1 //! The MIR is built from some high-level abstract IR
2 //! (HAIR). This section defines the HAIR 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
7 use rustc::mir::{BinOp, BorrowKind, Field, UnOp};
8 use rustc::hir::def_id::DefId;
9 use rustc::infer::canonical::Canonical;
10 use rustc::middle::region;
11 use rustc::ty::subst::SubstsRef;
12 use rustc::ty::{AdtDef, UpvarSubsts, Ty, Const, UserType};
13 use rustc::ty::adjustment::{PointerCast};
14 use rustc::ty::layout::VariantIdx;
23 pub use self::pattern::{BindingMode, Pat, PatKind, PatRange, FieldPat};
24 pub(crate) use self::pattern::PatTyProj;
28 #[derive(Copy, Clone, Debug)]
34 #[derive(Clone, Debug)]
35 pub struct Block<'tcx> {
36 pub targeted_by_break: bool,
37 pub region_scope: region::Scope,
38 pub opt_destruction_scope: Option<region::Scope>,
40 pub stmts: Vec<StmtRef<'tcx>>,
41 pub expr: Option<ExprRef<'tcx>>,
42 pub safety_mode: BlockSafety,
45 #[derive(Copy, Clone, Debug)]
46 pub enum BlockSafety {
48 ExplicitUnsafe(hir::HirId),
53 #[derive(Clone, Debug)]
54 pub enum StmtRef<'tcx> {
55 Mirror(Box<Stmt<'tcx>>),
58 #[derive(Clone, Debug)]
59 pub struct Stmt<'tcx> {
60 pub kind: StmtKind<'tcx>,
61 pub opt_destruction_scope: Option<region::Scope>,
64 #[derive(Clone, Debug)]
65 pub enum StmtKind<'tcx> {
67 /// scope for this statement; may be used as lifetime of temporaries
70 /// expression being evaluated in this statement
75 /// scope for variables bound in this let; covers this and
76 /// remaining statements in block
77 remainder_scope: region::Scope,
79 /// scope for the initialization itself; might be used as
80 /// lifetime of temporaries
81 init_scope: region::Scope,
85 /// if a type is included, it is added as an ascription pattern
88 /// let pat: ty = <INIT> ...
89 initializer: Option<ExprRef<'tcx>>,
91 /// the lint level for this let-statement
92 lint_level: LintLevel,
96 /// The Hair trait implementor lowers their expressions (`&'tcx H::Expr`)
97 /// into instances of this `Expr` enum. This lowering can be done
98 /// basically as lazily or as eagerly as desired: every recursive
99 /// reference to an expression in this enum is an `ExprRef<'tcx>`, which
100 /// may in turn be another instance of this enum (boxed), or else an
101 /// unlowered `&'tcx H::Expr`. Note that instances of `Expr` are very
102 /// short-lived. They are created by `Hair::to_expr`, analyzed and
103 /// converted into MIR, and then discarded.
105 /// If you compare `Expr` to the full compiler AST, you will see it is
106 /// a good bit simpler. In fact, a number of the more straight-forward
107 /// MIR simplifications are already done in the impl of `Hair`. For
108 /// example, method calls and overloaded operators are absent: they are
109 /// expected to be converted into `Expr::Call` instances.
110 #[derive(Clone, Debug)]
111 pub struct Expr<'tcx> {
112 /// type of this expression
115 /// lifetime of this expression if it should be spilled into a
116 /// temporary; should be None only if in a constant context
117 pub temp_lifetime: Option<region::Scope>,
119 /// span of the expression in the source
122 /// kind of expression
123 pub kind: ExprKind<'tcx>,
126 #[derive(Clone, Debug)]
127 pub enum ExprKind<'tcx> {
129 region_scope: region::Scope,
130 lint_level: LintLevel,
131 value: ExprRef<'tcx>,
134 value: ExprRef<'tcx>,
139 args: Vec<ExprRef<'tcx>>,
140 // Whether this is from a call in HIR, rather than from an overloaded
141 // operator. True for overloaded function call.
146 }, // NOT overloaded!
151 }, // NOT overloaded!
156 }, // NOT overloaded!
157 // LogicalOp is distinct from BinaryOp because of lazy evaluation of the operands.
161 }, // NOT overloaded!
163 source: ExprRef<'tcx>,
166 source: ExprRef<'tcx>,
167 }, // Use a lexpr to get a vexpr.
169 source: ExprRef<'tcx>,
173 source: ExprRef<'tcx>,
179 scrutinee: ExprRef<'tcx>,
180 arms: Vec<Arm<'tcx>>,
183 body: &'tcx hir::Block,
200 index: ExprRef<'tcx>,
205 /// first argument, used for self in a closure
211 borrow_kind: BorrowKind,
215 label: region::Scope,
216 value: Option<ExprRef<'tcx>>,
219 label: region::Scope,
222 value: Option<ExprRef<'tcx>>,
225 value: ExprRef<'tcx>,
229 fields: Vec<ExprRef<'tcx>>,
232 fields: Vec<ExprRef<'tcx>>,
235 adt_def: &'tcx AdtDef,
236 variant_index: VariantIdx,
237 substs: SubstsRef<'tcx>,
239 /// Optional user-given substs: for something like `let x =
240 /// Bar::<T> { ... }`.
241 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
243 fields: Vec<FieldExprRef<'tcx>>,
244 base: Option<FruInfo<'tcx>>
246 PlaceTypeAscription {
247 source: ExprRef<'tcx>,
248 /// Type that the user gave to this expression
249 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
251 ValueTypeAscription {
252 source: ExprRef<'tcx>,
253 /// Type that the user gave to this expression
254 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
258 substs: UpvarSubsts<'tcx>,
259 upvars: Vec<ExprRef<'tcx>>,
260 movability: Option<hir::GeneratorMovability>,
263 literal: &'tcx Const<'tcx>,
264 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
267 asm: &'tcx hir::InlineAsm,
268 outputs: Vec<ExprRef<'tcx>>,
269 inputs: Vec<ExprRef<'tcx>>
272 value: ExprRef<'tcx>,
276 #[derive(Clone, Debug)]
277 pub enum ExprRef<'tcx> {
278 Hair(&'tcx hir::Expr),
279 Mirror(Box<Expr<'tcx>>),
282 #[derive(Clone, Debug)]
283 pub struct FieldExprRef<'tcx> {
285 pub expr: ExprRef<'tcx>,
288 #[derive(Clone, Debug)]
289 pub struct FruInfo<'tcx> {
290 pub base: ExprRef<'tcx>,
291 pub field_types: Vec<Ty<'tcx>>
294 #[derive(Clone, Debug)]
295 pub struct Arm<'tcx> {
296 pub pattern: Pat<'tcx>,
297 pub guard: Option<Guard<'tcx>>,
298 pub body: ExprRef<'tcx>,
299 pub lint_level: LintLevel,
300 pub scope: region::Scope,
305 // HACK(or_patterns; Centril | dlrobertson): Remove this and
306 // correctly handle each case in which this method is used.
307 pub fn top_pats_hack(&self) -> &[Pat<'tcx>] {
308 match &*self.pattern.kind {
309 PatKind::Or { pats } => pats,
310 _ => std::slice::from_ref(&self.pattern),
315 #[derive(Clone, Debug)]
316 pub enum Guard<'tcx> {
320 #[derive(Copy, Clone, Debug)]
326 impl<'tcx> ExprRef<'tcx> {
327 pub fn span(&self) -> Span {
329 ExprRef::Hair(expr) => expr.span,
330 ExprRef::Mirror(expr) => expr.span,
335 ///////////////////////////////////////////////////////////////////////////
338 /// "Mirroring" is the process of converting from a HIR type into one
339 /// of the HAIR types defined in this file. This is basically a "on
340 /// the fly" desugaring step that hides a lot of the messiness in the
341 /// tcx. For example, the mirror of a `&'tcx hir::Expr` is an
344 /// Mirroring is gradual: when you mirror an outer expression like `e1
345 /// + e2`, the references to the inner expressions `e1` and `e2` are
346 /// `ExprRef<'tcx>` instances, and they may or may not be eagerly
347 /// mirrored. This allows a single AST node from the compiler to
348 /// expand into one or more Hair nodes, which lets the Hair nodes be
350 pub trait Mirror<'tcx> {
353 fn make_mirror(self, cx: &mut Cx<'_, 'tcx>) -> Self::Output;
356 impl<'tcx> Mirror<'tcx> for Expr<'tcx> {
357 type Output = Expr<'tcx>;
359 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Expr<'tcx> {
364 impl<'tcx> Mirror<'tcx> for ExprRef<'tcx> {
365 type Output = Expr<'tcx>;
367 fn make_mirror(self, hir: &mut Cx<'a, 'tcx>) -> Expr<'tcx> {
369 ExprRef::Hair(h) => h.make_mirror(hir),
370 ExprRef::Mirror(m) => *m,
375 impl<'tcx> Mirror<'tcx> for Stmt<'tcx> {
376 type Output = Stmt<'tcx>;
378 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Stmt<'tcx> {
383 impl<'tcx> Mirror<'tcx> for StmtRef<'tcx> {
384 type Output = Stmt<'tcx>;
386 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Stmt<'tcx> {
388 StmtRef::Mirror(m) => *m,
393 impl<'tcx> Mirror<'tcx> for Block<'tcx> {
394 type Output = Block<'tcx>;
396 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Block<'tcx> {