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:
97 #[deriving(Eq, IterBytes)]
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, IterBytes)]
108 pub enum InteriorKind {
109 InteriorField(FieldName),
110 InteriorElement(ElementKind),
113 #[deriving(Eq, IterBytes)]
115 NamedField(ast::Name),
116 PositionalField(uint)
119 #[deriving(Eq, IterBytes)]
120 pub enum ElementKind {
126 #[deriving(Eq, IterBytes)]
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 ToStr for MutabilityCategory {
277 fn to_str(&self) -> ~str {
278 format!("{:?}", *self)
282 impl MutabilityCategory {
283 pub fn from_mutbl(m: ast::Mutability) -> MutabilityCategory {
285 MutImmutable => McImmutable,
286 MutMutable => McDeclared
290 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
292 ty::ImmBorrow => McImmutable,
293 ty::UniqueImmBorrow => McImmutable,
294 ty::MutBorrow => McDeclared,
298 pub fn from_pointer_kind(base_mutbl: MutabilityCategory,
299 ptr: PointerKind) -> MutabilityCategory {
304 BorrowedPtr(borrow_kind, _) => {
305 MutabilityCategory::from_borrow_kind(borrow_kind)
311 MutabilityCategory::from_mutbl(m)
316 pub fn inherit(&self) -> MutabilityCategory {
318 McImmutable => McImmutable,
319 McDeclared => McInherited,
320 McInherited => McInherited,
324 pub fn is_mutable(&self) -> bool {
326 McImmutable => false,
332 pub fn is_immutable(&self) -> bool {
335 McDeclared | McInherited => false
339 pub fn to_user_str(&self) -> &'static str {
341 McDeclared | McInherited => "mutable",
342 McImmutable => "immutable",
351 Err(e) => { return Err(e); }
356 impl<TYPER:Typer> MemCategorizationContext<TYPER> {
357 fn tcx(&self) -> ty::ctxt {
361 fn adjustment(&mut self, id: ast::NodeId) -> Option<@ty::AutoAdjustment> {
362 self.typer.adjustment(id)
365 fn expr_ty(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
366 self.typer.node_ty(expr.id)
369 fn expr_ty_adjusted(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
370 let unadjusted_ty = if_ok!(self.expr_ty(expr));
371 let adjustment = self.adjustment(expr.id);
372 Ok(ty::adjust_ty(self.tcx(), expr.span, unadjusted_ty, adjustment))
375 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t> {
376 self.typer.node_ty(id)
379 fn pat_ty(&mut self, pat: @ast::Pat) -> McResult<ty::t> {
380 self.typer.node_ty(pat.id)
383 pub fn cat_expr(&mut self, expr: &ast::Expr) -> McResult<cmt> {
384 match self.adjustment(expr.id) {
387 self.cat_expr_unadjusted(expr)
390 Some(adjustment) => {
392 ty::AutoObject(..) => {
393 // Implicity casts a concrete object to trait object
394 // so just patch up the type
395 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
396 let expr_cmt = if_ok!(self.cat_expr_unadjusted(expr));
397 Ok(@cmt_ {ty: expr_ty, ..*expr_cmt})
400 ty::AutoAddEnv(..) => {
401 // Convert a bare fn to a closure by adding NULL env.
402 // Result is an rvalue.
403 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
404 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
409 autoref: Some(_), ..}) => {
410 // Equivalent to &*expr or something similar.
411 // Result is an rvalue.
412 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
413 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
418 autoref: None, autoderefs: autoderefs}) => {
419 // Equivalent to *expr or something similar.
420 self.cat_expr_autoderefd(expr, autoderefs)
427 pub fn cat_expr_autoderefd(&mut self, expr: &ast::Expr, autoderefs: uint)
429 let mut cmt = if_ok!(self.cat_expr_unadjusted(expr));
430 for deref in range(1u, autoderefs + 1) {
431 cmt = self.cat_deref(expr, cmt, deref);
436 pub fn cat_expr_unadjusted(&mut self, expr: &ast::Expr) -> McResult<cmt> {
437 debug!("cat_expr: id={} expr={}", expr.id, expr.repr(self.tcx()));
439 let expr_ty = if_ok!(self.expr_ty(expr));
441 ast::ExprUnary(_, ast::UnDeref, e_base) => {
442 if self.typer.is_method_call(expr.id) {
443 return Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty));
446 let base_cmt = if_ok!(self.cat_expr(e_base));
447 Ok(self.cat_deref(expr, base_cmt, 0))
450 ast::ExprField(base, f_name, _) => {
451 // Method calls are now a special syntactic form,
452 // so `a.b` should always be a field.
453 assert!(!self.typer.is_method_call(expr.id));
455 let base_cmt = if_ok!(self.cat_expr(base));
456 Ok(self.cat_field(expr, base_cmt, f_name, expr_ty))
459 ast::ExprIndex(_, base, _) => {
460 if self.typer.is_method_call(expr.id) {
461 return Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty));
464 let base_cmt = if_ok!(self.cat_expr(base));
465 Ok(self.cat_index(expr, base_cmt, 0))
468 ast::ExprPath(_) => {
469 let def_map = self.tcx().def_map.borrow();
470 let def = def_map.get().get_copy(&expr.id);
471 self.cat_def(expr.id, expr.span, expr_ty, def)
474 ast::ExprParen(e) => self.cat_expr_unadjusted(e),
476 ast::ExprAddrOf(..) | ast::ExprCall(..) |
477 ast::ExprAssign(..) | ast::ExprAssignOp(..) |
478 ast::ExprFnBlock(..) | ast::ExprProc(..) | ast::ExprRet(..) |
480 ast::ExprMethodCall(..) | ast::ExprCast(..) | ast::ExprVstore(..) |
481 ast::ExprVec(..) | ast::ExprTup(..) | ast::ExprIf(..) |
482 ast::ExprLogLevel | ast::ExprBinary(..) | ast::ExprWhile(..) |
483 ast::ExprBlock(..) | ast::ExprLoop(..) | ast::ExprMatch(..) |
484 ast::ExprLit(..) | ast::ExprBreak(..) | ast::ExprMac(..) |
485 ast::ExprAgain(..) | ast::ExprStruct(..) | ast::ExprRepeat(..) |
486 ast::ExprInlineAsm(..) | ast::ExprBox(..) => {
487 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
490 ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop")
494 pub fn cat_def(&mut self,
500 debug!("cat_def: id={} expr={}",
501 id, expr_ty.repr(self.tcx()));
504 ast::DefStruct(..) | ast::DefVariant(..) => {
505 Ok(self.cat_rvalue_node(id, span, expr_ty))
507 ast::DefFn(..) | ast::DefStaticMethod(..) | ast::DefMod(_) |
508 ast::DefForeignMod(_) | ast::DefStatic(_, false) |
509 ast::DefUse(_) | ast::DefTrait(_) | ast::DefTy(_) | ast::DefPrimTy(_) |
510 ast::DefTyParam(..) | ast::DefTyParamBinder(..) | ast::DefRegion(_) |
511 ast::DefLabel(_) | ast::DefSelfTy(..) | ast::DefMethod(..) => {
521 ast::DefStatic(_, true) => {
531 ast::DefArg(vid, binding_mode) => {
532 // Idea: make this could be rewritten to model by-ref
533 // stuff as `&const` and `&mut`?
535 // m: mutability of the argument
536 let m = match binding_mode {
537 ast::BindByValue(ast::MutMutable) => McDeclared,
549 ast::DefUpvar(var_id, _, fn_node_id, _) => {
550 let ty = if_ok!(self.node_ty(fn_node_id));
551 match ty::get(ty).sty {
552 ty::ty_closure(ref closure_ty) => {
553 // Decide whether to use implicit reference or by copy/move
554 // capture for the upvar. This, combined with the onceness,
555 // determines whether the closure can move out of it.
556 let var_is_refd = match (closure_ty.sigil, closure_ty.onceness) {
557 // Many-shot stack closures can never move out.
558 (ast::BorrowedSigil, ast::Many) => true,
559 // 1-shot stack closures can move out.
560 (ast::BorrowedSigil, ast::Once) => false,
561 // Heap closures always capture by copy/move, and can
562 // move out if they are once.
563 (ast::OwnedSigil, _) |
564 (ast::ManagedSigil, _) => false,
568 self.cat_upvar(id, span, var_id, fn_node_id)
570 // FIXME #2152 allow mutation of moved upvars
574 cat:cat_copied_upvar(CopiedUpvar {
576 onceness: closure_ty.onceness}),
583 self.tcx().sess.span_bug(
585 format!("Upvar of non-closure {} - {}",
586 fn_node_id, ty.repr(self.tcx())));
591 ast::DefLocal(vid, binding_mode) |
592 ast::DefBinding(vid, binding_mode) => {
593 // by-value/by-ref bindings are local variables
594 let m = match binding_mode {
595 ast::BindByValue(ast::MutMutable) => McDeclared,
610 fn cat_upvar(&mut self,
614 fn_node_id: ast::NodeId)
617 * Upvars through a closure are in fact indirect
618 * references. That is, when a closure refers to a
619 * variable from a parent stack frame like `x = 10`,
620 * that is equivalent to `*x_ = 10` where `x_` is a
621 * borrowed pointer (`&mut x`) created when the closure
622 * was created and store in the environment. This
623 * equivalence is expose in the mem-categorization.
626 let upvar_id = ty::UpvarId { var_id: var_id,
627 closure_expr_id: fn_node_id };
629 let upvar_borrow = self.typer.upvar_borrow(upvar_id);
631 let var_ty = if_ok!(self.node_ty(var_id));
633 // We can't actually represent the types of all upvars
634 // as user-describable types, since upvars support const
635 // and unique-imm borrows! Therefore, we cheat, and just
636 // give err type. Nobody should be inspecting this type anyhow.
637 let upvar_ty = ty::mk_err();
639 let base_cmt = @cmt_ {
642 cat:cat_upvar(upvar_id, upvar_borrow),
647 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
649 let deref_cmt = @cmt_ {
652 cat:cat_deref(base_cmt, 0, ptr),
653 mutbl:MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
660 pub fn cat_rvalue_node(&mut self,
665 match self.typer.temporary_scope(id) {
667 self.cat_rvalue(id, span, ty::ReScope(scope), expr_ty)
670 self.cat_rvalue(id, span, ty::ReStatic, expr_ty)
675 pub fn cat_rvalue(&mut self,
678 temp_scope: ty::Region,
679 expr_ty: ty::t) -> cmt {
683 cat:cat_rvalue(temp_scope),
689 /// inherited mutability: used in cases where the mutability of a
690 /// component is inherited from the base it is a part of. For
691 /// example, a record field is mutable if it is declared mutable
692 /// or if the container is mutable.
693 pub fn inherited_mutability(&mut self,
694 base_m: MutabilityCategory,
695 interior_m: ast::Mutability)
696 -> MutabilityCategory {
698 MutImmutable => base_m.inherit(),
699 MutMutable => McDeclared
703 pub fn cat_field<N:ast_node>(&mut self,
712 cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
713 mutbl: base_cmt.mutbl.inherit(),
718 pub fn cat_deref_fn_or_obj<N:ast_node>(&mut self,
723 // Bit of a hack: the "dereference" of a function pointer like
724 // `@fn()` is a mere logical concept. We interpret it as
725 // dereferencing the environment pointer; of course, we don't
726 // know what type lies at the other end, so we just call it
727 // `()` (the empty tuple).
729 let opaque_ty = ty::mk_tup(self.tcx(), ~[]);
730 return self.cat_deref_common(node, base_cmt, deref_cnt, opaque_ty);
733 pub fn cat_deref<N:ast_node>(&mut self,
738 let mt = match ty::deref(base_cmt.ty, true) {
741 self.tcx().sess.span_bug(
743 format!("Explicit deref of non-derefable type: {}",
744 base_cmt.ty.repr(self.tcx())));
748 return self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty);
751 pub fn cat_deref_common<N:ast_node>(&mut self,
757 match deref_kind(self.tcx(), base_cmt.ty) {
759 // for unique ptrs, we inherit mutability from the
761 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl,
767 cat:cat_deref(base_cmt, deref_cnt, ptr),
773 deref_interior(interior) => {
774 let m = base_cmt.mutbl.inherit();
778 cat:cat_interior(base_cmt, interior),
786 pub fn cat_index<N:ast_node>(&mut self,
791 //! Creates a cmt for an indexing operation (`[]`); this
792 //! indexing operation may occurs as part of an
793 //! AutoBorrowVec, which when converting a `~[]` to an `&[]`
794 //! effectively takes the address of the 0th element.
796 //! One subtle aspect of indexing that may not be
797 //! immediately obvious: for anything other than a fixed-length
798 //! vector, an operation like `x[y]` actually consists of two
799 //! disjoint (from the point of view of borrowck) operations.
800 //! The first is a deref of `x` to create a pointer `p` that points
801 //! at the first element in the array. The second operation is
802 //! an index which adds `y*sizeof(T)` to `p` to obtain the
803 //! pointer to `x[y]`. `cat_index` will produce a resulting
804 //! cmt containing both this deref and the indexing,
805 //! presuming that `base_cmt` is not of fixed-length type.
807 //! In the event that a deref is needed, the "deref count"
808 //! is taken from the parameter `derefs`. See the comment
809 //! on the def'n of `root_map_key` in borrowck/mod.rs
810 //! for more details about deref counts; the summary is
811 //! that `derefs` should be 0 for an explicit indexing
812 //! operation and N+1 for an indexing that is part of
813 //! an auto-adjustment, where N is the number of autoderefs
814 //! in that adjustment.
817 //! - `elt`: the AST node being indexed
818 //! - `base_cmt`: the cmt of `elt`
819 //! - `derefs`: the deref number to be used for
820 //! the implicit index deref, if any (see above)
822 let element_ty = match ty::index(base_cmt.ty) {
823 Some(ref mt) => mt.ty,
825 self.tcx().sess.span_bug(
827 format!("Explicit index of non-index type `{}`",
828 base_cmt.ty.repr(self.tcx())));
832 return match deref_kind(self.tcx(), base_cmt.ty) {
834 // for unique ptrs, we inherit mutability from the
836 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr);
838 // the deref is explicit in the resulting cmt
839 let deref_cmt = @cmt_ {
842 cat:cat_deref(base_cmt, derefs, ptr),
847 interior(elt, deref_cmt, base_cmt.ty, m.inherit(), element_ty)
850 deref_interior(_) => {
851 // fixed-length vectors have no deref
852 let m = base_cmt.mutbl.inherit();
853 interior(elt, base_cmt, base_cmt.ty, m, element_ty)
857 fn interior<N: ast_node>(elt: &N,
860 mutbl: MutabilityCategory,
861 element_ty: ty::t) -> cmt
866 cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
873 pub fn cat_slice_pattern(&mut self,
875 slice_pat: @ast::Pat)
876 -> McResult<(cmt, ast::Mutability, ty::Region)> {
878 * Given a pattern P like: `[_, ..Q, _]`, where `vec_cmt` is
879 * the cmt for `P`, `slice_pat` is the pattern `Q`, returns:
881 * - the mutability and region of the slice `Q`
883 * These last two bits of info happen to be things that
887 let slice_ty = if_ok!(self.node_ty(slice_pat.id));
888 let (slice_mutbl, slice_r) = vec_slice_info(self.tcx(),
891 let cmt_slice = self.cat_index(slice_pat, vec_cmt, 0);
892 return Ok((cmt_slice, slice_mutbl, slice_r));
894 fn vec_slice_info(tcx: ty::ctxt,
897 -> (ast::Mutability, ty::Region) {
899 * In a pattern like [a, b, ..c], normally `c` has slice type,
900 * but if you have [a, b, ..ref c], then the type of `ref c`
901 * will be `&&[]`, so to extract the slice details we have
902 * to recurse through rptrs.
905 match ty::get(slice_ty).sty {
906 ty::ty_vec(slice_mt, ty::vstore_slice(slice_r)) => {
907 (slice_mt.mutbl, slice_r)
910 ty::ty_rptr(_, ref mt) => {
911 vec_slice_info(tcx, pat, mt.ty)
917 format!("Type of slice pattern is not a slice"));
923 pub fn cat_imm_interior<N:ast_node>(&mut self,
927 interior: InteriorKind)
932 cat: cat_interior(base_cmt, interior),
933 mutbl: base_cmt.mutbl.inherit(),
938 pub fn cat_downcast<N:ast_node>(&mut self,
946 cat: cat_downcast(base_cmt),
947 mutbl: base_cmt.mutbl.inherit(),
952 pub fn cat_pattern(&mut self,
955 op: |&mut MemCategorizationContext<TYPER>,
959 // Here, `cmt` is the categorization for the value being
960 // matched and pat is the pattern it is being matched against.
962 // In general, the way that this works is that we walk down
963 // the pattern, constructing a cmt that represents the path
964 // that will be taken to reach the value being matched.
966 // When we encounter named bindings, we take the cmt that has
967 // been built up and pass it off to guarantee_valid() so that
968 // we can be sure that the binding will remain valid for the
969 // duration of the arm.
971 // (*2) There is subtlety concerning the correspondence between
972 // pattern ids and types as compared to *expression* ids and
973 // types. This is explained briefly. on the definition of the
974 // type `cmt`, so go off and read what it says there, then
975 // come back and I'll dive into a bit more detail here. :) OK,
978 // In general, the id of the cmt should be the node that
979 // "produces" the value---patterns aren't executable code
980 // exactly, but I consider them to "execute" when they match a
981 // value, and I consider them to produce the value that was
982 // matched. So if you have something like:
989 // In this case, the cmt and the relevant ids would be:
991 // CMT Id Type of Id Type of cmt
994 // ^~~~~~~^ `x` from discr @@int @@int
995 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
996 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
998 // You can see that the types of the id and the cmt are in
999 // sync in the first line, because that id is actually the id
1000 // of an expression. But once we get to pattern ids, the types
1001 // step out of sync again. So you'll see below that we always
1002 // get the type of the *subpattern* and use that.
1004 let tcx = self.tcx();
1005 debug!("cat_pattern: id={} pat={} cmt={}",
1006 pat.id, pprust::pat_to_str(pat),
1012 ast::PatWild | ast::PatWildMulti => {
1016 ast::PatEnum(_, None) => {
1019 ast::PatEnum(_, Some(ref subpats)) => {
1020 let def_map = self.tcx().def_map.borrow();
1021 match def_map.get().find(&pat.id) {
1022 Some(&ast::DefVariant(enum_did, _, _)) => {
1025 let downcast_cmt = {
1026 if ty::enum_is_univariant(self.tcx(), enum_did) {
1027 cmt // univariant, no downcast needed
1029 self.cat_downcast(pat, cmt, cmt.ty)
1033 for (i, &subpat) in subpats.iter().enumerate() {
1034 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1037 self.cat_imm_interior(
1038 pat, downcast_cmt, subpat_ty,
1039 InteriorField(PositionalField(i)));
1041 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1044 Some(&ast::DefFn(..)) |
1045 Some(&ast::DefStruct(..)) => {
1046 for (i, &subpat) in subpats.iter().enumerate() {
1047 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1049 self.cat_imm_interior(
1050 pat, cmt, subpat_ty,
1051 InteriorField(PositionalField(i)));
1052 if_ok!(self.cat_pattern(cmt_field, subpat, |x,y,z| op(x,y,z)));
1055 Some(&ast::DefStatic(..)) => {
1056 for &subpat in subpats.iter() {
1057 if_ok!(self.cat_pattern(cmt, subpat, |x,y,z| op(x,y,z)));
1061 self.tcx().sess.span_bug(
1063 "enum pattern didn't resolve to enum or struct");
1068 ast::PatIdent(_, _, Some(subpat)) => {
1069 if_ok!(self.cat_pattern(cmt, subpat, op));
1072 ast::PatIdent(_, _, None) => {
1073 // nullary variant or identifier: ignore
1076 ast::PatStruct(_, ref field_pats, _) => {
1077 // {f1: p1, ..., fN: pN}
1078 for fp in field_pats.iter() {
1079 let field_ty = if_ok!(self.pat_ty(fp.pat)); // see (*2)
1080 let cmt_field = self.cat_field(pat, cmt, fp.ident, field_ty);
1081 if_ok!(self.cat_pattern(cmt_field, fp.pat, |x,y,z| op(x,y,z)));
1085 ast::PatTup(ref subpats) => {
1087 for (i, &subpat) in subpats.iter().enumerate() {
1088 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1090 self.cat_imm_interior(
1091 pat, cmt, subpat_ty,
1092 InteriorField(PositionalField(i)));
1093 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1097 ast::PatUniq(subpat) | ast::PatRegion(subpat) => {
1099 let subcmt = self.cat_deref(pat, cmt, 0);
1100 if_ok!(self.cat_pattern(subcmt, subpat, op));
1103 ast::PatVec(ref before, slice, ref after) => {
1104 let elt_cmt = self.cat_index(pat, cmt, 0);
1105 for &before_pat in before.iter() {
1106 if_ok!(self.cat_pattern(elt_cmt, before_pat, |x,y,z| op(x,y,z)));
1108 for &slice_pat in slice.iter() {
1109 let slice_ty = if_ok!(self.pat_ty(slice_pat));
1110 let slice_cmt = self.cat_rvalue_node(pat.id(), pat.span(), slice_ty);
1111 if_ok!(self.cat_pattern(slice_cmt, slice_pat, |x,y,z| op(x,y,z)));
1113 for &after_pat in after.iter() {
1114 if_ok!(self.cat_pattern(elt_cmt, after_pat, |x,y,z| op(x,y,z)));
1118 ast::PatLit(_) | ast::PatRange(_, _) => {
1126 pub fn mut_to_str(&mut self, mutbl: ast::Mutability) -> ~str {
1128 MutMutable => ~"mutable",
1129 MutImmutable => ~"immutable"
1133 pub fn cmt_to_str(&self, cmt: cmt) -> ~str {
1135 cat_static_item => {
1138 cat_copied_upvar(_) => {
1139 ~"captured outer variable in a heap closure"
1150 cat_deref(base, _, pk) => {
1153 format!("captured outer variable")
1156 format!("dereference of `{}`-pointer", ptr_sigil(pk))
1160 cat_interior(_, InteriorField(NamedField(_))) => {
1163 cat_interior(_, InteriorField(PositionalField(_))) => {
1166 cat_interior(_, InteriorElement(VecElement)) => {
1169 cat_interior(_, InteriorElement(StrElement)) => {
1172 cat_interior(_, InteriorElement(OtherElement)) => {
1176 ~"captured outer variable"
1178 cat_discr(cmt, _) => {
1179 self.cmt_to_str(cmt)
1181 cat_downcast(cmt) => {
1182 self.cmt_to_str(cmt)
1187 pub fn region_to_str(&self, r: ty::Region) -> ~str {
1188 region_ptr_to_str(self.tcx(), r)
1192 /// The node_id here is the node of the expression that references the field.
1193 /// This function looks it up in the def map in case the type happens to be
1194 /// an enum to determine which variant is in use.
1195 pub fn field_mutbl(tcx: ty::ctxt,
1197 // FIXME #6993: change type to Name
1199 node_id: ast::NodeId)
1200 -> Option<ast::Mutability> {
1201 // Need to refactor so that struct/enum fields can be treated uniformly.
1202 match ty::get(base_ty).sty {
1203 ty::ty_struct(did, _) => {
1204 let r = ty::lookup_struct_fields(tcx, did);
1205 for fld in r.iter() {
1206 if fld.name == f_name.name {
1207 return Some(ast::MutImmutable);
1211 ty::ty_enum(..) => {
1212 let def_map = tcx.def_map.borrow();
1213 match def_map.get().get_copy(&node_id) {
1214 ast::DefVariant(_, variant_id, _) => {
1215 let r = ty::lookup_struct_fields(tcx, variant_id);
1216 for fld in r.iter() {
1217 if fld.name == f_name.name {
1218 return Some(ast::MutImmutable);
1231 pub enum AliasableReason {
1240 pub fn guarantor(self) -> cmt {
1241 //! Returns `self` after stripping away any owned pointer derefs or
1242 //! interior content. The return value is basically the `cmt` which
1243 //! determines how long the value in `self` remains live.
1248 cat_copied_upvar(..) |
1251 cat_deref(_, _, UnsafePtr(..)) |
1252 cat_deref(_, _, GcPtr(..)) |
1253 cat_deref(_, _, BorrowedPtr(..)) |
1259 cat_interior(b, _) |
1260 cat_deref(b, _, OwnedPtr) => {
1266 pub fn freely_aliasable(&self) -> Option<AliasableReason> {
1268 * Returns `Some(_)` if this lvalue represents a freely aliasable
1272 // Maybe non-obvious: copied upvars can only be considered
1273 // non-aliasable in once closures, since any other kind can be
1274 // aliased and eventually recused.
1277 cat_deref(b, _, BorrowedPtr(ty::MutBorrow, _)) |
1278 cat_deref(b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1280 cat_deref(b, _, OwnedPtr) |
1281 cat_interior(b, _) |
1282 cat_discr(b, _) => {
1283 // Aliasability depends on base cmt
1284 b.freely_aliasable()
1287 cat_copied_upvar(CopiedUpvar {onceness: ast::Once, ..}) |
1292 cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
1296 cat_copied_upvar(CopiedUpvar {onceness: ast::Many, ..}) => {
1297 Some(AliasableOther)
1300 cat_static_item(..) => {
1301 if self.mutbl.is_mutable() {
1302 Some(AliasableStaticMut)
1304 Some(AliasableStatic)
1308 cat_deref(_, _, GcPtr) => {
1309 Some(AliasableManaged)
1312 cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) => {
1313 Some(AliasableBorrowed)
1319 impl Repr for cmt_ {
1320 fn repr(&self, tcx: ty::ctxt) -> ~str {
1321 format!("\\{{} id:{} m:{:?} ty:{}\\}",
1329 impl Repr for categorization {
1330 fn repr(&self, tcx: ty::ctxt) -> ~str {
1334 cat_copied_upvar(..) |
1338 format!("{:?}", *self)
1340 cat_deref(cmt, derefs, ptr) => {
1341 format!("{}-{}{}->",
1346 cat_interior(cmt, interior) => {
1351 cat_downcast(cmt) => {
1352 format!("{}->(enum)", cmt.cat.repr(tcx))
1354 cat_discr(cmt, _) => {
1361 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1365 BorrowedPtr(ty::ImmBorrow, _) => "&",
1366 BorrowedPtr(ty::MutBorrow, _) => "&mut",
1367 BorrowedPtr(ty::UniqueImmBorrow, _) => "&unique",
1372 impl Repr for InteriorKind {
1373 fn repr(&self, _tcx: ty::ctxt) -> ~str {
1375 InteriorField(NamedField(fld)) => {
1376 token::get_name(fld).get().to_str()
1378 InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
1379 InteriorElement(_) => ~"[]",
1384 fn element_kind(t: ty::t) -> ElementKind {
1385 match ty::get(t).sty {
1386 ty::ty_vec(..) => VecElement,
1387 ty::ty_str(..) => StrElement,