compiler/rustc_middle/src/mir/query.rs - toolchain/rustc - Git at Google

 //! Values computed by queries that use MIR.

 use crate::mir::{abstract_const, Body, Promoted};
 use crate::ty::{self, Ty, TyCtxt};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::ErrorReported;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_index::bit_set::BitMatrix;
 use rustc_index::vec::IndexVec;
 use rustc_span::Span;
 use rustc_target::abi::VariantIdx;
 use smallvec::SmallVec;
 use std::cell::Cell;
 use std::fmt::{self, Debug};

 use super::{Field, SourceInfo};

 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 pub enum UnsafetyViolationKind {
     /// Unsafe operation outside `unsafe`.
     General,
     /// Unsafe operation in an `unsafe fn` but outside an `unsafe` block.
     /// Has to be handled as a lint for backwards compatibility.
     UnsafeFn,
 }

 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 pub enum UnsafetyViolationDetails {
     CallToUnsafeFunction,
     UseOfInlineAssembly,
     InitializingTypeWith,
     CastOfPointerToInt,
     BorrowOfPackedField,
     UseOfMutableStatic,
     UseOfExternStatic,
     DerefOfRawPointer,
     AssignToDroppingUnionField,
     AccessToUnionField,
     MutationOfLayoutConstrainedField,
     BorrowOfLayoutConstrainedField,
     CallToFunctionWith,
 }

 impl UnsafetyViolationDetails {
     pub fn description_and_note(&self) -> (&'static str, &'static str) {
         use UnsafetyViolationDetails::*;
         match self {
             CallToUnsafeFunction => (
                 "call to unsafe function",
                 "consult the function's documentation for information on how to avoid undefined \
                  behavior",
             ),
             UseOfInlineAssembly => (
                 "use of inline assembly",
                 "inline assembly is entirely unchecked and can cause undefined behavior",
             ),
             InitializingTypeWith => (
                 "initializing type with `rustc_layout_scalar_valid_range` attr",
                 "initializing a layout restricted type's field with a value outside the valid \
                  range is undefined behavior",
             ),
             CastOfPointerToInt => {
                 ("cast of pointer to int", "casting pointers to integers in constants")
             }
             BorrowOfPackedField => (
                 "borrow of packed field",
                 "fields of packed structs might be misaligned: dereferencing a misaligned pointer \
                  or even just creating a misaligned reference is undefined behavior",
             ),
             UseOfMutableStatic => (
                 "use of mutable static",
                 "mutable statics can be mutated by multiple threads: aliasing violations or data \
                  races will cause undefined behavior",
             ),
             UseOfExternStatic => (
                 "use of extern static",
                 "extern statics are not controlled by the Rust type system: invalid data, \
                  aliasing violations or data races will cause undefined behavior",
             ),
             DerefOfRawPointer => (
                 "dereference of raw pointer",
                 "raw pointers may be NULL, dangling or unaligned; they can violate aliasing rules \
                  and cause data races: all of these are undefined behavior",
             ),
             AssignToDroppingUnionField => (
                 "assignment to union field that might need dropping",
                 "the previous content of the field will be dropped, which causes undefined \
                  behavior if the field was not properly initialized",
             ),
             AccessToUnionField => (
                 "access to union field",
                 "the field may not be properly initialized: using uninitialized data will cause \
                  undefined behavior",
             ),
             MutationOfLayoutConstrainedField => (
                 "mutation of layout constrained field",
                 "mutating layout constrained fields cannot statically be checked for valid values",
             ),
             BorrowOfLayoutConstrainedField => (
                 "borrow of layout constrained field with interior mutability",
                 "references to fields of layout constrained fields lose the constraints. Coupled \
                  with interior mutability, the field can be changed to invalid values",
             ),
             CallToFunctionWith => (
                 "call to function with `#[target_feature]`",
                 "can only be called if the required target features are available",
             ),
         }
     }
 }

 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 pub struct UnsafetyViolation {
     pub source_info: SourceInfo,
     pub lint_root: hir::HirId,
     pub kind: UnsafetyViolationKind,
     pub details: UnsafetyViolationDetails,
 }

 #[derive(Clone, TyEncodable, TyDecodable, HashStable, Debug)]
 pub struct UnsafetyCheckResult {
     /// Violations that are propagated *upwards* from this function.
     pub violations: Lrc<[UnsafetyViolation]>,
     /// `unsafe` blocks in this function, along with whether they are used. This is
     /// used for the "unused_unsafe" lint.
     pub unsafe_blocks: Lrc<[(hir::HirId, bool)]>,
 }

 rustc_index::newtype_index! {
     pub struct GeneratorSavedLocal {
         derive [HashStable]
         DEBUG_FORMAT = "_{}",
     }
 }

 /// The layout of generator state.
 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
 pub struct GeneratorLayout<'tcx> {
     /// The type of every local stored inside the generator.
     pub field_tys: IndexVec<GeneratorSavedLocal, Ty<'tcx>>,

     /// Which of the above fields are in each variant. Note that one field may
     /// be stored in multiple variants.
     pub variant_fields: IndexVec<VariantIdx, IndexVec<Field, GeneratorSavedLocal>>,

     /// The source that led to each variant being created (usually, a yield or
     /// await).
     pub variant_source_info: IndexVec<VariantIdx, SourceInfo>,

     /// Which saved locals are storage-live at the same time. Locals that do not
     /// have conflicts with each other are allowed to overlap in the computed
     /// layout.
     pub storage_conflicts: BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal>,
 }

 impl Debug for GeneratorLayout<'_> {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         /// Prints an iterator of (key, value) tuples as a map.
         struct MapPrinter<'a, K, V>(Cell<Option<Box<dyn Iterator<Item = (K, V)> + 'a>>>);
         impl<'a, K, V> MapPrinter<'a, K, V> {
             fn new(iter: impl Iterator<Item = (K, V)> + 'a) -> Self {
                 Self(Cell::new(Some(Box::new(iter))))
             }
         }
         impl<'a, K: Debug, V: Debug> Debug for MapPrinter<'a, K, V> {
             fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
                 fmt.debug_map().entries(self.0.take().unwrap()).finish()
             }
         }

         /// Prints the generator variant name.
         struct GenVariantPrinter(VariantIdx);
         impl From<VariantIdx> for GenVariantPrinter {
             fn from(idx: VariantIdx) -> Self {
                 GenVariantPrinter(idx)
             }
         }
         impl Debug for GenVariantPrinter {
             fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
                 let variant_name = ty::GeneratorSubsts::variant_name(self.0);
                 if fmt.alternate() {
                     write!(fmt, "{:9}({:?})", variant_name, self.0)
                 } else {
                     write!(fmt, "{}", variant_name)
                 }
             }
         }

         /// Forces its contents to print in regular mode instead of alternate mode.
         struct OneLinePrinter<T>(T);
         impl<T: Debug> Debug for OneLinePrinter<T> {
             fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
                 write!(fmt, "{:?}", self.0)
             }
         }

         fmt.debug_struct("GeneratorLayout")
             .field("field_tys", &MapPrinter::new(self.field_tys.iter_enumerated()))
             .field(
                 "variant_fields",
                 &MapPrinter::new(
                     self.variant_fields
                         .iter_enumerated()
                         .map(|(k, v)| (GenVariantPrinter(k), OneLinePrinter(v))),
                 ),
             )
             .field("storage_conflicts", &self.storage_conflicts)
             .finish()
     }
 }

 #[derive(Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct BorrowCheckResult<'tcx> {
     /// All the opaque types that are restricted to concrete types
     /// by this function. Unlike the value in `TypeckResults`, this has
     /// unerased regions.
     pub concrete_opaque_types: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
     pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
     pub used_mut_upvars: SmallVec<[Field; 8]>,
 }

 /// The result of the `mir_const_qualif` query.
 ///
 /// Each field (except `error_occured`) corresponds to an implementer of the `Qualif` trait in
 /// `rustc_mir/src/transform/check_consts/qualifs.rs`. See that file for more information on each
 /// `Qualif`.
 #[derive(Clone, Copy, Debug, Default, TyEncodable, TyDecodable, HashStable)]
 pub struct ConstQualifs {
     pub has_mut_interior: bool,
     pub needs_drop: bool,
     pub custom_eq: bool,
     pub error_occured: Option<ErrorReported>,
 }

 /// After we borrow check a closure, we are left with various
 /// requirements that we have inferred between the free regions that
 /// appear in the closure's signature or on its field types. These
 /// requirements are then verified and proved by the closure's
 /// creating function. This struct encodes those requirements.
 ///
 /// The requirements are listed as being between various `RegionVid`. The 0th
 /// region refers to `'static`; subsequent region vids refer to the free
 /// regions that appear in the closure (or generator's) type, in order of
 /// appearance. (This numbering is actually defined by the `UniversalRegions`
 /// struct in the NLL region checker. See for example
 /// `UniversalRegions::closure_mapping`.) Note the free regions in the
 /// closure's signature and captures are erased.
 ///
 /// Example: If type check produces a closure with the closure substs:
 ///
 /// ```text
 /// ClosureSubsts = [
 ///     'a,                                         // From the parent.
 ///     'b,
 ///     i8,                                         // the "closure kind"
 ///     for<'x> fn(&'<erased> &'x u32) -> &'x u32,  // the "closure signature"
 ///     &'<erased> String,                          // some upvar
 /// ]
 /// ```
 ///
 /// We would "renumber" each free region to a unique vid, as follows:
 ///
 /// ```text
 /// ClosureSubsts = [
 ///     '1,                                         // From the parent.
 ///     '2,
 ///     i8,                                         // the "closure kind"
 ///     for<'x> fn(&'3 &'x u32) -> &'x u32,         // the "closure signature"
 ///     &'4 String,                                 // some upvar
 /// ]
 /// ```
 ///
 /// Now the code might impose a requirement like `'1: '2`. When an
 /// instance of the closure is created, the corresponding free regions
 /// can be extracted from its type and constrained to have the given
 /// outlives relationship.
 ///
 /// In some cases, we have to record outlives requirements between types and
 /// regions as well. In that case, if those types include any regions, those
 /// regions are recorded using their external names (`ReStatic`,
 /// `ReEarlyBound`, `ReFree`). We use these because in a query response we
 /// cannot use `ReVar` (which is what we use internally within the rest of the
 /// NLL code).
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct ClosureRegionRequirements<'tcx> {
     /// The number of external regions defined on the closure. In our
     /// example above, it would be 3 -- one for `'static`, then `'1`
     /// and `'2`. This is just used for a sanity check later on, to
     /// make sure that the number of regions we see at the callsite
     /// matches.
     pub num_external_vids: usize,

     /// Requirements between the various free regions defined in
     /// indices.
     pub outlives_requirements: Vec<ClosureOutlivesRequirement<'tcx>>,
 }

 /// Indicates an outlives-constraint between a type or between two
 /// free regions declared on the closure.
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct ClosureOutlivesRequirement<'tcx> {
     // This region or type ...
     pub subject: ClosureOutlivesSubject<'tcx>,

     // ... must outlive this one.
     pub outlived_free_region: ty::RegionVid,

     // If not, report an error here ...
     pub blame_span: Span,

     // ... due to this reason.
     pub category: ConstraintCategory,
 }

 /// Outlives-constraints can be categorized to determine whether and why they
 /// are interesting (for error reporting). Order of variants indicates sort
 /// order of the category, thereby influencing diagnostic output.
 ///
 /// See also `rustc_mir::borrow_check::constraints`.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 #[derive(TyEncodable, TyDecodable, HashStable)]
 pub enum ConstraintCategory {
     Return(ReturnConstraint),
     Yield,
     UseAsConst,
     UseAsStatic,
     TypeAnnotation,
     Cast,

     /// A constraint that came from checking the body of a closure.
     ///
     /// We try to get the category that the closure used when reporting this.
     ClosureBounds,
     CallArgument,
     CopyBound,
     SizedBound,
     Assignment,
     OpaqueType,
     ClosureUpvar(hir::HirId),

     /// A "boring" constraint (caused by the given location) is one that
     /// the user probably doesn't want to see described in diagnostics,
     /// because it is kind of an artifact of the type system setup.
     /// Example: `x = Foo { field: y }` technically creates
     /// intermediate regions representing the "type of `Foo { field: y
     /// }`", and data flows from `y` into those variables, but they
     /// are not very interesting. The assignment into `x` on the other
     /// hand might be.
     Boring,
     // Boring and applicable everywhere.
     BoringNoLocation,

     /// A constraint that doesn't correspond to anything the user sees.
     Internal,
 }

 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 #[derive(TyEncodable, TyDecodable, HashStable)]
 pub enum ReturnConstraint {
     Normal,
     ClosureUpvar(hir::HirId),
 }

 /// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
 /// that must outlive some region.
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub enum ClosureOutlivesSubject<'tcx> {
     /// Subject is a type, typically a type parameter, but could also
     /// be a projection. Indicates a requirement like `T: 'a` being
     /// passed to the caller, where the type here is `T`.
     ///
     /// The type here is guaranteed not to contain any free regions at
     /// present.
     Ty(Ty<'tcx>),

     /// Subject is a free region from the closure. Indicates a requirement
     /// like `'a: 'b` being passed to the caller; the region here is `'a`.
     Region(ty::RegionVid),
 }

 /// The constituent parts of an ADT or array.
 #[derive(Copy, Clone, Debug, HashStable)]
 pub struct DestructuredConst<'tcx> {
     pub variant: Option<VariantIdx>,
     pub fields: &'tcx [&'tcx ty::Const<'tcx>],
 }

 /// Coverage information summarized from a MIR if instrumented for source code coverage (see
 /// compiler option `-Zinstrument-coverage`). This information is generated by the
 /// `InstrumentCoverage` MIR pass and can be retrieved via the `coverageinfo` query.
 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable)]
 pub struct CoverageInfo {
     /// The total number of coverage region counters added to the MIR `Body`.
     pub num_counters: u32,

     /// The total number of coverage region counter expressions added to the MIR `Body`.
     pub num_expressions: u32,
 }

 /// Shims which make dealing with `WithOptConstParam` easier.
 ///
 /// For more information on why this is needed, consider looking
 /// at the docs for `WithOptConstParam` itself.
 impl<'tcx> TyCtxt<'tcx> {
     #[inline]
     pub fn mir_const_qualif_opt_const_arg(
         self,
         def: ty::WithOptConstParam<LocalDefId>,
     ) -> ConstQualifs {
         if let Some(param_did) = def.const_param_did {
             self.mir_const_qualif_const_arg((def.did, param_did))
         } else {
             self.mir_const_qualif(def.did)
         }
     }

     #[inline]
     pub fn promoted_mir_opt_const_arg(
         self,
         def: ty::WithOptConstParam<DefId>,
     ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
         if let Some((did, param_did)) = def.as_const_arg() {
             self.promoted_mir_of_const_arg((did, param_did))
         } else {
             self.promoted_mir(def.did)
         }
     }

     #[inline]
     pub fn mir_for_ctfe_opt_const_arg(self, def: ty::WithOptConstParam<DefId>) -> &'tcx Body<'tcx> {
         if let Some((did, param_did)) = def.as_const_arg() {
             self.mir_for_ctfe_of_const_arg((did, param_did))
         } else {
             self.mir_for_ctfe(def.did)
         }
     }

     #[inline]
     pub fn mir_abstract_const_opt_const_arg(
         self,
         def: ty::WithOptConstParam<DefId>,
     ) -> Result<Option<&'tcx [abstract_const::Node<'tcx>]>, ErrorReported> {
         if let Some((did, param_did)) = def.as_const_arg() {
             self.mir_abstract_const_of_const_arg((did, param_did))
         } else {
             self.mir_abstract_const(def.did)
         }
     }
 }
	//! Values computed by queries that use MIR.

	use crate::mir::{abstract_const, Body, Promoted};
	use crate::ty::{self, Ty, TyCtxt};
	use rustc_data_structures::fx::FxHashMap;
	use rustc_data_structures::sync::Lrc;
	use rustc_errors::ErrorReported;
	use rustc_hir as hir;
	use rustc_hir::def_id::{DefId, LocalDefId};
	use rustc_index::bit_set::BitMatrix;
	use rustc_index::vec::IndexVec;
	use rustc_span::Span;
	use rustc_target::abi::VariantIdx;
	use smallvec::SmallVec;
	use std::cell::Cell;
	use std::fmt::{self, Debug};

	use super::{Field, SourceInfo};

	#[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
	pub enum UnsafetyViolationKind {
	/// Unsafe operation outside `unsafe`.
	General,
	/// Unsafe operation in an `unsafe fn` but outside an `unsafe` block.
	/// Has to be handled as a lint for backwards compatibility.
	UnsafeFn,
	}

	#[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
	pub enum UnsafetyViolationDetails {
	CallToUnsafeFunction,
	UseOfInlineAssembly,
	InitializingTypeWith,
	CastOfPointerToInt,
	BorrowOfPackedField,
	UseOfMutableStatic,
	UseOfExternStatic,
	DerefOfRawPointer,
	AssignToDroppingUnionField,
	AccessToUnionField,
	MutationOfLayoutConstrainedField,
	BorrowOfLayoutConstrainedField,
	CallToFunctionWith,
	}

	impl UnsafetyViolationDetails {
	pub fn description_and_note(&self) -> (&'static str, &'static str) {
	use UnsafetyViolationDetails::*;
	match self {
	CallToUnsafeFunction => (
	"call to unsafe function",
	"consult the function's documentation for information on how to avoid undefined \
	behavior",
	),
	UseOfInlineAssembly => (
	"use of inline assembly",
	"inline assembly is entirely unchecked and can cause undefined behavior",
	),
	InitializingTypeWith => (
	"initializing type with `rustc_layout_scalar_valid_range` attr",
	"initializing a layout restricted type's field with a value outside the valid \
	range is undefined behavior",
	),
	CastOfPointerToInt => {
	("cast of pointer to int", "casting pointers to integers in constants")
	}
	BorrowOfPackedField => (
	"borrow of packed field",
	"fields of packed structs might be misaligned: dereferencing a misaligned pointer \
	or even just creating a misaligned reference is undefined behavior",
	),
	UseOfMutableStatic => (
	"use of mutable static",
	"mutable statics can be mutated by multiple threads: aliasing violations or data \
	races will cause undefined behavior",
	),
	UseOfExternStatic => (
	"use of extern static",
	"extern statics are not controlled by the Rust type system: invalid data, \
	aliasing violations or data races will cause undefined behavior",
	),
	DerefOfRawPointer => (
	"dereference of raw pointer",
	"raw pointers may be NULL, dangling or unaligned; they can violate aliasing rules \
	and cause data races: all of these are undefined behavior",
	),
	AssignToDroppingUnionField => (
	"assignment to union field that might need dropping",
	"the previous content of the field will be dropped, which causes undefined \
	behavior if the field was not properly initialized",
	),
	AccessToUnionField => (
	"access to union field",
	"the field may not be properly initialized: using uninitialized data will cause \
	undefined behavior",
	),
	MutationOfLayoutConstrainedField => (
	"mutation of layout constrained field",
	"mutating layout constrained fields cannot statically be checked for valid values",
	),
	BorrowOfLayoutConstrainedField => (
	"borrow of layout constrained field with interior mutability",
	"references to fields of layout constrained fields lose the constraints. Coupled \
	with interior mutability, the field can be changed to invalid values",
	),
	CallToFunctionWith => (
	"call to function with `#[target_feature]`",
	"can only be called if the required target features are available",
	),
	}
	}
	}

	#[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
	pub struct UnsafetyViolation {
	pub source_info: SourceInfo,
	pub lint_root: hir::HirId,
	pub kind: UnsafetyViolationKind,
	pub details: UnsafetyViolationDetails,
	}

	#[derive(Clone, TyEncodable, TyDecodable, HashStable, Debug)]
	pub struct UnsafetyCheckResult {
	/// Violations that are propagated upwards from this function.
	pub violations: Lrc<[UnsafetyViolation]>,
	/// `unsafe` blocks in this function, along with whether they are used. This is
	/// used for the "unused_unsafe" lint.
	pub unsafe_blocks: Lrc<[(hir::HirId, bool)]>,
	}

	rustc_index::newtype_index! {
	pub struct GeneratorSavedLocal {
	derive [HashStable]
	DEBUG_FORMAT = "_{}",
	}
	}

	/// The layout of generator state.
	#[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable)]
	pub struct GeneratorLayout<'tcx> {
	/// The type of every local stored inside the generator.
	pub field_tys: IndexVec<GeneratorSavedLocal, Ty<'tcx>>,

	/// Which of the above fields are in each variant. Note that one field may
	/// be stored in multiple variants.
	pub variant_fields: IndexVec<VariantIdx, IndexVec<Field, GeneratorSavedLocal>>,

	/// The source that led to each variant being created (usually, a yield or
	/// await).
	pub variant_source_info: IndexVec<VariantIdx, SourceInfo>,

	/// Which saved locals are storage-live at the same time. Locals that do not
	/// have conflicts with each other are allowed to overlap in the computed
	/// layout.
	pub storage_conflicts: BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal>,
	}

	impl Debug for GeneratorLayout<'_> {
	fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
	/// Prints an iterator of (key, value) tuples as a map.
	struct MapPrinter<'a, K, V>(Cell<Option<Box<dyn Iterator<Item = (K, V)> + 'a>>>);
	impl<'a, K, V> MapPrinter<'a, K, V> {
	fn new(iter: impl Iterator<Item = (K, V)> + 'a) -> Self {
	Self(Cell::new(Some(Box::new(iter))))
	}
	}
	impl<'a, K: Debug, V: Debug> Debug for MapPrinter<'a, K, V> {
	fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
	fmt.debug_map().entries(self.0.take().unwrap()).finish()
	}
	}

	/// Prints the generator variant name.
	struct GenVariantPrinter(VariantIdx);
	impl From<VariantIdx> for GenVariantPrinter {
	fn from(idx: VariantIdx) -> Self {
	GenVariantPrinter(idx)
	}
	}
	impl Debug for GenVariantPrinter {
	fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
	let variant_name = ty::GeneratorSubsts::variant_name(self.0);
	if fmt.alternate() {
	write!(fmt, "{:9}({:?})", variant_name, self.0)
	} else {
	write!(fmt, "{}", variant_name)
	}
	}
	}

	/// Forces its contents to print in regular mode instead of alternate mode.
	struct OneLinePrinter<T>(T);
	impl<T: Debug> Debug for OneLinePrinter<T> {
	fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
	write!(fmt, "{:?}", self.0)
	}
	}

	fmt.debug_struct("GeneratorLayout")
	.field("field_tys", &MapPrinter::new(self.field_tys.iter_enumerated()))
	.field(
	"variant_fields",
	&MapPrinter::new(
	self.variant_fields
	.iter_enumerated()
	.map(\|(k, v)\| (GenVariantPrinter(k), OneLinePrinter(v))),
	),
	)
	.field("storage_conflicts", &self.storage_conflicts)
	.finish()
	}
	}

	#[derive(Debug, TyEncodable, TyDecodable, HashStable)]
	pub struct BorrowCheckResult<'tcx> {
	/// All the opaque types that are restricted to concrete types
	/// by this function. Unlike the value in `TypeckResults`, this has
	/// unerased regions.
	pub concrete_opaque_types: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
	pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
	pub used_mut_upvars: SmallVec<[Field; 8]>,
	}

	/// The result of the `mir_const_qualif` query.
	///
	/// Each field (except `error_occured`) corresponds to an implementer of the `Qualif` trait in
	/// `rustc_mir/src/transform/check_consts/qualifs.rs`. See that file for more information on each
	/// `Qualif`.
	#[derive(Clone, Copy, Debug, Default, TyEncodable, TyDecodable, HashStable)]
	pub struct ConstQualifs {
	pub has_mut_interior: bool,
	pub needs_drop: bool,
	pub custom_eq: bool,
	pub error_occured: Option<ErrorReported>,
	}

	/// After we borrow check a closure, we are left with various
	/// requirements that we have inferred between the free regions that
	/// appear in the closure's signature or on its field types. These
	/// requirements are then verified and proved by the closure's
	/// creating function. This struct encodes those requirements.
	///
	/// The requirements are listed as being between various `RegionVid`. The 0th
	/// region refers to `'static`; subsequent region vids refer to the free
	/// regions that appear in the closure (or generator's) type, in order of
	/// appearance. (This numbering is actually defined by the `UniversalRegions`
	/// struct in the NLL region checker. See for example
	/// `UniversalRegions::closure_mapping`.) Note the free regions in the
	/// closure's signature and captures are erased.
	///
	/// Example: If type check produces a closure with the closure substs:
	///
	/// ```text
	/// ClosureSubsts = [
	/// 'a, // From the parent.
	/// 'b,
	/// i8, // the "closure kind"
	/// for<'x> fn(&'<erased> &'x u32) -> &'x u32, // the "closure signature"
	/// &'<erased> String, // some upvar
	/// ]
	/// ```
	///
	/// We would "renumber" each free region to a unique vid, as follows:
	///
	/// ```text
	/// ClosureSubsts = [
	/// '1, // From the parent.
	/// '2,
	/// i8, // the "closure kind"
	/// for<'x> fn(&'3 &'x u32) -> &'x u32, // the "closure signature"
	/// &'4 String, // some upvar
	/// ]
	/// ```
	///
	/// Now the code might impose a requirement like `'1: '2`. When an
	/// instance of the closure is created, the corresponding free regions
	/// can be extracted from its type and constrained to have the given
	/// outlives relationship.
	///
	/// In some cases, we have to record outlives requirements between types and
	/// regions as well. In that case, if those types include any regions, those
	/// regions are recorded using their external names (`ReStatic`,
	/// `ReEarlyBound`, `ReFree`). We use these because in a query response we
	/// cannot use `ReVar` (which is what we use internally within the rest of the
	/// NLL code).
	#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
	pub struct ClosureRegionRequirements<'tcx> {
	/// The number of external regions defined on the closure. In our
	/// example above, it would be 3 -- one for `'static`, then `'1`
	/// and `'2`. This is just used for a sanity check later on, to
	/// make sure that the number of regions we see at the callsite
	/// matches.
	pub num_external_vids: usize,

	/// Requirements between the various free regions defined in
	/// indices.
	pub outlives_requirements: Vec<ClosureOutlivesRequirement<'tcx>>,
	}

	/// Indicates an outlives-constraint between a type or between two
	/// free regions declared on the closure.
	#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
	pub struct ClosureOutlivesRequirement<'tcx> {
	// This region or type ...
	pub subject: ClosureOutlivesSubject<'tcx>,

	// ... must outlive this one.
	pub outlived_free_region: ty::RegionVid,

	// If not, report an error here ...
	pub blame_span: Span,

	// ... due to this reason.
	pub category: ConstraintCategory,
	}

	/// Outlives-constraints can be categorized to determine whether and why they
	/// are interesting (for error reporting). Order of variants indicates sort
	/// order of the category, thereby influencing diagnostic output.
	///
	/// See also `rustc_mir::borrow_check::constraints`.
	#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
	#[derive(TyEncodable, TyDecodable, HashStable)]
	pub enum ConstraintCategory {
	Return(ReturnConstraint),
	Yield,
	UseAsConst,
	UseAsStatic,
	TypeAnnotation,
	Cast,

	/// A constraint that came from checking the body of a closure.
	///
	/// We try to get the category that the closure used when reporting this.
	ClosureBounds,
	CallArgument,
	CopyBound,
	SizedBound,
	Assignment,
	OpaqueType,
	ClosureUpvar(hir::HirId),

	/// A "boring" constraint (caused by the given location) is one that
	/// the user probably doesn't want to see described in diagnostics,
	/// because it is kind of an artifact of the type system setup.
	/// Example: `x = Foo { field: y }` technically creates
	/// intermediate regions representing the "type of `Foo { field: y
	/// }`", and data flows from `y` into those variables, but they
	/// are not very interesting. The assignment into `x` on the other
	/// hand might be.
	Boring,
	// Boring and applicable everywhere.
	BoringNoLocation,

	/// A constraint that doesn't correspond to anything the user sees.
	Internal,
	}

	#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
	#[derive(TyEncodable, TyDecodable, HashStable)]
	pub enum ReturnConstraint {
	Normal,
	ClosureUpvar(hir::HirId),
	}

	/// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
	/// that must outlive some region.
	#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
	pub enum ClosureOutlivesSubject<'tcx> {
	/// Subject is a type, typically a type parameter, but could also
	/// be a projection. Indicates a requirement like `T: 'a` being
	/// passed to the caller, where the type here is `T`.
	///
	/// The type here is guaranteed not to contain any free regions at
	/// present.
	Ty(Ty<'tcx>),

	/// Subject is a free region from the closure. Indicates a requirement
	/// like `'a: 'b` being passed to the caller; the region here is `'a`.
	Region(ty::RegionVid),
	}

	/// The constituent parts of an ADT or array.
	#[derive(Copy, Clone, Debug, HashStable)]
	pub struct DestructuredConst<'tcx> {
	pub variant: Option<VariantIdx>,
	pub fields: &'tcx [&'tcx ty::Const<'tcx>],
	}

	/// Coverage information summarized from a MIR if instrumented for source code coverage (see
	/// compiler option `-Zinstrument-coverage`). This information is generated by the
	/// `InstrumentCoverage` MIR pass and can be retrieved via the `coverageinfo` query.
	#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable)]
	pub struct CoverageInfo {
	/// The total number of coverage region counters added to the MIR `Body`.
	pub num_counters: u32,

	/// The total number of coverage region counter expressions added to the MIR `Body`.
	pub num_expressions: u32,
	}

	/// Shims which make dealing with `WithOptConstParam` easier.
	///
	/// For more information on why this is needed, consider looking
	/// at the docs for `WithOptConstParam` itself.
	impl<'tcx> TyCtxt<'tcx> {
	#[inline]
	pub fn mir_const_qualif_opt_const_arg(
	self,
	def: ty::WithOptConstParam<LocalDefId>,
	) -> ConstQualifs {
	if let Some(param_did) = def.const_param_did {
	self.mir_const_qualif_const_arg((def.did, param_did))
	} else {
	self.mir_const_qualif(def.did)
	}
	}

	#[inline]
	pub fn promoted_mir_opt_const_arg(
	self,
	def: ty::WithOptConstParam<DefId>,
	) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
	if let Some((did, param_did)) = def.as_const_arg() {
	self.promoted_mir_of_const_arg((did, param_did))
	} else {
	self.promoted_mir(def.did)
	}
	}

	#[inline]
	pub fn mir_for_ctfe_opt_const_arg(self, def: ty::WithOptConstParam<DefId>) -> &'tcx Body<'tcx> {
	if let Some((did, param_did)) = def.as_const_arg() {
	self.mir_for_ctfe_of_const_arg((did, param_did))
	} else {
	self.mir_for_ctfe(def.did)
	}
	}

	#[inline]
	pub fn mir_abstract_const_opt_const_arg(
	self,
	def: ty::WithOptConstParam<DefId>,
	) -> Result<Option<&'tcx [abstract_const::Node<'tcx>]>, ErrorReported> {
	if let Some((did, param_did)) = def.as_const_arg() {
	self.mir_abstract_const_of_const_arg((did, param_did))
	} else {
	self.mir_abstract_const(def.did)
	}
	}
	}