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 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
86 pattern: Pattern<'tcx>,
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>,
176 condition: Option<ExprRef<'tcx>>,
180 scrutinee: ExprRef<'tcx>,
181 arms: Vec<Arm<'tcx>>,
184 body: &'tcx hir::Block,
201 index: ExprRef<'tcx>,
206 /// first argument, used for self in a closure
212 borrow_kind: BorrowKind,
216 label: region::Scope,
217 value: Option<ExprRef<'tcx>>,
220 label: region::Scope,
223 value: Option<ExprRef<'tcx>>,
226 value: ExprRef<'tcx>,
230 fields: Vec<ExprRef<'tcx>>,
233 fields: Vec<ExprRef<'tcx>>,
236 adt_def: &'tcx AdtDef,
237 variant_index: VariantIdx,
238 substs: SubstsRef<'tcx>,
240 /// Optional user-given substs: for something like `let x =
241 /// Bar::<T> { ... }`.
242 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
244 fields: Vec<FieldExprRef<'tcx>>,
245 base: Option<FruInfo<'tcx>>
247 PlaceTypeAscription {
248 source: ExprRef<'tcx>,
249 /// Type that the user gave to this expression
250 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
252 ValueTypeAscription {
253 source: ExprRef<'tcx>,
254 /// Type that the user gave to this expression
255 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
259 substs: UpvarSubsts<'tcx>,
260 upvars: Vec<ExprRef<'tcx>>,
261 movability: Option<hir::GeneratorMovability>,
264 literal: &'tcx Const<'tcx>,
265 user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
268 asm: &'tcx hir::InlineAsm,
269 outputs: Vec<ExprRef<'tcx>>,
270 inputs: Vec<ExprRef<'tcx>>
273 value: ExprRef<'tcx>,
277 #[derive(Clone, Debug)]
278 pub enum ExprRef<'tcx> {
279 Hair(&'tcx hir::Expr),
280 Mirror(Box<Expr<'tcx>>),
283 #[derive(Clone, Debug)]
284 pub struct FieldExprRef<'tcx> {
286 pub expr: ExprRef<'tcx>,
289 #[derive(Clone, Debug)]
290 pub struct FruInfo<'tcx> {
291 pub base: ExprRef<'tcx>,
292 pub field_types: Vec<Ty<'tcx>>
295 #[derive(Clone, Debug)]
296 pub struct Arm<'tcx> {
297 pub patterns: Vec<Pattern<'tcx>>,
298 pub guard: Option<Guard<'tcx>>,
299 pub body: ExprRef<'tcx>,
300 pub lint_level: LintLevel,
301 pub scope: region::Scope,
305 #[derive(Clone, Debug)]
306 pub enum Guard<'tcx> {
310 #[derive(Copy, Clone, Debug)]
316 impl<'tcx> ExprRef<'tcx> {
317 pub fn span(&self) -> Span {
319 ExprRef::Hair(expr) => expr.span,
320 ExprRef::Mirror(expr) => expr.span,
325 ///////////////////////////////////////////////////////////////////////////
328 /// "Mirroring" is the process of converting from a HIR type into one
329 /// of the HAIR types defined in this file. This is basically a "on
330 /// the fly" desugaring step that hides a lot of the messiness in the
331 /// tcx. For example, the mirror of a `&'tcx hir::Expr` is an
334 /// Mirroring is gradual: when you mirror an outer expression like `e1
335 /// + e2`, the references to the inner expressions `e1` and `e2` are
336 /// `ExprRef<'tcx>` instances, and they may or may not be eagerly
337 /// mirrored. This allows a single AST node from the compiler to
338 /// expand into one or more Hair nodes, which lets the Hair nodes be
340 pub trait Mirror<'tcx> {
343 fn make_mirror(self, cx: &mut Cx<'_, 'tcx>) -> Self::Output;
346 impl<'tcx> Mirror<'tcx> for Expr<'tcx> {
347 type Output = Expr<'tcx>;
349 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Expr<'tcx> {
354 impl<'tcx> Mirror<'tcx> for ExprRef<'tcx> {
355 type Output = Expr<'tcx>;
357 fn make_mirror(self, hir: &mut Cx<'a, 'tcx>) -> Expr<'tcx> {
359 ExprRef::Hair(h) => h.make_mirror(hir),
360 ExprRef::Mirror(m) => *m,
365 impl<'tcx> Mirror<'tcx> for Stmt<'tcx> {
366 type Output = Stmt<'tcx>;
368 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Stmt<'tcx> {
373 impl<'tcx> Mirror<'tcx> for StmtRef<'tcx> {
374 type Output = Stmt<'tcx>;
376 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Stmt<'tcx> {
378 StmtRef::Mirror(m) => *m,
383 impl<'tcx> Mirror<'tcx> for Block<'tcx> {
384 type Output = Block<'tcx>;
386 fn make_mirror(self, _: &mut Cx<'_, 'tcx>) -> Block<'tcx> {