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(ty::Region<'tcx>, ty::Region<'tcx>),
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, ty::Region<'tcx>),
120 UnsafePtr(hir::Mutability),
122 /// Implicit deref of the `&T` that results from an overloaded index `[]`.
123 Implicit(ty::BorrowKind, ty::Region<'tcx>),
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) {
455 debug!("By-ref binding of non-derefable type {:?}", base_ty);
462 debug!("pat_ty(pat={:?}) base_ty={:?} ret_ty={:?}",
463 pat, base_ty, ret_ty);
467 pub fn cat_expr(&self, expr: &hir::Expr) -> McResult<cmt<'tcx>> {
468 match self.infcx.tables.borrow().adjustments.get(&expr.id) {
471 self.cat_expr_unadjusted(expr)
474 Some(adjustment) => {
475 match adjustment.kind {
476 adjustment::Adjust::DerefRef {
481 // Equivalent to *expr or something similar.
482 self.cat_expr_autoderefd(expr, autoderefs)
485 adjustment::Adjust::NeverToAny |
486 adjustment::Adjust::ReifyFnPointer |
487 adjustment::Adjust::UnsafeFnPointer |
488 adjustment::Adjust::ClosureFnPointer |
489 adjustment::Adjust::MutToConstPointer |
490 adjustment::Adjust::DerefRef {..} => {
491 debug!("cat_expr({:?}): {:?}",
494 // Result is an rvalue.
495 let expr_ty = self.expr_ty_adjusted(expr)?;
496 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
503 pub fn cat_expr_autoderefd(&self,
506 -> McResult<cmt<'tcx>> {
507 let mut cmt = self.cat_expr_unadjusted(expr)?;
508 debug!("cat_expr_autoderefd: autoderefs={}, cmt={:?}",
511 for deref in 1..autoderefs + 1 {
512 cmt = self.cat_deref(expr, cmt, deref)?;
517 pub fn cat_expr_unadjusted(&self, expr: &hir::Expr) -> McResult<cmt<'tcx>> {
518 debug!("cat_expr: id={} expr={:?}", expr.id, expr);
520 let expr_ty = self.expr_ty(expr)?;
522 hir::ExprUnary(hir::UnDeref, ref e_base) => {
523 let base_cmt = self.cat_expr(&e_base)?;
524 self.cat_deref(expr, base_cmt, 0)
527 hir::ExprField(ref base, f_name) => {
528 let base_cmt = self.cat_expr(&base)?;
529 debug!("cat_expr(cat_field): id={} expr={:?} base={:?}",
533 Ok(self.cat_field(expr, base_cmt, f_name.node, expr_ty))
536 hir::ExprTupField(ref base, idx) => {
537 let base_cmt = self.cat_expr(&base)?;
538 Ok(self.cat_tup_field(expr, base_cmt, idx.node, expr_ty))
541 hir::ExprIndex(ref base, _) => {
542 let method_call = ty::MethodCall::expr(expr.id());
543 match self.infcx.node_method_ty(method_call) {
545 // If this is an index implemented by a method call, then it
546 // will include an implicit deref of the result.
547 let ret_ty = self.overloaded_method_return_ty(method_ty);
549 // The index method always returns an `&T`, so
550 // dereference it to find the result type.
551 let elem_ty = match ret_ty.sty {
552 ty::TyRef(_, mt) => mt.ty,
554 debug!("cat_expr_unadjusted: return type of overloaded index is {:?}?",
560 // The call to index() returns a `&T` value, which
561 // is an rvalue. That is what we will be
563 let base_cmt = self.cat_rvalue_node(expr.id(), expr.span(), ret_ty);
564 Ok(self.cat_deref_common(expr, base_cmt, 1, elem_ty, true))
567 self.cat_index(expr, self.cat_expr(&base)?, InteriorOffsetKind::Index)
572 hir::ExprPath(ref qpath) => {
573 let def = self.infcx.tables.borrow().qpath_def(qpath, expr.id);
574 self.cat_def(expr.id, expr.span, expr_ty, def)
577 hir::ExprType(ref e, _) => {
581 hir::ExprAddrOf(..) | hir::ExprCall(..) |
582 hir::ExprAssign(..) | hir::ExprAssignOp(..) |
583 hir::ExprClosure(..) | hir::ExprRet(..) |
585 hir::ExprMethodCall(..) | hir::ExprCast(..) |
586 hir::ExprArray(..) | hir::ExprTup(..) | hir::ExprIf(..) |
587 hir::ExprBinary(..) | hir::ExprWhile(..) |
588 hir::ExprBlock(..) | hir::ExprLoop(..) | hir::ExprMatch(..) |
589 hir::ExprLit(..) | hir::ExprBreak(..) |
590 hir::ExprAgain(..) | hir::ExprStruct(..) | hir::ExprRepeat(..) |
591 hir::ExprInlineAsm(..) | hir::ExprBox(..) => {
592 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
597 pub fn cat_def(&self,
602 -> McResult<cmt<'tcx>> {
603 debug!("cat_def: id={} expr={:?} def={:?}",
607 Def::StructCtor(..) | Def::VariantCtor(..) | Def::Const(..) |
608 Def::AssociatedConst(..) | Def::Fn(..) | Def::Method(..) => {
609 Ok(self.cat_rvalue_node(id, span, expr_ty))
612 Def::Static(_, mutbl) => {
616 cat:Categorization::StaticItem,
617 mutbl: if mutbl { McDeclared } else { McImmutable},
623 Def::Upvar(def_id, _, fn_node_id) => {
624 let var_id = self.tcx().hir.as_local_node_id(def_id).unwrap();
625 let ty = self.node_ty(fn_node_id)?;
627 ty::TyClosure(closure_id, _) => {
628 match self.infcx.closure_kind(closure_id) {
630 self.cat_upvar(id, span, var_id, fn_node_id, kind)
633 if !self.options.during_closure_kind_inference {
636 "No closure kind for {:?}",
640 // during closure kind inference, we
641 // don't know the closure kind yet, but
642 // it's ok because we detect that we are
643 // accessing an upvar and handle that
644 // case specially anyhow. Use Fn
646 self.cat_upvar(id, span, var_id, fn_node_id, ty::ClosureKind::Fn)
653 "Upvar of non-closure {} - {:?}",
660 Def::Local(def_id) => {
661 let vid = self.tcx().hir.as_local_node_id(def_id).unwrap();
665 cat: Categorization::Local(vid),
666 mutbl: MutabilityCategory::from_local(self.tcx(), vid),
672 def => span_bug!(span, "unexpected definition in memory categorization: {:?}", def)
676 // Categorize an upvar, complete with invisible derefs of closure
677 // environment and upvar reference as appropriate.
682 fn_node_id: ast::NodeId,
683 kind: ty::ClosureKind)
684 -> McResult<cmt<'tcx>>
686 // An upvar can have up to 3 components. We translate first to a
687 // `Categorization::Upvar`, which is itself a fiction -- it represents the reference to the
688 // field from the environment.
690 // `Categorization::Upvar`. Next, we add a deref through the implicit
691 // environment pointer with an anonymous free region 'env and
692 // appropriate borrow kind for closure kinds that take self by
693 // reference. Finally, if the upvar was captured
694 // by-reference, we add a deref through that reference. The
695 // region of this reference is an inference variable 'up that
696 // was previously generated and recorded in the upvar borrow
697 // map. The borrow kind bk is inferred by based on how the
700 // This results in the following table for concrete closure
704 // ---------------+----------------------+-------------------------------
705 // Fn | copied -> &'env | upvar -> &'env -> &'up bk
706 // FnMut | copied -> &'env mut | upvar -> &'env mut -> &'up bk
707 // FnOnce | copied | upvar -> &'up bk
709 let upvar_id = ty::UpvarId { var_id: var_id,
710 closure_expr_id: fn_node_id };
711 let var_ty = self.node_ty(var_id)?;
713 // Mutability of original variable itself
714 let var_mutbl = MutabilityCategory::from_local(self.tcx(), var_id);
716 // Construct the upvar. This represents access to the field
717 // from the environment (perhaps we should eventually desugar
718 // this field further, but it will do for now).
719 let cmt_result = cmt_ {
722 cat: Categorization::Upvar(Upvar {id: upvar_id, kind: kind}),
728 // If this is a `FnMut` or `Fn` closure, then the above is
729 // conceptually a `&mut` or `&` reference, so we have to add a
731 let cmt_result = match kind {
732 ty::ClosureKind::FnOnce => {
735 ty::ClosureKind::FnMut => {
736 self.env_deref(id, span, upvar_id, var_mutbl, ty::MutBorrow, cmt_result)
738 ty::ClosureKind::Fn => {
739 self.env_deref(id, span, upvar_id, var_mutbl, ty::ImmBorrow, cmt_result)
743 // If this is a by-ref capture, then the upvar we loaded is
744 // actually a reference, so we have to add an implicit deref
746 let upvar_id = ty::UpvarId { var_id: var_id,
747 closure_expr_id: fn_node_id };
748 let upvar_capture = self.infcx.upvar_capture(upvar_id).unwrap();
749 let cmt_result = match upvar_capture {
750 ty::UpvarCapture::ByValue => {
753 ty::UpvarCapture::ByRef(upvar_borrow) => {
754 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
758 cat: Categorization::Deref(Rc::new(cmt_result), 0, ptr),
759 mutbl: MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
761 note: NoteUpvarRef(upvar_id)
766 let ret = Rc::new(cmt_result);
767 debug!("cat_upvar ret={:?}", ret);
774 upvar_id: ty::UpvarId,
775 upvar_mutbl: MutabilityCategory,
776 env_borrow_kind: ty::BorrowKind,
777 cmt_result: cmt_<'tcx>)
780 // Look up the node ID of the closure body so we can construct
781 // a free region within it
783 let fn_expr = match self.tcx().hir.find(upvar_id.closure_expr_id) {
784 Some(hir_map::NodeExpr(e)) => e,
789 hir::ExprClosure(.., body_id, _) => body_id.node_id,
794 // Region of environment pointer
795 let env_region = self.tcx().mk_region(ty::ReFree(ty::FreeRegion {
796 // The environment of a closure is guaranteed to
797 // outlive any bindings introduced in the body of the
799 scope: Some(self.tcx().item_extent(fn_body_id)),
800 bound_region: ty::BrEnv
803 let env_ptr = BorrowedPtr(env_borrow_kind, env_region);
805 let var_ty = cmt_result.ty;
807 // We need to add the env deref. This means
808 // that the above is actually immutable and
809 // has a ref type. However, nothing should
810 // actually look at the type, so we can get
811 // away with stuffing a `TyError` in there
812 // instead of bothering to construct a proper
814 let cmt_result = cmt_ {
816 ty: self.tcx().types.err,
820 let mut deref_mutbl = MutabilityCategory::from_borrow_kind(env_borrow_kind);
822 // Issue #18335. If variable is declared as immutable, override the
823 // mutability from the environment and substitute an `&T` anyway.
825 McImmutable => { deref_mutbl = McImmutable; }
826 McDeclared | McInherited => { }
832 cat: Categorization::Deref(Rc::new(cmt_result), 0, env_ptr),
835 note: NoteClosureEnv(upvar_id)
838 debug!("env_deref ret {:?}", ret);
843 /// Returns the lifetime of a temporary created by expr with id `id`.
844 /// This could be `'static` if `id` is part of a constant expression.
845 pub fn temporary_scope(&self, id: ast::NodeId) -> (ty::Region<'tcx>, ty::Region<'tcx>)
847 let (scope, old_scope) =
848 self.tcx().region_maps().old_and_new_temporary_scope(self.tcx(), id);
849 (self.tcx().mk_region(match scope {
850 Some(scope) => ty::ReScope(scope),
853 self.tcx().mk_region(match old_scope {
854 Some(scope) => ty::ReScope(scope),
859 pub fn cat_rvalue_node(&self,
864 let promotable = self.tcx().rvalue_promotable_to_static.borrow().get(&id).cloned()
867 // When the corresponding feature isn't toggled, only promote `[T; 0]`.
868 let promotable = match expr_ty.sty {
869 ty::TyArray(_, 0) => true,
870 _ => promotable && self.tcx().sess.features.borrow().rvalue_static_promotion,
873 // Compute maximum lifetime of this rvalue. This is 'static if
874 // we can promote to a constant, otherwise equal to enclosing temp
876 let (re, old_re) = if promotable {
877 (self.tcx().types.re_static,
878 self.tcx().types.re_static)
880 self.temporary_scope(id)
882 let ret = self.cat_rvalue(id, span, re, old_re, expr_ty);
883 debug!("cat_rvalue_node ret {:?}", ret);
887 pub fn cat_rvalue(&self,
890 temp_scope: ty::Region<'tcx>,
891 old_temp_scope: ty::Region<'tcx>,
892 expr_ty: Ty<'tcx>) -> cmt<'tcx> {
893 let ret = Rc::new(cmt_ {
896 cat:Categorization::Rvalue(temp_scope, old_temp_scope),
901 debug!("cat_rvalue ret {:?}", ret);
905 pub fn cat_field<N:ast_node>(&self,
911 let ret = Rc::new(cmt_ {
914 mutbl: base_cmt.mutbl.inherit(),
915 cat: Categorization::Interior(base_cmt, InteriorField(NamedField(f_name))),
919 debug!("cat_field ret {:?}", ret);
923 pub fn cat_tup_field<N:ast_node>(&self,
929 let ret = Rc::new(cmt_ {
932 mutbl: base_cmt.mutbl.inherit(),
933 cat: Categorization::Interior(base_cmt, InteriorField(PositionalField(f_idx))),
937 debug!("cat_tup_field ret {:?}", ret);
941 fn cat_deref<N:ast_node>(&self,
945 -> McResult<cmt<'tcx>> {
946 let method_call = ty::MethodCall {
948 autoderef: deref_cnt as u32
950 let method_ty = self.infcx.node_method_ty(method_call);
952 debug!("cat_deref: method_call={:?} method_ty={:?}",
953 method_call, method_ty.map(|ty| ty));
955 let base_cmt = match method_ty {
958 self.tcx().no_late_bound_regions(&method_ty.fn_ret()).unwrap();
959 self.cat_rvalue_node(node.id(), node.span(), ref_ty)
963 let base_cmt_ty = base_cmt.ty;
964 match base_cmt_ty.builtin_deref(true, ty::NoPreference) {
966 let ret = self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty, false);
967 debug!("cat_deref ret {:?}", ret);
971 debug!("Explicit deref of non-derefable type: {:?}",
978 fn cat_deref_common<N:ast_node>(&self,
986 let ptr = match base_cmt.ty.sty {
987 ty::TyAdt(def, ..) if def.is_box() => Unique,
988 ty::TyRawPtr(ref mt) => UnsafePtr(mt.mutbl),
989 ty::TyRef(r, mt) => {
990 let bk = ty::BorrowKind::from_mutbl(mt.mutbl);
991 if implicit { Implicit(bk, r) } else { BorrowedPtr(bk, r) }
993 ref ty => bug!("unexpected type in cat_deref_common: {:?}", ty)
995 let ret = Rc::new(cmt_ {
998 // For unique ptrs, we inherit mutability from the owning reference.
999 mutbl: MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr),
1000 cat: Categorization::Deref(base_cmt, deref_cnt, ptr),
1004 debug!("cat_deref_common ret {:?}", ret);
1008 pub fn cat_index<N:ast_node>(&self,
1010 mut base_cmt: cmt<'tcx>,
1011 context: InteriorOffsetKind)
1012 -> McResult<cmt<'tcx>> {
1013 //! Creates a cmt for an indexing operation (`[]`).
1015 //! One subtle aspect of indexing that may not be
1016 //! immediately obvious: for anything other than a fixed-length
1017 //! vector, an operation like `x[y]` actually consists of two
1018 //! disjoint (from the point of view of borrowck) operations.
1019 //! The first is a deref of `x` to create a pointer `p` that points
1020 //! at the first element in the array. The second operation is
1021 //! an index which adds `y*sizeof(T)` to `p` to obtain the
1022 //! pointer to `x[y]`. `cat_index` will produce a resulting
1023 //! cmt containing both this deref and the indexing,
1024 //! presuming that `base_cmt` is not of fixed-length type.
1027 //! - `elt`: the AST node being indexed
1028 //! - `base_cmt`: the cmt of `elt`
1030 let method_call = ty::MethodCall::expr(elt.id());
1031 let method_ty = self.infcx.node_method_ty(method_call);
1033 let (element_ty, element_kind) = match method_ty {
1034 Some(method_ty) => {
1035 let ref_ty = self.overloaded_method_return_ty(method_ty);
1036 base_cmt = self.cat_rvalue_node(elt.id(), elt.span(), ref_ty);
1038 (ref_ty.builtin_deref(false, ty::NoPreference).unwrap().ty,
1039 ElementKind::OtherElement)
1042 match base_cmt.ty.builtin_index() {
1043 Some(ty) => (ty, ElementKind::VecElement),
1045 debug!("Explicit index of non-indexable type {:?}", base_cmt);
1052 let interior_elem = InteriorElement(context, element_kind);
1054 self.cat_imm_interior(elt, base_cmt.clone(), element_ty, interior_elem);
1055 debug!("cat_index ret {:?}", ret);
1059 pub fn cat_imm_interior<N:ast_node>(&self,
1061 base_cmt: cmt<'tcx>,
1062 interior_ty: Ty<'tcx>,
1063 interior: InteriorKind)
1065 let ret = Rc::new(cmt_ {
1068 mutbl: base_cmt.mutbl.inherit(),
1069 cat: Categorization::Interior(base_cmt, interior),
1073 debug!("cat_imm_interior ret={:?}", ret);
1077 pub fn cat_downcast<N:ast_node>(&self,
1079 base_cmt: cmt<'tcx>,
1080 downcast_ty: Ty<'tcx>,
1083 let ret = Rc::new(cmt_ {
1086 mutbl: base_cmt.mutbl.inherit(),
1087 cat: Categorization::Downcast(base_cmt, variant_did),
1091 debug!("cat_downcast ret={:?}", ret);
1095 pub fn cat_pattern<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, mut op: F) -> McResult<()>
1096 where F: FnMut(&MemCategorizationContext<'a, 'gcx, 'tcx>, cmt<'tcx>, &hir::Pat),
1098 self.cat_pattern_(cmt, pat, &mut op)
1101 // FIXME(#19596) This is a workaround, but there should be a better way to do this
1102 fn cat_pattern_<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, op: &mut F) -> McResult<()>
1103 where F : FnMut(&MemCategorizationContext<'a, 'gcx, 'tcx>, cmt<'tcx>, &hir::Pat)
1105 // Here, `cmt` is the categorization for the value being
1106 // matched and pat is the pattern it is being matched against.
1108 // In general, the way that this works is that we walk down
1109 // the pattern, constructing a cmt that represents the path
1110 // that will be taken to reach the value being matched.
1112 // When we encounter named bindings, we take the cmt that has
1113 // been built up and pass it off to guarantee_valid() so that
1114 // we can be sure that the binding will remain valid for the
1115 // duration of the arm.
1117 // (*2) There is subtlety concerning the correspondence between
1118 // pattern ids and types as compared to *expression* ids and
1119 // types. This is explained briefly. on the definition of the
1120 // type `cmt`, so go off and read what it says there, then
1121 // come back and I'll dive into a bit more detail here. :) OK,
1124 // In general, the id of the cmt should be the node that
1125 // "produces" the value---patterns aren't executable code
1126 // exactly, but I consider them to "execute" when they match a
1127 // value, and I consider them to produce the value that was
1128 // matched. So if you have something like:
1135 // In this case, the cmt and the relevant ids would be:
1137 // CMT Id Type of Id Type of cmt
1140 // ^~~~~~~^ `x` from discr @@int @@int
1141 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
1142 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
1144 // You can see that the types of the id and the cmt are in
1145 // sync in the first line, because that id is actually the id
1146 // of an expression. But once we get to pattern ids, the types
1147 // step out of sync again. So you'll see below that we always
1148 // get the type of the *subpattern* and use that.
1150 debug!("cat_pattern: {:?} cmt={:?}", pat, cmt);
1152 op(self, cmt.clone(), pat);
1154 // Note: This goes up here (rather than within the PatKind::TupleStruct arm
1155 // alone) because PatKind::Struct can also refer to variants.
1156 let cmt = match pat.node {
1157 PatKind::Path(hir::QPath::Resolved(_, ref path)) |
1158 PatKind::TupleStruct(hir::QPath::Resolved(_, ref path), ..) |
1159 PatKind::Struct(hir::QPath::Resolved(_, ref path), ..) => {
1162 debug!("access to unresolvable pattern {:?}", pat);
1165 Def::Variant(variant_did) |
1166 Def::VariantCtor(variant_did, ..) => {
1167 // univariant enums do not need downcasts
1168 let enum_did = self.tcx().parent_def_id(variant_did).unwrap();
1169 if !self.tcx().adt_def(enum_did).is_univariant() {
1170 self.cat_downcast(pat, cmt.clone(), cmt.ty, variant_did)
1182 PatKind::TupleStruct(ref qpath, ref subpats, ddpos) => {
1183 let def = self.infcx.tables.borrow().qpath_def(qpath, pat.id);
1184 let expected_len = match def {
1185 Def::VariantCtor(def_id, CtorKind::Fn) => {
1186 let enum_def = self.tcx().parent_def_id(def_id).unwrap();
1187 self.tcx().adt_def(enum_def).variant_with_id(def_id).fields.len()
1189 Def::StructCtor(_, CtorKind::Fn) => {
1190 match self.pat_ty(&pat)?.sty {
1191 ty::TyAdt(adt_def, _) => {
1192 adt_def.struct_variant().fields.len()
1195 span_bug!(pat.span, "tuple struct pattern unexpected type {:?}", ty);
1200 span_bug!(pat.span, "tuple struct pattern didn't resolve \
1201 to variant or struct {:?}", def);
1205 for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
1206 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
1207 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty,
1208 InteriorField(PositionalField(i)));
1209 self.cat_pattern_(subcmt, &subpat, op)?;
1213 PatKind::Struct(_, ref field_pats, _) => {
1214 // {f1: p1, ..., fN: pN}
1215 for fp in field_pats {
1216 let field_ty = self.pat_ty(&fp.node.pat)?; // see (*2)
1217 let cmt_field = self.cat_field(pat, cmt.clone(), fp.node.name, field_ty);
1218 self.cat_pattern_(cmt_field, &fp.node.pat, op)?;
1222 PatKind::Binding(.., Some(ref subpat)) => {
1223 self.cat_pattern_(cmt, &subpat, op)?;
1226 PatKind::Tuple(ref subpats, ddpos) => {
1228 let expected_len = match self.pat_ty(&pat)?.sty {
1229 ty::TyTuple(ref tys, _) => tys.len(),
1230 ref ty => span_bug!(pat.span, "tuple pattern unexpected type {:?}", ty),
1232 for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
1233 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
1234 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty,
1235 InteriorField(PositionalField(i)));
1236 self.cat_pattern_(subcmt, &subpat, op)?;
1240 PatKind::Box(ref subpat) | PatKind::Ref(ref subpat, _) => {
1241 // box p1, &p1, &mut p1. we can ignore the mutability of
1242 // PatKind::Ref since that information is already contained
1244 let subcmt = self.cat_deref(pat, cmt, 0)?;
1245 self.cat_pattern_(subcmt, &subpat, op)?;
1248 PatKind::Slice(ref before, ref slice, ref after) => {
1249 let context = InteriorOffsetKind::Pattern;
1250 let elt_cmt = self.cat_index(pat, cmt, context)?;
1251 for before_pat in before {
1252 self.cat_pattern_(elt_cmt.clone(), &before_pat, op)?;
1254 if let Some(ref slice_pat) = *slice {
1255 self.cat_pattern_(elt_cmt.clone(), &slice_pat, op)?;
1257 for after_pat in after {
1258 self.cat_pattern_(elt_cmt.clone(), &after_pat, op)?;
1262 PatKind::Path(_) | PatKind::Binding(.., None) |
1263 PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild => {
1271 fn overloaded_method_return_ty(&self,
1272 method_ty: Ty<'tcx>)
1275 // When we process an overloaded `*` or `[]` etc, we often
1276 // need to extract the return type of the method. These method
1277 // types are generated by method resolution and always have
1278 // all late-bound regions fully instantiated, so we just want
1279 // to skip past the binder.
1280 self.tcx().no_late_bound_regions(&method_ty.fn_ret())
1285 #[derive(Clone, Debug)]
1286 pub enum Aliasability {
1287 FreelyAliasable(AliasableReason),
1289 ImmutableUnique(Box<Aliasability>),
1292 #[derive(Copy, Clone, Debug)]
1293 pub enum AliasableReason {
1299 impl<'tcx> cmt_<'tcx> {
1300 pub fn guarantor(&self) -> cmt<'tcx> {
1301 //! Returns `self` after stripping away any derefs or
1302 //! interior content. The return value is basically the `cmt` which
1303 //! determines how long the value in `self` remains live.
1306 Categorization::Rvalue(..) |
1307 Categorization::StaticItem |
1308 Categorization::Local(..) |
1309 Categorization::Deref(.., UnsafePtr(..)) |
1310 Categorization::Deref(.., BorrowedPtr(..)) |
1311 Categorization::Deref(.., Implicit(..)) |
1312 Categorization::Upvar(..) => {
1313 Rc::new((*self).clone())
1315 Categorization::Downcast(ref b, _) |
1316 Categorization::Interior(ref b, _) |
1317 Categorization::Deref(ref b, _, Unique) => {
1323 /// Returns `FreelyAliasable(_)` if this lvalue represents a freely aliasable pointer type.
1324 pub fn freely_aliasable(&self) -> Aliasability {
1325 // Maybe non-obvious: copied upvars can only be considered
1326 // non-aliasable in once closures, since any other kind can be
1327 // aliased and eventually recused.
1330 Categorization::Deref(ref b, _, BorrowedPtr(ty::MutBorrow, _)) |
1331 Categorization::Deref(ref b, _, Implicit(ty::MutBorrow, _)) |
1332 Categorization::Deref(ref b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1333 Categorization::Deref(ref b, _, Implicit(ty::UniqueImmBorrow, _)) |
1334 Categorization::Deref(ref b, _, Unique) |
1335 Categorization::Downcast(ref b, _) |
1336 Categorization::Interior(ref b, _) => {
1337 // Aliasability depends on base cmt
1338 b.freely_aliasable()
1341 Categorization::Rvalue(..) |
1342 Categorization::Local(..) |
1343 Categorization::Upvar(..) |
1344 Categorization::Deref(.., UnsafePtr(..)) => { // yes, it's aliasable, but...
1348 Categorization::StaticItem => {
1349 if self.mutbl.is_mutable() {
1350 FreelyAliasable(AliasableStaticMut)
1352 FreelyAliasable(AliasableStatic)
1356 Categorization::Deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) |
1357 Categorization::Deref(_, _, Implicit(ty::ImmBorrow, _)) => {
1358 FreelyAliasable(AliasableBorrowed)
1363 // Digs down through one or two layers of deref and grabs the cmt
1364 // for the upvar if a note indicates there is one.
1365 pub fn upvar(&self) -> Option<cmt<'tcx>> {
1367 NoteClosureEnv(..) | NoteUpvarRef(..) => {
1368 Some(match self.cat {
1369 Categorization::Deref(ref inner, ..) => {
1371 Categorization::Deref(ref inner, ..) => inner.clone(),
1372 Categorization::Upvar(..) => inner.clone(),
1384 pub fn descriptive_string(&self, tcx: TyCtxt) -> String {
1386 Categorization::StaticItem => {
1387 "static item".to_string()
1389 Categorization::Rvalue(..) => {
1390 "non-lvalue".to_string()
1392 Categorization::Local(vid) => {
1393 if tcx.hir.is_argument(vid) {
1394 "argument".to_string()
1396 "local variable".to_string()
1399 Categorization::Deref(.., pk) => {
1400 let upvar = self.upvar();
1401 match upvar.as_ref().map(|i| &i.cat) {
1402 Some(&Categorization::Upvar(ref var)) => {
1409 format!("indexed content")
1412 format!("`Box` content")
1415 format!("dereference of raw pointer")
1417 BorrowedPtr(..) => {
1418 format!("borrowed content")
1424 Categorization::Interior(_, InteriorField(NamedField(_))) => {
1427 Categorization::Interior(_, InteriorField(PositionalField(_))) => {
1428 "anonymous field".to_string()
1430 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Index,
1432 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Index,
1434 "indexed content".to_string()
1436 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Pattern,
1438 Categorization::Interior(_, InteriorElement(InteriorOffsetKind::Pattern,
1440 "pattern-bound indexed content".to_string()
1442 Categorization::Upvar(ref var) => {
1445 Categorization::Downcast(ref cmt, _) => {
1446 cmt.descriptive_string(tcx)
1452 impl<'tcx> fmt::Debug for cmt_<'tcx> {
1453 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1454 write!(f, "{{{:?} id:{} m:{:?} ty:{:?}}}",
1462 impl<'tcx> fmt::Debug for Categorization<'tcx> {
1463 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1465 Categorization::StaticItem => write!(f, "static"),
1466 Categorization::Rvalue(r, or) => {
1467 write!(f, "rvalue({:?}, {:?})", r, or)
1469 Categorization::Local(id) => {
1470 let name = ty::tls::with(|tcx| tcx.local_var_name_str(id));
1471 write!(f, "local({})", name)
1473 Categorization::Upvar(upvar) => {
1474 write!(f, "upvar({:?})", upvar)
1476 Categorization::Deref(ref cmt, derefs, ptr) => {
1477 write!(f, "{:?}-{:?}{}->", cmt.cat, ptr, derefs)
1479 Categorization::Interior(ref cmt, interior) => {
1480 write!(f, "{:?}.{:?}", cmt.cat, interior)
1482 Categorization::Downcast(ref cmt, _) => {
1483 write!(f, "{:?}->(enum)", cmt.cat)
1489 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1492 BorrowedPtr(ty::ImmBorrow, _) |
1493 Implicit(ty::ImmBorrow, _) => "&",
1494 BorrowedPtr(ty::MutBorrow, _) |
1495 Implicit(ty::MutBorrow, _) => "&mut",
1496 BorrowedPtr(ty::UniqueImmBorrow, _) |
1497 Implicit(ty::UniqueImmBorrow, _) => "&unique",
1498 UnsafePtr(_) => "*",
1502 impl<'tcx> fmt::Debug for PointerKind<'tcx> {
1503 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1505 Unique => write!(f, "Box"),
1506 BorrowedPtr(ty::ImmBorrow, ref r) |
1507 Implicit(ty::ImmBorrow, ref r) => {
1508 write!(f, "&{:?}", r)
1510 BorrowedPtr(ty::MutBorrow, ref r) |
1511 Implicit(ty::MutBorrow, ref r) => {
1512 write!(f, "&{:?} mut", r)
1514 BorrowedPtr(ty::UniqueImmBorrow, ref r) |
1515 Implicit(ty::UniqueImmBorrow, ref r) => {
1516 write!(f, "&{:?} uniq", r)
1518 UnsafePtr(_) => write!(f, "*")
1523 impl fmt::Debug for InteriorKind {
1524 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1526 InteriorField(NamedField(fld)) => write!(f, "{}", fld),
1527 InteriorField(PositionalField(i)) => write!(f, "#{}", i),
1528 InteriorElement(..) => write!(f, "[]"),
1533 impl fmt::Debug for Upvar {
1534 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1535 write!(f, "{:?}/{:?}", self.id, self.kind)
1539 impl fmt::Display for Upvar {
1540 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1541 let kind = match self.kind {
1542 ty::ClosureKind::Fn => "Fn",
1543 ty::ClosureKind::FnMut => "FnMut",
1544 ty::ClosureKind::FnOnce => "FnOnce",
1546 write!(f, "captured outer variable in an `{}` closure", kind)