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, Pattern, PatternKind, PatternRange, FieldPattern};
24 pub(crate) use self::pattern::PatternTypeProjection;
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 StatementSpan(pub Span);
61 #[derive(Clone, Debug)]
62 pub struct Stmt<'tcx> {
63 pub kind: StmtKind<'tcx>,
64 pub opt_destruction_scope: Option<region::Scope>,
65 pub span: StatementSpan,
68 #[derive(Clone, Debug)]
69 pub enum StmtKind<'tcx> {
71 /// scope for this statement; may be used as lifetime of temporaries
74 /// expression being evaluated in this statement
79 /// scope for variables bound in this let; covers this and
80 /// remaining statements in block
81 remainder_scope: region::Scope,
83 /// scope for the initialization itself; might be used as
84 /// lifetime of temporaries
85 init_scope: region::Scope,
89 /// if a type is included, it is added as an ascription pattern
90 pattern: Pattern<'tcx>,
92 /// let pat: ty = <INIT> ...
93 initializer: Option<ExprRef<'tcx>>,
95 /// the lint level for this let-statement
96 lint_level: LintLevel,
100 /// The Hair trait implementor lowers their expressions (`&'tcx H::Expr`)
101 /// into instances of this `Expr` enum. This lowering can be done
102 /// basically as lazily or as eagerly as desired: every recursive
103 /// reference to an expression in this enum is an `ExprRef<'tcx>`, which
104 /// may in turn be another instance of this enum (boxed), or else an
105 /// unlowered `&'tcx H::Expr`. Note that instances of `Expr` are very
106 /// short-lived. They are created by `Hair::to_expr`, analyzed and
107 /// converted into MIR, and then discarded.
109 /// If you compare `Expr` to the full compiler AST, you will see it is
110 /// a good bit simpler. In fact, a number of the more straight-forward
111 /// MIR simplifications are already done in the impl of `Hair`. For
112 /// example, method calls and overloaded operators are absent: they are
113 /// expected to be converted into `Expr::Call` instances.
114 #[derive(Clone, Debug)]
115 pub struct Expr<'tcx> {
116 /// type of this expression
119 /// lifetime of this expression if it should be spilled into a
120 /// temporary; should be None only if in a constant context
121 pub temp_lifetime: Option<region::Scope>,
123 /// span of the expression in the source
126 /// kind of expression
127 pub kind: ExprKind<'tcx>,
130 #[derive(Clone, Debug)]
131 pub enum ExprKind<'tcx> {
133 region_scope: region::Scope,
134 lint_level: LintLevel,
135 value: ExprRef<'tcx>,
138 value: ExprRef<'tcx>,
143 args: Vec<ExprRef<'tcx>>,
144 // Whether this is from a call in HIR, rather than from an overloaded
145 // operator. True for overloaded function call.
150 }, // NOT overloaded!
155 }, // NOT overloaded!
160 }, // NOT overloaded!
161 // LogicalOp is distinct from BinaryOp because of lazy evaluation of the operands.
165 }, // NOT overloaded!
167 source: ExprRef<'tcx>,
170 source: ExprRef<'tcx>,
171 }, // Use a lexpr to get a vexpr.
173 source: ExprRef<'tcx>,
177 source: ExprRef<'tcx>,
180 condition: Option<ExprRef<'tcx>>,
184 scrutinee: ExprRef<'tcx>,
185 arms: Vec<Arm<'tcx>>,
188 body: &'tcx hir::Block,
205 index: ExprRef<'tcx>,
210 /// first argument, used for self in a closure
216 borrow_kind: BorrowKind,
220 label: region::Scope,
221 value: Option<ExprRef<'tcx>>,
224 label: region::Scope,
227 value: Option<ExprRef<'tcx>>,
230 value: ExprRef<'tcx>,
234 fields: Vec<ExprRef<'tcx>>,
237 fields: Vec<ExprRef<'tcx>>,
240 adt_def: &'tcx AdtDef,
241 variant_index: VariantIdx,
242 substs: SubstsRef<'tcx>,
244 /// Optional user-given substs: for something like `let x =
245 /// Bar::<T> { ... }`.
246 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
248 fields: Vec<FieldExprRef<'tcx>>,
249 base: Option<FruInfo<'tcx>>
251 PlaceTypeAscription {
252 source: ExprRef<'tcx>,
253 /// Type that the user gave to this expression
254 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
256 ValueTypeAscription {
257 source: ExprRef<'tcx>,
258 /// Type that the user gave to this expression
259 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
263 substs: UpvarSubsts<'tcx>,
264 upvars: Vec<ExprRef<'tcx>>,
265 movability: Option<hir::GeneratorMovability>,
268 literal: &'tcx Const<'tcx>,
269 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
272 asm: &'tcx hir::InlineAsm,
273 outputs: Vec<ExprRef<'tcx>>,
274 inputs: Vec<ExprRef<'tcx>>
277 value: ExprRef<'tcx>,
281 #[derive(Clone, Debug)]
282 pub enum ExprRef<'tcx> {
283 Hair(&'tcx hir::Expr),
284 Mirror(Box<Expr<'tcx>>),
287 #[derive(Clone, Debug)]
288 pub struct FieldExprRef<'tcx> {
290 pub expr: ExprRef<'tcx>,
293 #[derive(Clone, Debug)]
294 pub struct FruInfo<'tcx> {
295 pub base: ExprRef<'tcx>,
296 pub field_types: Vec<Ty<'tcx>>
299 #[derive(Clone, Debug)]
300 pub struct Arm<'tcx> {
301 pub patterns: Vec<Pattern<'tcx>>,
302 pub guard: Option<Guard<'tcx>>,
303 pub body: ExprRef<'tcx>,
304 pub lint_level: LintLevel,
305 pub scope: region::Scope,
309 #[derive(Clone, Debug)]
310 pub enum Guard<'tcx> {
314 #[derive(Copy, Clone, Debug)]
320 impl<'tcx> ExprRef<'tcx> {
321 pub fn span(&self) -> Span {
323 ExprRef::Hair(expr) => expr.span,
324 ExprRef::Mirror(expr) => expr.span,
329 ///////////////////////////////////////////////////////////////////////////
332 /// "Mirroring" is the process of converting from a HIR type into one
333 /// of the HAIR types defined in this file. This is basically a "on
334 /// the fly" desugaring step that hides a lot of the messiness in the
335 /// tcx. For example, the mirror of a `&'tcx hir::Expr` is an
338 /// Mirroring is gradual: when you mirror an outer expression like `e1
339 /// + e2`, the references to the inner expressions `e1` and `e2` are
340 /// `ExprRef<'tcx>` instances, and they may or may not be eagerly
341 /// mirrored. This allows a single AST node from the compiler to
342 /// expand into one or more Hair nodes, which lets the Hair nodes be
344 pub trait Mirror<'tcx> {
347 fn make_mirror<'a, 'gcx>(self, cx: &mut Cx<'a, 'gcx, 'tcx>) -> Self::Output;
350 impl<'tcx> Mirror<'tcx> for Expr<'tcx> {
351 type Output = Expr<'tcx>;
353 fn make_mirror<'a, 'gcx>(self, _: &mut Cx<'a, 'gcx, 'tcx>) -> Expr<'tcx> {
358 impl<'tcx> Mirror<'tcx> for ExprRef<'tcx> {
359 type Output = Expr<'tcx>;
361 fn make_mirror<'a, 'gcx>(self, hir: &mut Cx<'a, 'gcx, 'tcx>) -> Expr<'tcx> {
363 ExprRef::Hair(h) => h.make_mirror(hir),
364 ExprRef::Mirror(m) => *m,
369 impl<'tcx> Mirror<'tcx> for Stmt<'tcx> {
370 type Output = Stmt<'tcx>;
372 fn make_mirror<'a, 'gcx>(self, _: &mut Cx<'a, 'gcx, 'tcx>) -> Stmt<'tcx> {
377 impl<'tcx> Mirror<'tcx> for StmtRef<'tcx> {
378 type Output = Stmt<'tcx>;
380 fn make_mirror<'a, 'gcx>(self, _: &mut Cx<'a, 'gcx, 'tcx>) -> Stmt<'tcx> {
382 StmtRef::Mirror(m) => *m,
387 impl<'tcx> Mirror<'tcx> for Block<'tcx> {
388 type Output = Block<'tcx>;
390 fn make_mirror<'a, 'gcx>(self, _: &mut Cx<'a, 'gcx, 'tcx>) -> Block<'tcx> {