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:
99 pub enum PointerKind {
102 BorrowedPtr(ty::BorrowKind, ty::Region),
103 UnsafePtr(ast::Mutability),
106 // We use the term "interior" to mean "something reachable from the
107 // base without a pointer dereference", e.g. a field
108 #[deriving(Eq, Hash)]
109 pub enum InteriorKind {
110 InteriorField(FieldName),
111 InteriorElement(ElementKind),
114 #[deriving(Eq, Hash)]
116 NamedField(ast::Name),
117 PositionalField(uint)
120 #[deriving(Eq, Hash)]
121 pub enum ElementKind {
127 #[deriving(Eq, Hash, Show)]
128 pub enum MutabilityCategory {
129 McImmutable, // Immutable.
130 McDeclared, // Directly declared as mutable.
131 McInherited, // Inherited from the fact that owner is mutable.
134 // `cmt`: "Category, Mutability, and Type".
136 // a complete categorization of a value indicating where it originated
137 // and how it is located, as well as the mutability of the memory in
138 // which the value is stored.
140 // *WARNING* The field `cmt.type` is NOT necessarily the same as the
141 // result of `node_id_to_type(cmt.id)`. This is because the `id` is
142 // always the `id` of the node producing the type; in an expression
143 // like `*x`, the type of this deref node is the deref'd type (`T`),
144 // but in a pattern like `@x`, the `@x` pattern is again a
145 // dereference, but its type is the type *before* the dereference
146 // (`@T`). So use `cmt.type` to find the type of the value in a consistent
147 // fashion. For more details, see the method `cat_pattern`
150 id: ast::NodeId, // id of expr/pat producing this value
151 span: Span, // span of same expr/pat
152 cat: categorization, // categorization of expr
153 mutbl: MutabilityCategory, // mutability of expr as lvalue
154 ty: ty::t // type of the expr (*see WARNING above*)
157 pub type cmt = @cmt_;
159 // We pun on *T to mean both actual deref of a ptr as well
160 // as accessing of components:
161 pub enum deref_kind {
162 deref_ptr(PointerKind),
163 deref_interior(InteriorKind),
166 // Categorizes a derefable type. Note that we include vectors and strings as
167 // derefable (we model an index as the combination of a deref and then a
168 // pointer adjustment).
169 pub fn opt_deref_kind(t: ty::t) -> Option<deref_kind> {
170 match ty::get(t).sty {
172 ty::ty_trait(~ty::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_map = self.tcx().def_map.borrow();
459 let def = def_map.get().get_copy(&expr.id);
460 self.cat_def(expr.id, expr.span, expr_ty, def)
463 ast::ExprParen(e) => self.cat_expr_unadjusted(e),
465 ast::ExprAddrOf(..) | ast::ExprCall(..) |
466 ast::ExprAssign(..) | ast::ExprAssignOp(..) |
467 ast::ExprFnBlock(..) | ast::ExprProc(..) | ast::ExprRet(..) |
469 ast::ExprMethodCall(..) | ast::ExprCast(..) | ast::ExprVstore(..) |
470 ast::ExprVec(..) | ast::ExprTup(..) | ast::ExprIf(..) |
471 ast::ExprBinary(..) | ast::ExprWhile(..) |
472 ast::ExprBlock(..) | ast::ExprLoop(..) | ast::ExprMatch(..) |
473 ast::ExprLit(..) | ast::ExprBreak(..) | ast::ExprMac(..) |
474 ast::ExprAgain(..) | ast::ExprStruct(..) | ast::ExprRepeat(..) |
475 ast::ExprInlineAsm(..) | ast::ExprBox(..) => {
476 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
479 ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop")
483 pub fn cat_def(&mut self,
489 debug!("cat_def: id={} expr={}",
490 id, expr_ty.repr(self.tcx()));
493 ast::DefStruct(..) | ast::DefVariant(..) => {
494 Ok(self.cat_rvalue_node(id, span, expr_ty))
496 ast::DefFn(..) | ast::DefStaticMethod(..) | ast::DefMod(_) |
497 ast::DefForeignMod(_) | ast::DefStatic(_, false) |
498 ast::DefUse(_) | ast::DefTrait(_) | ast::DefTy(_) | ast::DefPrimTy(_) |
499 ast::DefTyParam(..) | ast::DefTyParamBinder(..) | ast::DefRegion(_) |
500 ast::DefLabel(_) | ast::DefSelfTy(..) | ast::DefMethod(..) => {
510 ast::DefStatic(_, true) => {
520 ast::DefArg(vid, binding_mode) => {
521 // Idea: make this could be rewritten to model by-ref
522 // stuff as `&const` and `&mut`?
524 // m: mutability of the argument
525 let m = match binding_mode {
526 ast::BindByValue(ast::MutMutable) => McDeclared,
538 ast::DefUpvar(var_id, _, fn_node_id, _) => {
539 let ty = if_ok!(self.node_ty(fn_node_id));
540 match ty::get(ty).sty {
541 ty::ty_closure(ref closure_ty) => {
542 // Decide whether to use implicit reference or by copy/move
543 // capture for the upvar. This, combined with the onceness,
544 // determines whether the closure can move out of it.
545 let var_is_refd = match (closure_ty.sigil, closure_ty.onceness) {
546 // Many-shot stack closures can never move out.
547 (ast::BorrowedSigil, ast::Many) => true,
548 // 1-shot stack closures can move out.
549 (ast::BorrowedSigil, ast::Once) => false,
550 // Heap closures always capture by copy/move, and can
551 // move out if they are once.
552 (ast::OwnedSigil, _) |
553 (ast::ManagedSigil, _) => false,
557 self.cat_upvar(id, span, var_id, fn_node_id)
559 // FIXME #2152 allow mutation of moved upvars
563 cat:cat_copied_upvar(CopiedUpvar {
565 onceness: closure_ty.onceness}),
572 self.tcx().sess.span_bug(
574 format!("Upvar of non-closure {} - {}",
575 fn_node_id, ty.repr(self.tcx())));
580 ast::DefLocal(vid, binding_mode) |
581 ast::DefBinding(vid, binding_mode) => {
582 // by-value/by-ref bindings are local variables
583 let m = match binding_mode {
584 ast::BindByValue(ast::MutMutable) => McDeclared,
599 fn cat_upvar(&mut self,
603 fn_node_id: ast::NodeId)
606 * Upvars through a closure are in fact indirect
607 * references. That is, when a closure refers to a
608 * variable from a parent stack frame like `x = 10`,
609 * that is equivalent to `*x_ = 10` where `x_` is a
610 * borrowed pointer (`&mut x`) created when the closure
611 * was created and store in the environment. This
612 * equivalence is expose in the mem-categorization.
615 let upvar_id = ty::UpvarId { var_id: var_id,
616 closure_expr_id: fn_node_id };
618 let upvar_borrow = self.typer.upvar_borrow(upvar_id);
620 let var_ty = if_ok!(self.node_ty(var_id));
622 // We can't actually represent the types of all upvars
623 // as user-describable types, since upvars support const
624 // and unique-imm borrows! Therefore, we cheat, and just
625 // give err type. Nobody should be inspecting this type anyhow.
626 let upvar_ty = ty::mk_err();
628 let base_cmt = @cmt_ {
631 cat:cat_upvar(upvar_id, upvar_borrow),
636 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
638 let deref_cmt = @cmt_ {
641 cat:cat_deref(base_cmt, 0, ptr),
642 mutbl:MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
649 pub fn cat_rvalue_node(&mut self,
654 match self.typer.temporary_scope(id) {
656 self.cat_rvalue(id, span, ty::ReScope(scope), expr_ty)
659 self.cat_rvalue(id, span, ty::ReStatic, expr_ty)
664 pub fn cat_rvalue(&mut self,
667 temp_scope: ty::Region,
668 expr_ty: ty::t) -> cmt {
672 cat:cat_rvalue(temp_scope),
678 /// inherited mutability: used in cases where the mutability of a
679 /// component is inherited from the base it is a part of. For
680 /// example, a record field is mutable if it is declared mutable
681 /// or if the container is mutable.
682 pub fn inherited_mutability(&mut self,
683 base_m: MutabilityCategory,
684 interior_m: ast::Mutability)
685 -> MutabilityCategory {
687 MutImmutable => base_m.inherit(),
688 MutMutable => McDeclared
692 pub fn cat_field<N:ast_node>(&mut self,
701 cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
702 mutbl: base_cmt.mutbl.inherit(),
707 pub fn cat_deref_fn_or_obj<N:ast_node>(&mut self,
712 // Bit of a hack: the "dereference" of a function pointer like
713 // `@fn()` is a mere logical concept. We interpret it as
714 // dereferencing the environment pointer; of course, we don't
715 // know what type lies at the other end, so we just call it
716 // `()` (the empty tuple).
718 let opaque_ty = ty::mk_tup(self.tcx(), Vec::new());
719 self.cat_deref_common(node, base_cmt, deref_cnt, opaque_ty)
722 fn cat_deref<N:ast_node>(&mut self,
727 let method_call = typeck::MethodCall {
729 autoderef: deref_cnt as u32
731 let method_ty = self.typer.node_method_ty(method_call);
733 debug!("cat_deref: method_call={:?} method_ty={}",
734 method_call, method_ty.map(|ty| ty.repr(self.tcx())));
736 let base_cmt = match method_ty {
738 let ref_ty = ty::ty_fn_ret(method_ty);
739 self.cat_rvalue_node(node.id(), node.span(), ref_ty)
743 match ty::deref(base_cmt.ty, true) {
744 Some(mt) => self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty),
746 self.tcx().sess.span_bug(
748 format!("Explicit deref of non-derefable type: {}",
749 base_cmt.ty.repr(self.tcx())));
754 fn cat_deref_common<N:ast_node>(&mut self,
760 let (m, cat) = match deref_kind(self.tcx(), base_cmt.ty) {
762 // for unique ptrs, we inherit mutability from the
764 (MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr),
765 cat_deref(base_cmt, deref_cnt, ptr))
767 deref_interior(interior) => {
768 (base_cmt.mutbl.inherit(), cat_interior(base_cmt, interior))
780 pub fn cat_index<N:ast_node>(&mut self,
785 //! Creates a cmt for an indexing operation (`[]`); this
786 //! indexing operation may occurs as part of an
787 //! AutoBorrowVec, which when converting a `~[]` to an `&[]`
788 //! effectively takes the address of the 0th element.
790 //! One subtle aspect of indexing that may not be
791 //! immediately obvious: for anything other than a fixed-length
792 //! vector, an operation like `x[y]` actually consists of two
793 //! disjoint (from the point of view of borrowck) operations.
794 //! The first is a deref of `x` to create a pointer `p` that points
795 //! at the first element in the array. The second operation is
796 //! an index which adds `y*sizeof(T)` to `p` to obtain the
797 //! pointer to `x[y]`. `cat_index` will produce a resulting
798 //! cmt containing both this deref and the indexing,
799 //! presuming that `base_cmt` is not of fixed-length type.
801 //! In the event that a deref is needed, the "deref count"
802 //! is taken from the parameter `derefs`. See the comment
803 //! on the def'n of `root_map_key` in borrowck/mod.rs
804 //! for more details about deref counts; the summary is
805 //! that `derefs` should be 0 for an explicit indexing
806 //! operation and N+1 for an indexing that is part of
807 //! an auto-adjustment, where N is the number of autoderefs
808 //! in that adjustment.
811 //! - `elt`: the AST node being indexed
812 //! - `base_cmt`: the cmt of `elt`
813 //! - `derefs`: the deref number to be used for
814 //! the implicit index deref, if any (see above)
816 let element_ty = match ty::index(base_cmt.ty) {
817 Some(ref mt) => mt.ty,
819 self.tcx().sess.span_bug(
821 format!("Explicit index of non-index type `{}`",
822 base_cmt.ty.repr(self.tcx())));
826 return match deref_kind(self.tcx(), base_cmt.ty) {
828 // for unique ptrs, we inherit mutability from the
830 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr);
832 // the deref is explicit in the resulting cmt
833 let deref_cmt = @cmt_ {
836 cat:cat_deref(base_cmt, derefs, ptr),
841 interior(elt, deref_cmt, base_cmt.ty, m.inherit(), element_ty)
844 deref_interior(_) => {
845 // fixed-length vectors have no deref
846 let m = base_cmt.mutbl.inherit();
847 interior(elt, base_cmt, base_cmt.ty, m, element_ty)
851 fn interior<N: ast_node>(elt: &N,
854 mutbl: MutabilityCategory,
855 element_ty: ty::t) -> cmt
860 cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
867 pub fn cat_slice_pattern(&mut self,
869 slice_pat: @ast::Pat)
870 -> McResult<(cmt, ast::Mutability, ty::Region)> {
872 * Given a pattern P like: `[_, ..Q, _]`, where `vec_cmt` is
873 * the cmt for `P`, `slice_pat` is the pattern `Q`, returns:
875 * - the mutability and region of the slice `Q`
877 * These last two bits of info happen to be things that
881 let slice_ty = if_ok!(self.node_ty(slice_pat.id));
882 let (slice_mutbl, slice_r) = vec_slice_info(self.tcx(),
885 let cmt_slice = self.cat_index(slice_pat, vec_cmt, 0);
886 return Ok((cmt_slice, slice_mutbl, slice_r));
888 fn vec_slice_info(tcx: &ty::ctxt,
891 -> (ast::Mutability, ty::Region) {
893 * In a pattern like [a, b, ..c], normally `c` has slice type,
894 * but if you have [a, b, ..ref c], then the type of `ref c`
895 * will be `&&[]`, so to extract the slice details we have
896 * to recurse through rptrs.
899 match ty::get(slice_ty).sty {
900 ty::ty_vec(slice_mt, ty::vstore_slice(slice_r)) => {
901 (slice_mt.mutbl, slice_r)
904 ty::ty_rptr(_, ref mt) => {
905 vec_slice_info(tcx, pat, mt.ty)
911 format!("Type of slice pattern is not a slice"));
917 pub fn cat_imm_interior<N:ast_node>(&mut self,
921 interior: InteriorKind)
926 cat: cat_interior(base_cmt, interior),
927 mutbl: base_cmt.mutbl.inherit(),
932 pub fn cat_downcast<N:ast_node>(&mut self,
940 cat: cat_downcast(base_cmt),
941 mutbl: base_cmt.mutbl.inherit(),
946 pub fn cat_pattern(&mut self,
949 op: |&mut MemCategorizationContext<TYPER>,
953 // Here, `cmt` is the categorization for the value being
954 // matched and pat is the pattern it is being matched against.
956 // In general, the way that this works is that we walk down
957 // the pattern, constructing a cmt that represents the path
958 // that will be taken to reach the value being matched.
960 // When we encounter named bindings, we take the cmt that has
961 // been built up and pass it off to guarantee_valid() so that
962 // we can be sure that the binding will remain valid for the
963 // duration of the arm.
965 // (*2) There is subtlety concerning the correspondence between
966 // pattern ids and types as compared to *expression* ids and
967 // types. This is explained briefly. on the definition of the
968 // type `cmt`, so go off and read what it says there, then
969 // come back and I'll dive into a bit more detail here. :) OK,
972 // In general, the id of the cmt should be the node that
973 // "produces" the value---patterns aren't executable code
974 // exactly, but I consider them to "execute" when they match a
975 // value, and I consider them to produce the value that was
976 // matched. So if you have something like:
983 // In this case, the cmt and the relevant ids would be:
985 // CMT Id Type of Id Type of cmt
988 // ^~~~~~~^ `x` from discr @@int @@int
989 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
990 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
992 // You can see that the types of the id and the cmt are in
993 // sync in the first line, because that id is actually the id
994 // of an expression. But once we get to pattern ids, the types
995 // step out of sync again. So you'll see below that we always
996 // get the type of the *subpattern* and use that.
998 debug!("cat_pattern: id={} pat={} cmt={}",
999 pat.id, pprust::pat_to_str(pat),
1000 cmt.repr(self.tcx()));
1005 ast::PatWild | ast::PatWildMulti => {
1009 ast::PatEnum(_, None) => {
1012 ast::PatEnum(_, Some(ref subpats)) => {
1013 let def_map = self.tcx().def_map.borrow();
1014 match def_map.get().find(&pat.id) {
1015 Some(&ast::DefVariant(enum_did, _, _)) => {
1018 let downcast_cmt = {
1019 if ty::enum_is_univariant(self.tcx(), enum_did) {
1020 cmt // univariant, no downcast needed
1022 self.cat_downcast(pat, cmt, cmt.ty)
1026 for (i, &subpat) in subpats.iter().enumerate() {
1027 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1030 self.cat_imm_interior(
1031 pat, downcast_cmt, subpat_ty,
1032 InteriorField(PositionalField(i)));
1034 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1037 Some(&ast::DefFn(..)) |
1038 Some(&ast::DefStruct(..)) => {
1039 for (i, &subpat) in subpats.iter().enumerate() {
1040 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1042 self.cat_imm_interior(
1043 pat, cmt, subpat_ty,
1044 InteriorField(PositionalField(i)));
1045 if_ok!(self.cat_pattern(cmt_field, subpat, |x,y,z| op(x,y,z)));
1048 Some(&ast::DefStatic(..)) => {
1049 for &subpat in subpats.iter() {
1050 if_ok!(self.cat_pattern(cmt, subpat, |x,y,z| op(x,y,z)));
1054 self.tcx().sess.span_bug(
1056 "enum pattern didn't resolve to enum or struct");
1061 ast::PatIdent(_, _, Some(subpat)) => {
1062 if_ok!(self.cat_pattern(cmt, subpat, op));
1065 ast::PatIdent(_, _, None) => {
1066 // nullary variant or identifier: ignore
1069 ast::PatStruct(_, ref field_pats, _) => {
1070 // {f1: p1, ..., fN: pN}
1071 for fp in field_pats.iter() {
1072 let field_ty = if_ok!(self.pat_ty(fp.pat)); // see (*2)
1073 let cmt_field = self.cat_field(pat, cmt, fp.ident, field_ty);
1074 if_ok!(self.cat_pattern(cmt_field, fp.pat, |x,y,z| op(x,y,z)));
1078 ast::PatTup(ref subpats) => {
1080 for (i, &subpat) in subpats.iter().enumerate() {
1081 let subpat_ty = if_ok!(self.pat_ty(subpat)); // see (*2)
1083 self.cat_imm_interior(
1084 pat, cmt, subpat_ty,
1085 InteriorField(PositionalField(i)));
1086 if_ok!(self.cat_pattern(subcmt, subpat, |x,y,z| op(x,y,z)));
1090 ast::PatUniq(subpat) | ast::PatRegion(subpat) => {
1092 let subcmt = self.cat_deref(pat, cmt, 0);
1093 if_ok!(self.cat_pattern(subcmt, subpat, op));
1096 ast::PatVec(ref before, slice, ref after) => {
1097 let elt_cmt = self.cat_index(pat, cmt, 0);
1098 for &before_pat in before.iter() {
1099 if_ok!(self.cat_pattern(elt_cmt, before_pat, |x,y,z| op(x,y,z)));
1101 for &slice_pat in slice.iter() {
1102 let slice_ty = if_ok!(self.pat_ty(slice_pat));
1103 let slice_cmt = self.cat_rvalue_node(pat.id(), pat.span(), slice_ty);
1104 if_ok!(self.cat_pattern(slice_cmt, slice_pat, |x,y,z| op(x,y,z)));
1106 for &after_pat in after.iter() {
1107 if_ok!(self.cat_pattern(elt_cmt, after_pat, |x,y,z| op(x,y,z)));
1111 ast::PatLit(_) | ast::PatRange(_, _) => {
1119 pub fn mut_to_str(&mut self, mutbl: ast::Mutability) -> ~str {
1121 MutMutable => ~"mutable",
1122 MutImmutable => ~"immutable"
1126 pub fn cmt_to_str(&self, cmt: cmt) -> ~str {
1128 cat_static_item => {
1131 cat_copied_upvar(_) => {
1132 ~"captured outer variable in a heap closure"
1143 cat_deref(base, _, pk) => {
1146 format!("captured outer variable")
1149 format!("dereference of `{}`-pointer", ptr_sigil(pk))
1153 cat_interior(_, InteriorField(NamedField(_))) => {
1156 cat_interior(_, InteriorField(PositionalField(_))) => {
1159 cat_interior(_, InteriorElement(VecElement)) => {
1162 cat_interior(_, InteriorElement(StrElement)) => {
1165 cat_interior(_, InteriorElement(OtherElement)) => {
1169 ~"captured outer variable"
1171 cat_discr(cmt, _) => {
1172 self.cmt_to_str(cmt)
1174 cat_downcast(cmt) => {
1175 self.cmt_to_str(cmt)
1180 pub fn region_to_str(&self, r: ty::Region) -> ~str {
1181 region_ptr_to_str(self.tcx(), r)
1185 /// The node_id here is the node of the expression that references the field.
1186 /// This function looks it up in the def map in case the type happens to be
1187 /// an enum to determine which variant is in use.
1188 pub fn field_mutbl(tcx: &ty::ctxt,
1190 // FIXME #6993: change type to Name
1192 node_id: ast::NodeId)
1193 -> Option<ast::Mutability> {
1194 // Need to refactor so that struct/enum fields can be treated uniformly.
1195 match ty::get(base_ty).sty {
1196 ty::ty_struct(did, _) => {
1197 let r = ty::lookup_struct_fields(tcx, did);
1198 for fld in r.iter() {
1199 if fld.name == f_name.name {
1200 return Some(ast::MutImmutable);
1204 ty::ty_enum(..) => {
1205 let def_map = tcx.def_map.borrow();
1206 match def_map.get().get_copy(&node_id) {
1207 ast::DefVariant(_, variant_id, _) => {
1208 let r = ty::lookup_struct_fields(tcx, variant_id);
1209 for fld in r.iter() {
1210 if fld.name == f_name.name {
1211 return Some(ast::MutImmutable);
1224 pub enum InteriorSafety {
1229 pub enum AliasableReason {
1233 AliasableStatic(InteriorSafety),
1234 AliasableStaticMut(InteriorSafety),
1238 pub fn guarantor(self) -> cmt {
1239 //! Returns `self` after stripping away any owned pointer derefs or
1240 //! interior content. The return value is basically the `cmt` which
1241 //! determines how long the value in `self` remains live.
1246 cat_copied_upvar(..) |
1249 cat_deref(_, _, UnsafePtr(..)) |
1250 cat_deref(_, _, GcPtr(..)) |
1251 cat_deref(_, _, BorrowedPtr(..)) |
1257 cat_interior(b, _) |
1258 cat_deref(b, _, OwnedPtr) => {
1264 pub fn freely_aliasable(&self, ctxt: &ty::ctxt) -> Option<AliasableReason> {
1266 * Returns `Some(_)` if this lvalue represents a freely aliasable
1270 // Maybe non-obvious: copied upvars can only be considered
1271 // non-aliasable in once closures, since any other kind can be
1272 // aliased and eventually recused.
1275 cat_deref(b, _, BorrowedPtr(ty::MutBorrow, _)) |
1276 cat_deref(b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1278 cat_deref(b, _, OwnedPtr) |
1279 cat_interior(b, _) |
1280 cat_discr(b, _) => {
1281 // Aliasability depends on base cmt
1282 b.freely_aliasable(ctxt)
1285 cat_copied_upvar(CopiedUpvar {onceness: ast::Once, ..}) |
1290 cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
1294 cat_copied_upvar(CopiedUpvar {onceness: ast::Many, ..}) => {
1295 Some(AliasableOther)
1298 cat_static_item(..) => {
1299 let int_safe = if ty::type_interior_is_unsafe(ctxt, self.ty) {
1305 if self.mutbl.is_mutable() {
1306 Some(AliasableStaticMut(int_safe))
1308 Some(AliasableStatic(int_safe))
1312 cat_deref(_, _, GcPtr) => {
1313 Some(AliasableManaged)
1316 cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) => {
1317 Some(AliasableBorrowed)
1323 impl Repr for cmt_ {
1324 fn repr(&self, tcx: &ty::ctxt) -> ~str {
1325 format!("\\{{} id:{} m:{:?} ty:{}\\}",
1333 impl Repr for categorization {
1334 fn repr(&self, tcx: &ty::ctxt) -> ~str {
1338 cat_copied_upvar(..) |
1342 format!("{:?}", *self)
1344 cat_deref(cmt, derefs, ptr) => {
1345 format!("{}-{}{}->",
1350 cat_interior(cmt, interior) => {
1355 cat_downcast(cmt) => {
1356 format!("{}->(enum)", cmt.cat.repr(tcx))
1358 cat_discr(cmt, _) => {
1365 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1369 BorrowedPtr(ty::ImmBorrow, _) => "&",
1370 BorrowedPtr(ty::MutBorrow, _) => "&mut",
1371 BorrowedPtr(ty::UniqueImmBorrow, _) => "&unique",
1376 impl Repr for InteriorKind {
1377 fn repr(&self, _tcx: &ty::ctxt) -> ~str {
1379 InteriorField(NamedField(fld)) => {
1380 token::get_name(fld).get().to_str()
1382 InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
1383 InteriorElement(_) => ~"[]",
1388 fn element_kind(t: ty::t) -> ElementKind {
1389 match ty::get(t).sty {
1390 ty::ty_vec(..) => VecElement,
1391 ty::ty_str(..) => StrElement,