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)];
67 use util::ppaux::{ty_to_str, region_ptr_to_str, Repr};
69 use syntax::ast::{MutImmutable, MutMutable};
71 use syntax::codemap::Span;
72 use syntax::print::pprust;
73 use syntax::parse::token;
76 pub enum categorization {
77 cat_rvalue(ty::Region), // temporary val, argument is its scope
79 cat_copied_upvar(CopiedUpvar), // upvar copied into @fn or ~fn env
80 cat_upvar(ty::UpvarId, ty::UpvarBorrow), // by ref upvar from stack closure
81 cat_local(ast::NodeId), // local variable
82 cat_arg(ast::NodeId), // formal argument
83 cat_deref(cmt, uint, PointerKind), // deref of a ptr
84 cat_interior(cmt, InteriorKind), // something interior: field, tuple, etc
85 cat_downcast(cmt), // selects a particular enum variant (*1)
86 cat_discr(cmt, ast::NodeId), // match discriminant (see preserve())
88 // (*1) downcast is only required if the enum has more than one variant
92 pub struct CopiedUpvar {
93 upvar_id: ast::NodeId,
94 onceness: ast::Onceness,
97 // different kinds of pointers:
98 #[deriving(Eq, TotalEq, Hash)]
99 pub enum PointerKind {
102 BorrowedPtr(ty::BorrowKind, ty::Region),
103 UnsafePtr(ast::Mutability),
106 // We use the term "interior" to mean "something reachable from the
107 // base without a pointer dereference", e.g. a field
108 #[deriving(Eq, TotalEq, Hash)]
109 pub enum InteriorKind {
110 InteriorField(FieldName),
111 InteriorElement(ElementKind),
114 #[deriving(Eq, TotalEq, Hash)]
116 NamedField(ast::Name),
117 PositionalField(uint)
120 #[deriving(Eq, TotalEq, Hash)]
121 pub enum ElementKind {
127 #[deriving(Eq, TotalEq, Hash, Show)]
128 pub enum MutabilityCategory {
129 McImmutable, // Immutable.
130 McDeclared, // Directly declared as mutable.
131 McInherited, // Inherited from the fact that owner is mutable.
134 // `cmt`: "Category, Mutability, and Type".
136 // a complete categorization of a value indicating where it originated
137 // and how it is located, as well as the mutability of the memory in
138 // which the value is stored.
140 // *WARNING* The field `cmt.type` is NOT necessarily the same as the
141 // result of `node_id_to_type(cmt.id)`. This is because the `id` is
142 // always the `id` of the node producing the type; in an expression
143 // like `*x`, the type of this deref node is the deref'd type (`T`),
144 // but in a pattern like `@x`, the `@x` pattern is again a
145 // dereference, but its type is the type *before* the dereference
146 // (`@T`). So use `cmt.type` to find the type of the value in a consistent
147 // fashion. For more details, see the method `cat_pattern`
150 id: ast::NodeId, // id of expr/pat producing this value
151 span: Span, // span of same expr/pat
152 cat: categorization, // categorization of expr
153 mutbl: MutabilityCategory, // mutability of expr as lvalue
154 ty: ty::t // type of the expr (*see WARNING above*)
157 pub type cmt = @cmt_;
159 // We pun on *T to mean both actual deref of a ptr as well
160 // as accessing of components:
161 pub enum deref_kind {
162 deref_ptr(PointerKind),
163 deref_interior(InteriorKind),
166 // Categorizes a derefable type. Note that we include vectors and strings as
167 // derefable (we model an index as the combination of a deref and then a
168 // pointer adjustment).
169 pub fn opt_deref_kind(t: ty::t) -> Option<deref_kind> {
170 match ty::get(t).sty {
172 ty::ty_trait(~ty::TyTrait { store: ty::UniqTraitStore, .. }) |
173 ty::ty_vec(_, ty::vstore_uniq) |
174 ty::ty_str(ty::vstore_uniq) |
175 ty::ty_closure(~ty::ClosureTy {sigil: ast::OwnedSigil, ..}) => {
176 Some(deref_ptr(OwnedPtr))
180 ty::ty_vec(mt, ty::vstore_slice(r)) => {
181 let kind = ty::BorrowKind::from_mutbl(mt.mutbl);
182 Some(deref_ptr(BorrowedPtr(kind, r)))
185 ty::ty_trait(~ty::TyTrait { store: ty::RegionTraitStore(r), mutability: m, .. }) => {
186 let kind = ty::BorrowKind::from_mutbl(m);
187 Some(deref_ptr(BorrowedPtr(kind, r)))
190 ty::ty_str(ty::vstore_slice(r)) |
191 ty::ty_closure(~ty::ClosureTy {sigil: ast::BorrowedSigil,
193 Some(deref_ptr(BorrowedPtr(ty::ImmBorrow, r)))
197 Some(deref_ptr(GcPtr))
200 ty::ty_ptr(ref mt) => {
201 Some(deref_ptr(UnsafePtr(mt.mutbl)))
205 ty::ty_struct(..) => { // newtype
206 Some(deref_interior(InteriorField(PositionalField(0))))
209 ty::ty_vec(_, ty::vstore_fixed(_)) |
210 ty::ty_str(ty::vstore_fixed(_)) => {
211 Some(deref_interior(InteriorElement(element_kind(t))))
218 pub fn deref_kind(tcx: &ty::ctxt, t: ty::t) -> deref_kind {
219 match opt_deref_kind(t) {
223 format!("deref_cat() invoked on non-derefable type {}",
230 fn id(&self) -> ast::NodeId;
231 fn span(&self) -> Span;
234 impl ast_node for ast::Expr {
235 fn id(&self) -> ast::NodeId { self.id }
236 fn span(&self) -> Span { self.span }
239 impl ast_node for ast::Pat {
240 fn id(&self) -> ast::NodeId { self.id }
241 fn span(&self) -> Span { self.span }
244 pub struct MemCategorizationContext<TYPER> {
248 pub type McResult<T> = Result<T, ()>;
251 * The `Typer` trait provides the interface for the mem-categorization
252 * module to the results of the type check. It can be used to query
253 * the type assigned to an expression node, to inquire after adjustments,
256 * This interface is needed because mem-categorization is used from
257 * two places: `regionck` and `borrowck`. `regionck` executes before
258 * type inference is complete, and hence derives types and so on from
259 * intermediate tables. This also implies that type errors can occur,
260 * and hence `node_ty()` and friends return a `Result` type -- any
261 * error will propagate back up through the mem-categorization
264 * In the borrow checker, in contrast, type checking is complete and we
265 * know that no errors have occurred, so we simply consult the tcx and we
266 * can be sure that only `Ok` results will occur.
269 fn tcx<'a>(&'a self) -> &'a ty::ctxt;
270 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t>;
271 fn node_method_ty(&self, method_call: typeck::MethodCall) -> Option<ty::t>;
272 fn adjustment(&mut self, node_id: ast::NodeId) -> Option<@ty::AutoAdjustment>;
273 fn is_method_call(&mut self, id: ast::NodeId) -> bool;
274 fn temporary_scope(&mut self, rvalue_id: ast::NodeId) -> Option<ast::NodeId>;
275 fn upvar_borrow(&mut self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow;
278 impl MutabilityCategory {
279 pub fn from_mutbl(m: ast::Mutability) -> MutabilityCategory {
281 MutImmutable => McImmutable,
282 MutMutable => McDeclared
286 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
288 ty::ImmBorrow => McImmutable,
289 ty::UniqueImmBorrow => McImmutable,
290 ty::MutBorrow => McDeclared,
294 pub fn from_pointer_kind(base_mutbl: MutabilityCategory,
295 ptr: PointerKind) -> MutabilityCategory {
300 BorrowedPtr(borrow_kind, _) => {
301 MutabilityCategory::from_borrow_kind(borrow_kind)
307 MutabilityCategory::from_mutbl(m)
312 pub fn inherit(&self) -> MutabilityCategory {
314 McImmutable => McImmutable,
315 McDeclared => McInherited,
316 McInherited => McInherited,
320 pub fn is_mutable(&self) -> bool {
322 McImmutable => false,
328 pub fn is_immutable(&self) -> bool {
331 McDeclared | McInherited => false
335 pub fn to_user_str(&self) -> &'static str {
337 McDeclared | McInherited => "mutable",
338 McImmutable => "immutable",
347 Err(e) => { return Err(e); }
352 impl<TYPER:Typer> MemCategorizationContext<TYPER> {
353 fn tcx<'a>(&'a self) -> &'a ty::ctxt {
357 fn adjustment(&mut self, id: ast::NodeId) -> Option<@ty::AutoAdjustment> {
358 self.typer.adjustment(id)
361 fn expr_ty(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
362 self.typer.node_ty(expr.id)
365 fn expr_ty_adjusted(&mut self, expr: &ast::Expr) -> McResult<ty::t> {
366 let unadjusted_ty = if_ok!(self.expr_ty(expr));
367 let adjustment = self.adjustment(expr.id);
368 Ok(ty::adjust_ty(self.tcx(), expr.span, expr.id, unadjusted_ty, adjustment,
369 |method_call| self.typer.node_method_ty(method_call)))
372 fn node_ty(&mut self, id: ast::NodeId) -> McResult<ty::t> {
373 self.typer.node_ty(id)
376 fn pat_ty(&mut self, pat: @ast::Pat) -> McResult<ty::t> {
377 self.typer.node_ty(pat.id)
380 pub fn cat_expr(&mut self, expr: &ast::Expr) -> McResult<cmt> {
381 match self.adjustment(expr.id) {
384 self.cat_expr_unadjusted(expr)
387 Some(adjustment) => {
389 ty::AutoObject(..) => {
390 // Implicity casts a concrete object to trait object
391 // so just patch up the type
392 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
393 let expr_cmt = if_ok!(self.cat_expr_unadjusted(expr));
394 Ok(@cmt_ {ty: expr_ty, ..*expr_cmt})
397 ty::AutoAddEnv(..) => {
398 // Convert a bare fn to a closure by adding NULL env.
399 // Result is an rvalue.
400 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
401 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
406 autoref: Some(_), ..}) => {
407 // Equivalent to &*expr or something similar.
408 // Result is an rvalue.
409 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
410 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
415 autoref: None, autoderefs: autoderefs}) => {
416 // Equivalent to *expr or something similar.
417 self.cat_expr_autoderefd(expr, autoderefs)
424 pub fn cat_expr_autoderefd(&mut self, expr: &ast::Expr, autoderefs: uint)
426 let mut cmt = if_ok!(self.cat_expr_unadjusted(expr));
427 for deref in range(1u, autoderefs + 1) {
428 cmt = self.cat_deref(expr, cmt, deref);
433 pub fn cat_expr_unadjusted(&mut self, expr: &ast::Expr) -> McResult<cmt> {
434 debug!("cat_expr: id={} expr={}", expr.id, expr.repr(self.tcx()));
436 let expr_ty = if_ok!(self.expr_ty(expr));
438 ast::ExprUnary(ast::UnDeref, e_base) => {
439 let base_cmt = if_ok!(self.cat_expr(e_base));
440 Ok(self.cat_deref(expr, base_cmt, 0))
443 ast::ExprField(base, f_name, _) => {
444 let base_cmt = if_ok!(self.cat_expr(base));
445 Ok(self.cat_field(expr, base_cmt, f_name, expr_ty))
448 ast::ExprIndex(base, _) => {
449 if self.typer.is_method_call(expr.id) {
450 return Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty));
453 let base_cmt = if_ok!(self.cat_expr(base));
454 Ok(self.cat_index(expr, base_cmt, 0))
457 ast::ExprPath(_) => {
458 let def = self.tcx().def_map.borrow().get_copy(&expr.id);
459 self.cat_def(expr.id, expr.span, expr_ty, def)
462 ast::ExprParen(e) => self.cat_expr_unadjusted(e),
464 ast::ExprAddrOf(..) | ast::ExprCall(..) |
465 ast::ExprAssign(..) | ast::ExprAssignOp(..) |
466 ast::ExprFnBlock(..) | ast::ExprProc(..) | ast::ExprRet(..) |
468 ast::ExprMethodCall(..) | ast::ExprCast(..) | ast::ExprVstore(..) |
469 ast::ExprVec(..) | ast::ExprTup(..) | ast::ExprIf(..) |
470 ast::ExprBinary(..) | ast::ExprWhile(..) |
471 ast::ExprBlock(..) | ast::ExprLoop(..) | ast::ExprMatch(..) |
472 ast::ExprLit(..) | ast::ExprBreak(..) | ast::ExprMac(..) |
473 ast::ExprAgain(..) | ast::ExprStruct(..) | ast::ExprRepeat(..) |
474 ast::ExprInlineAsm(..) | ast::ExprBox(..) => {
475 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
478 ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop")
482 pub fn cat_def(&mut self,
488 debug!("cat_def: id={} expr={}",
489 id, expr_ty.repr(self.tcx()));
492 ast::DefStruct(..) | ast::DefVariant(..) => {
493 Ok(self.cat_rvalue_node(id, span, expr_ty))
495 ast::DefFn(..) | ast::DefStaticMethod(..) | ast::DefMod(_) |
496 ast::DefForeignMod(_) | ast::DefStatic(_, false) |
497 ast::DefUse(_) | ast::DefTrait(_) | ast::DefTy(_) | ast::DefPrimTy(_) |
498 ast::DefTyParam(..) | ast::DefTyParamBinder(..) | ast::DefRegion(_) |
499 ast::DefLabel(_) | ast::DefSelfTy(..) | ast::DefMethod(..) => {
509 ast::DefStatic(_, true) => {
519 ast::DefArg(vid, binding_mode) => {
520 // Idea: make this could be rewritten to model by-ref
521 // stuff as `&const` and `&mut`?
523 // m: mutability of the argument
524 let m = match binding_mode {
525 ast::BindByValue(ast::MutMutable) => McDeclared,
537 ast::DefUpvar(var_id, _, fn_node_id, _) => {
538 let ty = if_ok!(self.node_ty(fn_node_id));
539 match ty::get(ty).sty {
540 ty::ty_closure(ref closure_ty) => {
541 // Decide whether to use implicit reference or by copy/move
542 // capture for the upvar. This, combined with the onceness,
543 // determines whether the closure can move out of it.
544 let var_is_refd = match (closure_ty.sigil, closure_ty.onceness) {
545 // Many-shot stack closures can never move out.
546 (ast::BorrowedSigil, ast::Many) => true,
547 // 1-shot stack closures can move out.
548 (ast::BorrowedSigil, ast::Once) => false,
549 // Heap closures always capture by copy/move, and can
550 // move out if they are once.
551 (ast::OwnedSigil, _) |
552 (ast::ManagedSigil, _) => false,
556 self.cat_upvar(id, span, var_id, fn_node_id)
558 // FIXME #2152 allow mutation of moved upvars
562 cat:cat_copied_upvar(CopiedUpvar {
564 onceness: closure_ty.onceness}),
571 self.tcx().sess.span_bug(
573 format!("Upvar of non-closure {} - {}",
574 fn_node_id, ty.repr(self.tcx())));
579 ast::DefLocal(vid, binding_mode) |
580 ast::DefBinding(vid, binding_mode) => {
581 // by-value/by-ref bindings are local variables
582 let m = match binding_mode {
583 ast::BindByValue(ast::MutMutable) => McDeclared,
598 fn cat_upvar(&mut self,
602 fn_node_id: ast::NodeId)
605 * Upvars through a closure are in fact indirect
606 * references. That is, when a closure refers to a
607 * variable from a parent stack frame like `x = 10`,
608 * that is equivalent to `*x_ = 10` where `x_` is a
609 * borrowed pointer (`&mut x`) created when the closure
610 * was created and store in the environment. This
611 * equivalence is expose in the mem-categorization.
614 let upvar_id = ty::UpvarId { var_id: var_id,
615 closure_expr_id: fn_node_id };
617 let upvar_borrow = self.typer.upvar_borrow(upvar_id);
619 let var_ty = if_ok!(self.node_ty(var_id));
621 // We can't actually represent the types of all upvars
622 // as user-describable types, since upvars support const
623 // and unique-imm borrows! Therefore, we cheat, and just
624 // give err type. Nobody should be inspecting this type anyhow.
625 let upvar_ty = ty::mk_err();
627 let base_cmt = @cmt_ {
630 cat:cat_upvar(upvar_id, upvar_borrow),
635 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
637 let deref_cmt = @cmt_ {
640 cat:cat_deref(base_cmt, 0, ptr),
641 mutbl:MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
648 pub fn cat_rvalue_node(&mut self,
653 match self.typer.temporary_scope(id) {
655 self.cat_rvalue(id, span, ty::ReScope(scope), expr_ty)
658 self.cat_rvalue(id, span, ty::ReStatic, expr_ty)
663 pub fn cat_rvalue(&mut self,
666 temp_scope: ty::Region,
667 expr_ty: ty::t) -> cmt {
671 cat:cat_rvalue(temp_scope),
677 /// inherited mutability: used in cases where the mutability of a
678 /// component is inherited from the base it is a part of. For
679 /// example, a record field is mutable if it is declared mutable
680 /// or if the container is mutable.
681 pub fn inherited_mutability(&mut self,
682 base_m: MutabilityCategory,
683 interior_m: ast::Mutability)
684 -> MutabilityCategory {
686 MutImmutable => base_m.inherit(),
687 MutMutable => McDeclared
691 pub fn cat_field<N:ast_node>(&mut self,
700 cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
701 mutbl: base_cmt.mutbl.inherit(),
706 pub fn cat_deref_fn_or_obj<N:ast_node>(&mut self,
711 // Bit of a hack: the "dereference" of a function pointer like
712 // `@fn()` is a mere logical concept. We interpret it as
713 // dereferencing the environment pointer; of course, we don't
714 // know what type lies at the other end, so we just call it
715 // `()` (the empty tuple).
717 let opaque_ty = ty::mk_tup(self.tcx(), Vec::new());
718 self.cat_deref_common(node, base_cmt, deref_cnt, opaque_ty)
721 fn cat_deref<N:ast_node>(&mut self,
726 let method_call = typeck::MethodCall {
728 autoderef: deref_cnt as u32
730 let method_ty = self.typer.node_method_ty(method_call);
732 debug!("cat_deref: method_call={:?} method_ty={}",
733 method_call, method_ty.map(|ty| ty.repr(self.tcx())));
735 let base_cmt = match method_ty {
737 let ref_ty = ty::ty_fn_ret(method_ty);
738 self.cat_rvalue_node(node.id(), node.span(), ref_ty)
742 match ty::deref(base_cmt.ty, true) {
743 Some(mt) => self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty),
745 self.tcx().sess.span_bug(
747 format!("Explicit deref of non-derefable type: {}",
748 base_cmt.ty.repr(self.tcx())));
753 fn cat_deref_common<N:ast_node>(&mut self,
759 let (m, cat) = match deref_kind(self.tcx(), base_cmt.ty) {
761 // for unique ptrs, we inherit mutability from the
763 (MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr),
764 cat_deref(base_cmt, deref_cnt, ptr))
766 deref_interior(interior) => {
767 (base_cmt.mutbl.inherit(), cat_interior(base_cmt, interior))
779 pub fn cat_index<N:ast_node>(&mut self,
784 //! Creates a cmt for an indexing operation (`[]`); this
785 //! indexing operation may occurs as part of an
786 //! AutoBorrowVec, which when converting a `~[]` to an `&[]`
787 //! effectively takes the address of the 0th element.
789 //! One subtle aspect of indexing that may not be
790 //! immediately obvious: for anything other than a fixed-length
791 //! vector, an operation like `x[y]` actually consists of two
792 //! disjoint (from the point of view of borrowck) operations.
793 //! The first is a deref of `x` to create a pointer `p` that points
794 //! at the first element in the array. The second operation is
795 //! an index which adds `y*sizeof(T)` to `p` to obtain the
796 //! pointer to `x[y]`. `cat_index` will produce a resulting
797 //! cmt containing both this deref and the indexing,
798 //! presuming that `base_cmt` is not of fixed-length type.
800 //! In the event that a deref is needed, the "deref count"
801 //! is taken from the parameter `derefs`. See the comment
802 //! on the def'n of `root_map_key` in borrowck/mod.rs
803 //! for more details about deref counts; the summary is
804 //! that `derefs` should be 0 for an explicit indexing
805 //! operation and N+1 for an indexing that is part of
806 //! an auto-adjustment, where N is the number of autoderefs
807 //! in that adjustment.
810 //! - `elt`: the AST node being indexed
811 //! - `base_cmt`: the cmt of `elt`
812 //! - `derefs`: the deref number to be used for
813 //! the implicit index deref, if any (see above)
815 let element_ty = match ty::index(base_cmt.ty) {
816 Some(ref mt) => mt.ty,
818 self.tcx().sess.span_bug(
820 format!("Explicit index of non-index type `{}`",
821 base_cmt.ty.repr(self.tcx())));
825 return match deref_kind(self.tcx(), base_cmt.ty) {
827 // for unique ptrs, we inherit mutability from the
829 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr);
831 // the deref is explicit in the resulting cmt
832 let deref_cmt = @cmt_ {
835 cat:cat_deref(base_cmt, derefs, ptr),
840 interior(elt, deref_cmt, base_cmt.ty, m.inherit(), element_ty)
843 deref_interior(_) => {
844 // fixed-length vectors have no deref
845 let m = base_cmt.mutbl.inherit();
846 interior(elt, base_cmt, base_cmt.ty, m, element_ty)
850 fn interior<N: ast_node>(elt: &N,
853 mutbl: MutabilityCategory,
854 element_ty: ty::t) -> cmt
859 cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
866 pub fn cat_slice_pattern(&mut self,
868 slice_pat: @ast::Pat)
869 -> McResult<(cmt, ast::Mutability, ty::Region)> {
871 * Given a pattern P like: `[_, ..Q, _]`, where `vec_cmt` is
872 * the cmt for `P`, `slice_pat` is the pattern `Q`, returns:
874 * - the mutability and region of the slice `Q`
876 * These last two bits of info happen to be things that
880 let slice_ty = if_ok!(self.node_ty(slice_pat.id));
881 let (slice_mutbl, slice_r) = vec_slice_info(self.tcx(),
884 let cmt_slice = self.cat_index(slice_pat, vec_cmt, 0);
885 return Ok((cmt_slice, slice_mutbl, slice_r));
887 fn vec_slice_info(tcx: &ty::ctxt,
890 -> (ast::Mutability, ty::Region) {
892 * In a pattern like [a, b, ..c], normally `c` has slice type,
893 * but if you have [a, b, ..ref c], then the type of `ref c`
894 * will be `&&[]`, so to extract the slice details we have
895 * to recurse through rptrs.
898 match ty::get(slice_ty).sty {
899 ty::ty_vec(slice_mt, ty::vstore_slice(slice_r)) => {
900 (slice_mt.mutbl, slice_r)
903 ty::ty_rptr(_, ref mt) => {
904 vec_slice_info(tcx, pat, mt.ty)
910 format!("Type of slice pattern is not a slice"));
916 pub fn cat_imm_interior<N:ast_node>(&mut self,
920 interior: InteriorKind)
925 cat: cat_interior(base_cmt, interior),
926 mutbl: base_cmt.mutbl.inherit(),
931 pub fn cat_downcast<N:ast_node>(&mut self,
939 cat: cat_downcast(base_cmt),
940 mutbl: base_cmt.mutbl.inherit(),
945 pub fn cat_pattern(&mut self,
948 op: |&mut MemCategorizationContext<TYPER>,
952 // Here, `cmt` is the categorization for the value being
953 // matched and pat is the pattern it is being matched against.
955 // In general, the way that this works is that we walk down
956 // the pattern, constructing a cmt that represents the path
957 // that will be taken to reach the value being matched.
959 // When we encounter named bindings, we take the cmt that has
960 // been built up and pass it off to guarantee_valid() so that
961 // we can be sure that the binding will remain valid for the
962 // duration of the arm.
964 // (*2) There is subtlety concerning the correspondence between
965 // pattern ids and types as compared to *expression* ids and
966 // types. This is explained briefly. on the definition of the
967 // type `cmt`, so go off and read what it says there, then
968 // come back and I'll dive into a bit more detail here. :) OK,
971 // In general, the id of the cmt should be the node that
972 // "produces" the value---patterns aren't executable code
973 // exactly, but I consider them to "execute" when they match a
974 // value, and I consider them to produce the value that was
975 // matched. So if you have something like:
982 // In this case, the cmt and the relevant ids would be:
984 // CMT Id Type of Id Type of cmt
987 // ^~~~~~~^ `x` from discr @@int @@int
988 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
989 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
991 // You can see that the types of the id and the cmt are in
992 // sync in the first line, because that id is actually the id
993 // of an expression. But once we get to pattern ids, the types
994 // step out of sync again. So you'll see below that we always
995 // get the type of the *subpattern* and use that.
997 debug!("cat_pattern: id={} pat={} cmt={}",
998 pat.id, pprust::pat_to_str(pat),
999 cmt.repr(self.tcx()));
1004 ast::PatWild | ast::PatWildMulti => {
1008 ast::PatEnum(_, None) => {
1011 ast::PatEnum(_, Some(ref subpats)) => {
1012 match self.tcx().def_map.borrow().find(&pat.id) {
1013 Some(&ast::DefVariant(enum_did, _, _)) => {
1016 let downcast_cmt = {
1017 if ty::enum_is_univariant(self.tcx(), enum_did) {
1018 cmt // univariant, no downcast needed
1020 self.cat_downcast(pat, cmt, cmt.ty)
1024 for (i, &subpat) in subpats.iter().enumerate() {
1025 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1028 self.cat_imm_interior(
1029 pat, downcast_cmt, subpat_ty,
1030 InteriorField(PositionalField(i)));
1032 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1035 Some(&ast::DefFn(..)) |
1036 Some(&ast::DefStruct(..)) => {
1037 for (i, &subpat) in subpats.iter().enumerate() {
1038 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1040 self.cat_imm_interior(
1041 pat, cmt, subpat_ty,
1042 InteriorField(PositionalField(i)));
1043 if_ok!(self.cat_pattern(cmt_field, subpat, |x,y,z| op(x,y,z)));
1046 Some(&ast::DefStatic(..)) => {
1047 for &subpat in subpats.iter() {
1048 if_ok!(self.cat_pattern(cmt, subpat, |x,y,z| op(x,y,z)));
1052 self.tcx().sess.span_bug(
1054 "enum pattern didn't resolve to enum or struct");
1059 ast::PatIdent(_, _, Some(subpat)) => {
1060 if_ok!(self.cat_pattern(cmt, subpat, op));
1063 ast::PatIdent(_, _, None) => {
1064 // nullary variant or identifier: ignore
1067 ast::PatStruct(_, ref field_pats, _) => {
1068 // {f1: p1, ..., fN: pN}
1069 for fp in field_pats.iter() {
1070 let field_ty = if_ok!(self.pat_ty(fp.pat)); // see (*2)
1071 let cmt_field = self.cat_field(pat, cmt, fp.ident, field_ty);
1072 if_ok!(self.cat_pattern(cmt_field, fp.pat, |x,y,z| op(x,y,z)));
1076 ast::PatTup(ref subpats) => {
1078 for (i, &subpat) in subpats.iter().enumerate() {
1079 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1081 self.cat_imm_interior(
1082 pat, cmt, subpat_ty,
1083 InteriorField(PositionalField(i)));
1084 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1088 ast::PatUniq(subpat) | ast::PatRegion(subpat) => {
1090 let subcmt = self.cat_deref(pat, cmt, 0);
1091 if_ok!(self.cat_pattern(subcmt, subpat, op));
1094 ast::PatVec(ref before, slice, ref after) => {
1095 let elt_cmt = self.cat_index(pat, cmt, 0);
1096 for &before_pat in before.iter() {
1097 if_ok!(self.cat_pattern(elt_cmt, before_pat, |x,y,z| op(x,y,z)));
1099 for &slice_pat in slice.iter() {
1100 let slice_ty = if_ok!(self.pat_ty(slice_pat));
1101 let slice_cmt = self.cat_rvalue_node(pat.id(), pat.span(), slice_ty);
1102 if_ok!(self.cat_pattern(slice_cmt, slice_pat, |x,y,z| op(x,y,z)));
1104 for &after_pat in after.iter() {
1105 if_ok!(self.cat_pattern(elt_cmt, after_pat, |x,y,z| op(x,y,z)));
1109 ast::PatLit(_) | ast::PatRange(_, _) => {
1117 pub fn mut_to_str(&mut self, mutbl: ast::Mutability) -> ~str {
1119 MutMutable => ~"mutable",
1120 MutImmutable => ~"immutable"
1124 pub fn cmt_to_str(&self, cmt: cmt) -> ~str {
1126 cat_static_item => {
1129 cat_copied_upvar(_) => {
1130 ~"captured outer variable in a heap closure"
1141 cat_deref(base, _, pk) => {
1144 format!("captured outer variable")
1147 format!("dereference of `{}`-pointer", ptr_sigil(pk))
1151 cat_interior(_, InteriorField(NamedField(_))) => {
1154 cat_interior(_, InteriorField(PositionalField(_))) => {
1157 cat_interior(_, InteriorElement(VecElement)) => {
1160 cat_interior(_, InteriorElement(StrElement)) => {
1163 cat_interior(_, InteriorElement(OtherElement)) => {
1167 ~"captured outer variable"
1169 cat_discr(cmt, _) => {
1170 self.cmt_to_str(cmt)
1172 cat_downcast(cmt) => {
1173 self.cmt_to_str(cmt)
1178 pub fn region_to_str(&self, r: ty::Region) -> ~str {
1179 region_ptr_to_str(self.tcx(), r)
1183 /// The node_id here is the node of the expression that references the field.
1184 /// This function looks it up in the def map in case the type happens to be
1185 /// an enum to determine which variant is in use.
1186 pub fn field_mutbl(tcx: &ty::ctxt,
1188 // FIXME #6993: change type to Name
1190 node_id: ast::NodeId)
1191 -> Option<ast::Mutability> {
1192 // Need to refactor so that struct/enum fields can be treated uniformly.
1193 match ty::get(base_ty).sty {
1194 ty::ty_struct(did, _) => {
1195 let r = ty::lookup_struct_fields(tcx, did);
1196 for fld in r.iter() {
1197 if fld.name == f_name.name {
1198 return Some(ast::MutImmutable);
1202 ty::ty_enum(..) => {
1203 match tcx.def_map.borrow().get_copy(&node_id) {
1204 ast::DefVariant(_, variant_id, _) => {
1205 let r = ty::lookup_struct_fields(tcx, variant_id);
1206 for fld in r.iter() {
1207 if fld.name == f_name.name {
1208 return Some(ast::MutImmutable);
1221 pub enum InteriorSafety {
1226 pub enum AliasableReason {
1230 AliasableStatic(InteriorSafety),
1231 AliasableStaticMut(InteriorSafety),
1235 pub fn guarantor(self) -> cmt {
1236 //! Returns `self` after stripping away any owned pointer derefs or
1237 //! interior content. The return value is basically the `cmt` which
1238 //! determines how long the value in `self` remains live.
1243 cat_copied_upvar(..) |
1246 cat_deref(_, _, UnsafePtr(..)) |
1247 cat_deref(_, _, GcPtr(..)) |
1248 cat_deref(_, _, BorrowedPtr(..)) |
1254 cat_interior(b, _) |
1255 cat_deref(b, _, OwnedPtr) => {
1261 pub fn freely_aliasable(&self, ctxt: &ty::ctxt) -> Option<AliasableReason> {
1263 * Returns `Some(_)` if this lvalue represents a freely aliasable
1267 // Maybe non-obvious: copied upvars can only be considered
1268 // non-aliasable in once closures, since any other kind can be
1269 // aliased and eventually recused.
1272 cat_deref(b, _, BorrowedPtr(ty::MutBorrow, _)) |
1273 cat_deref(b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1275 cat_deref(b, _, OwnedPtr) |
1276 cat_interior(b, _) |
1277 cat_discr(b, _) => {
1278 // Aliasability depends on base cmt
1279 b.freely_aliasable(ctxt)
1282 cat_copied_upvar(CopiedUpvar {onceness: ast::Once, ..}) |
1287 cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
1291 cat_copied_upvar(CopiedUpvar {onceness: ast::Many, ..}) => {
1292 Some(AliasableOther)
1295 cat_static_item(..) => {
1296 let int_safe = if ty::type_interior_is_unsafe(ctxt, self.ty) {
1302 if self.mutbl.is_mutable() {
1303 Some(AliasableStaticMut(int_safe))
1305 Some(AliasableStatic(int_safe))
1309 cat_deref(_, _, GcPtr) => {
1310 Some(AliasableManaged)
1313 cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) => {
1314 Some(AliasableBorrowed)
1320 impl Repr for cmt_ {
1321 fn repr(&self, tcx: &ty::ctxt) -> ~str {
1322 format!("\\{{} id:{} m:{:?} ty:{}\\}",
1330 impl Repr for categorization {
1331 fn repr(&self, tcx: &ty::ctxt) -> ~str {
1335 cat_copied_upvar(..) |
1339 format!("{:?}", *self)
1341 cat_deref(cmt, derefs, ptr) => {
1342 format!("{}-{}{}->",
1347 cat_interior(cmt, interior) => {
1352 cat_downcast(cmt) => {
1353 format!("{}->(enum)", cmt.cat.repr(tcx))
1355 cat_discr(cmt, _) => {
1362 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1366 BorrowedPtr(ty::ImmBorrow, _) => "&",
1367 BorrowedPtr(ty::MutBorrow, _) => "&mut",
1368 BorrowedPtr(ty::UniqueImmBorrow, _) => "&unique",
1373 impl Repr for InteriorKind {
1374 fn repr(&self, _tcx: &ty::ctxt) -> ~str {
1376 InteriorField(NamedField(fld)) => {
1377 token::get_name(fld).get().to_str()
1379 InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
1380 InteriorElement(_) => ~"[]",
1385 fn element_kind(t: ty::t) -> ElementKind {
1386 match ty::get(t).sty {
1387 ty::ty_vec(..) => VecElement,
1388 ty::ty_str(..) => StrElement,