1 //! The MIR is built from some typed high-level IR
2 //! (THIR). This section defines the THIR along with a trait for
3 //! accessing it. The intention is to allow MIR construction to be
4 //! unit-tested and separated from the Rust source and compiler data
8 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
10 use rustc_hir::def_id::DefId;
11 use rustc_middle::infer::canonical::Canonical;
12 use rustc_middle::middle::region;
13 use rustc_middle::mir::{BinOp, BorrowKind, Field, UnOp};
14 use rustc_middle::ty::adjustment::PointerCast;
15 use rustc_middle::ty::subst::SubstsRef;
16 use rustc_middle::ty::{AdtDef, Const, Ty, UpvarSubsts, UserType};
18 use rustc_target::abi::VariantIdx;
19 use rustc_target::asm::InlineAsmRegOrRegClass;
25 crate use self::pattern::PatTyProj;
26 crate use self::pattern::{BindingMode, FieldPat, Pat, PatKind, PatRange};
30 #[derive(Copy, Clone, Debug)]
31 crate enum LintLevel {
36 #[derive(Clone, Debug)]
37 crate struct Block<'tcx> {
38 crate targeted_by_break: bool,
39 crate region_scope: region::Scope,
40 crate opt_destruction_scope: Option<region::Scope>,
42 crate stmts: Vec<StmtRef<'tcx>>,
43 crate expr: Option<ExprRef<'tcx>>,
44 crate safety_mode: BlockSafety,
47 #[derive(Copy, Clone, Debug)]
48 crate enum BlockSafety {
50 ExplicitUnsafe(hir::HirId),
55 #[derive(Clone, Debug)]
56 crate enum StmtRef<'tcx> {
57 Mirror(Box<Stmt<'tcx>>),
60 #[derive(Clone, Debug)]
61 crate struct Stmt<'tcx> {
62 crate kind: StmtKind<'tcx>,
63 crate opt_destruction_scope: Option<region::Scope>,
66 #[derive(Clone, Debug)]
67 crate enum StmtKind<'tcx> {
69 /// scope for this statement; may be used as lifetime of temporaries
72 /// expression being evaluated in this statement
77 /// scope for variables bound in this let; covers this and
78 /// remaining statements in block
79 remainder_scope: region::Scope,
81 /// scope for the initialization itself; might be used as
82 /// lifetime of temporaries
83 init_scope: region::Scope,
87 /// if a type is included, it is added as an ascription pattern
90 /// let pat: ty = <INIT> ...
91 initializer: Option<ExprRef<'tcx>>,
93 /// the lint level for this let-statement
94 lint_level: LintLevel,
98 // `Expr` is used a lot. Make sure it doesn't unintentionally get bigger.
99 #[cfg(target_arch = "x86_64")]
100 rustc_data_structures::static_assert_size!(Expr<'_>, 168);
102 /// The Thir trait implementor lowers their expressions (`&'tcx H::Expr`)
103 /// into instances of this `Expr` enum. This lowering can be done
104 /// basically as lazily or as eagerly as desired: every recursive
105 /// reference to an expression in this enum is an `ExprRef<'tcx>`, which
106 /// may in turn be another instance of this enum (boxed), or else an
107 /// unlowered `&'tcx H::Expr`. Note that instances of `Expr` are very
108 /// short-lived. They are created by `Thir::to_expr`, analyzed and
109 /// converted into MIR, and then discarded.
111 /// If you compare `Expr` to the full compiler AST, you will see it is
112 /// a good bit simpler. In fact, a number of the more straight-forward
113 /// MIR simplifications are already done in the impl of `Thir`. For
114 /// example, method calls and overloaded operators are absent: they are
115 /// expected to be converted into `Expr::Call` instances.
116 #[derive(Clone, Debug)]
117 crate struct Expr<'tcx> {
118 /// type of this expression
121 /// lifetime of this expression if it should be spilled into a
122 /// temporary; should be None only if in a constant context
123 crate temp_lifetime: Option<region::Scope>,
125 /// span of the expression in the source
128 /// kind of expression
129 crate kind: ExprKind<'tcx>,
132 #[derive(Clone, Debug)]
133 crate enum ExprKind<'tcx> {
135 region_scope: region::Scope,
136 lint_level: LintLevel,
137 value: ExprRef<'tcx>,
140 value: ExprRef<'tcx>,
145 args: Vec<ExprRef<'tcx>>,
146 // Whether this is from a call in HIR, rather than from an overloaded
147 // operator. True for overloaded function call.
149 /// This `Span` is the span of the function, without the dot and receiver
150 /// (e.g. `foo(a, b)` in `x.foo(a, b)`
155 }, // NOT overloaded!
160 }, // NOT overloaded!
165 }, // NOT overloaded!
166 // LogicalOp is distinct from BinaryOp because of lazy evaluation of the operands.
170 }, // NOT overloaded!
172 source: ExprRef<'tcx>,
175 source: ExprRef<'tcx>,
176 }, // Use a lexpr to get a vexpr.
178 source: ExprRef<'tcx>,
182 source: ExprRef<'tcx>,
188 scrutinee: ExprRef<'tcx>,
189 arms: Vec<Arm<'tcx>>,
192 body: &'tcx hir::Block<'tcx>,
209 index: ExprRef<'tcx>,
214 /// first argument, used for self in a closure
217 borrow_kind: BorrowKind,
220 /// A `&raw [const|mut] $place_expr` raw borrow resulting in type `*[const|mut] T`.
222 mutability: hir::Mutability,
226 label: region::Scope,
227 value: Option<ExprRef<'tcx>>,
230 label: region::Scope,
233 value: Option<ExprRef<'tcx>>,
236 value: &'tcx Const<'tcx>,
239 value: ExprRef<'tcx>,
240 count: &'tcx Const<'tcx>,
243 fields: Vec<ExprRef<'tcx>>,
246 fields: Vec<ExprRef<'tcx>>,
249 adt_def: &'tcx AdtDef,
250 variant_index: VariantIdx,
251 substs: SubstsRef<'tcx>,
253 /// Optional user-given substs: for something like `let x =
254 /// Bar::<T> { ... }`.
255 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
257 fields: Vec<FieldExprRef<'tcx>>,
258 base: Option<FruInfo<'tcx>>,
260 PlaceTypeAscription {
261 source: ExprRef<'tcx>,
262 /// Type that the user gave to this expression
263 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
265 ValueTypeAscription {
266 source: ExprRef<'tcx>,
267 /// Type that the user gave to this expression
268 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
272 substs: UpvarSubsts<'tcx>,
273 upvars: Vec<ExprRef<'tcx>>,
274 movability: Option<hir::Movability>,
277 literal: &'tcx Const<'tcx>,
278 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
279 /// The `DefId` of the `const` item this literal
280 /// was produced from, if this is not a user-written
282 const_id: Option<DefId>,
284 /// A literal containing the address of a `static`.
286 /// This is only distinguished from `Literal` so that we can register some
287 /// info for diagnostics.
289 literal: &'tcx Const<'tcx>,
293 template: &'tcx [InlineAsmTemplatePiece],
294 operands: Vec<InlineAsmOperand<'tcx>>,
295 options: InlineAsmOptions,
296 line_spans: &'tcx [Span],
298 /// An expression taking a reference to a thread local.
299 ThreadLocalRef(DefId),
301 asm: &'tcx hir::LlvmInlineAsmInner,
302 outputs: Vec<ExprRef<'tcx>>,
303 inputs: Vec<ExprRef<'tcx>>,
306 value: ExprRef<'tcx>,
310 #[derive(Clone, Debug)]
311 crate enum ExprRef<'tcx> {
312 Thir(&'tcx hir::Expr<'tcx>),
313 Mirror(Box<Expr<'tcx>>),
316 #[derive(Clone, Debug)]
317 crate struct FieldExprRef<'tcx> {
319 crate expr: ExprRef<'tcx>,
322 #[derive(Clone, Debug)]
323 crate struct FruInfo<'tcx> {
324 crate base: ExprRef<'tcx>,
325 crate field_types: Vec<Ty<'tcx>>,
328 #[derive(Clone, Debug)]
329 crate struct Arm<'tcx> {
330 crate pattern: Pat<'tcx>,
331 crate guard: Option<Guard<'tcx>>,
332 crate body: ExprRef<'tcx>,
333 crate lint_level: LintLevel,
334 crate scope: region::Scope,
338 #[derive(Clone, Debug)]
339 crate enum Guard<'tcx> {
343 #[derive(Copy, Clone, Debug)]
344 crate enum LogicalOp {
349 impl<'tcx> ExprRef<'tcx> {
350 crate fn span(&self) -> Span {
352 ExprRef::Thir(expr) => expr.span,
353 ExprRef::Mirror(expr) => expr.span,
358 #[derive(Clone, Debug)]
359 crate enum InlineAsmOperand<'tcx> {
361 reg: InlineAsmRegOrRegClass,
365 reg: InlineAsmRegOrRegClass,
367 expr: Option<ExprRef<'tcx>>,
370 reg: InlineAsmRegOrRegClass,
375 reg: InlineAsmRegOrRegClass,
377 in_expr: ExprRef<'tcx>,
378 out_expr: Option<ExprRef<'tcx>>,
391 ///////////////////////////////////////////////////////////////////////////
394 /// "Mirroring" is the process of converting from a HIR type into one
395 /// of the THIR types defined in this file. This is basically a "on
396 /// the fly" desugaring step that hides a lot of the messiness in the
397 /// tcx. For example, the mirror of a `&'tcx hir::Expr` is an
400 /// Mirroring is gradual: when you mirror an outer expression like `e1
401 /// + e2`, the references to the inner expressions `e1` and `e2` are
402 /// `ExprRef<'tcx>` instances, and they may or may not be eagerly
403 /// mirrored. This allows a single AST node from the compiler to
404 /// expand into one or more Thir nodes, which lets the Thir nodes be
406 crate trait Mirror<'tcx> {
409 fn make_mirror(self, cx: &mut Cx<'_, 'tcx>) -> Self::Output;
412 impl<'tcx> Mirror<'tcx> for Expr<'tcx> {
413 type Output = Expr<'tcx>;
415 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Expr<'tcx> {
420 impl<'tcx> Mirror<'tcx> for ExprRef<'tcx> {
421 type Output = Expr<'tcx>;
423 fn make_mirror(self, hir: &mut Cx<'_, 'tcx>) -> Expr<'tcx> {
425 ExprRef::Thir(h) => h.make_mirror(hir),
426 ExprRef::Mirror(m) => *m,
431 impl<'tcx> Mirror<'tcx> for Stmt<'tcx> {
432 type Output = Stmt<'tcx>;
434 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Stmt<'tcx> {
439 impl<'tcx> Mirror<'tcx> for StmtRef<'tcx> {
440 type Output = Stmt<'tcx>;
442 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Stmt<'tcx> {
444 StmtRef::Mirror(m) => *m,
449 impl<'tcx> Mirror<'tcx> for Block<'tcx> {
450 type Output = Block<'tcx>;
452 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Block<'tcx> {