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) -> (&'tcx ty::AdtDef, &'tcx ty::FieldDef)
207 let adt_def = self.ty.ty_adt_def().unwrap_or_else(|| {
208 bug!("interior cmt {:?} is not an ADT", self)
210 let variant_def = match self.cat {
211 Categorization::Downcast(_, variant_did) => {
212 adt_def.variant_with_id(variant_did)
215 assert!(adt_def.is_univariant());
219 let field_def = match field_name {
220 NamedField(name) => variant_def.field_named(name),
221 PositionalField(idx) => &variant_def.fields[idx]
226 pub fn immutability_blame(&self) -> Option<ImmutabilityBlame<'tcx>> {
228 Categorization::Deref(ref base_cmt, _, BorrowedPtr(ty::ImmBorrow, _)) |
229 Categorization::Deref(ref base_cmt, _, Implicit(ty::ImmBorrow, _)) => {
230 // try to figure out where the immutable reference came from
232 Categorization::Local(node_id) =>
233 Some(ImmutabilityBlame::LocalDeref(node_id)),
234 Categorization::Interior(ref base_cmt, InteriorField(field_name)) => {
235 let (adt_def, field_def) = base_cmt.resolve_field(field_name);
236 Some(ImmutabilityBlame::AdtFieldDeref(adt_def, field_def))
238 Categorization::Upvar(Upvar { id, .. }) => {
239 if let NoteClosureEnv(..) = self.note {
240 Some(ImmutabilityBlame::ClosureEnv(id.closure_expr_id))
248 Categorization::Local(node_id) => {
249 Some(ImmutabilityBlame::ImmLocal(node_id))
251 Categorization::Rvalue(..) |
252 Categorization::Upvar(..) |
253 Categorization::Deref(.., UnsafePtr(..)) => {
254 // This should not be reachable up to inference limitations.
257 Categorization::Interior(ref base_cmt, _) |
258 Categorization::Downcast(ref base_cmt, _) |
259 Categorization::Deref(ref base_cmt, _, _) => {
260 base_cmt.immutability_blame()
262 Categorization::StaticItem => {
263 // Do we want to do something here?
271 fn id(&self) -> ast::NodeId;
272 fn span(&self) -> Span;
275 impl ast_node for hir::Expr {
276 fn id(&self) -> ast::NodeId { self.id }
277 fn span(&self) -> Span { self.span }
280 impl ast_node for hir::Pat {
281 fn id(&self) -> ast::NodeId { self.id }
282 fn span(&self) -> Span { self.span }
285 #[derive(Copy, Clone)]
286 pub struct MemCategorizationContext<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
287 pub infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
288 options: MemCategorizationOptions,
291 #[derive(Copy, Clone, Default)]
292 pub struct MemCategorizationOptions {
293 // If true, then when analyzing a closure upvar, if the closure
294 // has a missing kind, we treat it like a Fn closure. When false,
295 // we ICE if the closure has a missing kind. Should be false
296 // except during closure kind inference. It is used by the
297 // mem-categorization code to be able to have stricter assertions
298 // (which are always true except during upvar inference).
299 pub during_closure_kind_inference: bool,
302 pub type McResult<T> = Result<T, ()>;
304 impl MutabilityCategory {
305 pub fn from_mutbl(m: hir::Mutability) -> MutabilityCategory {
307 MutImmutable => McImmutable,
308 MutMutable => McDeclared
310 debug!("MutabilityCategory::{}({:?}) => {:?}",
311 "from_mutbl", m, ret);
315 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
316 let ret = match borrow_kind {
317 ty::ImmBorrow => McImmutable,
318 ty::UniqueImmBorrow => McImmutable,
319 ty::MutBorrow => McDeclared,
321 debug!("MutabilityCategory::{}({:?}) => {:?}",
322 "from_borrow_kind", borrow_kind, ret);
326 fn from_pointer_kind(base_mutbl: MutabilityCategory,
327 ptr: PointerKind) -> MutabilityCategory {
328 let ret = match ptr {
332 BorrowedPtr(borrow_kind, _) | Implicit(borrow_kind, _) => {
333 MutabilityCategory::from_borrow_kind(borrow_kind)
336 MutabilityCategory::from_mutbl(m)
339 debug!("MutabilityCategory::{}({:?}, {:?}) => {:?}",
340 "from_pointer_kind", base_mutbl, ptr, ret);
344 fn from_local(tcx: TyCtxt, id: ast::NodeId) -> MutabilityCategory {
345 let ret = match tcx.hir.get(id) {
346 hir_map::NodeLocal(p) => match p.node {
347 PatKind::Binding(bind_mode, ..) => {
348 if bind_mode == hir::BindByValue(hir::MutMutable) {
354 _ => span_bug!(p.span, "expected identifier pattern")
356 _ => span_bug!(tcx.hir.span(id), "expected identifier pattern")
358 debug!("MutabilityCategory::{}(tcx, id={:?}) => {:?}",
359 "from_local", id, ret);
363 pub fn inherit(&self) -> MutabilityCategory {
364 let ret = match *self {
365 McImmutable => McImmutable,
366 McDeclared => McInherited,
367 McInherited => McInherited,
369 debug!("{:?}.inherit() => {:?}", self, ret);
373 pub fn is_mutable(&self) -> bool {
374 let ret = match *self {
375 McImmutable => false,
379 debug!("{:?}.is_mutable() => {:?}", self, ret);
383 pub fn is_immutable(&self) -> bool {
384 let ret = match *self {
386 McDeclared | McInherited => false
388 debug!("{:?}.is_immutable() => {:?}", self, ret);
392 pub fn to_user_str(&self) -> &'static str {
394 McDeclared | McInherited => "mutable",
395 McImmutable => "immutable",
400 impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
401 pub fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>)
402 -> MemCategorizationContext<'a, 'gcx, 'tcx> {
403 MemCategorizationContext::with_options(infcx, MemCategorizationOptions::default())
406 pub fn with_options(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
407 options: MemCategorizationOptions)
408 -> MemCategorizationContext<'a, 'gcx, 'tcx> {
409 MemCategorizationContext {
415 fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
419 fn expr_ty(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
420 match self.infcx.node_ty(expr.id) {
423 debug!("expr_ty({:?}) yielded Err", expr);
429 fn expr_ty_adjusted(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
430 self.infcx.expr_ty_adjusted(expr)
433 fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
434 self.infcx.node_ty(id)
437 fn pat_ty(&self, pat: &hir::Pat) -> McResult<Ty<'tcx>> {
438 let base_ty = self.infcx.node_ty(pat.id)?;
439 // FIXME (Issue #18207): This code detects whether we are
440 // looking at a `ref x`, and if so, figures out what the type
441 // *being borrowed* is. But ideally we would put in a more
442 // fundamental fix to this conflated use of the node id.
443 let ret_ty = match pat.node {
444 PatKind::Binding(hir::BindByRef(_), ..) => {
445 // a bind-by-ref means that the base_ty will be the type of the ident itself,
446 // but what we want here is the type of the underlying value being borrowed.
447 // So peel off one-level, turning the &T into T.
448 match base_ty.builtin_deref(false, ty::NoPreference) {
450 None => { return Err(()); }
455 debug!("pat_ty(pat={:?}) base_ty={:?} ret_ty={:?}",
456 pat, base_ty, ret_ty);
460 pub fn cat_expr(&self, expr: &hir::Expr) -> McResult<cmt<'tcx>> {
461 match self.infcx.tables.borrow().adjustments.get(&expr.id) {
464 self.cat_expr_unadjusted(expr)
467 Some(adjustment) => {
468 match adjustment.kind {
469 adjustment::Adjust::DerefRef {
474 // Equivalent to *expr or something similar.
475 self.cat_expr_autoderefd(expr, autoderefs)
478 adjustment::Adjust::NeverToAny |
479 adjustment::Adjust::ReifyFnPointer |
480 adjustment::Adjust::UnsafeFnPointer |
481 adjustment::Adjust::ClosureFnPointer |
482 adjustment::Adjust::MutToConstPointer |
483 adjustment::Adjust::DerefRef {..} => {
484 debug!("cat_expr({:?}): {:?}",
487 // Result is an rvalue.
488 let expr_ty = self.expr_ty_adjusted(expr)?;
489 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
496 pub fn cat_expr_autoderefd(&self,
499 -> McResult<cmt<'tcx>> {
500 let mut cmt = self.cat_expr_unadjusted(expr)?;
501 debug!("cat_expr_autoderefd: autoderefs={}, cmt={:?}",
504 for deref in 1..autoderefs + 1 {
505 cmt = self.cat_deref(expr, cmt, deref)?;
510 pub fn cat_expr_unadjusted(&self, expr: &hir::Expr) -> McResult<cmt<'tcx>> {
511 debug!("cat_expr: id={} expr={:?}", expr.id, expr);
513 let expr_ty = self.expr_ty(expr)?;
515 hir::ExprUnary(hir::UnDeref, ref e_base) => {
516 let base_cmt = self.cat_expr(&e_base)?;
517 self.cat_deref(expr, base_cmt, 0)
520 hir::ExprField(ref base, f_name) => {
521 let base_cmt = self.cat_expr(&base)?;
522 debug!("cat_expr(cat_field): id={} expr={:?} base={:?}",
526 Ok(self.cat_field(expr, base_cmt, f_name.node, expr_ty))
529 hir::ExprTupField(ref base, idx) => {
530 let base_cmt = self.cat_expr(&base)?;
531 Ok(self.cat_tup_field(expr, base_cmt, idx.node, expr_ty))
534 hir::ExprIndex(ref base, _) => {
535 let method_call = ty::MethodCall::expr(expr.id());
536 match self.infcx.node_method_ty(method_call) {
538 // If this is an index implemented by a method call, then it
539 // will include an implicit deref of the result.
540 let ret_ty = self.overloaded_method_return_ty(method_ty);
542 // The index method always returns an `&T`, so
543 // dereference it to find the result type.
544 let elem_ty = match ret_ty.sty {
545 ty::TyRef(_, mt) => mt.ty,
547 debug!("cat_expr_unadjusted: return type of overloaded index is {:?}?",
553 // The call to index() returns a `&T` value, which
554 // is an rvalue. That is what we will be
556 let base_cmt = self.cat_rvalue_node(expr.id(), expr.span(), ret_ty);
557 Ok(self.cat_deref_common(expr, base_cmt, 1, elem_ty, true))
560 self.cat_index(expr, self.cat_expr(&base)?, InteriorOffsetKind::Index)
565 hir::ExprPath(ref qpath) => {
566 let def = self.infcx.tables.borrow().qpath_def(qpath, expr.id);
567 self.cat_def(expr.id, expr.span, expr_ty, def)
570 hir::ExprType(ref e, _) => {
574 hir::ExprAddrOf(..) | hir::ExprCall(..) |
575 hir::ExprAssign(..) | hir::ExprAssignOp(..) |
576 hir::ExprClosure(..) | hir::ExprRet(..) |
578 hir::ExprMethodCall(..) | hir::ExprCast(..) |
579 hir::ExprArray(..) | hir::ExprTup(..) | hir::ExprIf(..) |
580 hir::ExprBinary(..) | hir::ExprWhile(..) |
581 hir::ExprBlock(..) | hir::ExprLoop(..) | hir::ExprMatch(..) |
582 hir::ExprLit(..) | hir::ExprBreak(..) |
583 hir::ExprAgain(..) | hir::ExprStruct(..) | hir::ExprRepeat(..) |
584 hir::ExprInlineAsm(..) | hir::ExprBox(..) => {
585 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
590 pub fn cat_def(&self,
595 -> McResult<cmt<'tcx>> {
596 debug!("cat_def: id={} expr={:?} def={:?}",
600 Def::StructCtor(..) | Def::VariantCtor(..) | Def::Const(..) |
601 Def::AssociatedConst(..) | Def::Fn(..) | Def::Method(..) => {
602 Ok(self.cat_rvalue_node(id, span, expr_ty))
605 Def::Static(_, mutbl) => {
609 cat:Categorization::StaticItem,
610 mutbl: if mutbl { McDeclared } else { McImmutable},
616 Def::Upvar(def_id, _, fn_node_id) => {
617 let var_id = self.tcx().hir.as_local_node_id(def_id).unwrap();
618 let ty = self.node_ty(fn_node_id)?;
620 ty::TyClosure(closure_id, _) => {
621 match self.infcx.closure_kind(closure_id) {
623 self.cat_upvar(id, span, var_id, fn_node_id, kind)
626 if !self.options.during_closure_kind_inference {
629 "No closure kind for {:?}",
633 // during closure kind inference, we
634 // don't know the closure kind yet, but
635 // it's ok because we detect that we are
636 // accessing an upvar and handle that
637 // case specially anyhow. Use Fn
639 self.cat_upvar(id, span, var_id, fn_node_id, ty::ClosureKind::Fn)
646 "Upvar of non-closure {} - {:?}",
653 Def::Local(def_id) => {
654 let vid = self.tcx().hir.as_local_node_id(def_id).unwrap();
658 cat: Categorization::Local(vid),
659 mutbl: MutabilityCategory::from_local(self.tcx(), vid),
665 def => span_bug!(span, "unexpected definition in memory categorization: {:?}", def)
669 // Categorize an upvar, complete with invisible derefs of closure
670 // environment and upvar reference as appropriate.
675 fn_node_id: ast::NodeId,
676 kind: ty::ClosureKind)
677 -> McResult<cmt<'tcx>>
679 // An upvar can have up to 3 components. We translate first to a
680 // `Categorization::Upvar`, which is itself a fiction -- it represents the reference to the
681 // field from the environment.
683 // `Categorization::Upvar`. Next, we add a deref through the implicit
684 // environment pointer with an anonymous free region 'env and
685 // appropriate borrow kind for closure kinds that take self by
686 // reference. Finally, if the upvar was captured
687 // by-reference, we add a deref through that reference. The
688 // region of this reference is an inference variable 'up that
689 // was previously generated and recorded in the upvar borrow
690 // map. The borrow kind bk is inferred by based on how the
693 // This results in the following table for concrete closure
697 // ---------------+----------------------+-------------------------------
698 // Fn | copied -> &'env | upvar -> &'env -> &'up bk
699 // FnMut | copied -> &'env mut | upvar -> &'env mut -> &'up bk
700 // FnOnce | copied | upvar -> &'up bk
702 let upvar_id = ty::UpvarId { var_id: var_id,
703 closure_expr_id: fn_node_id };
704 let var_ty = self.node_ty(var_id)?;
706 // Mutability of original variable itself
707 let var_mutbl = MutabilityCategory::from_local(self.tcx(), var_id);
709 // Construct the upvar. This represents access to the field
710 // from the environment (perhaps we should eventually desugar
711 // this field further, but it will do for now).
712 let cmt_result = cmt_ {
715 cat: Categorization::Upvar(Upvar {id: upvar_id, kind: kind}),
721 // If this is a `FnMut` or `Fn` closure, then the above is
722 // conceptually a `&mut` or `&` reference, so we have to add a
724 let cmt_result = match kind {
725 ty::ClosureKind::FnOnce => {
728 ty::ClosureKind::FnMut => {
729 self.env_deref(id, span, upvar_id, var_mutbl, ty::MutBorrow, cmt_result)
731 ty::ClosureKind::Fn => {
732 self.env_deref(id, span, upvar_id, var_mutbl, ty::ImmBorrow, cmt_result)
736 // If this is a by-ref capture, then the upvar we loaded is
737 // actually a reference, so we have to add an implicit deref
739 let upvar_id = ty::UpvarId { var_id: var_id,
740 closure_expr_id: fn_node_id };
741 let upvar_capture = self.infcx.upvar_capture(upvar_id).unwrap();
742 let cmt_result = match upvar_capture {
743 ty::UpvarCapture::ByValue => {
746 ty::UpvarCapture::ByRef(upvar_borrow) => {
747 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
751 cat: Categorization::Deref(Rc::new(cmt_result), 0, ptr),
752 mutbl: MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
754 note: NoteUpvarRef(upvar_id)
759 let ret = Rc::new(cmt_result);
760 debug!("cat_upvar ret={:?}", ret);
767 upvar_id: ty::UpvarId,
768 upvar_mutbl: MutabilityCategory,
769 env_borrow_kind: ty::BorrowKind,
770 cmt_result: cmt_<'tcx>)
773 // Look up the node ID of the closure body so we can construct
774 // a free region within it
776 let fn_expr = match self.tcx().hir.find(upvar_id.closure_expr_id) {
777 Some(hir_map::NodeExpr(e)) => e,
782 hir::ExprClosure(.., body_id, _) => body_id.node_id,
787 // Region of environment pointer
788 let env_region = self.tcx().mk_region(ty::ReFree(ty::FreeRegion {
789 // The environment of a closure is guaranteed to
790 // outlive any bindings introduced in the body of the
792 scope: self.tcx().region_maps.item_extent(fn_body_id),
793 bound_region: ty::BrEnv
796 let env_ptr = BorrowedPtr(env_borrow_kind, env_region);
798 let var_ty = cmt_result.ty;
800 // We need to add the env deref. This means
801 // that the above is actually immutable and
802 // has a ref type. However, nothing should
803 // actually look at the type, so we can get
804 // away with stuffing a `TyError` in there
805 // instead of bothering to construct a proper
807 let cmt_result = cmt_ {
809 ty: self.tcx().types.err,
813 let mut deref_mutbl = MutabilityCategory::from_borrow_kind(env_borrow_kind);
815 // Issue #18335. If variable is declared as immutable, override the
816 // mutability from the environment and substitute an `&T` anyway.
818 McImmutable => { deref_mutbl = McImmutable; }
819 McDeclared | McInherited => { }
825 cat: Categorization::Deref(Rc::new(cmt_result), 0, env_ptr),
828 note: NoteClosureEnv(upvar_id)
831 debug!("env_deref ret {:?}", ret);
836 /// Returns the lifetime of a temporary created by expr with id `id`.
837 /// This could be `'static` if `id` is part of a constant expression.
838 pub fn temporary_scope(&self, id: ast::NodeId) -> (&'tcx ty::Region, &'tcx ty::Region)
840 let (scope, old_scope) =
841 self.tcx().region_maps.old_and_new_temporary_scope(id);
842 (self.tcx().mk_region(match scope {
843 Some(scope) => ty::ReScope(scope),
846 self.tcx().mk_region(match old_scope {
847 Some(scope) => ty::ReScope(scope),
852 pub fn cat_rvalue_node(&self,
857 let promotable = self.tcx().rvalue_promotable_to_static.borrow().get(&id).cloned()
860 // When the corresponding feature isn't toggled, only promote `[T; 0]`.
861 let promotable = match expr_ty.sty {
862 ty::TyArray(_, 0) => true,
863 _ => promotable && self.tcx().sess.features.borrow().rvalue_static_promotion,
866 // Compute maximum lifetime of this rvalue. This is 'static if
867 // we can promote to a constant, otherwise equal to enclosing temp
869 let (re, old_re) = if promotable {
870 (self.tcx().mk_region(ty::ReStatic),
871 self.tcx().mk_region(ty::ReStatic))
873 self.temporary_scope(id)
875 let ret = self.cat_rvalue(id, span, re, old_re, expr_ty);
876 debug!("cat_rvalue_node ret {:?}", ret);
880 pub fn cat_rvalue(&self,
883 temp_scope: &'tcx ty::Region,
884 old_temp_scope: &'tcx ty::Region,
885 expr_ty: Ty<'tcx>) -> cmt<'tcx> {
886 let ret = Rc::new(cmt_ {
889 cat:Categorization::Rvalue(temp_scope, old_temp_scope),
894 debug!("cat_rvalue ret {:?}", ret);
898 pub fn cat_field<N:ast_node>(&self,
904 let ret = Rc::new(cmt_ {
907 mutbl: base_cmt.mutbl.inherit(),
908 cat: Categorization::Interior(base_cmt, InteriorField(NamedField(f_name))),
912 debug!("cat_field ret {:?}", ret);
916 pub fn cat_tup_field<N:ast_node>(&self,
922 let ret = Rc::new(cmt_ {
925 mutbl: base_cmt.mutbl.inherit(),
926 cat: Categorization::Interior(base_cmt, InteriorField(PositionalField(f_idx))),
930 debug!("cat_tup_field ret {:?}", ret);
934 fn cat_deref<N:ast_node>(&self,
938 -> McResult<cmt<'tcx>> {
939 let method_call = ty::MethodCall {
941 autoderef: deref_cnt as u32
943 let method_ty = self.infcx.node_method_ty(method_call);
945 debug!("cat_deref: method_call={:?} method_ty={:?}",
946 method_call, method_ty.map(|ty| ty));
948 let base_cmt = match method_ty {
951 self.tcx().no_late_bound_regions(&method_ty.fn_ret()).unwrap();
952 self.cat_rvalue_node(node.id(), node.span(), ref_ty)
956 let base_cmt_ty = base_cmt.ty;
957 match base_cmt_ty.builtin_deref(true, ty::NoPreference) {
959 let ret = self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty, false);
960 debug!("cat_deref ret {:?}", ret);
964 debug!("Explicit deref of non-derefable type: {:?}",
971 fn cat_deref_common<N:ast_node>(&self,
979 let ptr = match base_cmt.ty.sty {
980 ty::TyAdt(def, ..) if def.is_box() => Unique,
981 ty::TyRawPtr(ref mt) => UnsafePtr(mt.mutbl),
982 ty::TyRef(r, mt) => {
983 let bk = ty::BorrowKind::from_mutbl(mt.mutbl);
984 if implicit { Implicit(bk, r) } else { BorrowedPtr(bk, r) }
986 ref ty => bug!("unexpected type in cat_deref_common: {:?}", ty)
988 let ret = Rc::new(cmt_ {
991 // For unique ptrs, we inherit mutability from the owning reference.
992 mutbl: MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr),
993 cat: Categorization::Deref(base_cmt, deref_cnt, ptr),
997 debug!("cat_deref_common ret {:?}", ret);
1001 pub fn cat_index<N:ast_node>(&self,
1003 mut base_cmt: cmt<'tcx>,
1004 context: InteriorOffsetKind)
1005 -> McResult<cmt<'tcx>> {
1006 //! Creates a cmt for an indexing operation (`[]`).
1008 //! One subtle aspect of indexing that may not be
1009 //! immediately obvious: for anything other than a fixed-length
1010 //! vector, an operation like `x[y]` actually consists of two
1011 //! disjoint (from the point of view of borrowck) operations.
1012 //! The first is a deref of `x` to create a pointer `p` that points
1013 //! at the first element in the array. The second operation is
1014 //! an index which adds `y*sizeof(T)` to `p` to obtain the
1015 //! pointer to `x[y]`. `cat_index` will produce a resulting
1016 //! cmt containing both this deref and the indexing,
1017 //! presuming that `base_cmt` is not of fixed-length type.
1020 //! - `elt`: the AST node being indexed
1021 //! - `base_cmt`: the cmt of `elt`
1023 let method_call = ty::MethodCall::expr(elt.id());
1024 let method_ty = self.infcx.node_method_ty(method_call);
1026 let (element_ty, element_kind) = match method_ty {
1027 Some(method_ty) => {
1028 let ref_ty = self.overloaded_method_return_ty(method_ty);
1029 base_cmt = self.cat_rvalue_node(elt.id(), elt.span(), ref_ty);
1031 (ref_ty.builtin_deref(false, ty::NoPreference).unwrap().ty,
1032 ElementKind::OtherElement)
1035 match base_cmt.ty.builtin_index() {
1036 Some(ty) => (ty, ElementKind::VecElement),
1044 let interior_elem = InteriorElement(context, element_kind);
1046 self.cat_imm_interior(elt, base_cmt.clone(), element_ty, interior_elem);
1047 debug!("cat_index ret {:?}", ret);
1051 pub fn cat_imm_interior<N:ast_node>(&self,
1053 base_cmt: cmt<'tcx>,
1054 interior_ty: Ty<'tcx>,
1055 interior: InteriorKind)
1057 let ret = Rc::new(cmt_ {
1060 mutbl: base_cmt.mutbl.inherit(),
1061 cat: Categorization::Interior(base_cmt, interior),
1065 debug!("cat_imm_interior ret={:?}", ret);
1069 pub fn cat_downcast<N:ast_node>(&self,
1071 base_cmt: cmt<'tcx>,
1072 downcast_ty: Ty<'tcx>,
1075 let ret = Rc::new(cmt_ {
1078 mutbl: base_cmt.mutbl.inherit(),
1079 cat: Categorization::Downcast(base_cmt, variant_did),
1083 debug!("cat_downcast ret={:?}", ret);
1087 pub fn cat_pattern<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, mut op: F) -> McResult<()>
1088 where F: FnMut(&MemCategorizationContext<'a, 'gcx, 'tcx>, cmt<'tcx>, &hir::Pat),
1090 self.cat_pattern_(cmt, pat, &mut op)
1093 // FIXME(#19596) This is a workaround, but there should be a better way to do this
1094 fn cat_pattern_<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, op: &mut F) -> McResult<()>
1095 where F : FnMut(&MemCategorizationContext<'a, 'gcx, 'tcx>, cmt<'tcx>, &hir::Pat)
1097 // Here, `cmt` is the categorization for the value being
1098 // matched and pat is the pattern it is being matched against.
1100 // In general, the way that this works is that we walk down
1101 // the pattern, constructing a cmt that represents the path
1102 // that will be taken to reach the value being matched.
1104 // When we encounter named bindings, we take the cmt that has
1105 // been built up and pass it off to guarantee_valid() so that
1106 // we can be sure that the binding will remain valid for the
1107 // duration of the arm.
1109 // (*2) There is subtlety concerning the correspondence between
1110 // pattern ids and types as compared to *expression* ids and
1111 // types. This is explained briefly. on the definition of the
1112 // type `cmt`, so go off and read what it says there, then
1113 // come back and I'll dive into a bit more detail here. :) OK,
1116 // In general, the id of the cmt should be the node that
1117 // "produces" the value---patterns aren't executable code
1118 // exactly, but I consider them to "execute" when they match a
1119 // value, and I consider them to produce the value that was
1120 // matched. So if you have something like:
1127 // In this case, the cmt and the relevant ids would be:
1129 // CMT Id Type of Id Type of cmt
1132 // ^~~~~~~^ `x` from discr @@int @@int
1133 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
1134 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
1136 // You can see that the types of the id and the cmt are in
1137 // sync in the first line, because that id is actually the id
1138 // of an expression. But once we get to pattern ids, the types
1139 // step out of sync again. So you'll see below that we always
1140 // get the type of the *subpattern* and use that.
1142 debug!("cat_pattern: {:?} cmt={:?}", pat, cmt);
1144 op(self, cmt.clone(), pat);
1146 // Note: This goes up here (rather than within the PatKind::TupleStruct arm
1147 // alone) because PatKind::Struct can also refer to variants.
1148 let cmt = match pat.node {
1149 PatKind::Path(hir::QPath::Resolved(_, ref path)) |
1150 PatKind::TupleStruct(hir::QPath::Resolved(_, ref path), ..) |
1151 PatKind::Struct(hir::QPath::Resolved(_, ref path), ..) => {
1153 Def::Err => return Err(()),
1154 Def::Variant(variant_did) |
1155 Def::VariantCtor(variant_did, ..) => {
1156 // univariant enums do not need downcasts
1157 let enum_did = self.tcx().parent_def_id(variant_did).unwrap();
1158 if !self.tcx().lookup_adt_def(enum_did).is_univariant() {
1159 self.cat_downcast(pat, cmt.clone(), cmt.ty, variant_did)
1171 PatKind::TupleStruct(ref qpath, ref subpats, ddpos) => {
1172 let def = self.infcx.tables.borrow().qpath_def(qpath, pat.id);
1173 let expected_len = match def {
1174 Def::VariantCtor(def_id, CtorKind::Fn) => {
1175 let enum_def = self.tcx().parent_def_id(def_id).unwrap();
1176 self.tcx().lookup_adt_def(enum_def).variant_with_id(def_id).fields.len()
1178 Def::StructCtor(_, CtorKind::Fn) => {
1179 match self.pat_ty(&pat)?.sty {
1180 ty::TyAdt(adt_def, _) => {
1181 adt_def.struct_variant().fields.len()
1184 span_bug!(pat.span, "tuple struct pattern unexpected type {:?}", ty);
1189 span_bug!(pat.span, "tuple struct pattern didn't resolve \
1190 to variant or struct {:?}", def);
1194 for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
1195 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
1196 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty,
1197 InteriorField(PositionalField(i)));
1198 self.cat_pattern_(subcmt, &subpat, op)?;
1202 PatKind::Struct(_, ref field_pats, _) => {
1203 // {f1: p1, ..., fN: pN}
1204 for fp in field_pats {
1205 let field_ty = self.pat_ty(&fp.node.pat)?; // see (*2)
1206 let cmt_field = self.cat_field(pat, cmt.clone(), fp.node.name, field_ty);
1207 self.cat_pattern_(cmt_field, &fp.node.pat, op)?;
1211 PatKind::Binding(.., Some(ref subpat)) => {
1212 self.cat_pattern_(cmt, &subpat, op)?;
1215 PatKind::Tuple(ref subpats, ddpos) => {
1217 let expected_len = match self.pat_ty(&pat)?.sty {
1218 ty::TyTuple(ref tys, _) => tys.len(),
1219 ref ty => span_bug!(pat.span, "tuple pattern unexpected type {:?}", ty),
1221 for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
1222 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
1223 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty,
1224 InteriorField(PositionalField(i)));
1225 self.cat_pattern_(subcmt, &subpat, op)?;
1229 PatKind::Box(ref subpat) | PatKind::Ref(ref subpat, _) => {
1230 // box p1, &p1, &mut p1. we can ignore the mutability of
1231 // PatKind::Ref since that information is already contained
1233 let subcmt = self.cat_deref(pat, cmt, 0)?;
1234 self.cat_pattern_(subcmt, &subpat, op)?;
1237 PatKind::Slice(ref before, ref slice, ref after) => {
1238 let context = InteriorOffsetKind::Pattern;
1239 let elt_cmt = self.cat_index(pat, cmt, context)?;
1240 for before_pat in before {
1241 self.cat_pattern_(elt_cmt.clone(), &before_pat, op)?;
1243 if let Some(ref slice_pat) = *slice {
1244 self.cat_pattern_(elt_cmt.clone(), &slice_pat, op)?;
1246 for after_pat in after {
1247 self.cat_pattern_(elt_cmt.clone(), &after_pat, op)?;
1251 PatKind::Path(_) | PatKind::Binding(.., None) |
1252 PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild => {
1260 fn overloaded_method_return_ty(&self,
1261 method_ty: Ty<'tcx>)
1264 // When we process an overloaded `*` or `[]` etc, we often
1265 // need to extract the return type of the method. These method
1266 // types are generated by method resolution and always have
1267 // all late-bound regions fully instantiated, so we just want
1268 // to skip past the binder.
1269 self.tcx().no_late_bound_regions(&method_ty.fn_ret())
1274 #[derive(Clone, Debug)]
1275 pub enum Aliasability {
1276 FreelyAliasable(AliasableReason),
1278 ImmutableUnique(Box<Aliasability>),
1281 #[derive(Copy, Clone, Debug)]
1282 pub enum AliasableReason {
1288 impl<'tcx> cmt_<'tcx> {
1289 pub fn guarantor(&self) -> cmt<'tcx> {
1290 //! Returns `self` after stripping away any derefs or
1291 //! interior content. The return value is basically the `cmt` which
1292 //! determines how long the value in `self` remains live.
1295 Categorization::Rvalue(..) |
1296 Categorization::StaticItem |
1297 Categorization::Local(..) |
1298 Categorization::Deref(.., UnsafePtr(..)) |
1299 Categorization::Deref(.., BorrowedPtr(..)) |
1300 Categorization::Deref(.., Implicit(..)) |
1301 Categorization::Upvar(..) => {
1302 Rc::new((*self).clone())
1304 Categorization::Downcast(ref b, _) |
1305 Categorization::Interior(ref b, _) |
1306 Categorization::Deref(ref b, _, Unique) => {
1312 /// Returns `FreelyAliasable(_)` if this lvalue represents a freely aliasable pointer type.
1313 pub fn freely_aliasable(&self) -> Aliasability {
1314 // Maybe non-obvious: copied upvars can only be considered
1315 // non-aliasable in once closures, since any other kind can be
1316 // aliased and eventually recused.
1319 Categorization::Deref(ref b, _, BorrowedPtr(ty::MutBorrow, _)) |
1320 Categorization::Deref(ref b, _, Implicit(ty::MutBorrow, _)) |
1321 Categorization::Deref(ref b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1322 Categorization::Deref(ref b, _, Implicit(ty::UniqueImmBorrow, _)) |
1323 Categorization::Deref(ref b, _, Unique) |
1324 Categorization::Downcast(ref b, _) |
1325 Categorization::Interior(ref b, _) => {
1326 // Aliasability depends on base cmt
1327 b.freely_aliasable()
1330 Categorization::Rvalue(..) |
1331 Categorization::Local(..) |
1332 Categorization::Upvar(..) |
1333 Categorization::Deref(.., UnsafePtr(..)) => { // yes, it's aliasable, but...
1337 Categorization::StaticItem => {
1338 if self.mutbl.is_mutable() {
1339 FreelyAliasable(AliasableStaticMut)
1341 FreelyAliasable(AliasableStatic)
1345 Categorization::Deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) |
1346 Categorization::Deref(_, _, Implicit(ty::ImmBorrow, _)) => {
1347 FreelyAliasable(AliasableBorrowed)
1352 // Digs down through one or two layers of deref and grabs the cmt
1353 // for the upvar if a note indicates there is one.
1354 pub fn upvar(&self) -> Option<cmt<'tcx>> {
1356 NoteClosureEnv(..) | NoteUpvarRef(..) => {
1357 Some(match self.cat {
1358 Categorization::Deref(ref inner, ..) => {
1360 Categorization::Deref(ref inner, ..) => inner.clone(),
1361 Categorization::Upvar(..) => inner.clone(),
1373 pub fn descriptive_string(&self, tcx: TyCtxt) -> String {
1375 Categorization::StaticItem => {
1376 "static item".to_string()
1378 Categorization::Rvalue(..) => {
1379 "non-lvalue".to_string()
1381 Categorization::Local(vid) => {
1382 if tcx.hir.is_argument(vid) {
1383 "argument".to_string()
1385 "local variable".to_string()
1388 Categorization::Deref(.., pk) => {
1389 let upvar = self.upvar();
1390 match upvar.as_ref().map(|i| &i.cat) {
1391 Some(&Categorization::Upvar(ref var)) => {
1398 format!("indexed content")
1401 format!("`Box` content")
1404 format!("dereference of raw pointer")
1406 BorrowedPtr(..) => {
1407 format!("borrowed content")
1413 Categorization::Interior(_, InteriorField(NamedField(_))) => {
1416 Categorization::Interior(_, InteriorField(PositionalField(_))) => {
1417 "anonymous field".to_string()
1419 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Index,
1421 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Index,
1423 "indexed content".to_string()
1425 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Pattern,
1427 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Pattern,
1429 "pattern-bound indexed content".to_string()
1431 Categorization::Upvar(ref var) => {
1434 Categorization::Downcast(ref cmt, _) => {
1435 cmt.descriptive_string(tcx)
1441 impl<'tcx> fmt::Debug for cmt_<'tcx> {
1442 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1443 write!(f, "{{{:?} id:{} m:{:?} ty:{:?}}}",
1451 impl<'tcx> fmt::Debug for Categorization<'tcx> {
1452 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1454 Categorization::StaticItem => write!(f, "static"),
1455 Categorization::Rvalue(r, or) => {
1456 write!(f, "rvalue({:?}, {:?})", r, or)
1458 Categorization::Local(id) => {
1459 let name = ty::tls::with(|tcx| tcx.local_var_name_str(id));
1460 write!(f, "local({})", name)
1462 Categorization::Upvar(upvar) => {
1463 write!(f, "upvar({:?})", upvar)
1465 Categorization::Deref(ref cmt, derefs, ptr) => {
1466 write!(f, "{:?}-{:?}{}->", cmt.cat, ptr, derefs)
1468 Categorization::Interior(ref cmt, interior) => {
1469 write!(f, "{:?}.{:?}", cmt.cat, interior)
1471 Categorization::Downcast(ref cmt, _) => {
1472 write!(f, "{:?}->(enum)", cmt.cat)
1478 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1481 BorrowedPtr(ty::ImmBorrow, _) |
1482 Implicit(ty::ImmBorrow, _) => "&",
1483 BorrowedPtr(ty::MutBorrow, _) |
1484 Implicit(ty::MutBorrow, _) => "&mut",
1485 BorrowedPtr(ty::UniqueImmBorrow, _) |
1486 Implicit(ty::UniqueImmBorrow, _) => "&unique",
1487 UnsafePtr(_) => "*",
1491 impl<'tcx> fmt::Debug for PointerKind<'tcx> {
1492 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1494 Unique => write!(f, "Box"),
1495 BorrowedPtr(ty::ImmBorrow, ref r) |
1496 Implicit(ty::ImmBorrow, ref r) => {
1497 write!(f, "&{:?}", r)
1499 BorrowedPtr(ty::MutBorrow, ref r) |
1500 Implicit(ty::MutBorrow, ref r) => {
1501 write!(f, "&{:?} mut", r)
1503 BorrowedPtr(ty::UniqueImmBorrow, ref r) |
1504 Implicit(ty::UniqueImmBorrow, ref r) => {
1505 write!(f, "&{:?} uniq", r)
1507 UnsafePtr(_) => write!(f, "*")
1512 impl fmt::Debug for InteriorKind {
1513 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1515 InteriorField(NamedField(fld)) => write!(f, "{}", fld),
1516 InteriorField(PositionalField(i)) => write!(f, "#{}", i),
1517 InteriorElement(..) => write!(f, "[]"),
1522 impl fmt::Debug for Upvar {
1523 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1524 write!(f, "{:?}/{:?}", self.id, self.kind)
1528 impl fmt::Display for Upvar {
1529 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1530 let kind = match self.kind {
1531 ty::ClosureKind::Fn => "Fn",
1532 ty::ClosureKind::FnMut => "FnMut",
1533 ty::ClosureKind::FnOnce => "FnOnce",
1535 write!(f, "captured outer variable in an `{}` closure", kind)