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() classifies 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 dereference 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)]
68 use util::nodemap::{DefIdMap, NodeMap};
69 use util::ppaux::{ty_to_string, Repr};
71 use syntax::ast::{MutImmutable, MutMutable};
74 use syntax::codemap::Span;
75 use syntax::print::pprust;
76 use syntax::parse::token;
78 use std::cell::RefCell;
81 #[deriving(Clone, PartialEq)]
82 pub enum categorization {
83 cat_rvalue(ty::Region), // temporary val, argument is its scope
85 cat_copied_upvar(CopiedUpvar), // upvar copied into proc env
86 cat_upvar(ty::UpvarId, ty::UpvarBorrow), // by ref upvar from stack closure
87 cat_local(ast::NodeId), // local variable
88 cat_deref(cmt, uint, PointerKind), // deref of a ptr
89 cat_interior(cmt, InteriorKind), // something interior: field, tuple, etc
90 cat_downcast(cmt), // selects a particular enum variant (*1)
91 cat_discr(cmt, ast::NodeId), // match discriminant (see preserve())
93 // (*1) downcast is only required if the enum has more than one variant
96 #[deriving(Clone, PartialEq)]
97 pub struct CopiedUpvar {
98 pub upvar_id: ast::NodeId,
99 pub onceness: ast::Onceness,
100 pub capturing_proc: ast::NodeId,
103 // different kinds of pointers:
104 #[deriving(Clone, PartialEq, Eq, Hash)]
105 pub enum PointerKind {
108 BorrowedPtr(ty::BorrowKind, ty::Region),
109 Implicit(ty::BorrowKind, ty::Region), // Implicit deref of a borrowed ptr.
110 UnsafePtr(ast::Mutability)
113 // We use the term "interior" to mean "something reachable from the
114 // base without a pointer dereference", e.g. a field
115 #[deriving(Clone, PartialEq, Eq, Hash)]
116 pub enum InteriorKind {
117 InteriorField(FieldName),
118 InteriorElement(ElementKind),
121 #[deriving(Clone, PartialEq, Eq, Hash)]
123 NamedField(ast::Name),
124 PositionalField(uint)
127 #[deriving(Clone, PartialEq, Eq, Hash)]
128 pub enum ElementKind {
133 #[deriving(Clone, PartialEq, Eq, Hash, Show)]
134 pub enum MutabilityCategory {
135 McImmutable, // Immutable.
136 McDeclared, // Directly declared as mutable.
137 McInherited, // Inherited from the fact that owner is mutable.
140 // `cmt`: "Category, Mutability, and Type".
142 // a complete categorization of a value indicating where it originated
143 // and how it is located, as well as the mutability of the memory in
144 // which the value is stored.
146 // *WARNING* The field `cmt.type` is NOT necessarily the same as the
147 // result of `node_id_to_type(cmt.id)`. This is because the `id` is
148 // always the `id` of the node producing the type; in an expression
149 // like `*x`, the type of this deref node is the deref'd type (`T`),
150 // but in a pattern like `@x`, the `@x` pattern is again a
151 // dereference, but its type is the type *before* the dereference
152 // (`@T`). So use `cmt.ty` to find the type of the value in a consistent
153 // fashion. For more details, see the method `cat_pattern`
154 #[deriving(Clone, PartialEq)]
156 pub id: ast::NodeId, // id of expr/pat producing this value
157 pub span: Span, // span of same expr/pat
158 pub cat: categorization, // categorization of expr
159 pub mutbl: MutabilityCategory, // mutability of expr as lvalue
160 pub ty: ty::t // type of the expr (*see WARNING above*)
163 pub type cmt = Rc<cmt_>;
165 // We pun on *T to mean both actual deref of a ptr as well
166 // as accessing of components:
167 pub enum deref_kind {
168 deref_ptr(PointerKind),
169 deref_interior(InteriorKind),
172 // Categorizes a derefable type. Note that we include vectors and strings as
173 // derefable (we model an index as the combination of a deref and then a
174 // pointer adjustment).
175 pub fn opt_deref_kind(t: ty::t) -> Option<deref_kind> {
176 match ty::get(t).sty {
178 ty::ty_closure(box ty::ClosureTy {store: ty::UniqTraitStore, ..}) => {
179 Some(deref_ptr(OwnedPtr))
182 ty::ty_rptr(r, mt) => {
183 let kind = ty::BorrowKind::from_mutbl(mt.mutbl);
184 Some(deref_ptr(BorrowedPtr(kind, r)))
187 ty::ty_closure(box ty::ClosureTy {
188 store: ty::RegionTraitStore(r, _),
191 Some(deref_ptr(BorrowedPtr(ty::ImmBorrow, r)))
195 Some(deref_ptr(GcPtr))
198 ty::ty_ptr(ref mt) => {
199 Some(deref_ptr(UnsafePtr(mt.mutbl)))
203 ty::ty_struct(..) => { // newtype
204 Some(deref_interior(InteriorField(PositionalField(0))))
207 ty::ty_vec(_, _) | ty::ty_str => {
208 Some(deref_interior(InteriorElement(element_kind(t))))
215 pub fn deref_kind(tcx: &ty::ctxt, t: ty::t) -> deref_kind {
216 debug!("deref_kind {}", ty_to_string(tcx, t));
217 match opt_deref_kind(t) {
221 format!("deref_kind() invoked on non-derefable type {}",
222 ty_to_string(tcx, t)).as_slice());
228 fn id(&self) -> ast::NodeId;
229 fn span(&self) -> Span;
232 impl ast_node for ast::Expr {
233 fn id(&self) -> ast::NodeId { self.id }
234 fn span(&self) -> Span { self.span }
237 impl ast_node for ast::Pat {
238 fn id(&self) -> ast::NodeId { self.id }
239 fn span(&self) -> Span { self.span }
242 pub struct MemCategorizationContext<'t,TYPER:'t> {
246 pub type McResult<T> = Result<T, ()>;
249 * The `Typer` trait provides the interface for the mem-categorization
250 * module to the results of the type check. It can be used to query
251 * the type assigned to an expression node, to inquire after adjustments,
254 * This interface is needed because mem-categorization is used from
255 * two places: `regionck` and `borrowck`. `regionck` executes before
256 * type inference is complete, and hence derives types and so on from
257 * intermediate tables. This also implies that type errors can occur,
258 * and hence `node_ty()` and friends return a `Result` type -- any
259 * error will propagate back up through the mem-categorization
262 * In the borrow checker, in contrast, type checking is complete and we
263 * know that no errors have occurred, so we simply consult the tcx and we
264 * can be sure that only `Ok` results will occur.
266 pub trait Typer<'tcx> {
267 fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx>;
268 fn node_ty(&self, id: ast::NodeId) -> McResult<ty::t>;
269 fn node_method_ty(&self, method_call: typeck::MethodCall) -> Option<ty::t>;
270 fn adjustments<'a>(&'a self) -> &'a RefCell<NodeMap<ty::AutoAdjustment>>;
271 fn is_method_call(&self, id: ast::NodeId) -> bool;
272 fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<ast::NodeId>;
273 fn upvar_borrow(&self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow;
274 fn capture_mode(&self, closure_expr_id: ast::NodeId)
275 -> ast::CaptureClause;
276 fn unboxed_closures<'a>(&'a self)
277 -> &'a RefCell<DefIdMap<ty::UnboxedClosure>>;
280 impl MutabilityCategory {
281 pub fn from_mutbl(m: ast::Mutability) -> MutabilityCategory {
283 MutImmutable => McImmutable,
284 MutMutable => McDeclared
288 pub fn from_borrow_kind(borrow_kind: ty::BorrowKind) -> MutabilityCategory {
290 ty::ImmBorrow => McImmutable,
291 ty::UniqueImmBorrow => McImmutable,
292 ty::MutBorrow => McDeclared,
296 pub fn from_pointer_kind(base_mutbl: MutabilityCategory,
297 ptr: PointerKind) -> MutabilityCategory {
302 BorrowedPtr(borrow_kind, _) | Implicit(borrow_kind, _) => {
303 MutabilityCategory::from_borrow_kind(borrow_kind)
309 MutabilityCategory::from_mutbl(m)
314 fn from_local(tcx: &ty::ctxt, id: ast::NodeId) -> MutabilityCategory {
315 match tcx.map.get(id) {
316 ast_map::NodeLocal(p) | ast_map::NodeArg(p) => match p.node {
317 ast::PatIdent(bind_mode, _, _) => {
318 if bind_mode == ast::BindByValue(ast::MutMutable) {
324 _ => tcx.sess.span_bug(p.span, "expected identifier pattern")
326 _ => tcx.sess.span_bug(tcx.map.span(id), "expected identifier pattern")
330 pub fn inherit(&self) -> MutabilityCategory {
332 McImmutable => McImmutable,
333 McDeclared => McInherited,
334 McInherited => McInherited,
338 pub fn is_mutable(&self) -> bool {
340 McImmutable => false,
346 pub fn is_immutable(&self) -> bool {
349 McDeclared | McInherited => false
353 pub fn to_user_str(&self) -> &'static str {
355 McDeclared | McInherited => "mutable",
356 McImmutable => "immutable",
365 Err(e) => { return Err(e); }
370 impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
371 pub fn new(typer: &'t TYPER) -> MemCategorizationContext<'t,TYPER> {
372 MemCategorizationContext { typer: typer }
375 fn tcx(&self) -> &'t ty::ctxt<'tcx> {
379 fn expr_ty(&self, expr: &ast::Expr) -> McResult<ty::t> {
380 self.typer.node_ty(expr.id)
383 fn expr_ty_adjusted(&self, expr: &ast::Expr) -> McResult<ty::t> {
384 let unadjusted_ty = if_ok!(self.expr_ty(expr));
385 Ok(ty::adjust_ty(self.tcx(), expr.span, expr.id, unadjusted_ty,
386 self.typer.adjustments().borrow().find(&expr.id),
387 |method_call| self.typer.node_method_ty(method_call)))
390 fn node_ty(&self, id: ast::NodeId) -> McResult<ty::t> {
391 self.typer.node_ty(id)
394 fn pat_ty(&self, pat: &ast::Pat) -> McResult<ty::t> {
395 self.typer.node_ty(pat.id)
398 pub fn cat_expr(&self, expr: &ast::Expr) -> McResult<cmt> {
399 match self.typer.adjustments().borrow().find(&expr.id) {
402 self.cat_expr_unadjusted(expr)
405 Some(adjustment) => {
407 ty::AdjustAddEnv(..) => {
408 debug!("cat_expr(AdjustAddEnv): {}",
409 expr.repr(self.tcx()));
410 // Convert a bare fn to a closure by adding NULL env.
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: Some(_), ..}) => {
419 debug!("cat_expr(AdjustDerefRef): {}",
420 expr.repr(self.tcx()));
421 // Equivalent to &*expr or something similar.
422 // Result is an rvalue.
423 let expr_ty = if_ok!(self.expr_ty_adjusted(expr));
424 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
429 autoref: None, autoderefs: autoderefs}) => {
430 // Equivalent to *expr or something similar.
431 self.cat_expr_autoderefd(expr, autoderefs)
438 pub fn cat_expr_autoderefd(&self,
442 let mut cmt = if_ok!(self.cat_expr_unadjusted(expr));
443 debug!("cat_expr_autoderefd: autoderefs={}, cmt={}",
445 cmt.repr(self.tcx()));
446 for deref in range(1u, autoderefs + 1) {
447 cmt = self.cat_deref(expr, cmt, deref, false);
452 pub fn cat_expr_unadjusted(&self, expr: &ast::Expr) -> McResult<cmt> {
453 debug!("cat_expr: id={} expr={}", expr.id, expr.repr(self.tcx()));
455 let expr_ty = if_ok!(self.expr_ty(expr));
457 ast::ExprUnary(ast::UnDeref, ref e_base) => {
458 let base_cmt = if_ok!(self.cat_expr(&**e_base));
459 Ok(self.cat_deref(expr, base_cmt, 0, false))
462 ast::ExprField(ref base, f_name, _) => {
463 let base_cmt = if_ok!(self.cat_expr(&**base));
464 debug!("cat_expr(cat_field): id={} expr={} base={}",
466 expr.repr(self.tcx()),
467 base_cmt.repr(self.tcx()));
468 Ok(self.cat_field(expr, base_cmt, f_name.node, expr_ty))
471 ast::ExprTupField(ref base, idx, _) => {
472 let base_cmt = if_ok!(self.cat_expr(&**base));
473 Ok(self.cat_tup_field(expr, base_cmt, idx.node, expr_ty))
476 ast::ExprIndex(ref base, _) => {
477 let method_call = typeck::MethodCall::expr(expr.id());
478 match self.typer.node_method_ty(method_call) {
480 // If this is an index implemented by a method call, then it will
481 // include an implicit deref of the result.
482 let ret_ty = ty::ty_fn_ret(method_ty);
483 Ok(self.cat_deref(expr,
484 self.cat_rvalue_node(expr.id(),
489 let base_cmt = if_ok!(self.cat_expr(&**base));
490 Ok(self.cat_index(expr, base_cmt))
495 ast::ExprPath(_) => {
496 let def = *self.tcx().def_map.borrow().get(&expr.id);
497 self.cat_def(expr.id, expr.span, expr_ty, def)
500 ast::ExprParen(ref e) => {
504 ast::ExprAddrOf(..) | ast::ExprCall(..) |
505 ast::ExprAssign(..) | ast::ExprAssignOp(..) |
506 ast::ExprFnBlock(..) | ast::ExprProc(..) |
507 ast::ExprUnboxedFn(..) | ast::ExprRet(..) |
508 ast::ExprUnary(..) | ast::ExprSlice(..) |
509 ast::ExprMethodCall(..) | ast::ExprCast(..) |
510 ast::ExprVec(..) | ast::ExprTup(..) | ast::ExprIf(..) |
511 ast::ExprBinary(..) | ast::ExprWhile(..) |
512 ast::ExprBlock(..) | ast::ExprLoop(..) | ast::ExprMatch(..) |
513 ast::ExprLit(..) | ast::ExprBreak(..) | ast::ExprMac(..) |
514 ast::ExprAgain(..) | ast::ExprStruct(..) | ast::ExprRepeat(..) |
515 ast::ExprInlineAsm(..) | ast::ExprBox(..) |
516 ast::ExprForLoop(..) => {
517 Ok(self.cat_rvalue_node(expr.id(), expr.span(), expr_ty))
520 ast::ExprIfLet(..) => {
521 self.tcx().sess.span_bug(expr.span, "non-desugared ExprIfLet");
526 pub fn cat_def(&self,
532 debug!("cat_def: id={} expr={} def={:?}",
533 id, expr_ty.repr(self.tcx()), def);
536 def::DefStruct(..) | def::DefVariant(..) | def::DefFn(..) |
537 def::DefStaticMethod(..) => {
538 Ok(self.cat_rvalue_node(id, span, expr_ty))
540 def::DefMod(_) | def::DefForeignMod(_) | def::DefUse(_) |
541 def::DefTrait(_) | def::DefTy(..) | def::DefPrimTy(_) |
542 def::DefTyParam(..) | def::DefTyParamBinder(..) | def::DefRegion(_) |
543 def::DefLabel(_) | def::DefSelfTy(..) | def::DefMethod(..) |
544 def::DefAssociatedTy(..) => {
554 def::DefStatic(_, mutbl) => {
559 mutbl: if mutbl { McDeclared } else { McImmutable},
564 def::DefUpvar(var_id, fn_node_id, _) => {
565 let ty = if_ok!(self.node_ty(fn_node_id));
566 match ty::get(ty).sty {
567 ty::ty_closure(ref closure_ty) => {
568 // Decide whether to use implicit reference or by copy/move
569 // capture for the upvar. This, combined with the onceness,
570 // determines whether the closure can move out of it.
571 let var_is_refd = match (closure_ty.store, closure_ty.onceness) {
572 // Many-shot stack closures can never move out.
573 (ty::RegionTraitStore(..), ast::Many) => true,
574 // 1-shot stack closures can move out.
575 (ty::RegionTraitStore(..), ast::Once) => false,
576 // Heap closures always capture by copy/move, and can
577 // move out if they are once.
578 (ty::UniqTraitStore, _) => false,
582 self.cat_upvar(id, span, var_id, fn_node_id)
587 cat:cat_copied_upvar(CopiedUpvar {
589 onceness: closure_ty.onceness,
590 capturing_proc: fn_node_id,
592 mutbl: MutabilityCategory::from_local(self.tcx(), var_id),
597 ty::ty_unboxed_closure(closure_id, _) => {
598 let unboxed_closures = self.typer
601 let kind = unboxed_closures.get(&closure_id).kind;
602 let onceness = match kind {
603 ty::FnUnboxedClosureKind |
604 ty::FnMutUnboxedClosureKind => ast::Many,
605 ty::FnOnceUnboxedClosureKind => ast::Once,
610 cat: cat_copied_upvar(CopiedUpvar {
613 capturing_proc: fn_node_id,
615 mutbl: MutabilityCategory::from_local(self.tcx(), var_id),
620 self.tcx().sess.span_bug(
622 format!("Upvar of non-closure {} - {}",
624 ty.repr(self.tcx())).as_slice());
629 def::DefLocal(vid) => {
634 mutbl: MutabilityCategory::from_local(self.tcx(), vid),
645 fn_node_id: ast::NodeId)
648 * Upvars through a closure are in fact indirect
649 * references. That is, when a closure refers to a
650 * variable from a parent stack frame like `x = 10`,
651 * that is equivalent to `*x_ = 10` where `x_` is a
652 * borrowed pointer (`&mut x`) created when the closure
653 * was created and store in the environment. This
654 * equivalence is expose in the mem-categorization.
657 let upvar_id = ty::UpvarId { var_id: var_id,
658 closure_expr_id: fn_node_id };
660 let upvar_borrow = self.typer.upvar_borrow(upvar_id);
662 let var_ty = if_ok!(self.node_ty(var_id));
664 // We can't actually represent the types of all upvars
665 // as user-describable types, since upvars support const
666 // and unique-imm borrows! Therefore, we cheat, and just
667 // give err type. Nobody should be inspecting this type anyhow.
668 let upvar_ty = ty::mk_err();
670 let base_cmt = Rc::new(cmt_ {
673 cat:cat_upvar(upvar_id, upvar_borrow),
678 let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
680 let deref_cmt = Rc::new(cmt_ {
683 cat:cat_deref(base_cmt, 0, ptr),
684 mutbl:MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
691 pub fn cat_rvalue_node(&self,
696 match self.typer.temporary_scope(id) {
698 match ty::get(expr_ty).sty {
699 ty::ty_vec(_, Some(0)) => self.cat_rvalue(id, span, ty::ReStatic, expr_ty),
700 _ => self.cat_rvalue(id, span, ty::ReScope(scope), expr_ty)
704 self.cat_rvalue(id, span, ty::ReStatic, expr_ty)
709 pub fn cat_rvalue(&self,
712 temp_scope: ty::Region,
713 expr_ty: ty::t) -> cmt {
717 cat:cat_rvalue(temp_scope),
723 pub fn cat_field<N:ast_node>(&self,
732 mutbl: base_cmt.mutbl.inherit(),
733 cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
738 pub fn cat_tup_field<N:ast_node>(&self,
747 mutbl: base_cmt.mutbl.inherit(),
748 cat: cat_interior(base_cmt, InteriorField(PositionalField(f_idx))),
753 fn cat_deref<N:ast_node>(&self,
759 let adjustment = match self.typer.adjustments().borrow().find(&node.id()) {
760 Some(adj) if ty::adjust_is_object(adj) => typeck::AutoObject,
761 _ if deref_cnt != 0 => typeck::AutoDeref(deref_cnt),
762 _ => typeck::NoAdjustment
765 let method_call = typeck::MethodCall {
767 adjustment: adjustment
769 let method_ty = self.typer.node_method_ty(method_call);
771 debug!("cat_deref: method_call={:?} method_ty={}",
772 method_call, method_ty.map(|ty| ty.repr(self.tcx())));
774 let base_cmt = match method_ty {
776 let ref_ty = ty::ty_fn_ret(method_ty);
777 self.cat_rvalue_node(node.id(), node.span(), ref_ty)
781 match ty::deref(base_cmt.ty, true) {
782 Some(mt) => self.cat_deref_common(node, base_cmt, deref_cnt, mt.ty, implicit),
784 self.tcx().sess.span_bug(
786 format!("Explicit deref of non-derefable type: {}",
787 base_cmt.ty.repr(self.tcx())).as_slice());
792 fn cat_deref_common<N:ast_node>(&self,
799 let (m, cat) = match deref_kind(self.tcx(), base_cmt.ty) {
801 let ptr = if implicit {
803 BorrowedPtr(bk, r) => Implicit(bk, r),
804 _ => self.tcx().sess.span_bug(node.span(),
805 "Implicit deref of non-borrowed pointer")
810 // for unique ptrs, we inherit mutability from the
812 (MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr),
813 cat_deref(base_cmt, deref_cnt, ptr))
815 deref_interior(interior) => {
816 (base_cmt.mutbl.inherit(), cat_interior(base_cmt, interior))
828 pub fn cat_index<N:ast_node>(&self,
832 //! Creates a cmt for an indexing operation (`[]`).
834 //! One subtle aspect of indexing that may not be
835 //! immediately obvious: for anything other than a fixed-length
836 //! vector, an operation like `x[y]` actually consists of two
837 //! disjoint (from the point of view of borrowck) operations.
838 //! The first is a deref of `x` to create a pointer `p` that points
839 //! at the first element in the array. The second operation is
840 //! an index which adds `y*sizeof(T)` to `p` to obtain the
841 //! pointer to `x[y]`. `cat_index` will produce a resulting
842 //! cmt containing both this deref and the indexing,
843 //! presuming that `base_cmt` is not of fixed-length type.
846 //! - `elt`: the AST node being indexed
847 //! - `base_cmt`: the cmt of `elt`
849 let method_call = typeck::MethodCall::expr(elt.id());
850 let method_ty = self.typer.node_method_ty(method_call);
852 let element_ty = match method_ty {
854 let ref_ty = ty::ty_fn_ret(method_ty);
855 base_cmt = self.cat_rvalue_node(elt.id(), elt.span(), ref_ty);
856 *ty::ty_fn_args(method_ty).get(0)
859 match ty::array_element_ty(base_cmt.ty) {
862 self.tcx().sess.span_bug(
864 format!("Explicit index of non-index type `{}`",
865 base_cmt.ty.repr(self.tcx())).as_slice());
871 let m = base_cmt.mutbl.inherit();
872 return interior(elt, base_cmt.clone(), base_cmt.ty, m, element_ty);
874 fn interior<N: ast_node>(elt: &N,
877 mutbl: MutabilityCategory,
878 element_ty: ty::t) -> cmt
883 cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
890 // Takes either a vec or a reference to a vec and returns the cmt for the
892 fn deref_vec<N:ast_node>(&self,
896 match deref_kind(self.tcx(), base_cmt.ty) {
898 // for unique ptrs, we inherit mutability from the
900 let m = MutabilityCategory::from_pointer_kind(base_cmt.mutbl, ptr);
902 // the deref is explicit in the resulting cmt
906 cat:cat_deref(base_cmt.clone(), 0, ptr),
908 ty: match ty::deref(base_cmt.ty, false) {
910 None => self.tcx().sess.bug("Found non-derefable type")
915 deref_interior(_) => {
921 pub fn cat_slice_pattern(&self,
923 slice_pat: &ast::Pat)
924 -> McResult<(cmt, ast::Mutability, ty::Region)> {
926 * Given a pattern P like: `[_, ..Q, _]`, where `vec_cmt` is
927 * the cmt for `P`, `slice_pat` is the pattern `Q`, returns:
929 * - the mutability and region of the slice `Q`
931 * These last two bits of info happen to be things that
935 let slice_ty = if_ok!(self.node_ty(slice_pat.id));
936 let (slice_mutbl, slice_r) = vec_slice_info(self.tcx(),
939 let cmt_slice = self.cat_index(slice_pat, self.deref_vec(slice_pat, vec_cmt));
940 return Ok((cmt_slice, slice_mutbl, slice_r));
942 fn vec_slice_info(tcx: &ty::ctxt,
945 -> (ast::Mutability, ty::Region) {
947 * In a pattern like [a, b, ..c], normally `c` has slice type,
948 * but if you have [a, b, ..ref c], then the type of `ref c`
949 * will be `&&[]`, so to extract the slice details we have
950 * to recurse through rptrs.
953 match ty::get(slice_ty).sty {
954 ty::ty_rptr(r, ref mt) => match ty::get(mt.ty).sty {
955 ty::ty_vec(_, None) => (mt.mutbl, r),
956 _ => vec_slice_info(tcx, pat, mt.ty),
960 tcx.sess.span_bug(pat.span,
961 "type of slice pattern is not a slice");
967 pub fn cat_imm_interior<N:ast_node>(&self,
971 interior: InteriorKind)
976 mutbl: base_cmt.mutbl.inherit(),
977 cat: cat_interior(base_cmt, interior),
982 pub fn cat_downcast<N:ast_node>(&self,
990 mutbl: base_cmt.mutbl.inherit(),
991 cat: cat_downcast(base_cmt),
996 pub fn cat_pattern(&self,
999 op: |&MemCategorizationContext<TYPER>,
1003 // Here, `cmt` is the categorization for the value being
1004 // matched and pat is the pattern it is being matched against.
1006 // In general, the way that this works is that we walk down
1007 // the pattern, constructing a cmt that represents the path
1008 // that will be taken to reach the value being matched.
1010 // When we encounter named bindings, we take the cmt that has
1011 // been built up and pass it off to guarantee_valid() so that
1012 // we can be sure that the binding will remain valid for the
1013 // duration of the arm.
1015 // (*2) There is subtlety concerning the correspondence between
1016 // pattern ids and types as compared to *expression* ids and
1017 // types. This is explained briefly. on the definition of the
1018 // type `cmt`, so go off and read what it says there, then
1019 // come back and I'll dive into a bit more detail here. :) OK,
1022 // In general, the id of the cmt should be the node that
1023 // "produces" the value---patterns aren't executable code
1024 // exactly, but I consider them to "execute" when they match a
1025 // value, and I consider them to produce the value that was
1026 // matched. So if you have something like:
1033 // In this case, the cmt and the relevant ids would be:
1035 // CMT Id Type of Id Type of cmt
1038 // ^~~~~~~^ `x` from discr @@int @@int
1039 // ^~~~~~~~~~^ `@@y` pattern node @@int @int
1040 // ^~~~~~~~~~~~~^ `@y` pattern node @int int
1042 // You can see that the types of the id and the cmt are in
1043 // sync in the first line, because that id is actually the id
1044 // of an expression. But once we get to pattern ids, the types
1045 // step out of sync again. So you'll see below that we always
1046 // get the type of the *subpattern* and use that.
1048 debug!("cat_pattern: id={} pat={} cmt={}",
1049 pat.id, pprust::pat_to_string(pat),
1050 cmt.repr(self.tcx()));
1052 op(self, cmt.clone(), pat);
1055 ast::PatWild(_) => {
1059 ast::PatEnum(_, None) => {
1062 ast::PatEnum(_, Some(ref subpats)) => {
1063 match self.tcx().def_map.borrow().find(&pat.id) {
1064 Some(&def::DefVariant(enum_did, _, _)) => {
1067 let downcast_cmt = {
1068 if ty::enum_is_univariant(self.tcx(), enum_did) {
1069 cmt // univariant, no downcast needed
1071 self.cat_downcast(pat, cmt.clone(), cmt.ty)
1075 for (i, subpat) in subpats.iter().enumerate() {
1076 let subpat_ty = if_ok!(self.pat_ty(&**subpat)); // see (*2)
1079 self.cat_imm_interior(
1080 pat, downcast_cmt.clone(), subpat_ty,
1081 InteriorField(PositionalField(i)));
1083 if_ok!(self.cat_pattern(subcmt, &**subpat, |x,y,z| op(x,y,z)));
1086 Some(&def::DefFn(..)) |
1087 Some(&def::DefStruct(..)) => {
1088 for (i, subpat) in subpats.iter().enumerate() {
1089 let subpat_ty = if_ok!(self.pat_ty(&**subpat)); // see (*2)
1091 self.cat_imm_interior(
1092 pat, cmt.clone(), subpat_ty,
1093 InteriorField(PositionalField(i)));
1094 if_ok!(self.cat_pattern(cmt_field, &**subpat,
1095 |x,y,z| op(x,y,z)));
1098 Some(&def::DefStatic(..)) => {
1099 for subpat in subpats.iter() {
1100 if_ok!(self.cat_pattern(cmt.clone(), &**subpat, |x,y,z| op(x,y,z)));
1104 self.tcx().sess.span_bug(
1106 "enum pattern didn't resolve to enum or struct");
1111 ast::PatIdent(_, _, Some(ref subpat)) => {
1112 if_ok!(self.cat_pattern(cmt, &**subpat, op));
1115 ast::PatIdent(_, _, None) => {
1116 // nullary variant or identifier: ignore
1119 ast::PatStruct(_, ref field_pats, _) => {
1120 // {f1: p1, ..., fN: pN}
1121 for fp in field_pats.iter() {
1122 let field_ty = if_ok!(self.pat_ty(&*fp.pat)); // see (*2)
1123 let cmt_field = self.cat_field(pat, cmt.clone(), fp.ident, field_ty);
1124 if_ok!(self.cat_pattern(cmt_field, &*fp.pat, |x,y,z| op(x,y,z)));
1128 ast::PatTup(ref subpats) => {
1130 for (i, subpat) in subpats.iter().enumerate() {
1131 let subpat_ty = if_ok!(self.pat_ty(&**subpat)); // see (*2)
1133 self.cat_imm_interior(
1134 pat, cmt.clone(), subpat_ty,
1135 InteriorField(PositionalField(i)));
1136 if_ok!(self.cat_pattern(subcmt, &**subpat, |x,y,z| op(x,y,z)));
1140 ast::PatBox(ref subpat) | ast::PatRegion(ref subpat) => {
1142 let subcmt = self.cat_deref(pat, cmt, 0, false);
1143 if_ok!(self.cat_pattern(subcmt, &**subpat, op));
1146 ast::PatVec(ref before, ref slice, ref after) => {
1147 let elt_cmt = self.cat_index(pat, self.deref_vec(pat, cmt));
1148 for before_pat in before.iter() {
1149 if_ok!(self.cat_pattern(elt_cmt.clone(), &**before_pat,
1150 |x,y,z| op(x,y,z)));
1152 for slice_pat in slice.iter() {
1153 let slice_ty = if_ok!(self.pat_ty(&**slice_pat));
1154 let slice_cmt = self.cat_rvalue_node(pat.id(), pat.span(), slice_ty);
1155 if_ok!(self.cat_pattern(slice_cmt, &**slice_pat, |x,y,z| op(x,y,z)));
1157 for after_pat in after.iter() {
1158 if_ok!(self.cat_pattern(elt_cmt.clone(), &**after_pat, |x,y,z| op(x,y,z)));
1162 ast::PatLit(_) | ast::PatRange(_, _) => {
1167 self.tcx().sess.span_bug(pat.span, "unexpanded macro");
1174 pub fn cmt_to_string(&self, cmt: &cmt_) -> String {
1176 cat_static_item => {
1177 "static item".to_string()
1179 cat_copied_upvar(_) => {
1180 "captured outer variable in a proc".to_string()
1183 "non-lvalue".to_string()
1186 match self.tcx().map.find(vid) {
1187 Some(ast_map::NodeArg(_)) => {
1188 "argument".to_string()
1190 _ => "local variable".to_string()
1193 cat_deref(ref base, _, pk) => {
1196 "captured outer variable".to_string()
1201 "dereference (dereference is implicit, due to indexing)".to_string()
1203 OwnedPtr | GcPtr => format!("dereference of `{}`", ptr_sigil(pk)),
1204 _ => format!("dereference of `{}`-pointer", ptr_sigil(pk))
1209 cat_interior(_, InteriorField(NamedField(_))) => {
1212 cat_interior(_, InteriorField(PositionalField(_))) => {
1213 "anonymous field".to_string()
1215 cat_interior(_, InteriorElement(VecElement)) => {
1216 "vec content".to_string()
1218 cat_interior(_, InteriorElement(OtherElement)) => {
1219 "indexed content".to_string()
1222 "captured outer variable".to_string()
1224 cat_discr(ref cmt, _) => {
1225 self.cmt_to_string(&**cmt)
1227 cat_downcast(ref cmt) => {
1228 self.cmt_to_string(&**cmt)
1234 pub enum InteriorSafety {
1239 pub enum AliasableReason {
1243 AliasableStatic(InteriorSafety),
1244 AliasableStaticMut(InteriorSafety),
1248 pub fn guarantor(&self) -> cmt {
1249 //! Returns `self` after stripping away any owned pointer derefs or
1250 //! interior content. The return value is basically the `cmt` which
1251 //! determines how long the value in `self` remains live.
1256 cat_copied_upvar(..) |
1258 cat_deref(_, _, UnsafePtr(..)) |
1259 cat_deref(_, _, GcPtr(..)) |
1260 cat_deref(_, _, BorrowedPtr(..)) |
1261 cat_deref(_, _, Implicit(..)) |
1263 Rc::new((*self).clone())
1265 cat_downcast(ref b) |
1266 cat_discr(ref b, _) |
1267 cat_interior(ref b, _) |
1268 cat_deref(ref b, _, OwnedPtr) => {
1274 pub fn freely_aliasable(&self, ctxt: &ty::ctxt) -> Option<AliasableReason> {
1276 * Returns `Some(_)` if this lvalue represents a freely aliasable
1280 // Maybe non-obvious: copied upvars can only be considered
1281 // non-aliasable in once closures, since any other kind can be
1282 // aliased and eventually recused.
1285 cat_deref(ref b, _, BorrowedPtr(ty::MutBorrow, _)) |
1286 cat_deref(ref b, _, Implicit(ty::MutBorrow, _)) |
1287 cat_deref(ref b, _, BorrowedPtr(ty::UniqueImmBorrow, _)) |
1288 cat_deref(ref b, _, Implicit(ty::UniqueImmBorrow, _)) |
1289 cat_downcast(ref b) |
1290 cat_deref(ref b, _, OwnedPtr) |
1291 cat_interior(ref b, _) |
1292 cat_discr(ref b, _) => {
1293 // Aliasability depends on base cmt
1294 b.freely_aliasable(ctxt)
1297 cat_copied_upvar(CopiedUpvar {onceness: ast::Once, ..}) |
1301 cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
1305 cat_copied_upvar(CopiedUpvar {onceness: ast::Many, ..}) => {
1306 Some(AliasableOther)
1309 cat_static_item(..) => {
1310 let int_safe = if ty::type_interior_is_unsafe(ctxt, self.ty) {
1316 if self.mutbl.is_mutable() {
1317 Some(AliasableStaticMut(int_safe))
1319 Some(AliasableStatic(int_safe))
1323 cat_deref(_, _, GcPtr) => {
1324 Some(AliasableManaged)
1327 cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) |
1328 cat_deref(_, _, Implicit(ty::ImmBorrow, _)) => {
1329 Some(AliasableBorrowed)
1335 impl Repr for cmt_ {
1336 fn repr(&self, tcx: &ty::ctxt) -> String {
1337 format!("{{{} id:{} m:{:?} ty:{}}}",
1345 impl Repr for categorization {
1346 fn repr(&self, tcx: &ty::ctxt) -> String {
1350 cat_copied_upvar(..) |
1353 format!("{:?}", *self)
1355 cat_deref(ref cmt, derefs, ptr) => {
1356 format!("{}-{}{}->", cmt.cat.repr(tcx), ptr_sigil(ptr), derefs)
1358 cat_interior(ref cmt, interior) => {
1359 format!("{}.{}", cmt.cat.repr(tcx), interior.repr(tcx))
1361 cat_downcast(ref cmt) => {
1362 format!("{}->(enum)", cmt.cat.repr(tcx))
1364 cat_discr(ref cmt, _) => {
1371 pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
1375 BorrowedPtr(ty::ImmBorrow, _) |
1376 Implicit(ty::ImmBorrow, _) => "&",
1377 BorrowedPtr(ty::MutBorrow, _) |
1378 Implicit(ty::MutBorrow, _) => "&mut",
1379 BorrowedPtr(ty::UniqueImmBorrow, _) |
1380 Implicit(ty::UniqueImmBorrow, _) => "&unique",
1385 impl Repr for InteriorKind {
1386 fn repr(&self, _tcx: &ty::ctxt) -> String {
1388 InteriorField(NamedField(fld)) => {
1389 token::get_name(fld).get().to_string()
1391 InteriorField(PositionalField(i)) => format!("#{:?}", i),
1392 InteriorElement(_) => "[]".to_string(),
1397 fn element_kind(t: ty::t) -> ElementKind {
1398 match ty::get(t).sty {
1399 ty::ty_rptr(_, ty::mt{ty:ty, ..}) |
1400 ty::ty_uniq(ty) => match ty::get(ty).sty {
1401 ty::ty_vec(_, None) => VecElement,
1404 ty::ty_vec(..) => VecElement,