + + /// Returns `true` if `def_id` refers to a closure (e.g., `|x| x * 2`). Note + /// that closures have a `DefId`, but the closure *expression* also + /// has a `HirId` that is located within the context where the + /// closure appears (and, sadly, a corresponding `NodeId`, since + /// those are not yet phased out). The parent of the closure's + /// `DefId` will also be the context where it appears. + pub fn is_closure(self, def_id: DefId) -> bool { + matches!(self.def_kind(def_id), DefKind::Closure | DefKind::Generator) + } + + /// Returns `true` if `def_id` refers to a trait (i.e., `trait Foo { ... }`). + pub fn is_trait(self, def_id: DefId) -> bool { + self.def_kind(def_id) == DefKind::Trait + } + + /// Returns `true` if `def_id` refers to a trait alias (i.e., `trait Foo = ...;`), + /// and `false` otherwise. + pub fn is_trait_alias(self, def_id: DefId) -> bool { + self.def_kind(def_id) == DefKind::TraitAlias + } + + /// Returns `true` if this `DefId` refers to the implicit constructor for + /// a tuple struct like `struct Foo(u32)`, and `false` otherwise. + pub fn is_constructor(self, def_id: DefId) -> bool { + matches!(self.def_kind(def_id), DefKind::Ctor(..)) + } + + /// Given the def-ID of a fn or closure, returns the def-ID of + /// the innermost fn item that the closure is contained within. + /// This is a significant `DefId` because, when we do + /// type-checking, we type-check this fn item and all of its + /// (transitive) closures together. Therefore, when we fetch the + /// `typeck` the closure, for example, we really wind up + /// fetching the `typeck` the enclosing fn item. + pub fn closure_base_def_id(self, def_id: DefId) -> DefId { + let mut def_id = def_id; + while self.is_closure(def_id) { + def_id = self.parent(def_id).unwrap_or_else(|| { + bug!("closure {:?} has no parent", def_id); + }); + } + def_id + } + + /// Given the `DefId` and substs a closure, creates the type of + /// `self` argument that the closure expects. For example, for a + /// `Fn` closure, this would return a reference type `&T` where + /// `T = closure_ty`. + /// + /// Returns `None` if this closure's kind has not yet been inferred. + /// This should only be possible during type checking. + /// + /// Note that the return value is a late-bound region and hence + /// wrapped in a binder. + pub fn closure_env_ty( + self, + closure_def_id: DefId, + closure_substs: SubstsRef<'tcx>, + ) -> Option<ty::Binder<Ty<'tcx>>> { + let closure_ty = self.mk_closure(closure_def_id, closure_substs); + let env_region = ty::ReLateBound(ty::INNERMOST, ty::BrEnv); + let closure_kind_ty = closure_substs.as_closure().kind_ty(); + let closure_kind = closure_kind_ty.to_opt_closure_kind()?; + let env_ty = match closure_kind { + ty::ClosureKind::Fn => self.mk_imm_ref(self.mk_region(env_region), closure_ty), + ty::ClosureKind::FnMut => self.mk_mut_ref(self.mk_region(env_region), closure_ty), + ty::ClosureKind::FnOnce => closure_ty, + }; + Some(ty::Binder::bind(env_ty)) + } + + /// Given the `DefId` of some item that has no type or const parameters, make + /// a suitable "empty substs" for it. + pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> SubstsRef<'tcx> { + InternalSubsts::for_item(self, item_def_id, |param, _| match param.kind { + GenericParamDefKind::Lifetime => self.lifetimes.re_erased.into(), + GenericParamDefKind::Type { .. } => { + bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id) + } + GenericParamDefKind::Const { .. } => { + bug!("empty_substs_for_def_id: {:?} has const parameters", item_def_id) + } + }) + } + + /// Returns `true` if the node pointed to by `def_id` is a `static` item. + pub fn is_static(&self, def_id: DefId) -> bool { + self.static_mutability(def_id).is_some() + } + + /// Returns `true` if this is a `static` item with the `#[thread_local]` attribute. + pub fn is_thread_local_static(&self, def_id: DefId) -> bool { + self.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) + } + + /// Returns `true` if the node pointed to by `def_id` is a mutable `static` item. + pub fn is_mutable_static(&self, def_id: DefId) -> bool { + self.static_mutability(def_id) == Some(hir::Mutability::Mut) + } + + /// Get the type of the pointer to the static that we use in MIR. + pub fn static_ptr_ty(&self, def_id: DefId) -> Ty<'tcx> { + // Make sure that any constants in the static's type are evaluated. + let static_ty = self.normalize_erasing_regions(ty::ParamEnv::empty(), self.type_of(def_id)); + + if self.is_mutable_static(def_id) { + self.mk_mut_ptr(static_ty) + } else { + self.mk_imm_ref(self.lifetimes.re_erased, static_ty) + } + } + + /// Expands the given impl trait type, stopping if the type is recursive. + pub fn try_expand_impl_trait_type( + self, + def_id: DefId, + substs: SubstsRef<'tcx>, + ) -> Result<Ty<'tcx>, Ty<'tcx>> { + let mut visitor = OpaqueTypeExpander { + seen_opaque_tys: FxHashSet::default(), + expanded_cache: FxHashMap::default(), + primary_def_id: Some(def_id), + found_recursion: false, + check_recursion: true, + tcx: self, + }; + + let expanded_type = visitor.expand_opaque_ty(def_id, substs).unwrap(); + if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) } + } +} + +struct OpaqueTypeExpander<'tcx> { + // Contains the DefIds of the opaque types that are currently being + // expanded. When we expand an opaque type we insert the DefId of + // that type, and when we finish expanding that type we remove the + // its DefId. + seen_opaque_tys: FxHashSet<DefId>, + // Cache of all expansions we've seen so far. This is a critical + // optimization for some large types produced by async fn trees. + expanded_cache: FxHashMap<(DefId, SubstsRef<'tcx>), Ty<'tcx>>, + primary_def_id: Option<DefId>, + found_recursion: bool, + /// Whether or not to check for recursive opaque types. + /// This is `true` when we're explicitly checking for opaque type + /// recursion, and 'false' otherwise to avoid unnecessary work. + check_recursion: bool, + tcx: TyCtxt<'tcx>, +} + +impl<'tcx> OpaqueTypeExpander<'tcx> { + fn expand_opaque_ty(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> Option<Ty<'tcx>> { + if self.found_recursion { + return None; + } + let substs = substs.fold_with(self); + if !self.check_recursion || self.seen_opaque_tys.insert(def_id) { + let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) { + Some(expanded_ty) => expanded_ty, + None => { + let generic_ty = self.tcx.type_of(def_id); + let concrete_ty = generic_ty.subst(self.tcx, substs); + let expanded_ty = self.fold_ty(concrete_ty); + self.expanded_cache.insert((def_id, substs), expanded_ty); + expanded_ty + } + }; + if self.check_recursion { + self.seen_opaque_tys.remove(&def_id); + } + Some(expanded_ty) + } else { + // If another opaque type that we contain is recursive, then it + // will report the error, so we don't have to. + self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap(); + None + } + } +} + +impl<'tcx> TypeFolder<'tcx> for OpaqueTypeExpander<'tcx> { + fn tcx(&self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + if let ty::Opaque(def_id, substs) = t.kind { + self.expand_opaque_ty(def_id, substs).unwrap_or(t) + } else if t.has_opaque_types() { + t.super_fold_with(self) + } else { + t + } + } +} + +impl<'tcx> ty::TyS<'tcx> { + /// Returns the maximum value for the given numeric type (including `char`s) + /// or returns `None` if the type is not numeric. + pub fn numeric_max_val(&'tcx self, tcx: TyCtxt<'tcx>) -> Option<&'tcx ty::Const<'tcx>> { + let val = match self.kind { + ty::Int(_) | ty::Uint(_) => { + let (size, signed) = int_size_and_signed(tcx, self); + let val = if signed { signed_max(size) as u128 } else { unsigned_max(size) }; + Some(val) + } + ty::Char => Some(std::char::MAX as u128), + ty::Float(fty) => Some(match fty { + ast::FloatTy::F32 => ::rustc_apfloat::ieee::Single::INFINITY.to_bits(), + ast::FloatTy::F64 => ::rustc_apfloat::ieee::Double::INFINITY.to_bits(), + }), + _ => None, + }; + val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self))) + } + + /// Returns the minimum value for the given numeric type (including `char`s) + /// or returns `None` if the type is not numeric. + pub fn numeric_min_val(&'tcx self, tcx: TyCtxt<'tcx>) -> Option<&'tcx ty::Const<'tcx>> { + let val = match self.kind { + ty::Int(_) | ty::Uint(_) => { + let (size, signed) = int_size_and_signed(tcx, self); + let val = if signed { truncate(signed_min(size) as u128, size) } else { 0 }; + Some(val) + } + ty::Char => Some(0), + ty::Float(fty) => Some(match fty { + ast::FloatTy::F32 => (-::rustc_apfloat::ieee::Single::INFINITY).to_bits(), + ast::FloatTy::F64 => (-::rustc_apfloat::ieee::Double::INFINITY).to_bits(), + }), + _ => None, + }; + val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self))) + } + + /// Checks whether values of this type `T` are *moved* or *copied* + /// when referenced -- this amounts to a check for whether `T: + /// Copy`, but note that we **don't** consider lifetimes when + /// doing this check. This means that we may generate MIR which + /// does copies even when the type actually doesn't satisfy the + /// full requirements for the `Copy` trait (cc #29149) -- this + /// winds up being reported as an error during NLL borrow check. + pub fn is_copy_modulo_regions( + &'tcx self, + tcx_at: TyCtxtAt<'tcx>, + param_env: ty::ParamEnv<'tcx>, + ) -> bool { + tcx_at.is_copy_raw(param_env.and(self)) + } + + /// Checks whether values of this type `T` have a size known at + /// compile time (i.e., whether `T: Sized`). Lifetimes are ignored + /// for the purposes of this check, so it can be an + /// over-approximation in generic contexts, where one can have + /// strange rules like `<T as Foo<'static>>::Bar: Sized` that + /// actually carry lifetime requirements. + pub fn is_sized(&'tcx self, tcx_at: TyCtxtAt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool { + self.is_trivially_sized(tcx_at.tcx) || tcx_at.is_sized_raw(param_env.and(self)) + } + + /// Checks whether values of this type `T` implement the `Freeze` + /// trait -- frozen types are those that do not contain a + /// `UnsafeCell` anywhere. This is a language concept used to + /// distinguish "true immutability", which is relevant to + /// optimization as well as the rules around static values. Note + /// that the `Freeze` trait is not exposed to end users and is + /// effectively an implementation detail. + // FIXME: use `TyCtxtAt` instead of separate `Span`. + pub fn is_freeze(&'tcx self, tcx_at: TyCtxtAt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool { + self.is_trivially_freeze() || tcx_at.is_freeze_raw(param_env.and(self)) + } + + /// Fast path helper for testing if a type is `Freeze`. + /// + /// Returning true means the type is known to be `Freeze`. Returning + /// `false` means nothing -- could be `Freeze`, might not be. + fn is_trivially_freeze(&self) -> bool { + match self.kind { + ty::Int(_) + | ty::Uint(_) + | ty::Float(_) + | ty::Bool + | ty::Char + | ty::Str + | ty::Never + | ty::Ref(..) + | ty::RawPtr(_) + | ty::FnDef(..) + | ty::Error(_) + | ty::FnPtr(_) => true, + ty::Tuple(_) => self.tuple_fields().all(Self::is_trivially_freeze), + ty::Slice(elem_ty) | ty::Array(elem_ty, _) => elem_ty.is_trivially_freeze(), + ty::Adt(..) + | ty::Bound(..) + | ty::Closure(..) + | ty::Dynamic(..) + | ty::Foreign(_) + | ty::Generator(..) + | ty::GeneratorWitness(_) + | ty::Infer(_) + | ty::Opaque(..) + | ty::Param(_) + | ty::Placeholder(_) + | ty::Projection(_) => false, + } + } + + /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely + /// non-copy and *might* have a destructor attached; if it returns + /// `false`, then `ty` definitely has no destructor (i.e., no drop glue). + /// + /// (Note that this implies that if `ty` has a destructor attached, + /// then `needs_drop` will definitely return `true` for `ty`.) + /// + /// Note that this method is used to check eligible types in unions. + #[inline] + pub fn needs_drop(&'tcx self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool { + // Avoid querying in simple cases. + match needs_drop_components(self, &tcx.data_layout) { + Err(AlwaysRequiresDrop) => true, + Ok(components) => { + let query_ty = match *components { + [] => return false, + // If we've got a single component, call the query with that + // to increase the chance that we hit the query cache. + [component_ty] => component_ty, + _ => self, + }; + // This doesn't depend on regions, so try to minimize distinct + // query keys used. + let erased = tcx.normalize_erasing_regions(param_env, query_ty); + tcx.needs_drop_raw(param_env.and(erased)) + } + } + } + + /// Returns `true` if equality for this type is both reflexive and structural. + /// + /// Reflexive equality for a type is indicated by an `Eq` impl for that type. + /// + /// Primitive types (`u32`, `str`) have structural equality by definition. For composite data + /// types, equality for the type as a whole is structural when it is the same as equality + /// between all components (fields, array elements, etc.) of that type. For ADTs, structural + /// equality is indicated by an implementation of `PartialStructuralEq` and `StructuralEq` for + /// that type. + /// + /// This function is "shallow" because it may return `true` for a composite type whose fields + /// are not `StructuralEq`. For example, `[T; 4]` has structural equality regardless of `T` + /// because equality for arrays is determined by the equality of each array element. If you + /// want to know whether a given call to `PartialEq::eq` will proceed structurally all the way + /// down, you will need to use a type visitor. + #[inline] + pub fn is_structural_eq_shallow(&'tcx self, tcx: TyCtxt<'tcx>) -> bool { + match self.kind { + // Look for an impl of both `PartialStructuralEq` and `StructuralEq`. + Adt(..) => tcx.has_structural_eq_impls(self), + + // Primitive types that satisfy `Eq`. + Bool | Char | Int(_) | Uint(_) | Str | Never => true, + + // Composite types that satisfy `Eq` when all of their fields do. + // + // Because this function is "shallow", we return `true` for these composites regardless + // of the type(s) contained within. + Ref(..) | Array(..) | Slice(_) | Tuple(..) => true, + + // Raw pointers use bitwise comparison. + RawPtr(_) | FnPtr(_) => true, + + // Floating point numbers are not `Eq`. + Float(_) => false, + + // Conservatively return `false` for all others... + + // Anonymous function types + FnDef(..) | Closure(..) | Dynamic(..) | Generator(..) => false, + + // Generic or inferred types + // + // FIXME(ecstaticmorse): Maybe we should `bug` here? This should probably only be + // called for known, fully-monomorphized types. + Projection(_) | Opaque(..) | Param(_) | Bound(..) | Placeholder(_) | Infer(_) => false, + + Foreign(_) | GeneratorWitness(..) | Error(_) => false, + } + } + + pub fn same_type(a: Ty<'tcx>, b: Ty<'tcx>) -> bool { + match (&a.kind, &b.kind) { + (&Adt(did_a, substs_a), &Adt(did_b, substs_b)) => { + if did_a != did_b { + return false; + } + + substs_a.types().zip(substs_b.types()).all(|(a, b)| Self::same_type(a, b)) + } + _ => a == b, + } + } + + /// Check whether a type is representable. This means it cannot contain unboxed + /// structural recursion. This check is needed for structs and enums. + pub fn is_representable(&'tcx self, tcx: TyCtxt<'tcx>, sp: Span) -> Representability { + // Iterate until something non-representable is found + fn fold_repr<It: Iterator<Item = Representability>>(iter: It) -> Representability { + iter.fold(Representability::Representable, |r1, r2| match (r1, r2) { + (Representability::SelfRecursive(v1), Representability::SelfRecursive(v2)) => { + Representability::SelfRecursive(v1.into_iter().chain(v2).collect()) + } + (r1, r2) => cmp::max(r1, r2), + }) + } + + fn are_inner_types_recursive<'tcx>( + tcx: TyCtxt<'tcx>, + sp: Span, + seen: &mut Vec<Ty<'tcx>>, + representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>, + ty: Ty<'tcx>, + ) -> Representability { + match ty.kind { + Tuple(..) => { + // Find non representable + fold_repr(ty.tuple_fields().map(|ty| { + is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty) + })) + } + // Fixed-length vectors. + // FIXME(#11924) Behavior undecided for zero-length vectors. + Array(ty, _) => { + is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty) + } + Adt(def, substs) => { + // Find non representable fields with their spans + fold_repr(def.all_fields().map(|field| { + let ty = field.ty(tcx, substs); + let span = match field + .did + .as_local() + .map(|id| tcx.hir().local_def_id_to_hir_id(id)) + .and_then(|id| tcx.hir().find(id)) + { + Some(hir::Node::Field(field)) => field.ty.span, + _ => sp, + }; + match is_type_structurally_recursive( + tcx, + span, + seen, + representable_cache, + ty, + ) { + Representability::SelfRecursive(_) => { + Representability::SelfRecursive(vec![span]) + } + x => x, + } + })) + } + Closure(..) => { + // this check is run on type definitions, so we don't expect + // to see closure types + bug!("requires check invoked on inapplicable type: {:?}", ty) + } + _ => Representability::Representable, + } + } + + fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool { + match ty.kind { + Adt(ty_def, _) => ty_def == def, + _ => false, + } + } + + // Does the type `ty` directly (without indirection through a pointer) + // contain any types on stack `seen`? + fn is_type_structurally_recursive<'tcx>( + tcx: TyCtxt<'tcx>, + sp: Span, + seen: &mut Vec<Ty<'tcx>>, + representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>, + ty: Ty<'tcx>, + ) -> Representability { + debug!("is_type_structurally_recursive: {:?} {:?}", ty, sp); + if let Some(representability) = representable_cache.get(ty) { + debug!( + "is_type_structurally_recursive: {:?} {:?} - (cached) {:?}", + ty, sp, representability + ); + return representability.clone(); + } + + let representability = + is_type_structurally_recursive_inner(tcx, sp, seen, representable_cache, ty); + + representable_cache.insert(ty, representability.clone()); + representability + } + + fn is_type_structurally_recursive_inner<'tcx>( + tcx: TyCtxt<'tcx>, + sp: Span, + seen: &mut Vec<Ty<'tcx>>, + representable_cache: &mut FxHashMap<Ty<'tcx>, Representability>, + ty: Ty<'tcx>, + ) -> Representability { + match ty.kind { + Adt(def, _) => { + { + // Iterate through stack of previously seen types. + let mut iter = seen.iter(); + + // The first item in `seen` is the type we are actually curious about. + // We want to return SelfRecursive if this type contains itself. + // It is important that we DON'T take generic parameters into account + // for this check, so that Bar<T> in this example counts as SelfRecursive: + // + // struct Foo; + // struct Bar<T> { x: Bar<Foo> } + + if let Some(&seen_type) = iter.next() { + if same_struct_or_enum(seen_type, def) { + debug!("SelfRecursive: {:?} contains {:?}", seen_type, ty); + return Representability::SelfRecursive(vec![sp]); + } + } + + // We also need to know whether the first item contains other types + // that are structurally recursive. If we don't catch this case, we + // will recurse infinitely for some inputs. + // + // It is important that we DO take generic parameters into account + // here, so that code like this is considered SelfRecursive, not + // ContainsRecursive: + // + // struct Foo { Option<Option<Foo>> } + + for &seen_type in iter { + if ty::TyS::same_type(ty, seen_type) { + debug!("ContainsRecursive: {:?} contains {:?}", seen_type, ty); + return Representability::ContainsRecursive; + } + } + } + + // For structs and enums, track all previously seen types by pushing them + // onto the 'seen' stack. + seen.push(ty); + let out = are_inner_types_recursive(tcx, sp, seen, representable_cache, ty); + seen.pop(); + out + } + _ => { + // No need to push in other cases. + are_inner_types_recursive(tcx, sp, seen, representable_cache, ty) + } + } + } + + debug!("is_type_representable: {:?}", self); + + // To avoid a stack overflow when checking an enum variant or struct that + // contains a different, structurally recursive type, maintain a stack + // of seen types and check recursion for each of them (issues #3008, #3779). + let mut seen: Vec<Ty<'_>> = Vec::new(); + let mut representable_cache = FxHashMap::default(); + let r = is_type_structurally_recursive(tcx, sp, &mut seen, &mut representable_cache, self); + debug!("is_type_representable: {:?} is {:?}", self, r); + r + } + + /// Peel off all reference types in this type until there are none left. + /// + /// This method is idempotent, i.e. `ty.peel_refs().peel_refs() == ty.peel_refs()`. + /// + /// # Examples + /// + /// - `u8` -> `u8` + /// - `&'a mut u8` -> `u8` + /// - `&'a &'b u8` -> `u8` + /// - `&'a *const &'b u8 -> *const &'b u8` + pub fn peel_refs(&'tcx self) -> Ty<'tcx> { + let mut ty = self; + while let Ref(_, inner_ty, _) = ty.kind { + ty = inner_ty; + } + ty + } +} + +pub enum ExplicitSelf<'tcx> { + ByValue, + ByReference(ty::Region<'tcx>, hir::Mutability), + ByRawPointer(hir::Mutability), + ByBox, + Other, +} + +impl<'tcx> ExplicitSelf<'tcx> { + /// Categorizes an explicit self declaration like `self: SomeType` + /// into either `self`, `&self`, `&mut self`, `Box<self>`, or + /// `Other`. + /// This is mainly used to require the arbitrary_self_types feature + /// in the case of `Other`, to improve error messages in the common cases, + /// and to make `Other` non-object-safe. + /// + /// Examples: + /// + /// ``` + /// impl<'a> Foo for &'a T { + /// // Legal declarations: + /// fn method1(self: &&'a T); // ExplicitSelf::ByReference + /// fn method2(self: &'a T); // ExplicitSelf::ByValue + /// fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox + /// fn method4(self: Rc<&'a T>); // ExplicitSelf::Other + /// + /// // Invalid cases will be caught by `check_method_receiver`: + /// fn method_err1(self: &'a mut T); // ExplicitSelf::Other + /// fn method_err2(self: &'static T) // ExplicitSelf::ByValue + /// fn method_err3(self: &&T) // ExplicitSelf::ByReference + /// } + /// ``` + /// + pub fn determine<P>(self_arg_ty: Ty<'tcx>, is_self_ty: P) -> ExplicitSelf<'tcx> + where + P: Fn(Ty<'tcx>) -> bool, + { + use self::ExplicitSelf::*; + + match self_arg_ty.kind { + _ if is_self_ty(self_arg_ty) => ByValue, + ty::Ref(region, ty, mutbl) if is_self_ty(ty) => ByReference(region, mutbl), + ty::RawPtr(ty::TypeAndMut { ty, mutbl }) if is_self_ty(ty) => ByRawPointer(mutbl), + ty::Adt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => ByBox, + _ => Other, + } + } +} + +/// Returns a list of types such that the given type needs drop if and only if +/// *any* of the returned types need drop. Returns `Err(AlwaysRequiresDrop)` if +/// this type always needs drop. +pub fn needs_drop_components( + ty: Ty<'tcx>, + target_layout: &TargetDataLayout, +) -> Result<SmallVec<[Ty<'tcx>; 2]>, AlwaysRequiresDrop> { + match ty.kind { + 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 => Ok(SmallVec::new()), + + // Foreign types can never have destructors. + ty::Foreign(..) => Ok(SmallVec::new()), + + ty::Dynamic(..) | ty::Error(_) => Err(AlwaysRequiresDrop), + + ty::Slice(ty) => needs_drop_components(ty, target_layout), + ty::Array(elem_ty, size) => { + match needs_drop_components(elem_ty, target_layout) { + Ok(v) if v.is_empty() => Ok(v), + res => match size.val.try_to_bits(target_layout.pointer_size) { + // Arrays of size zero don't need drop, even if their element + // type does. + Some(0) => Ok(SmallVec::new()), + Some(_) => res, + // We don't know which of the cases above we are in, so + // return the whole type and let the caller decide what to + // do. + None => Ok(smallvec![ty]), + }, + } + } + // If any field needs drop, then the whole tuple does. + ty::Tuple(..) => ty.tuple_fields().try_fold(SmallVec::new(), move |mut acc, elem| { + acc.extend(needs_drop_components(elem, target_layout)?); + Ok(acc) + }), + + // These require checking for `Copy` bounds or `Adt` destructors. + ty::Adt(..) + | ty::Projection(..) + | ty::Param(_) + | ty::Bound(..) + | ty::Placeholder(..) + | ty::Opaque(..) + | ty::Infer(_) + | ty::Closure(..) + | ty::Generator(..) => Ok(smallvec![ty]), + } +} + +#[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)] +pub struct AlwaysRequiresDrop; + +/// Normalizes all opaque types in the given value, replacing them +/// with their underlying types. +pub fn normalize_opaque_types( + tcx: TyCtxt<'tcx>, + val: &'tcx List<ty::Predicate<'tcx>>, +) -> &'tcx List<ty::Predicate<'tcx>> { + let mut visitor = OpaqueTypeExpander { + seen_opaque_tys: FxHashSet::default(), + expanded_cache: FxHashMap::default(), + primary_def_id: None, + found_recursion: false, + check_recursion: false, + tcx, + }; + val.fold_with(&mut visitor) +} + +pub fn provide(providers: &mut ty::query::Providers) { + *providers = ty::query::Providers { normalize_opaque_types, ..*providers } +} |