Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 821 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
new file mode 100644
index 000000000..b856af1d8
--- /dev/null
+++ b/compiler/rustc_middle/src/thir.rs
@@ -0,0 +1,821 @@
+//! THIR datatypes and definitions. See the [rustc dev guide] for more info.
+//!
+//! If you compare the THIR [`ExprKind`] to [`hir::ExprKind`], you will see it is
+//! a good bit simpler. In fact, a number of the more straight-forward
+//! MIR simplifications are already done in the lowering to THIR. For
+//! example, method calls and overloaded operators are absent: they are
+//! expected to be converted into [`ExprKind::Call`] instances.
+//!
+//! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/thir.html
+
+use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
+use rustc_hir as hir;
+use rustc_hir::def::CtorKind;
+use rustc_hir::def_id::DefId;
+use rustc_hir::RangeEnd;
+use rustc_index::newtype_index;
+use rustc_index::vec::IndexVec;
+use rustc_middle::infer::canonical::Canonical;
+use rustc_middle::middle::region;
+use rustc_middle::mir::interpret::AllocId;
+use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Field, Mutability, UnOp};
+use rustc_middle::ty::adjustment::PointerCast;
+use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::CanonicalUserTypeAnnotation;
+use rustc_middle::ty::{self, AdtDef, Ty, UpvarSubsts, UserType};
+use rustc_span::{Span, Symbol, DUMMY_SP};
+use rustc_target::abi::VariantIdx;
+use rustc_target::asm::InlineAsmRegOrRegClass;
+
+use rustc_span::def_id::LocalDefId;
+use std::fmt;
+use std::ops::Index;
+
+pub mod visit;
+
+newtype_index! {
+    /// An index to an [`Arm`] stored in [`Thir::arms`]
+    #[derive(HashStable)]
+    pub struct ArmId {
+        DEBUG_FORMAT = "a{}"
+    }
+}
+
+newtype_index! {
+    /// An index to an [`Expr`] stored in [`Thir::exprs`]
+    #[derive(HashStable)]
+    pub struct ExprId {
+        DEBUG_FORMAT = "e{}"
+    }
+}
+
+newtype_index! {
+    #[derive(HashStable)]
+    /// An index to a [`Stmt`] stored in [`Thir::stmts`]
+    pub struct StmtId {
+        DEBUG_FORMAT = "s{}"
+    }
+}
+
+macro_rules! thir_with_elements {
+    ($($name:ident: $id:ty => $value:ty,)*) => {
+        /// A container for a THIR body.
+        ///
+        /// This can be indexed directly by any THIR index (e.g. [`ExprId`]).
+        #[derive(Debug, HashStable, Clone)]
+        pub struct Thir<'tcx> {
+            $(
+                pub $name: IndexVec<$id, $value>,
+            )*
+        }
+
+        impl<'tcx> Thir<'tcx> {
+            pub fn new() -> Thir<'tcx> {
+                Thir {
+                    $(
+                        $name: IndexVec::new(),
+                    )*
+                }
+            }
+        }
+
+        $(
+            impl<'tcx> Index<$id> for Thir<'tcx> {
+                type Output = $value;
+                fn index(&self, index: $id) -> &Self::Output {
+                    &self.$name[index]
+                }
+            }
+        )*
+    }
+}
+
+thir_with_elements! {
+    arms: ArmId => Arm<'tcx>,
+    exprs: ExprId => Expr<'tcx>,
+    stmts: StmtId => Stmt<'tcx>,
+}
+
+#[derive(Copy, Clone, Debug, HashStable)]
+pub enum LintLevel {
+    Inherited,
+    Explicit(hir::HirId),
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub struct Block {
+    /// Whether the block itself has a label. Used by `label: {}`
+    /// and `try` blocks.
+    ///
+    /// This does *not* include labels on loops, e.g. `'label: loop {}`.
+    pub targeted_by_break: bool,
+    pub region_scope: region::Scope,
+    pub opt_destruction_scope: Option<region::Scope>,
+    /// The span of the block, including the opening braces,
+    /// the label, and the `unsafe` keyword, if present.
+    pub span: Span,
+    /// The statements in the blocK.
+    pub stmts: Box<[StmtId]>,
+    /// The trailing expression of the block, if any.
+    pub expr: Option<ExprId>,
+    pub safety_mode: BlockSafety,
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub struct Adt<'tcx> {
+    /// The ADT we're constructing.
+    pub adt_def: AdtDef<'tcx>,
+    /// The variant of the ADT.
+    pub variant_index: VariantIdx,
+    pub substs: SubstsRef<'tcx>,
+
+    /// Optional user-given substs: for something like `let x =
+    /// Bar::<T> { ... }`.
+    pub user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
+
+    pub fields: Box<[FieldExpr]>,
+    /// The base, e.g. `Foo {x: 1, .. base}`.
+    pub base: Option<FruInfo<'tcx>>,
+}
+
+#[derive(Copy, Clone, Debug, HashStable)]
+pub enum BlockSafety {
+    Safe,
+    /// A compiler-generated unsafe block
+    BuiltinUnsafe,
+    /// An `unsafe` block. The `HirId` is the ID of the block.
+    ExplicitUnsafe(hir::HirId),
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub struct Stmt<'tcx> {
+    pub kind: StmtKind<'tcx>,
+    pub opt_destruction_scope: Option<region::Scope>,
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub enum StmtKind<'tcx> {
+    /// An expression with a trailing semicolon.
+    Expr {
+        /// The scope for this statement; may be used as lifetime of temporaries.
+        scope: region::Scope,
+
+        /// The expression being evaluated in this statement.
+        expr: ExprId,
+    },
+
+    /// A `let` binding.
+    Let {
+        /// The scope for variables bound in this `let`; it covers this and
+        /// all the remaining statements in the block.
+        remainder_scope: region::Scope,
+
+        /// The scope for the initialization itself; might be used as
+        /// lifetime of temporaries.
+        init_scope: region::Scope,
+
+        /// `let <PAT> = ...`
+        ///
+        /// If a type annotation is included, it is added as an ascription pattern.
+        pattern: Pat<'tcx>,
+
+        /// `let pat: ty = <INIT>`
+        initializer: Option<ExprId>,
+
+        /// `let pat: ty = <INIT> else { <ELSE> }
+        else_block: Option<Block>,
+
+        /// The lint level for this `let` statement.
+        lint_level: LintLevel,
+    },
+}
+
+#[derive(Clone, Debug, Copy, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeFoldable, TypeVisitable)]
+pub struct LocalVarId(pub hir::HirId);
+
+/// A THIR expression.
+#[derive(Clone, Debug, HashStable)]
+pub struct Expr<'tcx> {
+    /// The type of this expression
+    pub ty: Ty<'tcx>,
+
+    /// The lifetime of this expression if it should be spilled into a
+    /// temporary; should be `None` only if in a constant context
+    pub temp_lifetime: Option<region::Scope>,
+
+    /// span of the expression in the source
+    pub span: Span,
+
+    /// kind of expression
+    pub kind: ExprKind<'tcx>,
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub enum ExprKind<'tcx> {
+    /// `Scope`s are used to explicitly mark destruction scopes,
+    /// and to track the `HirId` of the expressions within the scope.
+    Scope {
+        region_scope: region::Scope,
+        lint_level: LintLevel,
+        value: ExprId,
+    },
+    /// A `box <value>` expression.
+    Box {
+        value: ExprId,
+    },
+    /// An `if` expression.
+    If {
+        if_then_scope: region::Scope,
+        cond: ExprId,
+        then: ExprId,
+        else_opt: Option<ExprId>,
+    },
+    /// A function call. Method calls and overloaded operators are converted to plain function calls.
+    Call {
+        /// The type of the function. This is often a [`FnDef`] or a [`FnPtr`].
+        ///
+        /// [`FnDef`]: ty::TyKind::FnDef
+        /// [`FnPtr`]: ty::TyKind::FnPtr
+        ty: Ty<'tcx>,
+        /// The function itself.
+        fun: ExprId,
+        /// The arguments passed to the function.
+        ///
+        /// Note: in some cases (like calling a closure), the function call `f(...args)` gets
+        /// rewritten as a call to a function trait method (e.g. `FnOnce::call_once(f, (...args))`).
+        args: Box<[ExprId]>,
+        /// Whether this is from an overloaded operator rather than a
+        /// function call from HIR. `true` for overloaded function call.
+        from_hir_call: bool,
+        /// The span of the function, without the dot and receiver
+        /// (e.g. `foo(a, b)` in `x.foo(a, b)`).
+        fn_span: Span,
+    },
+    /// A *non-overloaded* dereference.
+    Deref {
+        arg: ExprId,
+    },
+    /// A *non-overloaded* binary operation.
+    Binary {
+        op: BinOp,
+        lhs: ExprId,
+        rhs: ExprId,
+    },
+    /// A logical operation. This is distinct from `BinaryOp` because
+    /// the operands need to be lazily evaluated.
+    LogicalOp {
+        op: LogicalOp,
+        lhs: ExprId,
+        rhs: ExprId,
+    },
+    /// A *non-overloaded* unary operation. Note that here the deref (`*`)
+    /// operator is represented by `ExprKind::Deref`.
+    Unary {
+        op: UnOp,
+        arg: ExprId,
+    },
+    /// A cast: `<source> as <type>`. The type we cast to is the type of
+    /// the parent expression.
+    Cast {
+        source: ExprId,
+    },
+    Use {
+        source: ExprId,
+    }, // Use a lexpr to get a vexpr.
+    /// A coercion from `!` to any type.
+    NeverToAny {
+        source: ExprId,
+    },
+    /// A pointer cast. More information can be found in [`PointerCast`].
+    Pointer {
+        cast: PointerCast,
+        source: ExprId,
+    },
+    /// A `loop` expression.
+    Loop {
+        body: ExprId,
+    },
+    Let {
+        expr: ExprId,
+        pat: Pat<'tcx>,
+    },
+    /// A `match` expression.
+    Match {
+        scrutinee: ExprId,
+        arms: Box<[ArmId]>,
+    },
+    /// A block.
+    Block {
+        body: Block,
+    },
+    /// An assignment: `lhs = rhs`.
+    Assign {
+        lhs: ExprId,
+        rhs: ExprId,
+    },
+    /// A *non-overloaded* operation assignment, e.g. `lhs += rhs`.
+    AssignOp {
+        op: BinOp,
+        lhs: ExprId,
+        rhs: ExprId,
+    },
+    /// Access to a field of a struct, a tuple, an union, or an enum.
+    Field {
+        lhs: ExprId,
+        /// Variant containing the field.
+        variant_index: VariantIdx,
+        /// This can be a named (`.foo`) or unnamed (`.0`) field.
+        name: Field,
+    },
+    /// A *non-overloaded* indexing operation.
+    Index {
+        lhs: ExprId,
+        index: ExprId,
+    },
+    /// A local variable.
+    VarRef {
+        id: LocalVarId,
+    },
+    /// Used to represent upvars mentioned in a closure/generator
+    UpvarRef {
+        /// DefId of the closure/generator
+        closure_def_id: DefId,
+
+        /// HirId of the root variable
+        var_hir_id: LocalVarId,
+    },
+    /// A borrow, e.g. `&arg`.
+    Borrow {
+        borrow_kind: BorrowKind,
+        arg: ExprId,
+    },
+    /// A `&raw [const|mut] $place_expr` raw borrow resulting in type `*[const|mut] T`.
+    AddressOf {
+        mutability: hir::Mutability,
+        arg: ExprId,
+    },
+    /// A `break` expression.
+    Break {
+        label: region::Scope,
+        value: Option<ExprId>,
+    },
+    /// A `continue` expression.
+    Continue {
+        label: region::Scope,
+    },
+    /// A `return` expression.
+    Return {
+        value: Option<ExprId>,
+    },
+    /// An inline `const` block, e.g. `const {}`.
+    ConstBlock {
+        did: DefId,
+        substs: SubstsRef<'tcx>,
+    },
+    /// An array literal constructed from one repeated element, e.g. `[1; 5]`.
+    Repeat {
+        value: ExprId,
+        count: ty::Const<'tcx>,
+    },
+    /// An array, e.g. `[a, b, c, d]`.
+    Array {
+        fields: Box<[ExprId]>,
+    },
+    /// A tuple, e.g. `(a, b, c, d)`.
+    Tuple {
+        fields: Box<[ExprId]>,
+    },
+    /// An ADT constructor, e.g. `Foo {x: 1, y: 2}`.
+    Adt(Box<Adt<'tcx>>),
+    /// A type ascription on a place.
+    PlaceTypeAscription {
+        source: ExprId,
+        /// Type that the user gave to this expression
+        user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
+    },
+    /// A type ascription on a value, e.g. `42: i32`.
+    ValueTypeAscription {
+        source: ExprId,
+        /// Type that the user gave to this expression
+        user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
+    },
+    /// A closure definition.
+    Closure {
+        closure_id: LocalDefId,
+        substs: UpvarSubsts<'tcx>,
+        upvars: Box<[ExprId]>,
+        movability: Option<hir::Movability>,
+        fake_reads: Vec<(ExprId, FakeReadCause, hir::HirId)>,
+    },
+    /// A literal.
+    Literal {
+        lit: &'tcx hir::Lit,
+        neg: bool,
+    },
+    /// For literals that don't correspond to anything in the HIR
+    NonHirLiteral {
+        lit: ty::ScalarInt,
+        user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
+    },
+    /// A literal of a ZST type.
+    ZstLiteral {
+        user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
+    },
+    /// Associated constants and named constants
+    NamedConst {
+        def_id: DefId,
+        substs: SubstsRef<'tcx>,
+        user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
+    },
+    ConstParam {
+        param: ty::ParamConst,
+        def_id: DefId,
+    },
+    // FIXME improve docs for `StaticRef` by distinguishing it from `NamedConst`
+    /// A literal containing the address of a `static`.
+    ///
+    /// This is only distinguished from `Literal` so that we can register some
+    /// info for diagnostics.
+    StaticRef {
+        alloc_id: AllocId,
+        ty: Ty<'tcx>,
+        def_id: DefId,
+    },
+    /// Inline assembly, i.e. `asm!()`.
+    InlineAsm {
+        template: &'tcx [InlineAsmTemplatePiece],
+        operands: Box<[InlineAsmOperand<'tcx>]>,
+        options: InlineAsmOptions,
+        line_spans: &'tcx [Span],
+    },
+    /// An expression taking a reference to a thread local.
+    ThreadLocalRef(DefId),
+    /// A `yield` expression.
+    Yield {
+        value: ExprId,
+    },
+}
+
+/// Represents the association of a field identifier and an expression.
+///
+/// This is used in struct constructors.
+#[derive(Clone, Debug, HashStable)]
+pub struct FieldExpr {
+    pub name: Field,
+    pub expr: ExprId,
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub struct FruInfo<'tcx> {
+    pub base: ExprId,
+    pub field_types: Box<[Ty<'tcx>]>,
+}
+
+/// A `match` arm.
+#[derive(Clone, Debug, HashStable)]
+pub struct Arm<'tcx> {
+    pub pattern: Pat<'tcx>,
+    pub guard: Option<Guard<'tcx>>,
+    pub body: ExprId,
+    pub lint_level: LintLevel,
+    pub scope: region::Scope,
+    pub span: Span,
+}
+
+/// A `match` guard.
+#[derive(Clone, Debug, HashStable)]
+pub enum Guard<'tcx> {
+    If(ExprId),
+    IfLet(Pat<'tcx>, ExprId),
+}
+
+#[derive(Copy, Clone, Debug, HashStable)]
+pub enum LogicalOp {
+    /// The `&&` operator.
+    And,
+    /// The `||` operator.
+    Or,
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub enum InlineAsmOperand<'tcx> {
+    In {
+        reg: InlineAsmRegOrRegClass,
+        expr: ExprId,
+    },
+    Out {
+        reg: InlineAsmRegOrRegClass,
+        late: bool,
+        expr: Option<ExprId>,
+    },
+    InOut {
+        reg: InlineAsmRegOrRegClass,
+        late: bool,
+        expr: ExprId,
+    },
+    SplitInOut {
+        reg: InlineAsmRegOrRegClass,
+        late: bool,
+        in_expr: ExprId,
+        out_expr: Option<ExprId>,
+    },
+    Const {
+        value: mir::ConstantKind<'tcx>,
+        span: Span,
+    },
+    SymFn {
+        value: mir::ConstantKind<'tcx>,
+        span: Span,
+    },
+    SymStatic {
+        def_id: DefId,
+    },
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, HashStable)]
+pub enum BindingMode {
+    ByValue,
+    ByRef(BorrowKind),
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub struct FieldPat<'tcx> {
+    pub field: Field,
+    pub pattern: Pat<'tcx>,
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub struct Pat<'tcx> {
+    pub ty: Ty<'tcx>,
+    pub span: Span,
+    pub kind: Box<PatKind<'tcx>>,
+}
+
+impl<'tcx> Pat<'tcx> {
+    pub fn wildcard_from_ty(ty: Ty<'tcx>) -> Self {
+        Pat { ty, span: DUMMY_SP, kind: Box::new(PatKind::Wild) }
+    }
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub struct Ascription<'tcx> {
+    pub annotation: CanonicalUserTypeAnnotation<'tcx>,
+    /// Variance to use when relating the `user_ty` to the **type of the value being
+    /// matched**. Typically, this is `Variance::Covariant`, since the value being matched must
+    /// have a type that is some subtype of the ascribed type.
+    ///
+    /// Note that this variance does not apply for any bindings within subpatterns. The type
+    /// assigned to those bindings must be exactly equal to the `user_ty` given here.
+    ///
+    /// The only place where this field is not `Covariant` is when matching constants, where
+    /// we currently use `Contravariant` -- this is because the constant type just needs to
+    /// be "comparable" to the type of the input value. So, for example:
+    ///
+    /// ```text
+    /// match x { "foo" => .. }
+    /// ```
+    ///
+    /// requires that `&'static str <: T_x`, where `T_x` is the type of `x`. Really, we should
+    /// probably be checking for a `PartialEq` impl instead, but this preserves the behavior
+    /// of the old type-check for now. See #57280 for details.
+    pub variance: ty::Variance,
+}
+
+#[derive(Clone, Debug, HashStable)]
+pub enum PatKind<'tcx> {
+    /// A wildcard pattern: `_`.
+    Wild,
+
+    AscribeUserType {
+        ascription: Ascription<'tcx>,
+        subpattern: Pat<'tcx>,
+    },
+
+    /// `x`, `ref x`, `x @ P`, etc.
+    Binding {
+        mutability: Mutability,
+        name: Symbol,
+        mode: BindingMode,
+        var: LocalVarId,
+        ty: Ty<'tcx>,
+        subpattern: Option<Pat<'tcx>>,
+        /// Is this the leftmost occurrence of the binding, i.e., is `var` the
+        /// `HirId` of this pattern?
+        is_primary: bool,
+    },
+
+    /// `Foo(...)` or `Foo{...}` or `Foo`, where `Foo` is a variant name from an ADT with
+    /// multiple variants.
+    Variant {
+        adt_def: AdtDef<'tcx>,
+        substs: SubstsRef<'tcx>,
+        variant_index: VariantIdx,
+        subpatterns: Vec<FieldPat<'tcx>>,
+    },
+
+    /// `(...)`, `Foo(...)`, `Foo{...}`, or `Foo`, where `Foo` is a variant name from an ADT with
+    /// a single variant.
+    Leaf {
+        subpatterns: Vec<FieldPat<'tcx>>,
+    },
+
+    /// `box P`, `&P`, `&mut P`, etc.
+    Deref {
+        subpattern: Pat<'tcx>,
+    },
+
+    /// One of the following:
+    /// * `&str`, which will be handled as a string pattern and thus exhaustiveness
+    ///   checking will detect if you use the same string twice in different patterns.
+    /// * integer, bool, char or float, which will be handled by exhaustiveness to cover exactly
+    ///   its own value, similar to `&str`, but these values are much simpler.
+    /// * Opaque constants, that must not be matched structurally. So anything that does not derive
+    ///   `PartialEq` and `Eq`.
+    Constant {
+        value: mir::ConstantKind<'tcx>,
+    },
+
+    Range(PatRange<'tcx>),
+
+    /// Matches against a slice, checking the length and extracting elements.
+    /// irrefutable when there is a slice pattern and both `prefix` and `suffix` are empty.
+    /// e.g., `&[ref xs @ ..]`.
+    Slice {
+        prefix: Vec<Pat<'tcx>>,
+        slice: Option<Pat<'tcx>>,
+        suffix: Vec<Pat<'tcx>>,
+    },
+
+    /// Fixed match against an array; irrefutable.
+    Array {
+        prefix: Vec<Pat<'tcx>>,
+        slice: Option<Pat<'tcx>>,
+        suffix: Vec<Pat<'tcx>>,
+    },
+
+    /// An or-pattern, e.g. `p | q`.
+    /// Invariant: `pats.len() >= 2`.
+    Or {
+        pats: Vec<Pat<'tcx>>,
+    },
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, HashStable)]
+pub struct PatRange<'tcx> {
+    pub lo: mir::ConstantKind<'tcx>,
+    pub hi: mir::ConstantKind<'tcx>,
+    pub end: RangeEnd,
+}
+
+impl<'tcx> fmt::Display for Pat<'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // Printing lists is a chore.
+        let mut first = true;
+        let mut start_or_continue = |s| {
+            if first {
+                first = false;
+                ""
+            } else {
+                s
+            }
+        };
+        let mut start_or_comma = || start_or_continue(", ");
+
+        match *self.kind {
+            PatKind::Wild => write!(f, "_"),
+            PatKind::AscribeUserType { ref subpattern, .. } => write!(f, "{}: _", subpattern),
+            PatKind::Binding { mutability, name, mode, ref subpattern, .. } => {
+                let is_mut = match mode {
+                    BindingMode::ByValue => mutability == Mutability::Mut,
+                    BindingMode::ByRef(bk) => {
+                        write!(f, "ref ")?;
+                        matches!(bk, BorrowKind::Mut { .. })
+                    }
+                };
+                if is_mut {
+                    write!(f, "mut ")?;
+                }
+                write!(f, "{}", name)?;
+                if let Some(ref subpattern) = *subpattern {
+                    write!(f, " @ {}", subpattern)?;
+                }
+                Ok(())
+            }
+            PatKind::Variant { ref subpatterns, .. } | PatKind::Leaf { ref subpatterns } => {
+                let variant = match *self.kind {
+                    PatKind::Variant { adt_def, variant_index, .. } => {
+                        Some(adt_def.variant(variant_index))
+                    }
+                    _ => self.ty.ty_adt_def().and_then(|adt| {
+                        if !adt.is_enum() { Some(adt.non_enum_variant()) } else { None }
+                    }),
+                };
+
+                if let Some(variant) = variant {
+                    write!(f, "{}", variant.name)?;
+
+                    // Only for Adt we can have `S {...}`,
+                    // which we handle separately here.
+                    if variant.ctor_kind == CtorKind::Fictive {
+                        write!(f, " {{ ")?;
+
+                        let mut printed = 0;
+                        for p in subpatterns {
+                            if let PatKind::Wild = *p.pattern.kind {
+                                continue;
+                            }
+                            let name = variant.fields[p.field.index()].name;
+                            write!(f, "{}{}: {}", start_or_comma(), name, p.pattern)?;
+                            printed += 1;
+                        }
+
+                        if printed < variant.fields.len() {
+                            write!(f, "{}..", start_or_comma())?;
+                        }
+
+                        return write!(f, " }}");
+                    }
+                }
+
+                let num_fields = variant.map_or(subpatterns.len(), |v| v.fields.len());
+                if num_fields != 0 || variant.is_none() {
+                    write!(f, "(")?;
+                    for i in 0..num_fields {
+                        write!(f, "{}", start_or_comma())?;
+
+                        // Common case: the field is where we expect it.
+                        if let Some(p) = subpatterns.get(i) {
+                            if p.field.index() == i {
+                                write!(f, "{}", p.pattern)?;
+                                continue;
+                            }
+                        }
+
+                        // Otherwise, we have to go looking for it.
+                        if let Some(p) = subpatterns.iter().find(|p| p.field.index() == i) {
+                            write!(f, "{}", p.pattern)?;
+                        } else {
+                            write!(f, "_")?;
+                        }
+                    }
+                    write!(f, ")")?;
+                }
+
+                Ok(())
+            }
+            PatKind::Deref { ref subpattern } => {
+                match self.ty.kind() {
+                    ty::Adt(def, _) if def.is_box() => write!(f, "box ")?,
+                    ty::Ref(_, _, mutbl) => {
+                        write!(f, "&{}", mutbl.prefix_str())?;
+                    }
+                    _ => bug!("{} is a bad Deref pattern type", self.ty),
+                }
+                write!(f, "{}", subpattern)
+            }
+            PatKind::Constant { value } => write!(f, "{}", value),
+            PatKind::Range(PatRange { lo, hi, end }) => {
+                write!(f, "{}", lo)?;
+                write!(f, "{}", end)?;
+                write!(f, "{}", hi)
+            }
+            PatKind::Slice { ref prefix, ref slice, ref suffix }
+            | PatKind::Array { ref prefix, ref slice, ref suffix } => {
+                write!(f, "[")?;
+                for p in prefix {
+                    write!(f, "{}{}", start_or_comma(), p)?;
+                }
+                if let Some(ref slice) = *slice {
+                    write!(f, "{}", start_or_comma())?;
+                    match *slice.kind {
+                        PatKind::Wild => {}
+                        _ => write!(f, "{}", slice)?,
+                    }
+                    write!(f, "..")?;
+                }
+                for p in suffix {
+                    write!(f, "{}{}", start_or_comma(), p)?;
+                }
+                write!(f, "]")
+            }
+            PatKind::Or { ref pats } => {
+                for pat in pats {
+                    write!(f, "{}{}", start_or_continue(" | "), pat)?;
+                }
+                Ok(())
+            }
+        }
+    }
+}
+
+// Some nodes are used a lot. Make sure they don't unintentionally get bigger.
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+mod size_asserts {
+    use super::*;
+    // These are in alphabetical order, which is easy to maintain.
+    rustc_data_structures::static_assert_size!(Block, 56);
+    rustc_data_structures::static_assert_size!(Expr<'_>, 104);
+    rustc_data_structures::static_assert_size!(Pat<'_>, 24);
+    rustc_data_structures::static_assert_size!(Stmt<'_>, 120);
+}