rustc_middle/thir.rs
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//! 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 std::cmp::Ordering;
use std::fmt;
use std::ops::Index;
use rustc_ast::{AsmMacro, InlineAsmOptions, InlineAsmTemplatePiece};
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_hir::{BindingMode, ByRef, HirId, MatchSource, RangeEnd};
use rustc_index::{IndexVec, newtype_index};
use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeVisitable};
use rustc_middle::middle::region;
use rustc_middle::mir::interpret::AllocId;
use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, UnOp};
use rustc_middle::ty::adjustment::PointerCoercion;
use rustc_middle::ty::layout::IntegerExt;
use rustc_middle::ty::{
self, AdtDef, CanonicalUserType, CanonicalUserTypeAnnotation, FnSig, GenericArgsRef, List, Ty,
TyCtxt, UpvarArgs,
};
use rustc_span::def_id::LocalDefId;
use rustc_span::{ErrorGuaranteed, Span, Symbol};
use rustc_target::abi::{FieldIdx, Integer, Size, VariantIdx};
use rustc_target::asm::InlineAsmRegOrRegClass;
use tracing::instrument;
pub mod visit;
macro_rules! thir_with_elements {
(
$($field_name:ident: $field_ty:ty,)*
@elements:
$($name:ident: $id:ty => $value:ty => $format:literal,)*
) => {
$(
newtype_index! {
#[derive(HashStable)]
#[debug_format = $format]
pub struct $id {}
}
)*
/// 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 $field_name: $field_ty,
)*
$(
pub $name: IndexVec<$id, $value>,
)*
}
impl<'tcx> Thir<'tcx> {
pub fn new($($field_name: $field_ty,)*) -> Thir<'tcx> {
Thir {
$(
$field_name,
)*
$(
$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! {
body_type: BodyTy<'tcx>,
@elements:
arms: ArmId => Arm<'tcx> => "a{}",
blocks: BlockId => Block => "b{}",
exprs: ExprId => Expr<'tcx> => "e{}",
stmts: StmtId => Stmt<'tcx> => "s{}",
params: ParamId => Param<'tcx> => "p{}",
}
#[derive(Debug, HashStable, Clone)]
pub enum BodyTy<'tcx> {
Const(Ty<'tcx>),
Fn(FnSig<'tcx>),
}
/// Description of a type-checked function parameter.
#[derive(Clone, Debug, HashStable)]
pub struct Param<'tcx> {
/// The pattern that appears in the parameter list, or None for implicit parameters.
pub pat: Option<Box<Pat<'tcx>>>,
/// The possibly inferred type.
pub ty: Ty<'tcx>,
/// Span of the explicitly provided type, or None if inferred for closures.
pub ty_span: Option<Span>,
/// Whether this param is `self`, and how it is bound.
pub self_kind: Option<hir::ImplicitSelfKind>,
/// HirId for lints.
pub hir_id: Option<HirId>,
}
#[derive(Copy, Clone, Debug, HashStable)]
pub enum LintLevel {
Inherited,
Explicit(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,
/// 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,
}
type UserTy<'tcx> = Option<Box<CanonicalUserType<'tcx>>>;
#[derive(Clone, Debug, HashStable)]
pub struct AdtExpr<'tcx> {
/// The ADT we're constructing.
pub adt_def: AdtDef<'tcx>,
/// The variant of the ADT.
pub variant_index: VariantIdx,
pub args: GenericArgsRef<'tcx>,
/// Optional user-given args: for something like `let x =
/// Bar::<T> { ... }`.
pub user_ty: UserTy<'tcx>,
pub fields: Box<[FieldExpr]>,
/// The base, e.g. `Foo {x: 1, .. base}`.
pub base: Option<FruInfo<'tcx>>,
}
#[derive(Clone, Debug, HashStable)]
pub struct ClosureExpr<'tcx> {
pub closure_id: LocalDefId,
pub args: UpvarArgs<'tcx>,
pub upvars: Box<[ExprId]>,
pub movability: Option<hir::Movability>,
pub fake_reads: Vec<(ExprId, FakeReadCause, HirId)>,
}
#[derive(Clone, Debug, HashStable)]
pub struct InlineAsmExpr<'tcx> {
pub asm_macro: AsmMacro,
pub template: &'tcx [InlineAsmTemplatePiece],
pub operands: Box<[InlineAsmOperand<'tcx>]>,
pub options: InlineAsmOptions,
pub line_spans: &'tcx [Span],
}
#[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(HirId),
}
#[derive(Clone, Debug, HashStable)]
pub struct Stmt<'tcx> {
pub kind: StmtKind<'tcx>,
}
#[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: Box<Pat<'tcx>>,
/// `let pat: ty = <INIT>`
initializer: Option<ExprId>,
/// `let pat: ty = <INIT> else { <ELSE> }`
else_block: Option<BlockId>,
/// The lint level for this `let` statement.
lint_level: LintLevel,
/// Span of the `let <PAT> = <INIT>` part.
span: Span,
},
}
#[derive(Clone, Debug, Copy, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
pub struct LocalVarId(pub HirId);
/// A THIR expression.
#[derive(Clone, Debug, HashStable)]
pub struct Expr<'tcx> {
/// kind of expression
pub kind: ExprKind<'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,
}
#[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,
},
/// Forces its contents to be treated as a value expression, not a place
/// expression. This is inserted in some places where an operation would
/// otherwise be erased completely (e.g. some no-op casts), but we still
/// need to ensure that its operand is treated as a value and not a place.
Use {
source: ExprId,
},
/// A coercion from `!` to any type.
NeverToAny {
source: ExprId,
},
/// A pointer coercion. More information can be found in [`PointerCoercion`].
/// Pointer casts that cannot be done by coercions are represented by [`ExprKind::Cast`].
PointerCoercion {
cast: PointerCoercion,
source: ExprId,
/// Whether this coercion is written with an `as` cast in the source code.
is_from_as_cast: bool,
},
/// A `loop` expression.
Loop {
body: ExprId,
},
/// Special expression representing the `let` part of an `if let` or similar construct
/// (including `if let` guards in match arms, and let-chains formed by `&&`).
///
/// This isn't considered a real expression in surface Rust syntax, so it can
/// only appear in specific situations, such as within the condition of an `if`.
///
/// (Not to be confused with [`StmtKind::Let`], which is a normal `let` statement.)
Let {
expr: ExprId,
pat: Box<Pat<'tcx>>,
},
/// A `match` expression.
Match {
scrutinee: ExprId,
scrutinee_hir_id: HirId,
arms: Box<[ArmId]>,
match_source: MatchSource,
},
/// A block.
Block {
block: BlockId,
},
/// 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: FieldIdx,
},
/// A *non-overloaded* indexing operation.
Index {
lhs: ExprId,
index: ExprId,
},
/// A local variable.
VarRef {
id: LocalVarId,
},
/// Used to represent upvars mentioned in a closure/coroutine
UpvarRef {
/// DefId of the closure/coroutine
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`.
RawBorrow {
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>,
},
/// A `become` expression.
Become {
value: ExprId,
},
/// An inline `const` block, e.g. `const {}`.
ConstBlock {
did: DefId,
args: GenericArgsRef<'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<AdtExpr<'tcx>>),
/// A type ascription on a place.
PlaceTypeAscription {
source: ExprId,
/// Type that the user gave to this expression
user_ty: UserTy<'tcx>,
user_ty_span: Span,
},
/// A type ascription on a value, e.g. `type_ascribe!(42, i32)` or `42 as i32`.
ValueTypeAscription {
source: ExprId,
/// Type that the user gave to this expression
user_ty: UserTy<'tcx>,
user_ty_span: Span,
},
/// A closure definition.
Closure(Box<ClosureExpr<'tcx>>),
/// 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: UserTy<'tcx>,
},
/// A literal of a ZST type.
ZstLiteral {
user_ty: UserTy<'tcx>,
},
/// Associated constants and named constants
NamedConst {
def_id: DefId,
args: GenericArgsRef<'tcx>,
user_ty: UserTy<'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(Box<InlineAsmExpr<'tcx>>),
/// Field offset (`offset_of!`)
OffsetOf {
container: Ty<'tcx>,
fields: &'tcx List<(VariantIdx, FieldIdx)>,
},
/// 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: FieldIdx,
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: Box<Pat<'tcx>>,
pub guard: Option<ExprId>,
pub body: ExprId,
pub lint_level: LintLevel,
pub scope: region::Scope,
pub span: Span,
}
#[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::Const<'tcx>,
span: Span,
},
SymFn {
value: mir::Const<'tcx>,
span: Span,
},
SymStatic {
def_id: DefId,
},
Label {
block: BlockId,
},
}
#[derive(Clone, Debug, HashStable, TypeVisitable)]
pub struct FieldPat<'tcx> {
pub field: FieldIdx,
pub pattern: Box<Pat<'tcx>>,
}
#[derive(Clone, Debug, HashStable, TypeVisitable)]
pub struct Pat<'tcx> {
pub ty: Ty<'tcx>,
pub span: Span,
pub kind: PatKind<'tcx>,
}
impl<'tcx> Pat<'tcx> {
pub fn simple_ident(&self) -> Option<Symbol> {
match self.kind {
PatKind::Binding {
name, mode: BindingMode(ByRef::No, _), subpattern: None, ..
} => Some(name),
_ => None,
}
}
/// Call `f` on every "binding" in a pattern, e.g., on `a` in
/// `match foo() { Some(a) => (), None => () }`
pub fn each_binding(&self, mut f: impl FnMut(Symbol, ByRef, Ty<'tcx>, Span)) {
self.walk_always(|p| {
if let PatKind::Binding { name, mode, ty, .. } = p.kind {
f(name, mode.0, ty, p.span);
}
});
}
/// Walk the pattern in left-to-right order.
///
/// If `it(pat)` returns `false`, the children are not visited.
pub fn walk(&self, mut it: impl FnMut(&Pat<'tcx>) -> bool) {
self.walk_(&mut it)
}
fn walk_(&self, it: &mut impl FnMut(&Pat<'tcx>) -> bool) {
if !it(self) {
return;
}
use PatKind::*;
match &self.kind {
Wild
| Never
| Range(..)
| Binding { subpattern: None, .. }
| Constant { .. }
| Error(_) => {}
AscribeUserType { subpattern, .. }
| Binding { subpattern: Some(subpattern), .. }
| Deref { subpattern }
| DerefPattern { subpattern, .. }
| InlineConstant { subpattern, .. } => subpattern.walk_(it),
Leaf { subpatterns } | Variant { subpatterns, .. } => {
subpatterns.iter().for_each(|field| field.pattern.walk_(it))
}
Or { pats } => pats.iter().for_each(|p| p.walk_(it)),
Array { box ref prefix, ref slice, box ref suffix }
| Slice { box ref prefix, ref slice, box ref suffix } => {
prefix.iter().chain(slice.iter()).chain(suffix.iter()).for_each(|p| p.walk_(it))
}
}
}
/// Whether the pattern has a `PatKind::Error` nested within.
pub fn pat_error_reported(&self) -> Result<(), ErrorGuaranteed> {
let mut error = None;
self.walk(|pat| {
if let PatKind::Error(e) = pat.kind
&& error.is_none()
{
error = Some(e);
}
error.is_none()
});
match error {
None => Ok(()),
Some(e) => Err(e),
}
}
/// Walk the pattern in left-to-right order.
///
/// If you always want to recurse, prefer this method over `walk`.
pub fn walk_always(&self, mut it: impl FnMut(&Pat<'tcx>)) {
self.walk(|p| {
it(p);
true
})
}
/// Whether this a never pattern.
pub fn is_never_pattern(&self) -> bool {
let mut is_never_pattern = false;
self.walk(|pat| match &pat.kind {
PatKind::Never => {
is_never_pattern = true;
false
}
PatKind::Or { pats } => {
is_never_pattern = pats.iter().all(|p| p.is_never_pattern());
false
}
_ => true,
});
is_never_pattern
}
}
#[derive(Clone, Debug, HashStable, TypeVisitable)]
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, TypeVisitable)]
pub enum PatKind<'tcx> {
/// A wildcard pattern: `_`.
Wild,
AscribeUserType {
ascription: Ascription<'tcx>,
subpattern: Box<Pat<'tcx>>,
},
/// `x`, `ref x`, `x @ P`, etc.
Binding {
name: Symbol,
#[type_visitable(ignore)]
mode: BindingMode,
#[type_visitable(ignore)]
var: LocalVarId,
ty: Ty<'tcx>,
subpattern: Option<Box<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>,
args: GenericArgsRef<'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: Box<Pat<'tcx>>,
},
/// Deref pattern, written `box P` for now.
DerefPattern {
subpattern: Box<Pat<'tcx>>,
mutability: hir::Mutability,
},
/// One of the following:
/// * `&str`/`&[u8]` (represented as a valtree), which will be handled as a string/slice pattern
/// and thus exhaustiveness checking will detect if you use the same string/slice twice in
/// different patterns.
/// * integer, bool, char or float (represented as a valtree), which will be handled by
/// exhaustiveness to cover exactly its own value, similar to `&str`, but these values are
/// much simpler.
/// * `String`, if `string_deref_patterns` is enabled.
Constant {
value: mir::Const<'tcx>,
},
/// Inline constant found while lowering a pattern.
InlineConstant {
/// [LocalDefId] of the constant, we need this so that we have a
/// reference that can be used by unsafety checking to visit nested
/// unevaluated constants.
def: LocalDefId,
/// If the inline constant is used in a range pattern, this subpattern
/// represents the range (if both ends are inline constants, there will
/// be multiple InlineConstant wrappers).
///
/// Otherwise, the actual pattern that the constant lowered to. As with
/// other constants, inline constants are matched structurally where
/// possible.
subpattern: Box<Pat<'tcx>>,
},
Range(Box<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: Box<[Box<Pat<'tcx>>]>,
slice: Option<Box<Pat<'tcx>>>,
suffix: Box<[Box<Pat<'tcx>>]>,
},
/// Fixed match against an array; irrefutable.
Array {
prefix: Box<[Box<Pat<'tcx>>]>,
slice: Option<Box<Pat<'tcx>>>,
suffix: Box<[Box<Pat<'tcx>>]>,
},
/// An or-pattern, e.g. `p | q`.
/// Invariant: `pats.len() >= 2`.
Or {
pats: Box<[Box<Pat<'tcx>>]>,
},
/// A never pattern `!`.
Never,
/// An error has been encountered during lowering. We probably shouldn't report more lints
/// related to this pattern.
Error(ErrorGuaranteed),
}
/// A range pattern.
/// The boundaries must be of the same type and that type must be numeric.
#[derive(Clone, Debug, PartialEq, HashStable, TypeVisitable)]
pub struct PatRange<'tcx> {
/// Must not be `PosInfinity`.
pub lo: PatRangeBoundary<'tcx>,
/// Must not be `NegInfinity`.
pub hi: PatRangeBoundary<'tcx>,
#[type_visitable(ignore)]
pub end: RangeEnd,
pub ty: Ty<'tcx>,
}
impl<'tcx> PatRange<'tcx> {
/// Whether this range covers the full extent of possible values (best-effort, we ignore floats).
#[inline]
pub fn is_full_range(&self, tcx: TyCtxt<'tcx>) -> Option<bool> {
let (min, max, size, bias) = match *self.ty.kind() {
ty::Char => (0, std::char::MAX as u128, Size::from_bits(32), 0),
ty::Int(ity) => {
let size = Integer::from_int_ty(&tcx, ity).size();
let max = size.truncate(u128::MAX);
let bias = 1u128 << (size.bits() - 1);
(0, max, size, bias)
}
ty::Uint(uty) => {
let size = Integer::from_uint_ty(&tcx, uty).size();
let max = size.unsigned_int_max();
(0, max, size, 0)
}
_ => return None,
};
// We want to compare ranges numerically, but the order of the bitwise representation of
// signed integers does not match their numeric order. Thus, to correct the ordering, we
// need to shift the range of signed integers to correct the comparison. This is achieved by
// XORing with a bias (see pattern/deconstruct_pat.rs for another pertinent example of this
// pattern).
//
// Also, for performance, it's important to only do the second `try_to_bits` if necessary.
let lo_is_min = match self.lo {
PatRangeBoundary::NegInfinity => true,
PatRangeBoundary::Finite(value) => {
let lo = value.try_to_bits(size).unwrap() ^ bias;
lo <= min
}
PatRangeBoundary::PosInfinity => false,
};
if lo_is_min {
let hi_is_max = match self.hi {
PatRangeBoundary::NegInfinity => false,
PatRangeBoundary::Finite(value) => {
let hi = value.try_to_bits(size).unwrap() ^ bias;
hi > max || hi == max && self.end == RangeEnd::Included
}
PatRangeBoundary::PosInfinity => true,
};
if hi_is_max {
return Some(true);
}
}
Some(false)
}
#[inline]
pub fn contains(
&self,
value: mir::Const<'tcx>,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<bool> {
use Ordering::*;
debug_assert_eq!(self.ty, value.ty());
let ty = self.ty;
let value = PatRangeBoundary::Finite(value);
// For performance, it's important to only do the second comparison if necessary.
Some(
match self.lo.compare_with(value, ty, tcx, param_env)? {
Less | Equal => true,
Greater => false,
} && match value.compare_with(self.hi, ty, tcx, param_env)? {
Less => true,
Equal => self.end == RangeEnd::Included,
Greater => false,
},
)
}
#[inline]
pub fn overlaps(
&self,
other: &Self,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<bool> {
use Ordering::*;
debug_assert_eq!(self.ty, other.ty);
// For performance, it's important to only do the second comparison if necessary.
Some(
match other.lo.compare_with(self.hi, self.ty, tcx, param_env)? {
Less => true,
Equal => self.end == RangeEnd::Included,
Greater => false,
} && match self.lo.compare_with(other.hi, self.ty, tcx, param_env)? {
Less => true,
Equal => other.end == RangeEnd::Included,
Greater => false,
},
)
}
}
impl<'tcx> fmt::Display for PatRange<'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if let PatRangeBoundary::Finite(value) = &self.lo {
write!(f, "{value}")?;
}
if let PatRangeBoundary::Finite(value) = &self.hi {
write!(f, "{}", self.end)?;
write!(f, "{value}")?;
} else {
// `0..` is parsed as an inclusive range, we must display it correctly.
write!(f, "..")?;
}
Ok(())
}
}
/// A (possibly open) boundary of a range pattern.
/// If present, the const must be of a numeric type.
#[derive(Copy, Clone, Debug, PartialEq, HashStable, TypeVisitable)]
pub enum PatRangeBoundary<'tcx> {
Finite(mir::Const<'tcx>),
NegInfinity,
PosInfinity,
}
impl<'tcx> PatRangeBoundary<'tcx> {
#[inline]
pub fn is_finite(self) -> bool {
matches!(self, Self::Finite(..))
}
#[inline]
pub fn as_finite(self) -> Option<mir::Const<'tcx>> {
match self {
Self::Finite(value) => Some(value),
Self::NegInfinity | Self::PosInfinity => None,
}
}
pub fn eval_bits(self, ty: Ty<'tcx>, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> u128 {
match self {
Self::Finite(value) => value.eval_bits(tcx, param_env),
Self::NegInfinity => {
// Unwrap is ok because the type is known to be numeric.
ty.numeric_min_and_max_as_bits(tcx).unwrap().0
}
Self::PosInfinity => {
// Unwrap is ok because the type is known to be numeric.
ty.numeric_min_and_max_as_bits(tcx).unwrap().1
}
}
}
#[instrument(skip(tcx, param_env), level = "debug", ret)]
pub fn compare_with(
self,
other: Self,
ty: Ty<'tcx>,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Option<Ordering> {
use PatRangeBoundary::*;
match (self, other) {
// When comparing with infinities, we must remember that `0u8..` and `0u8..=255`
// describe the same range. These two shortcuts are ok, but for the rest we must check
// bit values.
(PosInfinity, PosInfinity) => return Some(Ordering::Equal),
(NegInfinity, NegInfinity) => return Some(Ordering::Equal),
// This code is hot when compiling matches with many ranges. So we
// special-case extraction of evaluated scalars for speed, for types where
// we can do scalar comparisons. E.g. `unicode-normalization` has
// many ranges such as '\u{037A}'..='\u{037F}', and chars can be compared
// in this way.
(Finite(a), Finite(b)) if matches!(ty.kind(), ty::Int(_) | ty::Uint(_) | ty::Char) => {
if let (Some(a), Some(b)) = (a.try_to_scalar_int(), b.try_to_scalar_int()) {
let sz = ty.primitive_size(tcx);
let cmp = match ty.kind() {
ty::Uint(_) | ty::Char => a.to_uint(sz).cmp(&b.to_uint(sz)),
ty::Int(_) => a.to_int(sz).cmp(&b.to_int(sz)),
_ => unreachable!(),
};
return Some(cmp);
}
}
_ => {}
}
let a = self.eval_bits(ty, tcx, param_env);
let b = other.eval_bits(ty, tcx, param_env);
match ty.kind() {
ty::Float(ty::FloatTy::F16) => {
use rustc_apfloat::Float;
let a = rustc_apfloat::ieee::Half::from_bits(a);
let b = rustc_apfloat::ieee::Half::from_bits(b);
a.partial_cmp(&b)
}
ty::Float(ty::FloatTy::F32) => {
use rustc_apfloat::Float;
let a = rustc_apfloat::ieee::Single::from_bits(a);
let b = rustc_apfloat::ieee::Single::from_bits(b);
a.partial_cmp(&b)
}
ty::Float(ty::FloatTy::F64) => {
use rustc_apfloat::Float;
let a = rustc_apfloat::ieee::Double::from_bits(a);
let b = rustc_apfloat::ieee::Double::from_bits(b);
a.partial_cmp(&b)
}
ty::Float(ty::FloatTy::F128) => {
use rustc_apfloat::Float;
let a = rustc_apfloat::ieee::Quad::from_bits(a);
let b = rustc_apfloat::ieee::Quad::from_bits(b);
a.partial_cmp(&b)
}
ty::Int(ity) => {
let size = rustc_target::abi::Integer::from_int_ty(&tcx, *ity).size();
let a = size.sign_extend(a) as i128;
let b = size.sign_extend(b) as i128;
Some(a.cmp(&b))
}
ty::Uint(_) | ty::Char => Some(a.cmp(&b)),
_ => bug!(),
}
}
}
// Some nodes are used a lot. Make sure they don't unintentionally get bigger.
#[cfg(target_pointer_width = "64")]
mod size_asserts {
use rustc_data_structures::static_assert_size;
use super::*;
// tidy-alphabetical-start
static_assert_size!(Block, 48);
static_assert_size!(Expr<'_>, 64);
static_assert_size!(ExprKind<'_>, 40);
static_assert_size!(Pat<'_>, 64);
static_assert_size!(PatKind<'_>, 48);
static_assert_size!(Stmt<'_>, 48);
static_assert_size!(StmtKind<'_>, 48);
// tidy-alphabetical-end
}