1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 //! The job of the categorization module is to analyze an expression to
14 //! determine what kind of memory is used in evaluating it (for example,
15 //! where dereferences occur and what kind of pointer is dereferenced;
16 //! whether the memory is mutable; etc)
18 //! Categorization effectively transforms all of our expressions into
19 //! expressions of the following forms (the actual enum has many more
20 //! possibilities, naturally, but they are all variants of these base
23 //! E = rvalue // some computed rvalue
24 //! | x // address of a local variable or argument
25 //! | *E // deref of a ptr
26 //! | E.comp // access to an interior component
28 //! Imagine a routine ToAddr(Expr) that evaluates an expression and returns an
29 //! address where the result is to be found. If Expr is an lvalue, then this
30 //! is the address of the lvalue. If Expr is an rvalue, this is the address of
31 //! some temporary spot in memory where the result is stored.
33 //! Now, cat_expr() classifies the expression Expr and the address A=ToAddr(Expr)
36 //! - cat: what kind of expression was this? This is a subset of the
37 //! full expression forms which only includes those that we care about
38 //! for the purpose of the analysis.
39 //! - mutbl: mutability of the address A
40 //! - ty: the type of data found at the address A
42 //! The resulting categorization tree differs somewhat from the expressions
43 //! themselves. For example, auto-derefs are explicit. Also, an index a[b] is
44 //! decomposed into two operations: a dereference to reach the array data and
45 //! then an index to jump forward to the relevant item.
47 //! ## By-reference upvars
49 //! One part of the translation which may be non-obvious is that we translate
50 //! closure upvars into the dereference of a borrowed pointer; this more closely
51 //! resembles the runtime translation. So, for example, if we had:
55 //! let inc = || x += y;
57 //! Then when we categorize `x` (*within* the closure) we would yield a
58 //! result of `*x'`, effectively, where `x'` is a `Categorization::Upvar` reference
59 //! tied to `x`. The type of `x'` will be a borrowed pointer.
61 #![allow(non_camel_case_types)]
63 pub use self::PointerKind::*;
64 pub use self::InteriorKind::*;
65 pub use self::FieldName::*;
66 pub use self::ElementKind::*;
67 pub use self::MutabilityCategory::*;
68 pub use self::AliasableReason::*;
69 pub use self::Note::*;
71 use self::Aliasability::*;
73 use hir::def_id::DefId;
74 use hir::map as hir_map;
76 use hir::def::{Def, CtorKind};
78 use ty::{self, Ty, TyCtxt};
80 use hir::{MutImmutable, MutMutable, PatKind};
81 use hir::pat_util::EnumerateAndAdjustIterator;
89 #[derive(Clone, PartialEq)]
90 pub enum Categorization<'tcx> {
91 // temporary val, argument is its scope
92 Rvalue(&'tcx ty::Region, &'tcx ty::Region),
94 Upvar(Upvar), // upvar referenced by closure env
95 Local(ast::NodeId), // local variable
96 Deref(cmt<'tcx>, usize, PointerKind<'tcx>), // deref of a ptr
97 Interior(cmt<'tcx>, InteriorKind), // something interior: field, tuple, etc
98 Downcast(cmt<'tcx>, DefId), // selects a particular enum variant (*1)
100 // (*1) downcast is only required if the enum has more than one variant
103 // Represents any kind of upvar
104 #[derive(Clone, Copy, PartialEq)]
107 pub kind: ty::ClosureKind
110 // different kinds of pointers:
111 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
112 pub enum PointerKind<'tcx> {
117 BorrowedPtr(ty::BorrowKind, &'tcx ty::Region),
120 UnsafePtr(hir::Mutability),
122 /// Implicit deref of the `&T` that results from an overloaded index `[]`.
123 Implicit(ty::BorrowKind, &'tcx ty::Region),
126 // We use the term "interior" to mean "something reachable from the
127 // base without a pointer dereference", e.g. a field
128 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
129 pub enum InteriorKind {
130 InteriorField(FieldName),
131 InteriorElement(InteriorOffsetKind, ElementKind),
134 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
136 NamedField(ast::Name),
137 PositionalField(usize)
140 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
141 pub enum InteriorOffsetKind {
142 Index, // e.g. `array_expr[index_expr]`
143 Pattern, // e.g. `fn foo([_, a, _, _]: [A; 4]) { ... }`
146 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
147 pub enum ElementKind {
152 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
153 pub enum MutabilityCategory {
154 McImmutable, // Immutable.
155 McDeclared, // Directly declared as mutable.
156 McInherited, // Inherited from the fact that owner is mutable.
159 // A note about the provenance of a `cmt`. This is used for
160 // special-case handling of upvars such as mutability inference.
161 // Upvar categorization can generate a variable number of nested
162 // derefs. The note allows detecting them without deep pattern
163 // matching on the categorization.
164 #[derive(Clone, Copy, PartialEq, Debug)]
166 NoteClosureEnv(ty::UpvarId), // Deref through closure env
167 NoteUpvarRef(ty::UpvarId), // Deref through by-ref upvar
168 NoteNone // Nothing special
171 // `cmt`: "Category, Mutability, and Type".
173 // a complete categorization of a value indicating where it originated
174 // and how it is located, as well as the mutability of the memory in
175 // which the value is stored.
177 // *WARNING* The field `cmt.type` is NOT necessarily the same as the
178 // result of `node_id_to_type(cmt.id)`. This is because the `id` is
179 // always the `id` of the node producing the type; in an expression
180 // like `*x`, the type of this deref node is the deref'd type (`T`),
181 // but in a pattern like `@x`, the `@x` pattern is again a
182 // dereference, but its type is the type *before* the dereference
183 // (`@T`). So use `cmt.ty` to find the type of the value in a consistent
184 // fashion. For more details, see the method `cat_pattern`
185 #[derive(Clone, PartialEq)]
186 pub struct cmt_<'tcx> {
187 pub id: ast::NodeId, // id of expr/pat producing this value
188 pub span: Span, // span of same expr/pat
189 pub cat: Categorization<'tcx>, // categorization of expr
190 pub mutbl: MutabilityCategory, // mutability of expr as lvalue
191 pub ty: Ty<'tcx>, // type of the expr (*see WARNING above*)
192 pub note: Note, // Note about the provenance of this cmt
195 pub type cmt<'tcx> = Rc<cmt_<'tcx>>;
197 pub enum ImmutabilityBlame<'tcx> {
198 ImmLocal(ast::NodeId),
199 ClosureEnv(ast::NodeId),
200 LocalDeref(ast::NodeId),
201 AdtFieldDeref(&'tcx ty::AdtDef, &'tcx ty::FieldDef)
204 impl<'tcx> cmt_<'tcx> {
205 fn resolve_field(&self, field_name: FieldName) -> Option<(&'tcx ty::AdtDef, &'tcx ty::FieldDef)>
207 let adt_def = match self.ty.sty {
208 ty::TyAdt(def, _) => def,
209 ty::TyTuple(..) => return None,
210 // closures get `Categorization::Upvar` rather than `Categorization::Interior`
211 _ => bug!("interior cmt {:?} is not an ADT", self)
213 let variant_def = match self.cat {
214 Categorization::Downcast(_, variant_did) => {
215 adt_def.variant_with_id(variant_did)
218 assert!(adt_def.is_univariant());
222 let field_def = match field_name {
223 NamedField(name) => variant_def.field_named(name),
224 PositionalField(idx) => &variant_def.fields[idx]
226 Some((adt_def, field_def))
229 pub fn immutability_blame(&self) -> Option<ImmutabilityBlame<'tcx>> {
231 Categorization::Deref(ref base_cmt, _, BorrowedPtr(ty::ImmBorrow, _)) |
232 Categorization::Deref(ref base_cmt, _, Implicit(ty::ImmBorrow, _)) => {
233 // try to figure out where the immutable reference came from
235 Categorization::Local(node_id) =>
236 Some(ImmutabilityBlame::LocalDeref(node_id)),
237 Categorization::Interior(ref base_cmt, InteriorField(field_name)) => {
238 base_cmt.resolve_field(field_name).map(|(adt_def, field_def)| {
239 ImmutabilityBlame::AdtFieldDeref(adt_def, field_def)
242 Categorization::Upvar(Upvar { id, .. }) => {
243 if let NoteClosureEnv(..) = self.note {
244 Some(ImmutabilityBlame::ClosureEnv(id.closure_expr_id))
252 Categorization::Local(node_id) => {
253 Some(ImmutabilityBlame::ImmLocal(node_id))
255 Categorization::Rvalue(..) |
256 Categorization::Upvar(..) |
257 Categorization::Deref(.., UnsafePtr(..)) => {
258 // This should not be reachable up to inference limitations.
261 Categorization::Interior(ref base_cmt, _) |
262 Categorization::Downcast(ref base_cmt, _) |
263 Categorization::Deref(ref base_cmt, _, _) => {
264 base_cmt.immutability_blame()
266 Categorization::StaticItem => {
267 // Do we want to do something here?
275 fn id(&self) -> ast::NodeId;
276 fn span(&self) -> Span;
279 impl ast_node for hir::Expr {
280 fn id(&self) -> ast::NodeId { self.id }
281 fn span(&self) -> Span { self.span }
284 impl ast_node for hir::Pat {
285 fn id(&self) -> ast::NodeId { self.id }
286 fn span(&self) -> Span { self.span }
289 #[derive(Copy, Clone)]
290 pub struct MemCategorizationContext<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
291 pub infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
292 options: MemCategorizationOptions,
295 #[derive(Copy, Clone, Default)]
296 pub struct MemCategorizationOptions {
297 // If true, then when analyzing a closure upvar, if the closure
298 // has a missing kind, we treat it like a Fn closure. When false,
299 // we ICE if the closure has a missing kind. Should be false
300 // except during closure kind inference. It is used by the
301 // mem-categorization code to be able to have stricter assertions
302 // (which are always true except during upvar inference).
303 pub during_closure_kind_inference: bool,
306 pub type McResult<T> = Result<T, ()>;
308 impl MutabilityCategory {
309 pub fn from_mutbl(m: hir::Mutability) -> MutabilityCategory {
311 MutImmutable => McImmutable,
312 MutMutable => McDeclared
314 debug!("MutabilityCategory::{}({:?}) => {:?}",
315 "from_mutbl", m, ret);
319 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
320 let ret = match borrow_kind {
321 ty::ImmBorrow => McImmutable,
322 ty::UniqueImmBorrow => McImmutable,
323 ty::MutBorrow => McDeclared,
325 debug!("MutabilityCategory::{}({:?}) => {:?}",
326 "from_borrow_kind", borrow_kind, ret);
330 fn from_pointer_kind(base_mutbl: MutabilityCategory,
331 ptr: PointerKind) -> MutabilityCategory {
332 let ret = match ptr {
336 BorrowedPtr(borrow_kind, _) | Implicit(borrow_kind, _) => {
337 MutabilityCategory::from_borrow_kind(borrow_kind)
340 MutabilityCategory::from_mutbl(m)
343 debug!("MutabilityCategory::{}({:?}, {:?}) => {:?}",
344 "from_pointer_kind", base_mutbl, ptr, ret);
348 fn from_local(tcx: TyCtxt, id: ast::NodeId) -> MutabilityCategory {
349 let ret = match tcx.hir.get(id) {
350 hir_map::NodeLocal(p) => match p.node {
351 PatKind::Binding(bind_mode, ..) => {
352 if bind_mode == hir::BindByValue(hir::MutMutable) {
358 _ => span_bug!(p.span, "expected identifier pattern")
360 _ => span_bug!(tcx.hir.span(id), "expected identifier pattern")
362 debug!("MutabilityCategory::{}(tcx, id={:?}) => {:?}",
363 "from_local", id, ret);
367 pub fn inherit(&self) -> MutabilityCategory {
368 let ret = match *self {
369 McImmutable => McImmutable,
370 McDeclared => McInherited,
371 McInherited => McInherited,
373 debug!("{:?}.inherit() => {:?}", self, ret);
377 pub fn is_mutable(&self) -> bool {
378 let ret = match *self {
379 McImmutable => false,
383 debug!("{:?}.is_mutable() => {:?}", self, ret);
387 pub fn is_immutable(&self) -> bool {
388 let ret = match *self {
390 McDeclared | McInherited => false
392 debug!("{:?}.is_immutable() => {:?}", self, ret);
396 pub fn to_user_str(&self) -> &'static str {
398 McDeclared | McInherited => "mutable",
399 McImmutable => "immutable",
404 impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
405 pub fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>)
406 -> MemCategorizationContext<'a, 'gcx, 'tcx> {
407 MemCategorizationContext::with_options(infcx, MemCategorizationOptions::default())
410 pub fn with_options(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
411 options: MemCategorizationOptions)
412 -> MemCategorizationContext<'a, 'gcx, 'tcx> {
413 MemCategorizationContext {
419 fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
423 fn expr_ty(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
424 match self.infcx.node_ty(expr.id) {
427 debug!("expr_ty({:?}) yielded Err", expr);
433 fn expr_ty_adjusted(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
434 self.infcx.expr_ty_adjusted(expr)
437 fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
438 self.infcx.node_ty(id)
441 fn pat_ty(&self, pat: &hir::Pat) -> McResult<Ty<'tcx>> {
442 let base_ty = self.infcx.node_ty(pat.id)?;
443 // FIXME (Issue #18207): This code detects whether we are
444 // looking at a `ref x`, and if so, figures out what the type
445 // *being borrowed* is. But ideally we would put in a more
446 // fundamental fix to this conflated use of the node id.
447 let ret_ty = match pat.node {
448 PatKind::Binding(hir::BindByRef(_), ..) => {
449 // a bind-by-ref means that the base_ty will be the type of the ident itself,
450 // but what we want here is the type of the underlying value being borrowed.
451 // So peel off one-level, turning the &T into T.
452 match base_ty.builtin_deref(false, ty::NoPreference) {
454 None => { return Err(()); }
459 debug!("pat_ty(pat={:?}) base_ty={:?} ret_ty={:?}",
460 pat, base_ty, ret_ty);
464 pub fn cat_expr(&self, expr: &hir::Expr) -> McResult<cmt<'tcx>> {
465 match self.infcx.tables.borrow().adjustments.get(&expr.id) {
468 self.cat_expr_unadjusted(expr)
471 Some(adjustment) => {
472 match adjustment.kind {
473 adjustment::Adjust::DerefRef {
478 // Equivalent to *expr or something similar.
479 self.cat_expr_autoderefd(expr, autoderefs)
482 adjustment::Adjust::NeverToAny |
483 adjustment::Adjust::ReifyFnPointer |
484 adjustment::Adjust::UnsafeFnPointer |
485 adjustment::Adjust::ClosureFnPointer |
486 adjustment::Adjust::MutToConstPointer |
487 adjustment::Adjust::DerefRef {..} => {
488 debug!("cat_expr({:?}): {:?}",
491 // Result is an rvalue.
492 let expr_ty = self.expr_ty_adjusted(expr)?;
493 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
500 pub fn cat_expr_autoderefd(&self,
503 -> McResult<cmt<'tcx>> {
504 let mut cmt = self.cat_expr_unadjusted(expr)?;
505 debug!("cat_expr_autoderefd: autoderefs={}, cmt={:?}",
508 for deref in 1..autoderefs + 1 {
509 cmt = self.cat_deref(expr, cmt, deref)?;
514 pub fn cat_expr_unadjusted(&self, expr: &hir::Expr) -> McResult<cmt<'tcx>> {
515 debug!("cat_expr: id={} expr={:?}", expr.id, expr);
517 let expr_ty = self.expr_ty(expr)?;
519 hir::ExprUnary(hir::UnDeref, ref e_base) => {
520 let base_cmt = self.cat_expr(&e_base)?;
521 self.cat_deref(expr, base_cmt, 0)
524 hir::ExprField(ref base, f_name) => {
525 let base_cmt = self.cat_expr(&base)?;
526 debug!("cat_expr(cat_field): id={} expr={:?} base={:?}",
530 Ok(self.cat_field(expr, base_cmt, f_name.node, expr_ty))
533 hir::ExprTupField(ref base, idx) => {
534 let base_cmt = self.cat_expr(&base)?;
535 Ok(self.cat_tup_field(expr, base_cmt, idx.node, expr_ty))
538 hir::ExprIndex(ref base, _) => {
539 let method_call = ty::MethodCall::expr(expr.id());
540 match self.infcx.node_method_ty(method_call) {
542 // If this is an index implemented by a method call, then it
543 // will include an implicit deref of the result.
544 let ret_ty = self.overloaded_method_return_ty(method_ty);
546 // The index method always returns an `&T`, so
547 // dereference it to find the result type.
548 let elem_ty = match ret_ty.sty {
549 ty::TyRef(_, mt) => mt.ty,
551 debug!("cat_expr_unadjusted: return type of overloaded index is {:?}?",
557 // The call to index() returns a `&T` value, which
558 // is an rvalue. That is what we will be
560 let base_cmt = self.cat_rvalue_node(expr.id(), expr.span(), ret_ty);
561 Ok(self.cat_deref_common(expr, base_cmt, 1, elem_ty, true))
564 self.cat_index(expr, self.cat_expr(&base)?, InteriorOffsetKind::Index)
569 hir::ExprPath(ref qpath) => {
570 let def = self.infcx.tables.borrow().qpath_def(qpath, expr.id);
571 self.cat_def(expr.id, expr.span, expr_ty, def)
574 hir::ExprType(ref e, _) => {
578 hir::ExprAddrOf(..) | hir::ExprCall(..) |
579 hir::ExprAssign(..) | hir::ExprAssignOp(..) |
580 hir::ExprClosure(..) | hir::ExprRet(..) |
582 hir::ExprMethodCall(..) | hir::ExprCast(..) |
583 hir::ExprArray(..) | hir::ExprTup(..) | hir::ExprIf(..) |
584 hir::ExprBinary(..) | hir::ExprWhile(..) |
585 hir::ExprBlock(..) | hir::ExprLoop(..) | hir::ExprMatch(..) |
586 hir::ExprLit(..) | hir::ExprBreak(..) |
587 hir::ExprAgain(..) | hir::ExprStruct(..) | hir::ExprRepeat(..) |
588 hir::ExprInlineAsm(..) | hir::ExprBox(..) => {
589 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
594 pub fn cat_def(&self,
599 -> McResult<cmt<'tcx>> {
600 debug!("cat_def: id={} expr={:?} def={:?}",
604 Def::StructCtor(..) | Def::VariantCtor(..) | Def::Const(..) |
605 Def::AssociatedConst(..) | Def::Fn(..) | Def::Method(..) => {
606 Ok(self.cat_rvalue_node(id, span, expr_ty))
609 Def::Static(_, mutbl) => {
613 cat:Categorization::StaticItem,
614 mutbl: if mutbl { McDeclared } else { McImmutable},
620 Def::Upvar(def_id, _, fn_node_id) => {
621 let var_id = self.tcx().hir.as_local_node_id(def_id).unwrap();
622 let ty = self.node_ty(fn_node_id)?;
624 ty::TyClosure(closure_id, _) => {
625 match self.infcx.closure_kind(closure_id) {
627 self.cat_upvar(id, span, var_id, fn_node_id, kind)
630 if !self.options.during_closure_kind_inference {
633 "No closure kind for {:?}",
637 // during closure kind inference, we
638 // don't know the closure kind yet, but
639 // it's ok because we detect that we are
640 // accessing an upvar and handle that
641 // case specially anyhow. Use Fn
643 self.cat_upvar(id, span, var_id, fn_node_id, ty::ClosureKind::Fn)
650 "Upvar of non-closure {} - {:?}",
657 Def::Local(def_id) => {
658 let vid = self.tcx().hir.as_local_node_id(def_id).unwrap();
662 cat: Categorization::Local(vid),
663 mutbl: MutabilityCategory::from_local(self.tcx(), vid),
669 def => span_bug!(span, "unexpected definition in memory categorization: {:?}", def)
673 // Categorize an upvar, complete with invisible derefs of closure
674 // environment and upvar reference as appropriate.
679 fn_node_id: ast::NodeId,
680 kind: ty::ClosureKind)
681 -> McResult<cmt<'tcx>>
683 // An upvar can have up to 3 components. We translate first to a
684 // `Categorization::Upvar`, which is itself a fiction -- it represents the reference to the
685 // field from the environment.
687 // `Categorization::Upvar`. Next, we add a deref through the implicit
688 // environment pointer with an anonymous free region 'env and
689 // appropriate borrow kind for closure kinds that take self by
690 // reference. Finally, if the upvar was captured
691 // by-reference, we add a deref through that reference. The
692 // region of this reference is an inference variable 'up that
693 // was previously generated and recorded in the upvar borrow
694 // map. The borrow kind bk is inferred by based on how the
697 // This results in the following table for concrete closure
701 // ---------------+----------------------+-------------------------------
702 // Fn | copied -> &'env | upvar -> &'env -> &'up bk
703 // FnMut | copied -> &'env mut | upvar -> &'env mut -> &'up bk
704 // FnOnce | copied | upvar -> &'up bk
706 let upvar_id = ty::UpvarId { var_id: var_id,
707 closure_expr_id: fn_node_id };
708 let var_ty = self.node_ty(var_id)?;
710 // Mutability of original variable itself
711 let var_mutbl = MutabilityCategory::from_local(self.tcx(), var_id);
713 // Construct the upvar. This represents access to the field
714 // from the environment (perhaps we should eventually desugar
715 // this field further, but it will do for now).
716 let cmt_result = cmt_ {
719 cat: Categorization::Upvar(Upvar {id: upvar_id, kind: kind}),
725 // If this is a `FnMut` or `Fn` closure, then the above is
726 // conceptually a `&mut` or `&` reference, so we have to add a
728 let cmt_result = match kind {
729 ty::ClosureKind::FnOnce => {
732 ty::ClosureKind::FnMut => {
733 self.env_deref(id, span, upvar_id, var_mutbl, ty::MutBorrow, cmt_result)
735 ty::ClosureKind::Fn => {
736 self.env_deref(id, span, upvar_id, var_mutbl, ty::ImmBorrow, cmt_result)
740 // If this is a by-ref capture, then the upvar we loaded is
741 // actually a reference, so we have to add an implicit deref
743 let upvar_id = ty::UpvarId { var_id: var_id,
744 closure_expr_id: fn_node_id };
745 let upvar_capture = self.infcx.upvar_capture(upvar_id).unwrap();
746 let cmt_result = match upvar_capture {
747 ty::UpvarCapture::ByValue => {
750 ty::UpvarCapture::ByRef(upvar_borrow) => {
751 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
755 cat: Categorization::Deref(Rc::new(cmt_result), 0, ptr),
756 mutbl: MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
758 note: NoteUpvarRef(upvar_id)
763 let ret = Rc::new(cmt_result);
764 debug!("cat_upvar ret={:?}", ret);
771 upvar_id: ty::UpvarId,
772 upvar_mutbl: MutabilityCategory,
773 env_borrow_kind: ty::BorrowKind,
774 cmt_result: cmt_<'tcx>)
777 // Look up the node ID of the closure body so we can construct
778 // a free region within it
780 let fn_expr = match self.tcx().hir.find(upvar_id.closure_expr_id) {
781 Some(hir_map::NodeExpr(e)) => e,
786 hir::ExprClosure(.., body_id, _) => body_id.node_id,
791 // Region of environment pointer
792 let env_region = self.tcx().mk_region(ty::ReFree(ty::FreeRegion {
793 // The environment of a closure is guaranteed to
794 // outlive any bindings introduced in the body of the
796 scope: self.tcx().region_maps.item_extent(fn_body_id),
797 bound_region: ty::BrEnv
800 let env_ptr = BorrowedPtr(env_borrow_kind, env_region);
802 let var_ty = cmt_result.ty;
804 // We need to add the env deref. This means
805 // that the above is actually immutable and
806 // has a ref type. However, nothing should
807 // actually look at the type, so we can get
808 // away with stuffing a `TyError` in there
809 // instead of bothering to construct a proper
811 let cmt_result = cmt_ {
813 ty: self.tcx().types.err,
817 let mut deref_mutbl = MutabilityCategory::from_borrow_kind(env_borrow_kind);
819 // Issue #18335. If variable is declared as immutable, override the
820 // mutability from the environment and substitute an `&T` anyway.
822 McImmutable => { deref_mutbl = McImmutable; }
823 McDeclared | McInherited => { }
829 cat: Categorization::Deref(Rc::new(cmt_result), 0, env_ptr),
832 note: NoteClosureEnv(upvar_id)
835 debug!("env_deref ret {:?}", ret);
840 /// Returns the lifetime of a temporary created by expr with id `id`.
841 /// This could be `'static` if `id` is part of a constant expression.
842 pub fn temporary_scope(&self, id: ast::NodeId) -> (&'tcx ty::Region, &'tcx ty::Region)
844 let (scope, old_scope) =
845 self.tcx().region_maps.old_and_new_temporary_scope(id);
846 (self.tcx().mk_region(match scope {
847 Some(scope) => ty::ReScope(scope),
850 self.tcx().mk_region(match old_scope {
851 Some(scope) => ty::ReScope(scope),
856 pub fn cat_rvalue_node(&self,
861 let promotable = self.tcx().rvalue_promotable_to_static.borrow().get(&id).cloned()
864 // When the corresponding feature isn't toggled, only promote `[T; 0]`.
865 let promotable = match expr_ty.sty {
866 ty::TyArray(_, 0) => true,
867 _ => promotable && self.tcx().sess.features.borrow().rvalue_static_promotion,
870 // Compute maximum lifetime of this rvalue. This is 'static if
871 // we can promote to a constant, otherwise equal to enclosing temp
873 let (re, old_re) = if promotable {
874 (self.tcx().types.re_static,
875 self.tcx().types.re_static)
877 self.temporary_scope(id)
879 let ret = self.cat_rvalue(id, span, re, old_re, expr_ty);
880 debug!("cat_rvalue_node ret {:?}", ret);
884 pub fn cat_rvalue(&self,
887 temp_scope: &'tcx ty::Region,
888 old_temp_scope: &'tcx ty::Region,
889 expr_ty: Ty<'tcx>) -> cmt<'tcx> {
890 let ret = Rc::new(cmt_ {
893 cat:Categorization::Rvalue(temp_scope, old_temp_scope),
898 debug!("cat_rvalue ret {:?}", ret);
902 pub fn cat_field<N:ast_node>(&self,
908 let ret = Rc::new(cmt_ {
911 mutbl: base_cmt.mutbl.inherit(),
912 cat: Categorization::Interior(base_cmt, InteriorField(NamedField(f_name))),
916 debug!("cat_field ret {:?}", ret);
920 pub fn cat_tup_field<N:ast_node>(&self,
926 let ret = Rc::new(cmt_ {
929 mutbl: base_cmt.mutbl.inherit(),
930 cat: Categorization::Interior(base_cmt, InteriorField(PositionalField(f_idx))),
934 debug!("cat_tup_field ret {:?}", ret);
938 fn cat_deref<N:ast_node>(&self,
942 -> McResult<cmt<'tcx>> {
943 let method_call = ty::MethodCall {
945 autoderef: deref_cnt as u32
947 let method_ty = self.infcx.node_method_ty(method_call);
949 debug!("cat_deref: method_call={:?} method_ty={:?}",
950 method_call, method_ty.map(|ty| ty));
952 let base_cmt = match method_ty {
955 self.tcx().no_late_bound_regions(&method_ty.fn_ret()).unwrap();
956 self.cat_rvalue_node(node.id(), node.span(), ref_ty)
960 let base_cmt_ty = base_cmt.ty;
961 match base_cmt_ty.builtin_deref(true, ty::NoPreference) {
963 let ret = self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty, false);
964 debug!("cat_deref ret {:?}", ret);
968 debug!("Explicit deref of non-derefable type: {:?}",
975 fn cat_deref_common<N:ast_node>(&self,
983 let ptr = match base_cmt.ty.sty {
984 ty::TyAdt(def, ..) if def.is_box() => Unique,
985 ty::TyRawPtr(ref mt) => UnsafePtr(mt.mutbl),
986 ty::TyRef(r, mt) => {
987 let bk = ty::BorrowKind::from_mutbl(mt.mutbl);
988 if implicit { Implicit(bk, r) } else { BorrowedPtr(bk, r) }
990 ref ty => bug!("unexpected type in cat_deref_common: {:?}", ty)
992 let ret = Rc::new(cmt_ {
995 // For unique ptrs, we inherit mutability from the owning reference.
996 mutbl: MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr),
997 cat: Categorization::Deref(base_cmt, deref_cnt, ptr),
1001 debug!("cat_deref_common ret {:?}", ret);
1005 pub fn cat_index<N:ast_node>(&self,
1007 mut base_cmt: cmt<'tcx>,
1008 context: InteriorOffsetKind)
1009 -> McResult<cmt<'tcx>> {
1010 //! Creates a cmt for an indexing operation (`[]`).
1012 //! One subtle aspect of indexing that may not be
1013 //! immediately obvious: for anything other than a fixed-length
1014 //! vector, an operation like `x[y]` actually consists of two
1015 //! disjoint (from the point of view of borrowck) operations.
1016 //! The first is a deref of `x` to create a pointer `p` that points
1017 //! at the first element in the array. The second operation is
1018 //! an index which adds `y*sizeof(T)` to `p` to obtain the
1019 //! pointer to `x[y]`. `cat_index` will produce a resulting
1020 //! cmt containing both this deref and the indexing,
1021 //! presuming that `base_cmt` is not of fixed-length type.
1024 //! - `elt`: the AST node being indexed
1025 //! - `base_cmt`: the cmt of `elt`
1027 let method_call = ty::MethodCall::expr(elt.id());
1028 let method_ty = self.infcx.node_method_ty(method_call);
1030 let (element_ty, element_kind) = match method_ty {
1031 Some(method_ty) => {
1032 let ref_ty = self.overloaded_method_return_ty(method_ty);
1033 base_cmt = self.cat_rvalue_node(elt.id(), elt.span(), ref_ty);
1035 (ref_ty.builtin_deref(false, ty::NoPreference).unwrap().ty,
1036 ElementKind::OtherElement)
1039 match base_cmt.ty.builtin_index() {
1040 Some(ty) => (ty, ElementKind::VecElement),
1048 let interior_elem = InteriorElement(context, element_kind);
1050 self.cat_imm_interior(elt, base_cmt.clone(), element_ty, interior_elem);
1051 debug!("cat_index ret {:?}", ret);
1055 pub fn cat_imm_interior<N:ast_node>(&self,
1057 base_cmt: cmt<'tcx>,
1058 interior_ty: Ty<'tcx>,
1059 interior: InteriorKind)
1061 let ret = Rc::new(cmt_ {
1064 mutbl: base_cmt.mutbl.inherit(),
1065 cat: Categorization::Interior(base_cmt, interior),
1069 debug!("cat_imm_interior ret={:?}", ret);
1073 pub fn cat_downcast<N:ast_node>(&self,
1075 base_cmt: cmt<'tcx>,
1076 downcast_ty: Ty<'tcx>,
1079 let ret = Rc::new(cmt_ {
1082 mutbl: base_cmt.mutbl.inherit(),
1083 cat: Categorization::Downcast(base_cmt, variant_did),
1087 debug!("cat_downcast ret={:?}", ret);
1091 pub fn cat_pattern<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, mut op: F) -> McResult<()>
1092 where F: FnMut(&MemCategorizationContext<'a, 'gcx, 'tcx>, cmt<'tcx>, &hir::Pat),
1094 self.cat_pattern_(cmt, pat, &mut op)
1097 // FIXME(#19596) This is a workaround, but there should be a better way to do this
1098 fn cat_pattern_<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, op: &mut F) -> McResult<()>
1099 where F : FnMut(&MemCategorizationContext<'a, 'gcx, 'tcx>, cmt<'tcx>, &hir::Pat)
1101 // Here, `cmt` is the categorization for the value being
1102 // matched and pat is the pattern it is being matched against.
1104 // In general, the way that this works is that we walk down
1105 // the pattern, constructing a cmt that represents the path
1106 // that will be taken to reach the value being matched.
1108 // When we encounter named bindings, we take the cmt that has
1109 // been built up and pass it off to guarantee_valid() so that
1110 // we can be sure that the binding will remain valid for the
1111 // duration of the arm.
1113 // (*2) There is subtlety concerning the correspondence between
1114 // pattern ids and types as compared to *expression* ids and
1115 // types. This is explained briefly. on the definition of the
1116 // type `cmt`, so go off and read what it says there, then
1117 // come back and I'll dive into a bit more detail here. :) OK,
1120 // In general, the id of the cmt should be the node that
1121 // "produces" the value---patterns aren't executable code
1122 // exactly, but I consider them to "execute" when they match a
1123 // value, and I consider them to produce the value that was
1124 // matched. So if you have something like:
1131 // In this case, the cmt and the relevant ids would be:
1133 // CMT Id Type of Id Type of cmt
1136 // ^~~~~~~^ `x` from discr @@int @@int
1137 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
1138 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
1140 // You can see that the types of the id and the cmt are in
1141 // sync in the first line, because that id is actually the id
1142 // of an expression. But once we get to pattern ids, the types
1143 // step out of sync again. So you'll see below that we always
1144 // get the type of the *subpattern* and use that.
1146 debug!("cat_pattern: {:?} cmt={:?}", pat, cmt);
1148 op(self, cmt.clone(), pat);
1150 // Note: This goes up here (rather than within the PatKind::TupleStruct arm
1151 // alone) because PatKind::Struct can also refer to variants.
1152 let cmt = match pat.node {
1153 PatKind::Path(hir::QPath::Resolved(_, ref path)) |
1154 PatKind::TupleStruct(hir::QPath::Resolved(_, ref path), ..) |
1155 PatKind::Struct(hir::QPath::Resolved(_, ref path), ..) => {
1157 Def::Err => return Err(()),
1158 Def::Variant(variant_did) |
1159 Def::VariantCtor(variant_did, ..) => {
1160 // univariant enums do not need downcasts
1161 let enum_did = self.tcx().parent_def_id(variant_did).unwrap();
1162 if !self.tcx().adt_def(enum_did).is_univariant() {
1163 self.cat_downcast(pat, cmt.clone(), cmt.ty, variant_did)
1175 PatKind::TupleStruct(ref qpath, ref subpats, ddpos) => {
1176 let def = self.infcx.tables.borrow().qpath_def(qpath, pat.id);
1177 let expected_len = match def {
1178 Def::VariantCtor(def_id, CtorKind::Fn) => {
1179 let enum_def = self.tcx().parent_def_id(def_id).unwrap();
1180 self.tcx().adt_def(enum_def).variant_with_id(def_id).fields.len()
1182 Def::StructCtor(_, CtorKind::Fn) => {
1183 match self.pat_ty(&pat)?.sty {
1184 ty::TyAdt(adt_def, _) => {
1185 adt_def.struct_variant().fields.len()
1188 span_bug!(pat.span, "tuple struct pattern unexpected type {:?}", ty);
1193 span_bug!(pat.span, "tuple struct pattern didn't resolve \
1194 to variant or struct {:?}", def);
1198 for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
1199 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
1200 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty,
1201 InteriorField(PositionalField(i)));
1202 self.cat_pattern_(subcmt, &subpat, op)?;
1206 PatKind::Struct(_, ref field_pats, _) => {
1207 // {f1: p1, ..., fN: pN}
1208 for fp in field_pats {
1209 let field_ty = self.pat_ty(&fp.node.pat)?; // see (*2)
1210 let cmt_field = self.cat_field(pat, cmt.clone(), fp.node.name, field_ty);
1211 self.cat_pattern_(cmt_field, &fp.node.pat, op)?;
1215 PatKind::Binding(.., Some(ref subpat)) => {
1216 self.cat_pattern_(cmt, &subpat, op)?;
1219 PatKind::Tuple(ref subpats, ddpos) => {
1221 let expected_len = match self.pat_ty(&pat)?.sty {
1222 ty::TyTuple(ref tys, _) => tys.len(),
1223 ref ty => span_bug!(pat.span, "tuple pattern unexpected type {:?}", ty),
1225 for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
1226 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
1227 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty,
1228 InteriorField(PositionalField(i)));
1229 self.cat_pattern_(subcmt, &subpat, op)?;
1233 PatKind::Box(ref subpat) | PatKind::Ref(ref subpat, _) => {
1234 // box p1, &p1, &mut p1. we can ignore the mutability of
1235 // PatKind::Ref since that information is already contained
1237 let subcmt = self.cat_deref(pat, cmt, 0)?;
1238 self.cat_pattern_(subcmt, &subpat, op)?;
1241 PatKind::Slice(ref before, ref slice, ref after) => {
1242 let context = InteriorOffsetKind::Pattern;
1243 let elt_cmt = self.cat_index(pat, cmt, context)?;
1244 for before_pat in before {
1245 self.cat_pattern_(elt_cmt.clone(), &before_pat, op)?;
1247 if let Some(ref slice_pat) = *slice {
1248 self.cat_pattern_(elt_cmt.clone(), &slice_pat, op)?;
1250 for after_pat in after {
1251 self.cat_pattern_(elt_cmt.clone(), &after_pat, op)?;
1255 PatKind::Path(_) | PatKind::Binding(.., None) |
1256 PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild => {
1264 fn overloaded_method_return_ty(&self,
1265 method_ty: Ty<'tcx>)
1268 // When we process an overloaded `*` or `[]` etc, we often
1269 // need to extract the return type of the method. These method
1270 // types are generated by method resolution and always have
1271 // all late-bound regions fully instantiated, so we just want
1272 // to skip past the binder.
1273 self.tcx().no_late_bound_regions(&method_ty.fn_ret())
1278 #[derive(Clone, Debug)]
1279 pub enum Aliasability {
1280 FreelyAliasable(AliasableReason),
1282 ImmutableUnique(Box<Aliasability>),
1285 #[derive(Copy, Clone, Debug)]
1286 pub enum AliasableReason {
1292 impl<'tcx> cmt_<'tcx> {
1293 pub fn guarantor(&self) -> cmt<'tcx> {
1294 //! Returns `self` after stripping away any derefs or
1295 //! interior content. The return value is basically the `cmt` which
1296 //! determines how long the value in `self` remains live.
1299 Categorization::Rvalue(..) |
1300 Categorization::StaticItem |
1301 Categorization::Local(..) |
1302 Categorization::Deref(.., UnsafePtr(..)) |
1303 Categorization::Deref(.., BorrowedPtr(..)) |
1304 Categorization::Deref(.., Implicit(..)) |
1305 Categorization::Upvar(..) => {
1306 Rc::new((*self).clone())
1308 Categorization::Downcast(ref b, _) |
1309 Categorization::Interior(ref b, _) |
1310 Categorization::Deref(ref b, _, Unique) => {
1316 /// Returns `FreelyAliasable(_)` if this lvalue represents a freely aliasable pointer type.
1317 pub fn freely_aliasable(&self) -> Aliasability {
1318 // Maybe non-obvious: copied upvars can only be considered
1319 // non-aliasable in once closures, since any other kind can be
1320 // aliased and eventually recused.
1323 Categorization::Deref(ref b, _, BorrowedPtr(ty::MutBorrow, _)) |
1324 Categorization::Deref(ref b, _, Implicit(ty::MutBorrow, _)) |
1325 Categorization::Deref(ref b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1326 Categorization::Deref(ref b, _, Implicit(ty::UniqueImmBorrow, _)) |
1327 Categorization::Deref(ref b, _, Unique) |
1328 Categorization::Downcast(ref b, _) |
1329 Categorization::Interior(ref b, _) => {
1330 // Aliasability depends on base cmt
1331 b.freely_aliasable()
1334 Categorization::Rvalue(..) |
1335 Categorization::Local(..) |
1336 Categorization::Upvar(..) |
1337 Categorization::Deref(.., UnsafePtr(..)) => { // yes, it's aliasable, but...
1341 Categorization::StaticItem => {
1342 if self.mutbl.is_mutable() {
1343 FreelyAliasable(AliasableStaticMut)
1345 FreelyAliasable(AliasableStatic)
1349 Categorization::Deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) |
1350 Categorization::Deref(_, _, Implicit(ty::ImmBorrow, _)) => {
1351 FreelyAliasable(AliasableBorrowed)
1356 // Digs down through one or two layers of deref and grabs the cmt
1357 // for the upvar if a note indicates there is one.
1358 pub fn upvar(&self) -> Option<cmt<'tcx>> {
1360 NoteClosureEnv(..) | NoteUpvarRef(..) => {
1361 Some(match self.cat {
1362 Categorization::Deref(ref inner, ..) => {
1364 Categorization::Deref(ref inner, ..) => inner.clone(),
1365 Categorization::Upvar(..) => inner.clone(),
1377 pub fn descriptive_string(&self, tcx: TyCtxt) -> String {
1379 Categorization::StaticItem => {
1380 "static item".to_string()
1382 Categorization::Rvalue(..) => {
1383 "non-lvalue".to_string()
1385 Categorization::Local(vid) => {
1386 if tcx.hir.is_argument(vid) {
1387 "argument".to_string()
1389 "local variable".to_string()
1392 Categorization::Deref(.., pk) => {
1393 let upvar = self.upvar();
1394 match upvar.as_ref().map(|i| &i.cat) {
1395 Some(&Categorization::Upvar(ref var)) => {
1402 format!("indexed content")
1405 format!("`Box` content")
1408 format!("dereference of raw pointer")
1410 BorrowedPtr(..) => {
1411 format!("borrowed content")
1417 Categorization::Interior(_, InteriorField(NamedField(_))) => {
1420 Categorization::Interior(_, InteriorField(PositionalField(_))) => {
1421 "anonymous field".to_string()
1423 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Index,
1425 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Index,
1427 "indexed content".to_string()
1429 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Pattern,
1431 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Pattern,
1433 "pattern-bound indexed content".to_string()
1435 Categorization::Upvar(ref var) => {
1438 Categorization::Downcast(ref cmt, _) => {
1439 cmt.descriptive_string(tcx)
1445 impl<'tcx> fmt::Debug for cmt_<'tcx> {
1446 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1447 write!(f, "{{{:?} id:{} m:{:?} ty:{:?}}}",
1455 impl<'tcx> fmt::Debug for Categorization<'tcx> {
1456 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1458 Categorization::StaticItem => write!(f, "static"),
1459 Categorization::Rvalue(r, or) => {
1460 write!(f, "rvalue({:?}, {:?})", r, or)
1462 Categorization::Local(id) => {
1463 let name = ty::tls::with(|tcx| tcx.local_var_name_str(id));
1464 write!(f, "local({})", name)
1466 Categorization::Upvar(upvar) => {
1467 write!(f, "upvar({:?})", upvar)
1469 Categorization::Deref(ref cmt, derefs, ptr) => {
1470 write!(f, "{:?}-{:?}{}->", cmt.cat, ptr, derefs)
1472 Categorization::Interior(ref cmt, interior) => {
1473 write!(f, "{:?}.{:?}", cmt.cat, interior)
1475 Categorization::Downcast(ref cmt, _) => {
1476 write!(f, "{:?}->(enum)", cmt.cat)
1482 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1485 BorrowedPtr(ty::ImmBorrow, _) |
1486 Implicit(ty::ImmBorrow, _) => "&",
1487 BorrowedPtr(ty::MutBorrow, _) |
1488 Implicit(ty::MutBorrow, _) => "&mut",
1489 BorrowedPtr(ty::UniqueImmBorrow, _) |
1490 Implicit(ty::UniqueImmBorrow, _) => "&unique",
1491 UnsafePtr(_) => "*",
1495 impl<'tcx> fmt::Debug for PointerKind<'tcx> {
1496 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1498 Unique => write!(f, "Box"),
1499 BorrowedPtr(ty::ImmBorrow, ref r) |
1500 Implicit(ty::ImmBorrow, ref r) => {
1501 write!(f, "&{:?}", r)
1503 BorrowedPtr(ty::MutBorrow, ref r) |
1504 Implicit(ty::MutBorrow, ref r) => {
1505 write!(f, "&{:?} mut", r)
1507 BorrowedPtr(ty::UniqueImmBorrow, ref r) |
1508 Implicit(ty::UniqueImmBorrow, ref r) => {
1509 write!(f, "&{:?} uniq", r)
1511 UnsafePtr(_) => write!(f, "*")
1516 impl fmt::Debug for InteriorKind {
1517 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1519 InteriorField(NamedField(fld)) => write!(f, "{}", fld),
1520 InteriorField(PositionalField(i)) => write!(f, "#{}", i),
1521 InteriorElement(..) => write!(f, "[]"),
1526 impl fmt::Debug for Upvar {
1527 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1528 write!(f, "{:?}/{:?}", self.id, self.kind)
1532 impl fmt::Display for Upvar {
1533 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1534 let kind = match self.kind {
1535 ty::ClosureKind::Fn => "Fn",
1536 ty::ClosureKind::FnMut => "FnMut",
1537 ty::ClosureKind::FnOnce => "FnOnce",
1539 write!(f, "captured outer variable in an `{}` closure", kind)