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 node_method_ty(&mut self, id: ast::NodeId) -> Option<ty::t>;
271 fn adjustment(&mut self, node_id: ast::NodeId) -> Option<@ty::AutoAdjustment>;
272 fn is_method_call(&mut self, id: ast::NodeId) -> bool;
273 fn temporary_scope(&mut self, rvalue_id: ast::NodeId) -> Option<ast::NodeId>;
274 fn upvar_borrow(&mut self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow;
277 impl MutabilityCategory {
278 pub fn from_mutbl(m: ast::Mutability) -> MutabilityCategory {
280 MutImmutable => McImmutable,
281 MutMutable => McDeclared
285 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
287 ty::ImmBorrow => McImmutable,
288 ty::UniqueImmBorrow => McImmutable,
289 ty::MutBorrow => McDeclared,
293 pub fn from_pointer_kind(base_mutbl: MutabilityCategory,
294 ptr: PointerKind) -> MutabilityCategory {
299 BorrowedPtr(borrow_kind, _) => {
300 MutabilityCategory::from_borrow_kind(borrow_kind)
306 MutabilityCategory::from_mutbl(m)
311 pub fn inherit(&self) -> MutabilityCategory {
313 McImmutable => McImmutable,
314 McDeclared => McInherited,
315 McInherited => McInherited,
319 pub fn is_mutable(&self) -> bool {
321 McImmutable => false,
327 pub fn is_immutable(&self) -> bool {
330 McDeclared | McInherited => false
334 pub fn to_user_str(&self) -> &'static str {
336 McDeclared | McInherited => "mutable",
337 McImmutable => "immutable",
346 Err(e) => { return Err(e); }
351 impl<TYPER:Typer> MemCategorizationContext<TYPER> {
352 fn tcx(&self) -> ty::ctxt {
356 fn adjustment(&mut self, id: ast::NodeId) -> Option<@ty::AutoAdjustment> {
357 self.typer.adjustment(id)
360 fn expr_ty(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
361 self.typer.node_ty(expr.id)
364 fn expr_ty_adjusted(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
365 let unadjusted_ty = if_ok!(self.expr_ty(expr));
366 let adjustment = self.adjustment(expr.id);
367 Ok(ty::adjust_ty(self.tcx(), expr.span, unadjusted_ty, adjustment))
370 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t> {
371 self.typer.node_ty(id)
374 fn pat_ty(&mut self, pat: @ast::Pat) -> McResult<ty::t> {
375 self.typer.node_ty(pat.id)
378 pub fn cat_expr(&mut self, expr: &ast::Expr) -> McResult<cmt> {
379 match self.adjustment(expr.id) {
382 self.cat_expr_unadjusted(expr)
385 Some(adjustment) => {
387 ty::AutoObject(..) => {
388 // Implicity casts a concrete object to trait object
389 // so just patch up the type
390 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
391 let expr_cmt = if_ok!(self.cat_expr_unadjusted(expr));
392 Ok(@cmt_ {ty: expr_ty, ..*expr_cmt})
395 ty::AutoAddEnv(..) => {
396 // Convert a bare fn to a closure by adding NULL env.
397 // Result is an rvalue.
398 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
399 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
404 autoref: Some(_), ..}) => {
405 // Equivalent to &*expr or something similar.
406 // Result is an rvalue.
407 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
408 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
413 autoref: None, autoderefs: autoderefs}) => {
414 // Equivalent to *expr or something similar.
415 self.cat_expr_autoderefd(expr, autoderefs)
422 pub fn cat_expr_autoderefd(&mut self, expr: &ast::Expr, autoderefs: uint)
424 let mut cmt = if_ok!(self.cat_expr_unadjusted(expr));
425 for deref in range(1u, autoderefs + 1) {
426 cmt = self.cat_deref(expr, cmt, deref);
431 pub fn cat_expr_unadjusted(&mut self, expr: &ast::Expr) -> McResult<cmt> {
432 debug!("cat_expr: id={} expr={}", expr.id, expr.repr(self.tcx()));
434 let expr_ty = if_ok!(self.expr_ty(expr));
436 ast::ExprUnary(ast::UnDeref, e_base) => {
437 let base_cmt = match self.typer.node_method_ty(expr.id) {
439 let ref_ty = ty::ty_fn_ret(method_ty);
440 self.cat_rvalue_node(expr.id(), expr.span(), ref_ty)
442 None => if_ok!(self.cat_expr(e_base))
444 Ok(self.cat_deref(expr, base_cmt, 0))
447 ast::ExprField(base, f_name, _) => {
448 // Method calls are now a special syntactic form,
449 // so `a.b` should always be a field.
450 assert!(!self.typer.is_method_call(expr.id));
452 let base_cmt = if_ok!(self.cat_expr(base));
453 Ok(self.cat_field(expr, base_cmt, f_name, expr_ty))
456 ast::ExprIndex(base, _) => {
457 if self.typer.is_method_call(expr.id) {
458 return Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty));
461 let base_cmt = if_ok!(self.cat_expr(base));
462 Ok(self.cat_index(expr, base_cmt, 0))
465 ast::ExprPath(_) => {
466 let def_map = self.tcx().def_map.borrow();
467 let def = def_map.get().get_copy(&expr.id);
468 self.cat_def(expr.id, expr.span, expr_ty, def)
471 ast::ExprParen(e) => self.cat_expr_unadjusted(e),
473 ast::ExprAddrOf(..) | ast::ExprCall(..) |
474 ast::ExprAssign(..) | ast::ExprAssignOp(..) |
475 ast::ExprFnBlock(..) | ast::ExprProc(..) | ast::ExprRet(..) |
477 ast::ExprMethodCall(..) | ast::ExprCast(..) | ast::ExprVstore(..) |
478 ast::ExprVec(..) | ast::ExprTup(..) | ast::ExprIf(..) |
479 ast::ExprLogLevel | ast::ExprBinary(..) | ast::ExprWhile(..) |
480 ast::ExprBlock(..) | ast::ExprLoop(..) | ast::ExprMatch(..) |
481 ast::ExprLit(..) | ast::ExprBreak(..) | ast::ExprMac(..) |
482 ast::ExprAgain(..) | ast::ExprStruct(..) | ast::ExprRepeat(..) |
483 ast::ExprInlineAsm(..) | ast::ExprBox(..) => {
484 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
487 ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop")
491 pub fn cat_def(&mut self,
497 debug!("cat_def: id={} expr={}",
498 id, expr_ty.repr(self.tcx()));
501 ast::DefStruct(..) | ast::DefVariant(..) => {
502 Ok(self.cat_rvalue_node(id, span, expr_ty))
504 ast::DefFn(..) | ast::DefStaticMethod(..) | ast::DefMod(_) |
505 ast::DefForeignMod(_) | ast::DefStatic(_, false) |
506 ast::DefUse(_) | ast::DefTrait(_) | ast::DefTy(_) | ast::DefPrimTy(_) |
507 ast::DefTyParam(..) | ast::DefTyParamBinder(..) | ast::DefRegion(_) |
508 ast::DefLabel(_) | ast::DefSelfTy(..) | ast::DefMethod(..) => {
518 ast::DefStatic(_, true) => {
528 ast::DefArg(vid, binding_mode) => {
529 // Idea: make this could be rewritten to model by-ref
530 // stuff as `&const` and `&mut`?
532 // m: mutability of the argument
533 let m = match binding_mode {
534 ast::BindByValue(ast::MutMutable) => McDeclared,
546 ast::DefUpvar(var_id, _, fn_node_id, _) => {
547 let ty = if_ok!(self.node_ty(fn_node_id));
548 match ty::get(ty).sty {
549 ty::ty_closure(ref closure_ty) => {
550 // Decide whether to use implicit reference or by copy/move
551 // capture for the upvar. This, combined with the onceness,
552 // determines whether the closure can move out of it.
553 let var_is_refd = match (closure_ty.sigil, closure_ty.onceness) {
554 // Many-shot stack closures can never move out.
555 (ast::BorrowedSigil, ast::Many) => true,
556 // 1-shot stack closures can move out.
557 (ast::BorrowedSigil, ast::Once) => false,
558 // Heap closures always capture by copy/move, and can
559 // move out if they are once.
560 (ast::OwnedSigil, _) |
561 (ast::ManagedSigil, _) => false,
565 self.cat_upvar(id, span, var_id, fn_node_id)
567 // FIXME #2152 allow mutation of moved upvars
571 cat:cat_copied_upvar(CopiedUpvar {
573 onceness: closure_ty.onceness}),
580 self.tcx().sess.span_bug(
582 format!("Upvar of non-closure {} - {}",
583 fn_node_id, ty.repr(self.tcx())));
588 ast::DefLocal(vid, binding_mode) |
589 ast::DefBinding(vid, binding_mode) => {
590 // by-value/by-ref bindings are local variables
591 let m = match binding_mode {
592 ast::BindByValue(ast::MutMutable) => McDeclared,
607 fn cat_upvar(&mut self,
611 fn_node_id: ast::NodeId)
614 * Upvars through a closure are in fact indirect
615 * references. That is, when a closure refers to a
616 * variable from a parent stack frame like `x = 10`,
617 * that is equivalent to `*x_ = 10` where `x_` is a
618 * borrowed pointer (`&mut x`) created when the closure
619 * was created and store in the environment. This
620 * equivalence is expose in the mem-categorization.
623 let upvar_id = ty::UpvarId { var_id: var_id,
624 closure_expr_id: fn_node_id };
626 let upvar_borrow = self.typer.upvar_borrow(upvar_id);
628 let var_ty = if_ok!(self.node_ty(var_id));
630 // We can't actually represent the types of all upvars
631 // as user-describable types, since upvars support const
632 // and unique-imm borrows! Therefore, we cheat, and just
633 // give err type. Nobody should be inspecting this type anyhow.
634 let upvar_ty = ty::mk_err();
636 let base_cmt = @cmt_ {
639 cat:cat_upvar(upvar_id, upvar_borrow),
644 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
646 let deref_cmt = @cmt_ {
649 cat:cat_deref(base_cmt, 0, ptr),
650 mutbl:MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
657 pub fn cat_rvalue_node(&mut self,
662 match self.typer.temporary_scope(id) {
664 self.cat_rvalue(id, span, ty::ReScope(scope), expr_ty)
667 self.cat_rvalue(id, span, ty::ReStatic, expr_ty)
672 pub fn cat_rvalue(&mut self,
675 temp_scope: ty::Region,
676 expr_ty: ty::t) -> cmt {
680 cat:cat_rvalue(temp_scope),
686 /// inherited mutability: used in cases where the mutability of a
687 /// component is inherited from the base it is a part of. For
688 /// example, a record field is mutable if it is declared mutable
689 /// or if the container is mutable.
690 pub fn inherited_mutability(&mut self,
691 base_m: MutabilityCategory,
692 interior_m: ast::Mutability)
693 -> MutabilityCategory {
695 MutImmutable => base_m.inherit(),
696 MutMutable => McDeclared
700 pub fn cat_field<N:ast_node>(&mut self,
709 cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
710 mutbl: base_cmt.mutbl.inherit(),
715 pub fn cat_deref_fn_or_obj<N:ast_node>(&mut self,
720 // Bit of a hack: the "dereference" of a function pointer like
721 // `@fn()` is a mere logical concept. We interpret it as
722 // dereferencing the environment pointer; of course, we don't
723 // know what type lies at the other end, so we just call it
724 // `()` (the empty tuple).
726 let opaque_ty = ty::mk_tup(self.tcx(), ~[]);
727 return self.cat_deref_common(node, base_cmt, deref_cnt, opaque_ty);
730 pub fn cat_deref<N:ast_node>(&mut self,
735 let mt = match ty::deref(base_cmt.ty, true) {
738 self.tcx().sess.span_bug(
740 format!("Explicit deref of non-derefable type: {}",
741 base_cmt.ty.repr(self.tcx())));
745 return self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty);
748 pub fn cat_deref_common<N:ast_node>(&mut self,
754 match deref_kind(self.tcx(), base_cmt.ty) {
756 // for unique ptrs, we inherit mutability from the
758 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl,
764 cat:cat_deref(base_cmt, deref_cnt, ptr),
770 deref_interior(interior) => {
771 let m = base_cmt.mutbl.inherit();
775 cat:cat_interior(base_cmt, interior),
783 pub fn cat_index<N:ast_node>(&mut self,
788 //! Creates a cmt for an indexing operation (`[]`); this
789 //! indexing operation may occurs as part of an
790 //! AutoBorrowVec, which when converting a `~[]` to an `&[]`
791 //! effectively takes the address of the 0th element.
793 //! One subtle aspect of indexing that may not be
794 //! immediately obvious: for anything other than a fixed-length
795 //! vector, an operation like `x[y]` actually consists of two
796 //! disjoint (from the point of view of borrowck) operations.
797 //! The first is a deref of `x` to create a pointer `p` that points
798 //! at the first element in the array. The second operation is
799 //! an index which adds `y*sizeof(T)` to `p` to obtain the
800 //! pointer to `x[y]`. `cat_index` will produce a resulting
801 //! cmt containing both this deref and the indexing,
802 //! presuming that `base_cmt` is not of fixed-length type.
804 //! In the event that a deref is needed, the "deref count"
805 //! is taken from the parameter `derefs`. See the comment
806 //! on the def'n of `root_map_key` in borrowck/mod.rs
807 //! for more details about deref counts; the summary is
808 //! that `derefs` should be 0 for an explicit indexing
809 //! operation and N+1 for an indexing that is part of
810 //! an auto-adjustment, where N is the number of autoderefs
811 //! in that adjustment.
814 //! - `elt`: the AST node being indexed
815 //! - `base_cmt`: the cmt of `elt`
816 //! - `derefs`: the deref number to be used for
817 //! the implicit index deref, if any (see above)
819 let element_ty = match ty::index(base_cmt.ty) {
820 Some(ref mt) => mt.ty,
822 self.tcx().sess.span_bug(
824 format!("Explicit index of non-index type `{}`",
825 base_cmt.ty.repr(self.tcx())));
829 return match deref_kind(self.tcx(), base_cmt.ty) {
831 // for unique ptrs, we inherit mutability from the
833 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr);
835 // the deref is explicit in the resulting cmt
836 let deref_cmt = @cmt_ {
839 cat:cat_deref(base_cmt, derefs, ptr),
844 interior(elt, deref_cmt, base_cmt.ty, m.inherit(), element_ty)
847 deref_interior(_) => {
848 // fixed-length vectors have no deref
849 let m = base_cmt.mutbl.inherit();
850 interior(elt, base_cmt, base_cmt.ty, m, element_ty)
854 fn interior<N: ast_node>(elt: &N,
857 mutbl: MutabilityCategory,
858 element_ty: ty::t) -> cmt
863 cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
870 pub fn cat_slice_pattern(&mut self,
872 slice_pat: @ast::Pat)
873 -> McResult<(cmt, ast::Mutability, ty::Region)> {
875 * Given a pattern P like: `[_, ..Q, _]`, where `vec_cmt` is
876 * the cmt for `P`, `slice_pat` is the pattern `Q`, returns:
878 * - the mutability and region of the slice `Q`
880 * These last two bits of info happen to be things that
884 let slice_ty = if_ok!(self.node_ty(slice_pat.id));
885 let (slice_mutbl, slice_r) = vec_slice_info(self.tcx(),
888 let cmt_slice = self.cat_index(slice_pat, vec_cmt, 0);
889 return Ok((cmt_slice, slice_mutbl, slice_r));
891 fn vec_slice_info(tcx: ty::ctxt,
894 -> (ast::Mutability, ty::Region) {
896 * In a pattern like [a, b, ..c], normally `c` has slice type,
897 * but if you have [a, b, ..ref c], then the type of `ref c`
898 * will be `&&[]`, so to extract the slice details we have
899 * to recurse through rptrs.
902 match ty::get(slice_ty).sty {
903 ty::ty_vec(slice_mt, ty::vstore_slice(slice_r)) => {
904 (slice_mt.mutbl, slice_r)
907 ty::ty_rptr(_, ref mt) => {
908 vec_slice_info(tcx, pat, mt.ty)
914 format!("Type of slice pattern is not a slice"));
920 pub fn cat_imm_interior<N:ast_node>(&mut self,
924 interior: InteriorKind)
929 cat: cat_interior(base_cmt, interior),
930 mutbl: base_cmt.mutbl.inherit(),
935 pub fn cat_downcast<N:ast_node>(&mut self,
943 cat: cat_downcast(base_cmt),
944 mutbl: base_cmt.mutbl.inherit(),
949 pub fn cat_pattern(&mut self,
952 op: |&mut MemCategorizationContext<TYPER>,
956 // Here, `cmt` is the categorization for the value being
957 // matched and pat is the pattern it is being matched against.
959 // In general, the way that this works is that we walk down
960 // the pattern, constructing a cmt that represents the path
961 // that will be taken to reach the value being matched.
963 // When we encounter named bindings, we take the cmt that has
964 // been built up and pass it off to guarantee_valid() so that
965 // we can be sure that the binding will remain valid for the
966 // duration of the arm.
968 // (*2) There is subtlety concerning the correspondence between
969 // pattern ids and types as compared to *expression* ids and
970 // types. This is explained briefly. on the definition of the
971 // type `cmt`, so go off and read what it says there, then
972 // come back and I'll dive into a bit more detail here. :) OK,
975 // In general, the id of the cmt should be the node that
976 // "produces" the value---patterns aren't executable code
977 // exactly, but I consider them to "execute" when they match a
978 // value, and I consider them to produce the value that was
979 // matched. So if you have something like:
986 // In this case, the cmt and the relevant ids would be:
988 // CMT Id Type of Id Type of cmt
991 // ^~~~~~~^ `x` from discr @@int @@int
992 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
993 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
995 // You can see that the types of the id and the cmt are in
996 // sync in the first line, because that id is actually the id
997 // of an expression. But once we get to pattern ids, the types
998 // step out of sync again. So you'll see below that we always
999 // get the type of the *subpattern* and use that.
1001 let tcx = self.tcx();
1002 debug!("cat_pattern: id={} pat={} cmt={}",
1003 pat.id, pprust::pat_to_str(pat),
1009 ast::PatWild | ast::PatWildMulti => {
1013 ast::PatEnum(_, None) => {
1016 ast::PatEnum(_, Some(ref subpats)) => {
1017 let def_map = self.tcx().def_map.borrow();
1018 match def_map.get().find(&pat.id) {
1019 Some(&ast::DefVariant(enum_did, _, _)) => {
1022 let downcast_cmt = {
1023 if ty::enum_is_univariant(self.tcx(), enum_did) {
1024 cmt // univariant, no downcast needed
1026 self.cat_downcast(pat, cmt, cmt.ty)
1030 for (i, &subpat) in subpats.iter().enumerate() {
1031 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1034 self.cat_imm_interior(
1035 pat, downcast_cmt, subpat_ty,
1036 InteriorField(PositionalField(i)));
1038 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1041 Some(&ast::DefFn(..)) |
1042 Some(&ast::DefStruct(..)) => {
1043 for (i, &subpat) in subpats.iter().enumerate() {
1044 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1046 self.cat_imm_interior(
1047 pat, cmt, subpat_ty,
1048 InteriorField(PositionalField(i)));
1049 if_ok!(self.cat_pattern(cmt_field, subpat, |x,y,z| op(x,y,z)));
1052 Some(&ast::DefStatic(..)) => {
1053 for &subpat in subpats.iter() {
1054 if_ok!(self.cat_pattern(cmt, subpat, |x,y,z| op(x,y,z)));
1058 self.tcx().sess.span_bug(
1060 "enum pattern didn't resolve to enum or struct");
1065 ast::PatIdent(_, _, Some(subpat)) => {
1066 if_ok!(self.cat_pattern(cmt, subpat, op));
1069 ast::PatIdent(_, _, None) => {
1070 // nullary variant or identifier: ignore
1073 ast::PatStruct(_, ref field_pats, _) => {
1074 // {f1: p1, ..., fN: pN}
1075 for fp in field_pats.iter() {
1076 let field_ty = if_ok!(self.pat_ty(fp.pat)); // see (*2)
1077 let cmt_field = self.cat_field(pat, cmt, fp.ident, field_ty);
1078 if_ok!(self.cat_pattern(cmt_field, fp.pat, |x,y,z| op(x,y,z)));
1082 ast::PatTup(ref subpats) => {
1084 for (i, &subpat) in subpats.iter().enumerate() {
1085 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1087 self.cat_imm_interior(
1088 pat, cmt, subpat_ty,
1089 InteriorField(PositionalField(i)));
1090 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1094 ast::PatUniq(subpat) | ast::PatRegion(subpat) => {
1096 let subcmt = self.cat_deref(pat, cmt, 0);
1097 if_ok!(self.cat_pattern(subcmt, subpat, op));
1100 ast::PatVec(ref before, slice, ref after) => {
1101 let elt_cmt = self.cat_index(pat, cmt, 0);
1102 for &before_pat in before.iter() {
1103 if_ok!(self.cat_pattern(elt_cmt, before_pat, |x,y,z| op(x,y,z)));
1105 for &slice_pat in slice.iter() {
1106 let slice_ty = if_ok!(self.pat_ty(slice_pat));
1107 let slice_cmt = self.cat_rvalue_node(pat.id(), pat.span(), slice_ty);
1108 if_ok!(self.cat_pattern(slice_cmt, slice_pat, |x,y,z| op(x,y,z)));
1110 for &after_pat in after.iter() {
1111 if_ok!(self.cat_pattern(elt_cmt, after_pat, |x,y,z| op(x,y,z)));
1115 ast::PatLit(_) | ast::PatRange(_, _) => {
1123 pub fn mut_to_str(&mut self, mutbl: ast::Mutability) -> ~str {
1125 MutMutable => ~"mutable",
1126 MutImmutable => ~"immutable"
1130 pub fn cmt_to_str(&self, cmt: cmt) -> ~str {
1132 cat_static_item => {
1135 cat_copied_upvar(_) => {
1136 ~"captured outer variable in a heap closure"
1147 cat_deref(base, _, pk) => {
1150 format!("captured outer variable")
1153 format!("dereference of `{}`-pointer", ptr_sigil(pk))
1157 cat_interior(_, InteriorField(NamedField(_))) => {
1160 cat_interior(_, InteriorField(PositionalField(_))) => {
1163 cat_interior(_, InteriorElement(VecElement)) => {
1166 cat_interior(_, InteriorElement(StrElement)) => {
1169 cat_interior(_, InteriorElement(OtherElement)) => {
1173 ~"captured outer variable"
1175 cat_discr(cmt, _) => {
1176 self.cmt_to_str(cmt)
1178 cat_downcast(cmt) => {
1179 self.cmt_to_str(cmt)
1184 pub fn region_to_str(&self, r: ty::Region) -> ~str {
1185 region_ptr_to_str(self.tcx(), r)
1189 /// The node_id here is the node of the expression that references the field.
1190 /// This function looks it up in the def map in case the type happens to be
1191 /// an enum to determine which variant is in use.
1192 pub fn field_mutbl(tcx: ty::ctxt,
1194 // FIXME #6993: change type to Name
1196 node_id: ast::NodeId)
1197 -> Option<ast::Mutability> {
1198 // Need to refactor so that struct/enum fields can be treated uniformly.
1199 match ty::get(base_ty).sty {
1200 ty::ty_struct(did, _) => {
1201 let r = ty::lookup_struct_fields(tcx, did);
1202 for fld in r.iter() {
1203 if fld.name == f_name.name {
1204 return Some(ast::MutImmutable);
1208 ty::ty_enum(..) => {
1209 let def_map = tcx.def_map.borrow();
1210 match def_map.get().get_copy(&node_id) {
1211 ast::DefVariant(_, variant_id, _) => {
1212 let r = ty::lookup_struct_fields(tcx, variant_id);
1213 for fld in r.iter() {
1214 if fld.name == f_name.name {
1215 return Some(ast::MutImmutable);
1228 pub enum AliasableReason {
1237 pub fn guarantor(self) -> cmt {
1238 //! Returns `self` after stripping away any owned pointer derefs or
1239 //! interior content. The return value is basically the `cmt` which
1240 //! determines how long the value in `self` remains live.
1245 cat_copied_upvar(..) |
1248 cat_deref(_, _, UnsafePtr(..)) |
1249 cat_deref(_, _, GcPtr(..)) |
1250 cat_deref(_, _, BorrowedPtr(..)) |
1256 cat_interior(b, _) |
1257 cat_deref(b, _, OwnedPtr) => {
1263 pub fn freely_aliasable(&self) -> Option<AliasableReason> {
1265 * Returns `Some(_)` if this lvalue represents a freely aliasable
1269 // Maybe non-obvious: copied upvars can only be considered
1270 // non-aliasable in once closures, since any other kind can be
1271 // aliased and eventually recused.
1274 cat_deref(b, _, BorrowedPtr(ty::MutBorrow, _)) |
1275 cat_deref(b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1277 cat_deref(b, _, OwnedPtr) |
1278 cat_interior(b, _) |
1279 cat_discr(b, _) => {
1280 // Aliasability depends on base cmt
1281 b.freely_aliasable()
1284 cat_copied_upvar(CopiedUpvar {onceness: ast::Once, ..}) |
1289 cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
1293 cat_copied_upvar(CopiedUpvar {onceness: ast::Many, ..}) => {
1294 Some(AliasableOther)
1297 cat_static_item(..) => {
1298 if self.mutbl.is_mutable() {
1299 Some(AliasableStaticMut)
1301 Some(AliasableStatic)
1305 cat_deref(_, _, GcPtr) => {
1306 Some(AliasableManaged)
1309 cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) => {
1310 Some(AliasableBorrowed)
1316 impl Repr for cmt_ {
1317 fn repr(&self, tcx: ty::ctxt) -> ~str {
1318 format!("\\{{} id:{} m:{:?} ty:{}\\}",
1326 impl Repr for categorization {
1327 fn repr(&self, tcx: ty::ctxt) -> ~str {
1331 cat_copied_upvar(..) |
1335 format!("{:?}", *self)
1337 cat_deref(cmt, derefs, ptr) => {
1338 format!("{}-{}{}->",
1343 cat_interior(cmt, interior) => {
1348 cat_downcast(cmt) => {
1349 format!("{}->(enum)", cmt.cat.repr(tcx))
1351 cat_discr(cmt, _) => {
1358 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1362 BorrowedPtr(ty::ImmBorrow, _) => "&",
1363 BorrowedPtr(ty::MutBorrow, _) => "&mut",
1364 BorrowedPtr(ty::UniqueImmBorrow, _) => "&unique",
1369 impl Repr for InteriorKind {
1370 fn repr(&self, _tcx: ty::ctxt) -> ~str {
1372 InteriorField(NamedField(fld)) => {
1373 token::get_name(fld).get().to_str()
1375 InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
1376 InteriorElement(_) => ~"[]",
1381 fn element_kind(t: ty::t) -> ElementKind {
1382 match ty::get(t).sty {
1383 ty::ty_vec(..) => VecElement,
1384 ty::ty_str(..) => StrElement,