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};
68 use syntax::ast::{MutImmutable, MutMutable};
70 use syntax::codemap::Span;
71 use syntax::print::pprust;
72 use syntax::parse::token;
75 pub enum categorization {
76 cat_rvalue(ty::Region), // temporary val, argument is its scope
78 cat_copied_upvar(CopiedUpvar), // upvar copied into @fn or ~fn env
79 cat_upvar(ty::UpvarId, ty::UpvarBorrow), // by ref upvar from stack closure
80 cat_local(ast::NodeId), // local variable
81 cat_arg(ast::NodeId), // formal argument
82 cat_deref(cmt, uint, PointerKind), // deref of a ptr
83 cat_interior(cmt, InteriorKind), // something interior: field, tuple, etc
84 cat_downcast(cmt), // selects a particular enum variant (*1)
85 cat_discr(cmt, ast::NodeId), // match discriminant (see preserve())
87 // (*1) downcast is only required if the enum has more than one variant
91 pub struct CopiedUpvar {
92 upvar_id: ast::NodeId,
93 onceness: ast::Onceness,
96 // different kinds of pointers:
98 pub enum PointerKind {
101 BorrowedPtr(ty::BorrowKind, ty::Region),
102 UnsafePtr(ast::Mutability),
105 // We use the term "interior" to mean "something reachable from the
106 // base without a pointer dereference", e.g. a field
107 #[deriving(Eq, Hash)]
108 pub enum InteriorKind {
109 InteriorField(FieldName),
110 InteriorElement(ElementKind),
113 #[deriving(Eq, Hash)]
115 NamedField(ast::Name),
116 PositionalField(uint)
119 #[deriving(Eq, Hash)]
120 pub enum ElementKind {
126 #[deriving(Eq, Hash, Show)]
127 pub enum MutabilityCategory {
128 McImmutable, // Immutable.
129 McDeclared, // Directly declared as mutable.
130 McInherited, // Inherited from the fact that owner is mutable.
133 // `cmt`: "Category, Mutability, and Type".
135 // a complete categorization of a value indicating where it originated
136 // and how it is located, as well as the mutability of the memory in
137 // which the value is stored.
139 // *WARNING* The field `cmt.type` is NOT necessarily the same as the
140 // result of `node_id_to_type(cmt.id)`. This is because the `id` is
141 // always the `id` of the node producing the type; in an expression
142 // like `*x`, the type of this deref node is the deref'd type (`T`),
143 // but in a pattern like `@x`, the `@x` pattern is again a
144 // dereference, but its type is the type *before* the dereference
145 // (`@T`). So use `cmt.type` to find the type of the value in a consistent
146 // fashion. For more details, see the method `cat_pattern`
149 id: ast::NodeId, // id of expr/pat producing this value
150 span: Span, // span of same expr/pat
151 cat: categorization, // categorization of expr
152 mutbl: MutabilityCategory, // mutability of expr as lvalue
153 ty: ty::t // type of the expr (*see WARNING above*)
156 pub type cmt = @cmt_;
158 // We pun on *T to mean both actual deref of a ptr as well
159 // as accessing of components:
160 pub enum deref_kind {
161 deref_ptr(PointerKind),
162 deref_interior(InteriorKind),
165 // Categorizes a derefable type. Note that we include vectors and strings as
166 // derefable (we model an index as the combination of a deref and then a
167 // pointer adjustment).
168 pub fn opt_deref_kind(t: ty::t) -> Option<deref_kind> {
169 match ty::get(t).sty {
171 ty::ty_trait(_, _, ty::UniqTraitStore, _, _) |
172 ty::ty_vec(_, ty::vstore_uniq) |
173 ty::ty_str(ty::vstore_uniq) |
174 ty::ty_closure(ty::ClosureTy {sigil: ast::OwnedSigil, ..}) => {
175 Some(deref_ptr(OwnedPtr))
179 ty::ty_vec(mt, ty::vstore_slice(r)) => {
180 let kind = ty::BorrowKind::from_mutbl(mt.mutbl);
181 Some(deref_ptr(BorrowedPtr(kind, r)))
184 ty::ty_trait(_, _, ty::RegionTraitStore(r), m, _) => {
185 let kind = ty::BorrowKind::from_mutbl(m);
186 Some(deref_ptr(BorrowedPtr(kind, r)))
189 ty::ty_str(ty::vstore_slice(r)) |
190 ty::ty_closure(ty::ClosureTy {sigil: ast::BorrowedSigil,
192 Some(deref_ptr(BorrowedPtr(ty::ImmBorrow, r)))
196 Some(deref_ptr(GcPtr))
199 ty::ty_ptr(ref mt) => {
200 Some(deref_ptr(UnsafePtr(mt.mutbl)))
204 ty::ty_struct(..) => { // newtype
205 Some(deref_interior(InteriorField(PositionalField(0))))
208 ty::ty_vec(_, ty::vstore_fixed(_)) |
209 ty::ty_str(ty::vstore_fixed(_)) => {
210 Some(deref_interior(InteriorElement(element_kind(t))))
217 pub fn deref_kind(tcx: ty::ctxt, t: ty::t) -> deref_kind {
218 match opt_deref_kind(t) {
222 format!("deref_cat() invoked on non-derefable type {}",
229 fn id(&self) -> ast::NodeId;
230 fn span(&self) -> Span;
233 impl ast_node for ast::Expr {
234 fn id(&self) -> ast::NodeId { self.id }
235 fn span(&self) -> Span { self.span }
238 impl ast_node for ast::Pat {
239 fn id(&self) -> ast::NodeId { self.id }
240 fn span(&self) -> Span { self.span }
243 pub struct MemCategorizationContext<TYPER> {
247 pub type McResult<T> = Result<T, ()>;
250 * The `Typer` trait provides the interface for the mem-categorization
251 * module to the results of the type check. It can be used to query
252 * the type assigned to an expression node, to inquire after adjustments,
255 * This interface is needed because mem-categorization is used from
256 * two places: `regionck` and `borrowck`. `regionck` executes before
257 * type inference is complete, and hence derives types and so on from
258 * intermediate tables. This also implies that type errors can occur,
259 * and hence `node_ty()` and friends return a `Result` type -- any
260 * error will propagate back up through the mem-categorization
263 * In the borrow checker, in contrast, type checking is complete and we
264 * know that no errors have occurred, so we simply consult the tcx and we
265 * can be sure that only `Ok` results will occur.
268 fn tcx(&self) -> ty::ctxt;
269 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t>;
270 fn adjustment(&mut self, node_id: ast::NodeId) -> Option<@ty::AutoAdjustment>;
271 fn is_method_call(&mut self, id: ast::NodeId) -> bool;
272 fn temporary_scope(&mut self, rvalue_id: ast::NodeId) -> Option<ast::NodeId>;
273 fn upvar_borrow(&mut self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow;
276 impl MutabilityCategory {
277 pub fn from_mutbl(m: ast::Mutability) -> MutabilityCategory {
279 MutImmutable => McImmutable,
280 MutMutable => McDeclared
284 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
286 ty::ImmBorrow => McImmutable,
287 ty::UniqueImmBorrow => McImmutable,
288 ty::MutBorrow => McDeclared,
292 pub fn from_pointer_kind(base_mutbl: MutabilityCategory,
293 ptr: PointerKind) -> MutabilityCategory {
298 BorrowedPtr(borrow_kind, _) => {
299 MutabilityCategory::from_borrow_kind(borrow_kind)
305 MutabilityCategory::from_mutbl(m)
310 pub fn inherit(&self) -> MutabilityCategory {
312 McImmutable => McImmutable,
313 McDeclared => McInherited,
314 McInherited => McInherited,
318 pub fn is_mutable(&self) -> bool {
320 McImmutable => false,
326 pub fn is_immutable(&self) -> bool {
329 McDeclared | McInherited => false
333 pub fn to_user_str(&self) -> &'static str {
335 McDeclared | McInherited => "mutable",
336 McImmutable => "immutable",
345 Err(e) => { return Err(e); }
350 impl<TYPER:Typer> MemCategorizationContext<TYPER> {
351 fn tcx(&self) -> ty::ctxt {
355 fn adjustment(&mut self, id: ast::NodeId) -> Option<@ty::AutoAdjustment> {
356 self.typer.adjustment(id)
359 fn expr_ty(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
360 self.typer.node_ty(expr.id)
363 fn expr_ty_adjusted(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
364 let unadjusted_ty = if_ok!(self.expr_ty(expr));
365 let adjustment = self.adjustment(expr.id);
366 Ok(ty::adjust_ty(self.tcx(), expr.span, unadjusted_ty, adjustment))
369 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t> {
370 self.typer.node_ty(id)
373 fn pat_ty(&mut self, pat: @ast::Pat) -> McResult<ty::t> {
374 self.typer.node_ty(pat.id)
377 pub fn cat_expr(&mut self, expr: &ast::Expr) -> McResult<cmt> {
378 match self.adjustment(expr.id) {
381 self.cat_expr_unadjusted(expr)
384 Some(adjustment) => {
386 ty::AutoObject(..) => {
387 // Implicity casts a concrete object to trait object
388 // so just patch up the type
389 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
390 let expr_cmt = if_ok!(self.cat_expr_unadjusted(expr));
391 Ok(@cmt_ {ty: expr_ty, ..*expr_cmt})
394 ty::AutoAddEnv(..) => {
395 // Convert a bare fn to a closure by adding NULL env.
396 // Result is an rvalue.
397 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
398 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
403 autoref: Some(_), ..}) => {
404 // Equivalent to &*expr or something similar.
405 // Result is an rvalue.
406 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
407 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
412 autoref: None, autoderefs: autoderefs}) => {
413 // Equivalent to *expr or something similar.
414 self.cat_expr_autoderefd(expr, autoderefs)
421 pub fn cat_expr_autoderefd(&mut self, expr: &ast::Expr, autoderefs: uint)
423 let mut cmt = if_ok!(self.cat_expr_unadjusted(expr));
424 for deref in range(1u, autoderefs + 1) {
425 cmt = self.cat_deref(expr, cmt, deref);
430 pub fn cat_expr_unadjusted(&mut self, expr: &ast::Expr) -> McResult<cmt> {
431 debug!("cat_expr: id={} expr={}", expr.id, expr.repr(self.tcx()));
433 let expr_ty = if_ok!(self.expr_ty(expr));
435 ast::ExprUnary(_, ast::UnDeref, e_base) => {
436 if self.typer.is_method_call(expr.id) {
437 return Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty));
440 let base_cmt = if_ok!(self.cat_expr(e_base));
441 Ok(self.cat_deref(expr, base_cmt, 0))
444 ast::ExprField(base, f_name, _) => {
445 // Method calls are now a special syntactic form,
446 // so `a.b` should always be a field.
447 assert!(!self.typer.is_method_call(expr.id));
449 let base_cmt = if_ok!(self.cat_expr(base));
450 Ok(self.cat_field(expr, base_cmt, f_name, expr_ty))
453 ast::ExprIndex(_, base, _) => {
454 if self.typer.is_method_call(expr.id) {
455 return Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty));
458 let base_cmt = if_ok!(self.cat_expr(base));
459 Ok(self.cat_index(expr, base_cmt, 0))
462 ast::ExprPath(_) => {
463 let def_map = self.tcx().def_map.borrow();
464 let def = def_map.get().get_copy(&expr.id);
465 self.cat_def(expr.id, expr.span, expr_ty, def)
468 ast::ExprParen(e) => self.cat_expr_unadjusted(e),
470 ast::ExprAddrOf(..) | ast::ExprCall(..) |
471 ast::ExprAssign(..) | ast::ExprAssignOp(..) |
472 ast::ExprFnBlock(..) | ast::ExprProc(..) | ast::ExprRet(..) |
474 ast::ExprMethodCall(..) | ast::ExprCast(..) | ast::ExprVstore(..) |
475 ast::ExprVec(..) | ast::ExprTup(..) | ast::ExprIf(..) |
476 ast::ExprLogLevel | ast::ExprBinary(..) | ast::ExprWhile(..) |
477 ast::ExprBlock(..) | ast::ExprLoop(..) | ast::ExprMatch(..) |
478 ast::ExprLit(..) | ast::ExprBreak(..) | ast::ExprMac(..) |
479 ast::ExprAgain(..) | ast::ExprStruct(..) | ast::ExprRepeat(..) |
480 ast::ExprInlineAsm(..) | ast::ExprBox(..) => {
481 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
484 ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop")
488 pub fn cat_def(&mut self,
494 debug!("cat_def: id={} expr={}",
495 id, expr_ty.repr(self.tcx()));
498 ast::DefStruct(..) | ast::DefVariant(..) => {
499 Ok(self.cat_rvalue_node(id, span, expr_ty))
501 ast::DefFn(..) | ast::DefStaticMethod(..) | ast::DefMod(_) |
502 ast::DefForeignMod(_) | ast::DefStatic(_, false) |
503 ast::DefUse(_) | ast::DefTrait(_) | ast::DefTy(_) | ast::DefPrimTy(_) |
504 ast::DefTyParam(..) | ast::DefTyParamBinder(..) | ast::DefRegion(_) |
505 ast::DefLabel(_) | ast::DefSelfTy(..) | ast::DefMethod(..) => {
515 ast::DefStatic(_, true) => {
525 ast::DefArg(vid, binding_mode) => {
526 // Idea: make this could be rewritten to model by-ref
527 // stuff as `&const` and `&mut`?
529 // m: mutability of the argument
530 let m = match binding_mode {
531 ast::BindByValue(ast::MutMutable) => McDeclared,
543 ast::DefUpvar(var_id, _, fn_node_id, _) => {
544 let ty = if_ok!(self.node_ty(fn_node_id));
545 match ty::get(ty).sty {
546 ty::ty_closure(ref closure_ty) => {
547 // Decide whether to use implicit reference or by copy/move
548 // capture for the upvar. This, combined with the onceness,
549 // determines whether the closure can move out of it.
550 let var_is_refd = match (closure_ty.sigil, closure_ty.onceness) {
551 // Many-shot stack closures can never move out.
552 (ast::BorrowedSigil, ast::Many) => true,
553 // 1-shot stack closures can move out.
554 (ast::BorrowedSigil, ast::Once) => false,
555 // Heap closures always capture by copy/move, and can
556 // move out if they are once.
557 (ast::OwnedSigil, _) |
558 (ast::ManagedSigil, _) => false,
562 self.cat_upvar(id, span, var_id, fn_node_id)
564 // FIXME #2152 allow mutation of moved upvars
568 cat:cat_copied_upvar(CopiedUpvar {
570 onceness: closure_ty.onceness}),
577 self.tcx().sess.span_bug(
579 format!("Upvar of non-closure {} - {}",
580 fn_node_id, ty.repr(self.tcx())));
585 ast::DefLocal(vid, binding_mode) |
586 ast::DefBinding(vid, binding_mode) => {
587 // by-value/by-ref bindings are local variables
588 let m = match binding_mode {
589 ast::BindByValue(ast::MutMutable) => McDeclared,
604 fn cat_upvar(&mut self,
608 fn_node_id: ast::NodeId)
611 * Upvars through a closure are in fact indirect
612 * references. That is, when a closure refers to a
613 * variable from a parent stack frame like `x = 10`,
614 * that is equivalent to `*x_ = 10` where `x_` is a
615 * borrowed pointer (`&mut x`) created when the closure
616 * was created and store in the environment. This
617 * equivalence is expose in the mem-categorization.
620 let upvar_id = ty::UpvarId { var_id: var_id,
621 closure_expr_id: fn_node_id };
623 let upvar_borrow = self.typer.upvar_borrow(upvar_id);
625 let var_ty = if_ok!(self.node_ty(var_id));
627 // We can't actually represent the types of all upvars
628 // as user-describable types, since upvars support const
629 // and unique-imm borrows! Therefore, we cheat, and just
630 // give err type. Nobody should be inspecting this type anyhow.
631 let upvar_ty = ty::mk_err();
633 let base_cmt = @cmt_ {
636 cat:cat_upvar(upvar_id, upvar_borrow),
641 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
643 let deref_cmt = @cmt_ {
646 cat:cat_deref(base_cmt, 0, ptr),
647 mutbl:MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
654 pub fn cat_rvalue_node(&mut self,
659 match self.typer.temporary_scope(id) {
661 self.cat_rvalue(id, span, ty::ReScope(scope), expr_ty)
664 self.cat_rvalue(id, span, ty::ReStatic, expr_ty)
669 pub fn cat_rvalue(&mut self,
672 temp_scope: ty::Region,
673 expr_ty: ty::t) -> cmt {
677 cat:cat_rvalue(temp_scope),
683 /// inherited mutability: used in cases where the mutability of a
684 /// component is inherited from the base it is a part of. For
685 /// example, a record field is mutable if it is declared mutable
686 /// or if the container is mutable.
687 pub fn inherited_mutability(&mut self,
688 base_m: MutabilityCategory,
689 interior_m: ast::Mutability)
690 -> MutabilityCategory {
692 MutImmutable => base_m.inherit(),
693 MutMutable => McDeclared
697 pub fn cat_field<N:ast_node>(&mut self,
706 cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
707 mutbl: base_cmt.mutbl.inherit(),
712 pub fn cat_deref_fn_or_obj<N:ast_node>(&mut self,
717 // Bit of a hack: the "dereference" of a function pointer like
718 // `@fn()` is a mere logical concept. We interpret it as
719 // dereferencing the environment pointer; of course, we don't
720 // know what type lies at the other end, so we just call it
721 // `()` (the empty tuple).
723 let opaque_ty = ty::mk_tup(self.tcx(), ~[]);
724 return self.cat_deref_common(node, base_cmt, deref_cnt, opaque_ty);
727 pub fn cat_deref<N:ast_node>(&mut self,
732 let mt = match ty::deref(base_cmt.ty, true) {
735 self.tcx().sess.span_bug(
737 format!("Explicit deref of non-derefable type: {}",
738 base_cmt.ty.repr(self.tcx())));
742 return self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty);
745 pub fn cat_deref_common<N:ast_node>(&mut self,
751 match deref_kind(self.tcx(), base_cmt.ty) {
753 // for unique ptrs, we inherit mutability from the
755 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl,
761 cat:cat_deref(base_cmt, deref_cnt, ptr),
767 deref_interior(interior) => {
768 let m = base_cmt.mutbl.inherit();
772 cat:cat_interior(base_cmt, interior),
780 pub fn cat_index<N:ast_node>(&mut self,
785 //! Creates a cmt for an indexing operation (`[]`); this
786 //! indexing operation may occurs as part of an
787 //! AutoBorrowVec, which when converting a `~[]` to an `&[]`
788 //! effectively takes the address of the 0th element.
790 //! One subtle aspect of indexing that may not be
791 //! immediately obvious: for anything other than a fixed-length
792 //! vector, an operation like `x[y]` actually consists of two
793 //! disjoint (from the point of view of borrowck) operations.
794 //! The first is a deref of `x` to create a pointer `p` that points
795 //! at the first element in the array. The second operation is
796 //! an index which adds `y*sizeof(T)` to `p` to obtain the
797 //! pointer to `x[y]`. `cat_index` will produce a resulting
798 //! cmt containing both this deref and the indexing,
799 //! presuming that `base_cmt` is not of fixed-length type.
801 //! In the event that a deref is needed, the "deref count"
802 //! is taken from the parameter `derefs`. See the comment
803 //! on the def'n of `root_map_key` in borrowck/mod.rs
804 //! for more details about deref counts; the summary is
805 //! that `derefs` should be 0 for an explicit indexing
806 //! operation and N+1 for an indexing that is part of
807 //! an auto-adjustment, where N is the number of autoderefs
808 //! in that adjustment.
811 //! - `elt`: the AST node being indexed
812 //! - `base_cmt`: the cmt of `elt`
813 //! - `derefs`: the deref number to be used for
814 //! the implicit index deref, if any (see above)
816 let element_ty = match ty::index(base_cmt.ty) {
817 Some(ref mt) => mt.ty,
819 self.tcx().sess.span_bug(
821 format!("Explicit index of non-index type `{}`",
822 base_cmt.ty.repr(self.tcx())));
826 return match deref_kind(self.tcx(), base_cmt.ty) {
828 // for unique ptrs, we inherit mutability from the
830 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr);
832 // the deref is explicit in the resulting cmt
833 let deref_cmt = @cmt_ {
836 cat:cat_deref(base_cmt, derefs, ptr),
841 interior(elt, deref_cmt, base_cmt.ty, m.inherit(), element_ty)
844 deref_interior(_) => {
845 // fixed-length vectors have no deref
846 let m = base_cmt.mutbl.inherit();
847 interior(elt, base_cmt, base_cmt.ty, m, element_ty)
851 fn interior<N: ast_node>(elt: &N,
854 mutbl: MutabilityCategory,
855 element_ty: ty::t) -> cmt
860 cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
867 pub fn cat_slice_pattern(&mut self,
869 slice_pat: @ast::Pat)
870 -> McResult<(cmt, ast::Mutability, ty::Region)> {
872 * Given a pattern P like: `[_, ..Q, _]`, where `vec_cmt` is
873 * the cmt for `P`, `slice_pat` is the pattern `Q`, returns:
875 * - the mutability and region of the slice `Q`
877 * These last two bits of info happen to be things that
881 let slice_ty = if_ok!(self.node_ty(slice_pat.id));
882 let (slice_mutbl, slice_r) = vec_slice_info(self.tcx(),
885 let cmt_slice = self.cat_index(slice_pat, vec_cmt, 0);
886 return Ok((cmt_slice, slice_mutbl, slice_r));
888 fn vec_slice_info(tcx: ty::ctxt,
891 -> (ast::Mutability, ty::Region) {
893 * In a pattern like [a, b, ..c], normally `c` has slice type,
894 * but if you have [a, b, ..ref c], then the type of `ref c`
895 * will be `&&[]`, so to extract the slice details we have
896 * to recurse through rptrs.
899 match ty::get(slice_ty).sty {
900 ty::ty_vec(slice_mt, ty::vstore_slice(slice_r)) => {
901 (slice_mt.mutbl, slice_r)
904 ty::ty_rptr(_, ref mt) => {
905 vec_slice_info(tcx, pat, mt.ty)
911 format!("Type of slice pattern is not a slice"));
917 pub fn cat_imm_interior<N:ast_node>(&mut self,
921 interior: InteriorKind)
926 cat: cat_interior(base_cmt, interior),
927 mutbl: base_cmt.mutbl.inherit(),
932 pub fn cat_downcast<N:ast_node>(&mut self,
940 cat: cat_downcast(base_cmt),
941 mutbl: base_cmt.mutbl.inherit(),
946 pub fn cat_pattern(&mut self,
949 op: |&mut MemCategorizationContext<TYPER>,
953 // Here, `cmt` is the categorization for the value being
954 // matched and pat is the pattern it is being matched against.
956 // In general, the way that this works is that we walk down
957 // the pattern, constructing a cmt that represents the path
958 // that will be taken to reach the value being matched.
960 // When we encounter named bindings, we take the cmt that has
961 // been built up and pass it off to guarantee_valid() so that
962 // we can be sure that the binding will remain valid for the
963 // duration of the arm.
965 // (*2) There is subtlety concerning the correspondence between
966 // pattern ids and types as compared to *expression* ids and
967 // types. This is explained briefly. on the definition of the
968 // type `cmt`, so go off and read what it says there, then
969 // come back and I'll dive into a bit more detail here. :) OK,
972 // In general, the id of the cmt should be the node that
973 // "produces" the value---patterns aren't executable code
974 // exactly, but I consider them to "execute" when they match a
975 // value, and I consider them to produce the value that was
976 // matched. So if you have something like:
983 // In this case, the cmt and the relevant ids would be:
985 // CMT Id Type of Id Type of cmt
988 // ^~~~~~~^ `x` from discr @@int @@int
989 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
990 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
992 // You can see that the types of the id and the cmt are in
993 // sync in the first line, because that id is actually the id
994 // of an expression. But once we get to pattern ids, the types
995 // step out of sync again. So you'll see below that we always
996 // get the type of the *subpattern* and use that.
998 let tcx = self.tcx();
999 debug!("cat_pattern: id={} pat={} cmt={}",
1000 pat.id, pprust::pat_to_str(pat),
1006 ast::PatWild | ast::PatWildMulti => {
1010 ast::PatEnum(_, None) => {
1013 ast::PatEnum(_, Some(ref subpats)) => {
1014 let def_map = self.tcx().def_map.borrow();
1015 match def_map.get().find(&pat.id) {
1016 Some(&ast::DefVariant(enum_did, _, _)) => {
1019 let downcast_cmt = {
1020 if ty::enum_is_univariant(self.tcx(), enum_did) {
1021 cmt // univariant, no downcast needed
1023 self.cat_downcast(pat, cmt, cmt.ty)
1027 for (i, &subpat) in subpats.iter().enumerate() {
1028 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1031 self.cat_imm_interior(
1032 pat, downcast_cmt, subpat_ty,
1033 InteriorField(PositionalField(i)));
1035 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1038 Some(&ast::DefFn(..)) |
1039 Some(&ast::DefStruct(..)) => {
1040 for (i, &subpat) in subpats.iter().enumerate() {
1041 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1043 self.cat_imm_interior(
1044 pat, cmt, subpat_ty,
1045 InteriorField(PositionalField(i)));
1046 if_ok!(self.cat_pattern(cmt_field, subpat, |x,y,z| op(x,y,z)));
1049 Some(&ast::DefStatic(..)) => {
1050 for &subpat in subpats.iter() {
1051 if_ok!(self.cat_pattern(cmt, subpat, |x,y,z| op(x,y,z)));
1055 self.tcx().sess.span_bug(
1057 "enum pattern didn't resolve to enum or struct");
1062 ast::PatIdent(_, _, Some(subpat)) => {
1063 if_ok!(self.cat_pattern(cmt, subpat, op));
1066 ast::PatIdent(_, _, None) => {
1067 // nullary variant or identifier: ignore
1070 ast::PatStruct(_, ref field_pats, _) => {
1071 // {f1: p1, ..., fN: pN}
1072 for fp in field_pats.iter() {
1073 let field_ty = if_ok!(self.pat_ty(fp.pat)); // see (*2)
1074 let cmt_field = self.cat_field(pat, cmt, fp.ident, field_ty);
1075 if_ok!(self.cat_pattern(cmt_field, fp.pat, |x,y,z| op(x,y,z)));
1079 ast::PatTup(ref subpats) => {
1081 for (i, &subpat) in subpats.iter().enumerate() {
1082 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1084 self.cat_imm_interior(
1085 pat, cmt, subpat_ty,
1086 InteriorField(PositionalField(i)));
1087 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1091 ast::PatUniq(subpat) | ast::PatRegion(subpat) => {
1093 let subcmt = self.cat_deref(pat, cmt, 0);
1094 if_ok!(self.cat_pattern(subcmt, subpat, op));
1097 ast::PatVec(ref before, slice, ref after) => {
1098 let elt_cmt = self.cat_index(pat, cmt, 0);
1099 for &before_pat in before.iter() {
1100 if_ok!(self.cat_pattern(elt_cmt, before_pat, |x,y,z| op(x,y,z)));
1102 for &slice_pat in slice.iter() {
1103 let slice_ty = if_ok!(self.pat_ty(slice_pat));
1104 let slice_cmt = self.cat_rvalue_node(pat.id(), pat.span(), slice_ty);
1105 if_ok!(self.cat_pattern(slice_cmt, slice_pat, |x,y,z| op(x,y,z)));
1107 for &after_pat in after.iter() {
1108 if_ok!(self.cat_pattern(elt_cmt, after_pat, |x,y,z| op(x,y,z)));
1112 ast::PatLit(_) | ast::PatRange(_, _) => {
1120 pub fn mut_to_str(&mut self, mutbl: ast::Mutability) -> ~str {
1122 MutMutable => ~"mutable",
1123 MutImmutable => ~"immutable"
1127 pub fn cmt_to_str(&self, cmt: cmt) -> ~str {
1129 cat_static_item => {
1132 cat_copied_upvar(_) => {
1133 ~"captured outer variable in a heap closure"
1144 cat_deref(base, _, pk) => {
1147 format!("captured outer variable")
1150 format!("dereference of `{}`-pointer", ptr_sigil(pk))
1154 cat_interior(_, InteriorField(NamedField(_))) => {
1157 cat_interior(_, InteriorField(PositionalField(_))) => {
1160 cat_interior(_, InteriorElement(VecElement)) => {
1163 cat_interior(_, InteriorElement(StrElement)) => {
1166 cat_interior(_, InteriorElement(OtherElement)) => {
1170 ~"captured outer variable"
1172 cat_discr(cmt, _) => {
1173 self.cmt_to_str(cmt)
1175 cat_downcast(cmt) => {
1176 self.cmt_to_str(cmt)
1181 pub fn region_to_str(&self, r: ty::Region) -> ~str {
1182 region_ptr_to_str(self.tcx(), r)
1186 /// The node_id here is the node of the expression that references the field.
1187 /// This function looks it up in the def map in case the type happens to be
1188 /// an enum to determine which variant is in use.
1189 pub fn field_mutbl(tcx: ty::ctxt,
1191 // FIXME #6993: change type to Name
1193 node_id: ast::NodeId)
1194 -> Option<ast::Mutability> {
1195 // Need to refactor so that struct/enum fields can be treated uniformly.
1196 match ty::get(base_ty).sty {
1197 ty::ty_struct(did, _) => {
1198 let r = ty::lookup_struct_fields(tcx, did);
1199 for fld in r.iter() {
1200 if fld.name == f_name.name {
1201 return Some(ast::MutImmutable);
1205 ty::ty_enum(..) => {
1206 let def_map = tcx.def_map.borrow();
1207 match def_map.get().get_copy(&node_id) {
1208 ast::DefVariant(_, variant_id, _) => {
1209 let r = ty::lookup_struct_fields(tcx, variant_id);
1210 for fld in r.iter() {
1211 if fld.name == f_name.name {
1212 return Some(ast::MutImmutable);
1225 pub enum AliasableReason {
1234 pub fn guarantor(self) -> cmt {
1235 //! Returns `self` after stripping away any owned pointer derefs or
1236 //! interior content. The return value is basically the `cmt` which
1237 //! determines how long the value in `self` remains live.
1242 cat_copied_upvar(..) |
1245 cat_deref(_, _, UnsafePtr(..)) |
1246 cat_deref(_, _, GcPtr(..)) |
1247 cat_deref(_, _, BorrowedPtr(..)) |
1253 cat_interior(b, _) |
1254 cat_deref(b, _, OwnedPtr) => {
1260 pub fn freely_aliasable(&self) -> Option<AliasableReason> {
1262 * Returns `Some(_)` if this lvalue represents a freely aliasable
1266 // Maybe non-obvious: copied upvars can only be considered
1267 // non-aliasable in once closures, since any other kind can be
1268 // aliased and eventually recused.
1271 cat_deref(b, _, BorrowedPtr(ty::MutBorrow, _)) |
1272 cat_deref(b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1274 cat_deref(b, _, OwnedPtr) |
1275 cat_interior(b, _) |
1276 cat_discr(b, _) => {
1277 // Aliasability depends on base cmt
1278 b.freely_aliasable()
1281 cat_copied_upvar(CopiedUpvar {onceness: ast::Once, ..}) |
1286 cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
1290 cat_copied_upvar(CopiedUpvar {onceness: ast::Many, ..}) => {
1291 Some(AliasableOther)
1294 cat_static_item(..) => {
1295 if self.mutbl.is_mutable() {
1296 Some(AliasableStaticMut)
1298 Some(AliasableStatic)
1302 cat_deref(_, _, GcPtr) => {
1303 Some(AliasableManaged)
1306 cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) => {
1307 Some(AliasableBorrowed)
1313 impl Repr for cmt_ {
1314 fn repr(&self, tcx: ty::ctxt) -> ~str {
1315 format!("\\{{} id:{} m:{:?} ty:{}\\}",
1323 impl Repr for categorization {
1324 fn repr(&self, tcx: ty::ctxt) -> ~str {
1328 cat_copied_upvar(..) |
1332 format!("{:?}", *self)
1334 cat_deref(cmt, derefs, ptr) => {
1335 format!("{}-{}{}->",
1340 cat_interior(cmt, interior) => {
1345 cat_downcast(cmt) => {
1346 format!("{}->(enum)", cmt.cat.repr(tcx))
1348 cat_discr(cmt, _) => {
1355 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1359 BorrowedPtr(ty::ImmBorrow, _) => "&",
1360 BorrowedPtr(ty::MutBorrow, _) => "&mut",
1361 BorrowedPtr(ty::UniqueImmBorrow, _) => "&unique",
1366 impl Repr for InteriorKind {
1367 fn repr(&self, _tcx: ty::ctxt) -> ~str {
1369 InteriorField(NamedField(fld)) => {
1370 token::get_name(fld).get().to_str()
1372 InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
1373 InteriorElement(_) => ~"[]",
1378 fn element_kind(t: ty::t) -> ElementKind {
1379 match ty::get(t).sty {
1380 ty::ty_vec(..) => VecElement,
1381 ty::ty_str(..) => StrElement,