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.
14 * The job of the categorization module is to analyze an expression to
15 * determine what kind of memory is used in evaluating it (for example,
16 * where dereferences occur and what kind of pointer is dereferenced;
17 * whether the memory is mutable; etc)
19 * Categorization effectively transforms all of our expressions into
20 * expressions of the following forms (the actual enum has many more
21 * possibilities, naturally, but they are all variants of these base
24 * E = rvalue // some computed rvalue
25 * | x // address of a local variable or argument
26 * | *E // deref of a ptr
27 * | E.comp // access to an interior component
29 * Imagine a routine ToAddr(Expr) that evaluates an expression and returns an
30 * address where the result is to be found. If Expr is an lvalue, then this
31 * is the address of the lvalue. If Expr is an rvalue, this is the address of
32 * some temporary spot in memory where the result is stored.
34 * Now, cat_expr() classies the expression Expr and the address A=ToAddr(Expr)
37 * - cat: what kind of expression was this? This is a subset of the
38 * full expression forms which only includes those that we care about
39 * for the purpose of the analysis.
40 * - mutbl: mutability of the address A
41 * - ty: the type of data found at the address A
43 * The resulting categorization tree differs somewhat from the expressions
44 * themselves. For example, auto-derefs are explicit. Also, an index a[b] is
45 * decomposed into two operations: a derefence to reach the array data and
46 * then an index to jump forward to the relevant item.
48 * ## By-reference upvars
50 * One part of the translation which may be non-obvious is that we translate
51 * closure upvars into the dereference of a borrowed pointer; this more closely
52 * resembles the runtime translation. So, for example, if we had:
56 * let inc = || x += y;
58 * Then when we categorize `x` (*within* the closure) we would yield a
59 * result of `*x'`, effectively, where `x'` is a `cat_upvar` reference
60 * tied to `x`. The type of `x'` will be a borrowed pointer.
63 #[allow(non_camel_case_types)];
66 use util::ppaux::{ty_to_str, region_ptr_to_str, Repr};
69 use syntax::ast::{MutImmutable, MutMutable};
71 use syntax::codemap::Span;
72 use syntax::print::pprust;
73 use syntax::parse::token;
76 pub enum categorization {
77 cat_rvalue(ty::Region), // temporary val, argument is its scope
79 cat_copied_upvar(CopiedUpvar), // upvar copied into @fn or ~fn env
80 cat_upvar(ty::UpvarId, ty::UpvarBorrow), // by ref upvar from stack closure
81 cat_local(ast::NodeId), // local variable
82 cat_arg(ast::NodeId), // formal argument
83 cat_deref(cmt, uint, PointerKind), // deref of a ptr
84 cat_interior(cmt, InteriorKind), // something interior: field, tuple, etc
85 cat_downcast(cmt), // selects a particular enum variant (*1)
86 cat_discr(cmt, ast::NodeId), // match discriminant (see preserve())
88 // (*1) downcast is only required if the enum has more than one variant
92 pub struct CopiedUpvar {
93 upvar_id: ast::NodeId,
94 onceness: ast::Onceness,
97 // different kinds of pointers:
99 pub enum PointerKind {
102 BorrowedPtr(ty::BorrowKind, ty::Region),
103 UnsafePtr(ast::Mutability),
106 // We use the term "interior" to mean "something reachable from the
107 // base without a pointer dereference", e.g. a field
108 #[deriving(Eq, Hash)]
109 pub enum InteriorKind {
110 InteriorField(FieldName),
111 InteriorElement(ElementKind),
114 #[deriving(Eq, Hash)]
116 NamedField(ast::Name),
117 PositionalField(uint)
120 #[deriving(Eq, Hash)]
121 pub enum ElementKind {
127 #[deriving(Eq, Hash, Show)]
128 pub enum MutabilityCategory {
129 McImmutable, // Immutable.
130 McDeclared, // Directly declared as mutable.
131 McInherited, // Inherited from the fact that owner is mutable.
134 // `cmt`: "Category, Mutability, and Type".
136 // a complete categorization of a value indicating where it originated
137 // and how it is located, as well as the mutability of the memory in
138 // which the value is stored.
140 // *WARNING* The field `cmt.type` is NOT necessarily the same as the
141 // result of `node_id_to_type(cmt.id)`. This is because the `id` is
142 // always the `id` of the node producing the type; in an expression
143 // like `*x`, the type of this deref node is the deref'd type (`T`),
144 // but in a pattern like `@x`, the `@x` pattern is again a
145 // dereference, but its type is the type *before* the dereference
146 // (`@T`). So use `cmt.type` to find the type of the value in a consistent
147 // fashion. For more details, see the method `cat_pattern`
150 id: ast::NodeId, // id of expr/pat producing this value
151 span: Span, // span of same expr/pat
152 cat: categorization, // categorization of expr
153 mutbl: MutabilityCategory, // mutability of expr as lvalue
154 ty: ty::t // type of the expr (*see WARNING above*)
157 pub type cmt = @cmt_;
159 // We pun on *T to mean both actual deref of a ptr as well
160 // as accessing of components:
161 pub enum deref_kind {
162 deref_ptr(PointerKind),
163 deref_interior(InteriorKind),
166 // Categorizes a derefable type. Note that we include vectors and strings as
167 // derefable (we model an index as the combination of a deref and then a
168 // pointer adjustment).
169 pub fn opt_deref_kind(t: ty::t) -> Option<deref_kind> {
170 match ty::get(t).sty {
172 ty::ty_trait(_, _, ty::UniqTraitStore, _, _) |
173 ty::ty_vec(_, ty::vstore_uniq) |
174 ty::ty_str(ty::vstore_uniq) |
175 ty::ty_closure(ty::ClosureTy {sigil: ast::OwnedSigil, ..}) => {
176 Some(deref_ptr(OwnedPtr))
180 ty::ty_vec(mt, ty::vstore_slice(r)) => {
181 let kind = ty::BorrowKind::from_mutbl(mt.mutbl);
182 Some(deref_ptr(BorrowedPtr(kind, r)))
185 ty::ty_trait(_, _, ty::RegionTraitStore(r), m, _) => {
186 let kind = ty::BorrowKind::from_mutbl(m);
187 Some(deref_ptr(BorrowedPtr(kind, r)))
190 ty::ty_str(ty::vstore_slice(r)) |
191 ty::ty_closure(ty::ClosureTy {sigil: ast::BorrowedSigil,
193 Some(deref_ptr(BorrowedPtr(ty::ImmBorrow, r)))
197 Some(deref_ptr(GcPtr))
200 ty::ty_ptr(ref mt) => {
201 Some(deref_ptr(UnsafePtr(mt.mutbl)))
205 ty::ty_struct(..) => { // newtype
206 Some(deref_interior(InteriorField(PositionalField(0))))
209 ty::ty_vec(_, ty::vstore_fixed(_)) |
210 ty::ty_str(ty::vstore_fixed(_)) => {
211 Some(deref_interior(InteriorElement(element_kind(t))))
218 pub fn deref_kind(tcx: ty::ctxt, t: ty::t) -> deref_kind {
219 match opt_deref_kind(t) {
223 format!("deref_cat() invoked on non-derefable type {}",
230 fn id(&self) -> ast::NodeId;
231 fn span(&self) -> Span;
234 impl ast_node for ast::Expr {
235 fn id(&self) -> ast::NodeId { self.id }
236 fn span(&self) -> Span { self.span }
239 impl ast_node for ast::Pat {
240 fn id(&self) -> ast::NodeId { self.id }
241 fn span(&self) -> Span { self.span }
244 pub struct MemCategorizationContext<TYPER> {
248 pub type McResult<T> = Result<T, ()>;
251 * The `Typer` trait provides the interface for the mem-categorization
252 * module to the results of the type check. It can be used to query
253 * the type assigned to an expression node, to inquire after adjustments,
256 * This interface is needed because mem-categorization is used from
257 * two places: `regionck` and `borrowck`. `regionck` executes before
258 * type inference is complete, and hence derives types and so on from
259 * intermediate tables. This also implies that type errors can occur,
260 * and hence `node_ty()` and friends return a `Result` type -- any
261 * error will propagate back up through the mem-categorization
264 * In the borrow checker, in contrast, type checking is complete and we
265 * know that no errors have occurred, so we simply consult the tcx and we
266 * can be sure that only `Ok` results will occur.
269 fn tcx(&self) -> ty::ctxt;
270 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t>;
271 fn node_method_ty(&mut self, id: ast::NodeId) -> Option<ty::t>;
272 fn adjustment(&mut self, node_id: ast::NodeId) -> Option<@ty::AutoAdjustment>;
273 fn is_method_call(&mut self, id: ast::NodeId) -> bool;
274 fn temporary_scope(&mut self, rvalue_id: ast::NodeId) -> Option<ast::NodeId>;
275 fn upvar_borrow(&mut self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow;
278 impl MutabilityCategory {
279 pub fn from_mutbl(m: ast::Mutability) -> MutabilityCategory {
281 MutImmutable => McImmutable,
282 MutMutable => McDeclared
286 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
288 ty::ImmBorrow => McImmutable,
289 ty::UniqueImmBorrow => McImmutable,
290 ty::MutBorrow => McDeclared,
294 pub fn from_pointer_kind(base_mutbl: MutabilityCategory,
295 ptr: PointerKind) -> MutabilityCategory {
300 BorrowedPtr(borrow_kind, _) => {
301 MutabilityCategory::from_borrow_kind(borrow_kind)
307 MutabilityCategory::from_mutbl(m)
312 pub fn inherit(&self) -> MutabilityCategory {
314 McImmutable => McImmutable,
315 McDeclared => McInherited,
316 McInherited => McInherited,
320 pub fn is_mutable(&self) -> bool {
322 McImmutable => false,
328 pub fn is_immutable(&self) -> bool {
331 McDeclared | McInherited => false
335 pub fn to_user_str(&self) -> &'static str {
337 McDeclared | McInherited => "mutable",
338 McImmutable => "immutable",
347 Err(e) => { return Err(e); }
352 impl<TYPER:Typer> MemCategorizationContext<TYPER> {
353 fn tcx(&self) -> ty::ctxt {
357 fn adjustment(&mut self, id: ast::NodeId) -> Option<@ty::AutoAdjustment> {
358 self.typer.adjustment(id)
361 fn expr_ty(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
362 self.typer.node_ty(expr.id)
365 fn expr_ty_adjusted(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
366 let unadjusted_ty = if_ok!(self.expr_ty(expr));
367 let adjustment = self.adjustment(expr.id);
368 Ok(ty::adjust_ty(self.tcx(), expr.span, unadjusted_ty, adjustment))
371 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t> {
372 self.typer.node_ty(id)
375 fn pat_ty(&mut self, pat: @ast::Pat) -> McResult<ty::t> {
376 self.typer.node_ty(pat.id)
379 pub fn cat_expr(&mut self, expr: &ast::Expr) -> McResult<cmt> {
380 match self.adjustment(expr.id) {
383 self.cat_expr_unadjusted(expr)
386 Some(adjustment) => {
388 ty::AutoObject(..) => {
389 // Implicity casts a concrete object to trait object
390 // so just patch up the type
391 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
392 let expr_cmt = if_ok!(self.cat_expr_unadjusted(expr));
393 Ok(@cmt_ {ty: expr_ty, ..*expr_cmt})
396 ty::AutoAddEnv(..) => {
397 // Convert a bare fn to a closure by adding NULL env.
398 // Result is an rvalue.
399 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
400 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
405 autoref: Some(_), ..}) => {
406 // Equivalent to &*expr or something similar.
407 // Result is an rvalue.
408 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
409 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
414 autoref: None, autoderefs: autoderefs}) => {
415 // Equivalent to *expr or something similar.
416 self.cat_expr_autoderefd(expr, autoderefs)
423 pub fn cat_expr_autoderefd(&mut self, expr: &ast::Expr, autoderefs: uint)
425 let mut cmt = if_ok!(self.cat_expr_unadjusted(expr));
426 for deref in range(1u, autoderefs + 1) {
427 cmt = self.cat_deref(expr, cmt, deref);
432 pub fn cat_expr_unadjusted(&mut self, expr: &ast::Expr) -> McResult<cmt> {
433 debug!("cat_expr: id={} expr={}", expr.id, expr.repr(self.tcx()));
435 let expr_ty = if_ok!(self.expr_ty(expr));
437 ast::ExprUnary(ast::UnDeref, e_base) => {
438 let base_cmt = match self.typer.node_method_ty(expr.id) {
440 let ref_ty = ty::ty_fn_ret(method_ty);
441 self.cat_rvalue_node(expr.id(), expr.span(), ref_ty)
443 None => if_ok!(self.cat_expr(e_base))
445 Ok(self.cat_deref(expr, base_cmt, 0))
448 ast::ExprField(base, f_name, _) => {
449 // Method calls are now a special syntactic form,
450 // so `a.b` should always be a field.
451 assert!(!self.typer.is_method_call(expr.id));
453 let base_cmt = if_ok!(self.cat_expr(base));
454 Ok(self.cat_field(expr, base_cmt, f_name, expr_ty))
457 ast::ExprIndex(base, _) => {
458 if self.typer.is_method_call(expr.id) {
459 return Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty));
462 let base_cmt = if_ok!(self.cat_expr(base));
463 Ok(self.cat_index(expr, base_cmt, 0))
466 ast::ExprPath(_) => {
467 let def_map = self.tcx().def_map.borrow();
468 let def = def_map.get().get_copy(&expr.id);
469 self.cat_def(expr.id, expr.span, expr_ty, def)
472 ast::ExprParen(e) => self.cat_expr_unadjusted(e),
474 ast::ExprAddrOf(..) | ast::ExprCall(..) |
475 ast::ExprAssign(..) | ast::ExprAssignOp(..) |
476 ast::ExprFnBlock(..) | ast::ExprProc(..) | ast::ExprRet(..) |
478 ast::ExprMethodCall(..) | ast::ExprCast(..) | ast::ExprVstore(..) |
479 ast::ExprVec(..) | ast::ExprTup(..) | ast::ExprIf(..) |
480 ast::ExprLogLevel | ast::ExprBinary(..) | ast::ExprWhile(..) |
481 ast::ExprBlock(..) | ast::ExprLoop(..) | ast::ExprMatch(..) |
482 ast::ExprLit(..) | ast::ExprBreak(..) | ast::ExprMac(..) |
483 ast::ExprAgain(..) | ast::ExprStruct(..) | ast::ExprRepeat(..) |
484 ast::ExprInlineAsm(..) | ast::ExprBox(..) => {
485 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
488 ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop")
492 pub fn cat_def(&mut self,
498 debug!("cat_def: id={} expr={}",
499 id, expr_ty.repr(self.tcx()));
502 ast::DefStruct(..) | ast::DefVariant(..) => {
503 Ok(self.cat_rvalue_node(id, span, expr_ty))
505 ast::DefFn(..) | ast::DefStaticMethod(..) | ast::DefMod(_) |
506 ast::DefForeignMod(_) | ast::DefStatic(_, false) |
507 ast::DefUse(_) | ast::DefTrait(_) | ast::DefTy(_) | ast::DefPrimTy(_) |
508 ast::DefTyParam(..) | ast::DefTyParamBinder(..) | ast::DefRegion(_) |
509 ast::DefLabel(_) | ast::DefSelfTy(..) | ast::DefMethod(..) => {
519 ast::DefStatic(_, true) => {
529 ast::DefArg(vid, binding_mode) => {
530 // Idea: make this could be rewritten to model by-ref
531 // stuff as `&const` and `&mut`?
533 // m: mutability of the argument
534 let m = match binding_mode {
535 ast::BindByValue(ast::MutMutable) => McDeclared,
547 ast::DefUpvar(var_id, _, fn_node_id, _) => {
548 let ty = if_ok!(self.node_ty(fn_node_id));
549 match ty::get(ty).sty {
550 ty::ty_closure(ref closure_ty) => {
551 // Decide whether to use implicit reference or by copy/move
552 // capture for the upvar. This, combined with the onceness,
553 // determines whether the closure can move out of it.
554 let var_is_refd = match (closure_ty.sigil, closure_ty.onceness) {
555 // Many-shot stack closures can never move out.
556 (ast::BorrowedSigil, ast::Many) => true,
557 // 1-shot stack closures can move out.
558 (ast::BorrowedSigil, ast::Once) => false,
559 // Heap closures always capture by copy/move, and can
560 // move out if they are once.
561 (ast::OwnedSigil, _) |
562 (ast::ManagedSigil, _) => false,
566 self.cat_upvar(id, span, var_id, fn_node_id)
568 // FIXME #2152 allow mutation of moved upvars
572 cat:cat_copied_upvar(CopiedUpvar {
574 onceness: closure_ty.onceness}),
581 self.tcx().sess.span_bug(
583 format!("Upvar of non-closure {} - {}",
584 fn_node_id, ty.repr(self.tcx())));
589 ast::DefLocal(vid, binding_mode) |
590 ast::DefBinding(vid, binding_mode) => {
591 // by-value/by-ref bindings are local variables
592 let m = match binding_mode {
593 ast::BindByValue(ast::MutMutable) => McDeclared,
608 fn cat_upvar(&mut self,
612 fn_node_id: ast::NodeId)
615 * Upvars through a closure are in fact indirect
616 * references. That is, when a closure refers to a
617 * variable from a parent stack frame like `x = 10`,
618 * that is equivalent to `*x_ = 10` where `x_` is a
619 * borrowed pointer (`&mut x`) created when the closure
620 * was created and store in the environment. This
621 * equivalence is expose in the mem-categorization.
624 let upvar_id = ty::UpvarId { var_id: var_id,
625 closure_expr_id: fn_node_id };
627 let upvar_borrow = self.typer.upvar_borrow(upvar_id);
629 let var_ty = if_ok!(self.node_ty(var_id));
631 // We can't actually represent the types of all upvars
632 // as user-describable types, since upvars support const
633 // and unique-imm borrows! Therefore, we cheat, and just
634 // give err type. Nobody should be inspecting this type anyhow.
635 let upvar_ty = ty::mk_err();
637 let base_cmt = @cmt_ {
640 cat:cat_upvar(upvar_id, upvar_borrow),
645 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
647 let deref_cmt = @cmt_ {
650 cat:cat_deref(base_cmt, 0, ptr),
651 mutbl:MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
658 pub fn cat_rvalue_node(&mut self,
663 match self.typer.temporary_scope(id) {
665 self.cat_rvalue(id, span, ty::ReScope(scope), expr_ty)
668 self.cat_rvalue(id, span, ty::ReStatic, expr_ty)
673 pub fn cat_rvalue(&mut self,
676 temp_scope: ty::Region,
677 expr_ty: ty::t) -> cmt {
681 cat:cat_rvalue(temp_scope),
687 /// inherited mutability: used in cases where the mutability of a
688 /// component is inherited from the base it is a part of. For
689 /// example, a record field is mutable if it is declared mutable
690 /// or if the container is mutable.
691 pub fn inherited_mutability(&mut self,
692 base_m: MutabilityCategory,
693 interior_m: ast::Mutability)
694 -> MutabilityCategory {
696 MutImmutable => base_m.inherit(),
697 MutMutable => McDeclared
701 pub fn cat_field<N:ast_node>(&mut self,
710 cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
711 mutbl: base_cmt.mutbl.inherit(),
716 pub fn cat_deref_fn_or_obj<N:ast_node>(&mut self,
721 // Bit of a hack: the "dereference" of a function pointer like
722 // `@fn()` is a mere logical concept. We interpret it as
723 // dereferencing the environment pointer; of course, we don't
724 // know what type lies at the other end, so we just call it
725 // `()` (the empty tuple).
727 let opaque_ty = ty::mk_tup(self.tcx(), Vec::new());
728 return self.cat_deref_common(node, base_cmt, deref_cnt, opaque_ty);
731 pub fn cat_deref<N:ast_node>(&mut self,
736 let mt = match ty::deref(base_cmt.ty, true) {
739 self.tcx().sess.span_bug(
741 format!("Explicit deref of non-derefable type: {}",
742 base_cmt.ty.repr(self.tcx())));
746 return self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty);
749 pub fn cat_deref_common<N:ast_node>(&mut self,
755 match deref_kind(self.tcx(), base_cmt.ty) {
757 // for unique ptrs, we inherit mutability from the
759 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl,
765 cat:cat_deref(base_cmt, deref_cnt, ptr),
771 deref_interior(interior) => {
772 let m = base_cmt.mutbl.inherit();
776 cat:cat_interior(base_cmt, interior),
784 pub fn cat_index<N:ast_node>(&mut self,
789 //! Creates a cmt for an indexing operation (`[]`); this
790 //! indexing operation may occurs as part of an
791 //! AutoBorrowVec, which when converting a `~[]` to an `&[]`
792 //! effectively takes the address of the 0th element.
794 //! One subtle aspect of indexing that may not be
795 //! immediately obvious: for anything other than a fixed-length
796 //! vector, an operation like `x[y]` actually consists of two
797 //! disjoint (from the point of view of borrowck) operations.
798 //! The first is a deref of `x` to create a pointer `p` that points
799 //! at the first element in the array. The second operation is
800 //! an index which adds `y*sizeof(T)` to `p` to obtain the
801 //! pointer to `x[y]`. `cat_index` will produce a resulting
802 //! cmt containing both this deref and the indexing,
803 //! presuming that `base_cmt` is not of fixed-length type.
805 //! In the event that a deref is needed, the "deref count"
806 //! is taken from the parameter `derefs`. See the comment
807 //! on the def'n of `root_map_key` in borrowck/mod.rs
808 //! for more details about deref counts; the summary is
809 //! that `derefs` should be 0 for an explicit indexing
810 //! operation and N+1 for an indexing that is part of
811 //! an auto-adjustment, where N is the number of autoderefs
812 //! in that adjustment.
815 //! - `elt`: the AST node being indexed
816 //! - `base_cmt`: the cmt of `elt`
817 //! - `derefs`: the deref number to be used for
818 //! the implicit index deref, if any (see above)
820 let element_ty = match ty::index(base_cmt.ty) {
821 Some(ref mt) => mt.ty,
823 self.tcx().sess.span_bug(
825 format!("Explicit index of non-index type `{}`",
826 base_cmt.ty.repr(self.tcx())));
830 return match deref_kind(self.tcx(), base_cmt.ty) {
832 // for unique ptrs, we inherit mutability from the
834 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr);
836 // the deref is explicit in the resulting cmt
837 let deref_cmt = @cmt_ {
840 cat:cat_deref(base_cmt, derefs, ptr),
845 interior(elt, deref_cmt, base_cmt.ty, m.inherit(), element_ty)
848 deref_interior(_) => {
849 // fixed-length vectors have no deref
850 let m = base_cmt.mutbl.inherit();
851 interior(elt, base_cmt, base_cmt.ty, m, element_ty)
855 fn interior<N: ast_node>(elt: &N,
858 mutbl: MutabilityCategory,
859 element_ty: ty::t) -> cmt
864 cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
871 pub fn cat_slice_pattern(&mut self,
873 slice_pat: @ast::Pat)
874 -> McResult<(cmt, ast::Mutability, ty::Region)> {
876 * Given a pattern P like: `[_, ..Q, _]`, where `vec_cmt` is
877 * the cmt for `P`, `slice_pat` is the pattern `Q`, returns:
879 * - the mutability and region of the slice `Q`
881 * These last two bits of info happen to be things that
885 let slice_ty = if_ok!(self.node_ty(slice_pat.id));
886 let (slice_mutbl, slice_r) = vec_slice_info(self.tcx(),
889 let cmt_slice = self.cat_index(slice_pat, vec_cmt, 0);
890 return Ok((cmt_slice, slice_mutbl, slice_r));
892 fn vec_slice_info(tcx: ty::ctxt,
895 -> (ast::Mutability, ty::Region) {
897 * In a pattern like [a, b, ..c], normally `c` has slice type,
898 * but if you have [a, b, ..ref c], then the type of `ref c`
899 * will be `&&[]`, so to extract the slice details we have
900 * to recurse through rptrs.
903 match ty::get(slice_ty).sty {
904 ty::ty_vec(slice_mt, ty::vstore_slice(slice_r)) => {
905 (slice_mt.mutbl, slice_r)
908 ty::ty_rptr(_, ref mt) => {
909 vec_slice_info(tcx, pat, mt.ty)
915 format!("Type of slice pattern is not a slice"));
921 pub fn cat_imm_interior<N:ast_node>(&mut self,
925 interior: InteriorKind)
930 cat: cat_interior(base_cmt, interior),
931 mutbl: base_cmt.mutbl.inherit(),
936 pub fn cat_downcast<N:ast_node>(&mut self,
944 cat: cat_downcast(base_cmt),
945 mutbl: base_cmt.mutbl.inherit(),
950 pub fn cat_pattern(&mut self,
953 op: |&mut MemCategorizationContext<TYPER>,
957 // Here, `cmt` is the categorization for the value being
958 // matched and pat is the pattern it is being matched against.
960 // In general, the way that this works is that we walk down
961 // the pattern, constructing a cmt that represents the path
962 // that will be taken to reach the value being matched.
964 // When we encounter named bindings, we take the cmt that has
965 // been built up and pass it off to guarantee_valid() so that
966 // we can be sure that the binding will remain valid for the
967 // duration of the arm.
969 // (*2) There is subtlety concerning the correspondence between
970 // pattern ids and types as compared to *expression* ids and
971 // types. This is explained briefly. on the definition of the
972 // type `cmt`, so go off and read what it says there, then
973 // come back and I'll dive into a bit more detail here. :) OK,
976 // In general, the id of the cmt should be the node that
977 // "produces" the value---patterns aren't executable code
978 // exactly, but I consider them to "execute" when they match a
979 // value, and I consider them to produce the value that was
980 // matched. So if you have something like:
987 // In this case, the cmt and the relevant ids would be:
989 // CMT Id Type of Id Type of cmt
992 // ^~~~~~~^ `x` from discr @@int @@int
993 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
994 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
996 // You can see that the types of the id and the cmt are in
997 // sync in the first line, because that id is actually the id
998 // of an expression. But once we get to pattern ids, the types
999 // step out of sync again. So you'll see below that we always
1000 // get the type of the *subpattern* and use that.
1002 let tcx = self.tcx();
1003 debug!("cat_pattern: id={} pat={} cmt={}",
1004 pat.id, pprust::pat_to_str(pat),
1010 ast::PatWild | ast::PatWildMulti => {
1014 ast::PatEnum(_, None) => {
1017 ast::PatEnum(_, Some(ref subpats)) => {
1018 let def_map = self.tcx().def_map.borrow();
1019 match def_map.get().find(&pat.id) {
1020 Some(&ast::DefVariant(enum_did, _, _)) => {
1023 let downcast_cmt = {
1024 if ty::enum_is_univariant(self.tcx(), enum_did) {
1025 cmt // univariant, no downcast needed
1027 self.cat_downcast(pat, cmt, cmt.ty)
1031 for (i, &subpat) in subpats.iter().enumerate() {
1032 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1035 self.cat_imm_interior(
1036 pat, downcast_cmt, subpat_ty,
1037 InteriorField(PositionalField(i)));
1039 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1042 Some(&ast::DefFn(..)) |
1043 Some(&ast::DefStruct(..)) => {
1044 for (i, &subpat) in subpats.iter().enumerate() {
1045 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1047 self.cat_imm_interior(
1048 pat, cmt, subpat_ty,
1049 InteriorField(PositionalField(i)));
1050 if_ok!(self.cat_pattern(cmt_field, subpat, |x,y,z| op(x,y,z)));
1053 Some(&ast::DefStatic(..)) => {
1054 for &subpat in subpats.iter() {
1055 if_ok!(self.cat_pattern(cmt, subpat, |x,y,z| op(x,y,z)));
1059 self.tcx().sess.span_bug(
1061 "enum pattern didn't resolve to enum or struct");
1066 ast::PatIdent(_, _, Some(subpat)) => {
1067 if_ok!(self.cat_pattern(cmt, subpat, op));
1070 ast::PatIdent(_, _, None) => {
1071 // nullary variant or identifier: ignore
1074 ast::PatStruct(_, ref field_pats, _) => {
1075 // {f1: p1, ..., fN: pN}
1076 for fp in field_pats.iter() {
1077 let field_ty = if_ok!(self.pat_ty(fp.pat)); // see (*2)
1078 let cmt_field = self.cat_field(pat, cmt, fp.ident, field_ty);
1079 if_ok!(self.cat_pattern(cmt_field, fp.pat, |x,y,z| op(x,y,z)));
1083 ast::PatTup(ref subpats) => {
1085 for (i, &subpat) in subpats.iter().enumerate() {
1086 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1088 self.cat_imm_interior(
1089 pat, cmt, subpat_ty,
1090 InteriorField(PositionalField(i)));
1091 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1095 ast::PatUniq(subpat) | ast::PatRegion(subpat) => {
1097 let subcmt = self.cat_deref(pat, cmt, 0);
1098 if_ok!(self.cat_pattern(subcmt, subpat, op));
1101 ast::PatVec(ref before, slice, ref after) => {
1102 let elt_cmt = self.cat_index(pat, cmt, 0);
1103 for &before_pat in before.iter() {
1104 if_ok!(self.cat_pattern(elt_cmt, before_pat, |x,y,z| op(x,y,z)));
1106 for &slice_pat in slice.iter() {
1107 let slice_ty = if_ok!(self.pat_ty(slice_pat));
1108 let slice_cmt = self.cat_rvalue_node(pat.id(), pat.span(), slice_ty);
1109 if_ok!(self.cat_pattern(slice_cmt, slice_pat, |x,y,z| op(x,y,z)));
1111 for &after_pat in after.iter() {
1112 if_ok!(self.cat_pattern(elt_cmt, after_pat, |x,y,z| op(x,y,z)));
1116 ast::PatLit(_) | ast::PatRange(_, _) => {
1124 pub fn mut_to_str(&mut self, mutbl: ast::Mutability) -> ~str {
1126 MutMutable => ~"mutable",
1127 MutImmutable => ~"immutable"
1131 pub fn cmt_to_str(&self, cmt: cmt) -> ~str {
1133 cat_static_item => {
1136 cat_copied_upvar(_) => {
1137 ~"captured outer variable in a heap closure"
1148 cat_deref(base, _, pk) => {
1151 format!("captured outer variable")
1154 format!("dereference of `{}`-pointer", ptr_sigil(pk))
1158 cat_interior(_, InteriorField(NamedField(_))) => {
1161 cat_interior(_, InteriorField(PositionalField(_))) => {
1164 cat_interior(_, InteriorElement(VecElement)) => {
1167 cat_interior(_, InteriorElement(StrElement)) => {
1170 cat_interior(_, InteriorElement(OtherElement)) => {
1174 ~"captured outer variable"
1176 cat_discr(cmt, _) => {
1177 self.cmt_to_str(cmt)
1179 cat_downcast(cmt) => {
1180 self.cmt_to_str(cmt)
1185 pub fn region_to_str(&self, r: ty::Region) -> ~str {
1186 region_ptr_to_str(self.tcx(), r)
1190 /// The node_id here is the node of the expression that references the field.
1191 /// This function looks it up in the def map in case the type happens to be
1192 /// an enum to determine which variant is in use.
1193 pub fn field_mutbl(tcx: ty::ctxt,
1195 // FIXME #6993: change type to Name
1197 node_id: ast::NodeId)
1198 -> Option<ast::Mutability> {
1199 // Need to refactor so that struct/enum fields can be treated uniformly.
1200 match ty::get(base_ty).sty {
1201 ty::ty_struct(did, _) => {
1202 let r = ty::lookup_struct_fields(tcx, did);
1203 for fld in r.iter() {
1204 if fld.name == f_name.name {
1205 return Some(ast::MutImmutable);
1209 ty::ty_enum(..) => {
1210 let def_map = tcx.def_map.borrow();
1211 match def_map.get().get_copy(&node_id) {
1212 ast::DefVariant(_, variant_id, _) => {
1213 let r = ty::lookup_struct_fields(tcx, variant_id);
1214 for fld in r.iter() {
1215 if fld.name == f_name.name {
1216 return Some(ast::MutImmutable);
1229 pub enum AliasableReason {
1238 pub fn guarantor(self) -> cmt {
1239 //! Returns `self` after stripping away any owned pointer derefs or
1240 //! interior content. The return value is basically the `cmt` which
1241 //! determines how long the value in `self` remains live.
1246 cat_copied_upvar(..) |
1249 cat_deref(_, _, UnsafePtr(..)) |
1250 cat_deref(_, _, GcPtr(..)) |
1251 cat_deref(_, _, BorrowedPtr(..)) |
1257 cat_interior(b, _) |
1258 cat_deref(b, _, OwnedPtr) => {
1264 pub fn freely_aliasable(&self) -> Option<AliasableReason> {
1266 * Returns `Some(_)` if this lvalue represents a freely aliasable
1270 // Maybe non-obvious: copied upvars can only be considered
1271 // non-aliasable in once closures, since any other kind can be
1272 // aliased and eventually recused.
1275 cat_deref(b, _, BorrowedPtr(ty::MutBorrow, _)) |
1276 cat_deref(b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1278 cat_deref(b, _, OwnedPtr) |
1279 cat_interior(b, _) |
1280 cat_discr(b, _) => {
1281 // Aliasability depends on base cmt
1282 b.freely_aliasable()
1285 cat_copied_upvar(CopiedUpvar {onceness: ast::Once, ..}) |
1290 cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
1294 cat_copied_upvar(CopiedUpvar {onceness: ast::Many, ..}) => {
1295 Some(AliasableOther)
1298 cat_static_item(..) => {
1299 if self.mutbl.is_mutable() {
1300 Some(AliasableStaticMut)
1302 Some(AliasableStatic)
1306 cat_deref(_, _, GcPtr) => {
1307 Some(AliasableManaged)
1310 cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) => {
1311 Some(AliasableBorrowed)
1317 impl Repr for cmt_ {
1318 fn repr(&self, tcx: ty::ctxt) -> ~str {
1319 format!("\\{{} id:{} m:{:?} ty:{}\\}",
1327 impl Repr for categorization {
1328 fn repr(&self, tcx: ty::ctxt) -> ~str {
1332 cat_copied_upvar(..) |
1336 format!("{:?}", *self)
1338 cat_deref(cmt, derefs, ptr) => {
1339 format!("{}-{}{}->",
1344 cat_interior(cmt, interior) => {
1349 cat_downcast(cmt) => {
1350 format!("{}->(enum)", cmt.cat.repr(tcx))
1352 cat_discr(cmt, _) => {
1359 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1363 BorrowedPtr(ty::ImmBorrow, _) => "&",
1364 BorrowedPtr(ty::MutBorrow, _) => "&mut",
1365 BorrowedPtr(ty::UniqueImmBorrow, _) => "&unique",
1370 impl Repr for InteriorKind {
1371 fn repr(&self, _tcx: ty::ctxt) -> ~str {
1373 InteriorField(NamedField(fld)) => {
1374 token::get_name(fld).get().to_str()
1376 InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
1377 InteriorElement(_) => ~"[]",
1382 fn element_kind(t: ty::t) -> ElementKind {
1383 match ty::get(t).sty {
1384 ty::ty_vec(..) => VecElement,
1385 ty::ty_str(..) => StrElement,