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Fix soundness bug in treatment of closure upvars by regionck

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- Unify the representations of `cat_upvar` and `cat_copied_upvar`
- In `link_reborrowed_region`, account for the ability of upvars to
  change their mutability due to later processing.  A map of recursive
  region links we may want to establish in the future is maintained,
  with the links being established when the kind of the borrow is
  adjusted.
- When categorizing upvars, add an explicit deref that represents the
  closure environment pointer for closures that do not take the
  environment by value.  The region for the implicit pointer is an
  anonymous free region type introduced for this purpose.  This
  creates the necessary constraint to prevent unsound reborrows from
  the environment.
- Add a note to categorizations to make it easier to tell when extra
  dereferences have been inserted by an upvar without having to
  perform deep pattern matching.
- Adjust borrowck to deal with the changes.  Where `cat_upvar` and
  `cat_copied_upvar` were previously treated differently, they are
  now both treated roughly like local variables within the closure
  body, as the explicit derefs now ensure proper behavior.  However,
  error diagnostics had to be changed to explicitly look through the
  extra dereferences to avoid producing confusing messages about
  references not present in the source code.

Closes issue #17403.  Remaining work:

- The error diagnostics that result from failed region inference are
  pretty inscrutible and should be improved.

Code like the following is now rejected:

    let mut x = 0u;
    let f = || &mut x;
    let y = f();
    let z = f(); // multiple mutable references to the same location

This also breaks code that uses a similar construction even if it does
not go on to violate aliasability semantics.  Such code will need to
be reworked in some way, such as by using a capture-by-value closure
type.

[breaking-change]
This commit is contained in:
Brian Koropoff 2014-10-07 20:04:45 -07:00
parent 1868a262f3
commit 9094aabb12
15 changed files with 443 additions and 266 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
src/librustc/metadata/tydecode.rs
View File

@ -277,6 +277,7 @@ fn parse_bound_region(st: &mut PState, conv: conv_did) -> ty::BoundRegion {
assert_eq!(next(st), '|');
ty::BrFresh(id)
}
'e' => ty::BrEnv,
_ => fail!("parse_bound_region: bad input")
}
}

3
src/librustc/metadata/tyencode.rs
View File

@ -175,6 +175,9 @@ fn enc_bound_region(w: &mut SeekableMemWriter, cx: &ctxt, br: ty::BoundRegion) {
ty::BrFresh(id) => {
mywrite!(w, "f{}|", id);
}
ty::BrEnv => {
mywrite!(w, "e|");
}
}
}

3
src/librustc/middle/astencode.rs
View File

@ -516,7 +516,8 @@ impl tr for ty::BoundRegion {
fn tr(&self, dcx: &DecodeContext) -> ty::BoundRegion {
match *self {
ty::BrAnon(_) |
ty::BrFresh(_) => *self,
ty::BrFresh(_) |
ty::BrEnv => *self,
ty::BrNamed(id, ident) => ty::BrNamed(dcx.tr_def_id(id),
ident),
}

25
src/librustc/middle/borrowck/check_loans.rs
View File

@ -775,7 +775,17 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
}
// Otherwise, just a plain error.
match opt_loan_path(&assignee_cmt) {
match assignee_cmt.note {
mc::NoteClosureEnv(upvar_id) => {
self.bccx.span_err(
assignment_span,
format!("cannot assign to {}",
self.bccx.cmt_to_string(&*assignee_cmt)).as_slice());
self.bccx.span_note(
self.tcx().map.span(upvar_id.closure_expr_id),
"consider changing this closure to take self by mutable reference");
}
_ => match opt_loan_path(&assignee_cmt) {
Some(lp) => {
self.bccx.span_err(
assignment_span,
@ -792,6 +802,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
self.bccx.cmt_to_string(&*assignee_cmt)).as_slice());
}
}
}
return;
fn mark_variable_as_used_mut(this: &CheckLoanCtxt,
@ -805,16 +816,12 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
loop {
debug!("mark_variable_as_used_mut(cmt={})", cmt.repr(this.tcx()));
match cmt.cat.clone() {
mc::cat_copied_upvar(mc::CopiedUpvar { upvar_id: id, .. }) |
mc::cat_upvar(mc::Upvar { id: ty::UpvarId { var_id: id, .. }, .. }) |
mc::cat_local(id) => {
this.tcx().used_mut_nodes.borrow_mut().insert(id);
return;
}
mc::cat_upvar(..) => {
return;
}
mc::cat_rvalue(..) |
mc::cat_static_item |
mc::cat_deref(_, _, mc::UnsafePtr(..)) |
@ -854,12 +861,6 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
check_for_aliasability_violation(this, span, b.clone());
}
mc::cat_copied_upvar(mc::CopiedUpvar {
kind: mc::Unboxed(ty::FnUnboxedClosureKind), ..}) => {
// Prohibit writes to capture-by-move upvars in non-once closures
check_for_aliasability_violation(this, span, guarantor.clone());
}
_ => {}
}

12
src/librustc/middle/borrowck/gather_loans/gather_moves.rs
View File

@ -133,19 +133,13 @@ fn check_and_get_illegal_move_origin(bccx: &BorrowckCtxt,
mc::cat_deref(_, _, mc::BorrowedPtr(..)) |
mc::cat_deref(_, _, mc::Implicit(..)) |
mc::cat_deref(_, _, mc::UnsafePtr(..)) |
mc::cat_upvar(..) | mc::cat_static_item => {
mc::cat_static_item => {
Some(cmt.clone())
}
mc::cat_copied_upvar(mc::CopiedUpvar { kind: kind, .. }) => {
match kind.onceness() {
ast::Once => None,
ast::Many => Some(cmt.clone())
}
}
mc::cat_rvalue(..) |
mc::cat_local(..) => {
mc::cat_local(..) |
mc::cat_upvar(..) => {
None
}

4
src/librustc/middle/borrowck/gather_loans/lifetime.rs
View File

@ -67,7 +67,6 @@ impl<'a, 'tcx> GuaranteeLifetimeContext<'a, 'tcx> {
match cmt.cat {
mc::cat_rvalue(..) |
mc::cat_copied_upvar(..) | // L-Local
mc::cat_local(..) | // L-Local
mc::cat_upvar(..) |
mc::cat_deref(_, _, mc::BorrowedPtr(..)) | // L-Deref-Borrowed
@ -165,8 +164,7 @@ impl<'a, 'tcx> GuaranteeLifetimeContext<'a, 'tcx> {
mc::cat_rvalue(temp_scope) => {
temp_scope
}
mc::cat_upvar(..) |
mc::cat_copied_upvar(_) => {
mc::cat_upvar(..) => {
ty::ReScope(self.item_scope_id)
}
mc::cat_static_item => {

10
src/librustc/middle/borrowck/gather_loans/move_error.rs
View File

@ -115,15 +115,7 @@ fn report_cannot_move_out_of(bccx: &BorrowckCtxt, move_from: mc::cmt) {
mc::cat_deref(_, _, mc::BorrowedPtr(..)) |
mc::cat_deref(_, _, mc::Implicit(..)) |
mc::cat_deref(_, _, mc::UnsafePtr(..)) |
mc::cat_upvar(..) | mc::cat_static_item => {
bccx.span_err(
move_from.span,
format!("cannot move out of {}",
bccx.cmt_to_string(&*move_from)).as_slice());
}
mc::cat_copied_upvar(mc::CopiedUpvar { kind: kind, .. })
if kind.onceness() == ast::Many => {
mc::cat_static_item => {
bccx.span_err(
move_from.span,
format!("cannot move out of {}",

10
src/librustc/middle/borrowck/gather_loans/restrictions.rs
View File

@ -73,15 +73,9 @@ impl<'a, 'tcx> RestrictionsContext<'a, 'tcx> {
SafeIf(lp.clone(), vec![lp])
}
mc::cat_upvar(upvar_id, _, _) => {
mc::cat_upvar(mc::Upvar { id, .. }) => {
// R-Variable, captured into closure
let lp = Rc::new(LpUpvar(upvar_id));
SafeIf(lp.clone(), vec![lp])
}
mc::cat_copied_upvar(mc::CopiedUpvar { upvar_id, .. }) => {
// R-Variable, copied/moved into closure
let lp = Rc::new(LpVar(upvar_id));
let lp = Rc::new(LpUpvar(id));
SafeIf(lp.clone(), vec![lp])
}

36
src/librustc/middle/borrowck/mod.rs
View File

@ -359,21 +359,12 @@ pub fn opt_loan_path(cmt: &mc::cmt) -> Option<Rc<LoanPath>> {
None
}
mc::cat_copied_upvar(mc::CopiedUpvar { kind: kind, .. })
if kind.onceness() == ast::Many => {
None
}
mc::cat_local(id) => {
Some(Rc::new(LpVar(id)))
}
mc::cat_upvar(ty::UpvarId {var_id: id, closure_expr_id: proc_id}, _, _) |
mc::cat_copied_upvar(mc::CopiedUpvar { upvar_id: id,
kind: _,
capturing_proc: proc_id }) => {
let upvar_id = ty::UpvarId{ var_id: id, closure_expr_id: proc_id };
Some(Rc::new(LpUpvar(upvar_id)))
mc::cat_upvar(mc::Upvar { id, .. }) => {
Some(Rc::new(LpUpvar(id)))
}
mc::cat_deref(ref cmt_base, _, pk) => {
@ -630,7 +621,11 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
pub fn bckerr_to_string(&self, err: &BckError) -> String {
match err.code {
err_mutbl => {
let descr = match opt_loan_path(&err.cmt) {
let descr = match err.cmt.note {
mc::NoteClosureEnv(_) => {
self.cmt_to_string(&*err.cmt)
}
_ => match opt_loan_path(&err.cmt) {
None => {
format!("{} {}",
err.cmt.mutbl.to_user_str(),
@ -642,6 +637,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
self.cmt_to_string(&*err.cmt),
self.loan_path_to_string(&*lp))
}
}
};
match err.cause {
@ -732,8 +728,8 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
}
mc::AliasableClosure(id) => {
self.tcx.sess.span_err(span,
format!("{} in a free variable from an \
immutable unboxed closure", prefix).as_slice());
format!("{} in a captured outer \
variable in an `Fn` closure", prefix).as_slice());
span_note!(self.tcx.sess, self.tcx.map.span(id),
"consider changing this closure to take self by mutable reference");
}
@ -760,7 +756,17 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
pub fn note_and_explain_bckerr(&self, err: BckError) {
let code = err.code;
match code {
err_mutbl(..) => { }
err_mutbl(..) => {
match err.cmt.note {
mc::NoteClosureEnv(upvar_id) => {
self.tcx.sess.span_note(
self.tcx.map.span(upvar_id.closure_expr_id),
"consider changing this closure to take \
self by mutable reference");
}
_ => {}
}
}
err_out_of_scope(super_scope, sub_scope) => {
note_and_explain_region(

2
src/librustc/middle/check_static.rs
View File

@ -264,7 +264,6 @@ impl euv::Delegate for GlobalChecker {
mc::cat_interior(ref cmt, _) => cur = cmt,
mc::cat_rvalue(..) |
mc::cat_copied_upvar(..) |
mc::cat_upvar(..) |
mc::cat_local(..) => break,
}
@ -299,7 +298,6 @@ impl euv::Delegate for GlobalChecker {
mc::cat_downcast(..) |
mc::cat_discr(..) |
mc::cat_copied_upvar(..) |
mc::cat_upvar(..) |
mc::cat_local(..) => unreachable!(),
}

395
src/librustc/middle/mem_categorization.rs
View File

@ -82,9 +82,7 @@ use std::rc::Rc;
pub enum categorization {
cat_rvalue(ty::Region), // temporary val, argument is its scope
cat_static_item,
cat_copied_upvar(CopiedUpvar), // upvar copied into proc env
cat_upvar(ty::UpvarId, ty::UpvarBorrow,
Option<ty::UnboxedClosureKind>), // by ref upvar from stack or unboxed closure
cat_upvar(Upvar), // upvar referenced by closure env
cat_local(ast::NodeId), // local variable
cat_deref(cmt, uint, PointerKind), // deref of a ptr
cat_interior(cmt, InteriorKind), // something interior: field, tuple, etc
@ -94,28 +92,14 @@ pub enum categorization {
// (*1) downcast is only required if the enum has more than one variant
}
// Represents any kind of upvar
#[deriving(Clone, PartialEq, Show)]
pub enum CopiedUpvarKind {
Boxed(ast::Onceness),
Unboxed(ty::UnboxedClosureKind)
}
impl CopiedUpvarKind {
pub fn onceness(&self) -> ast::Onceness {
match *self {
Boxed(onceness) => onceness,
Unboxed(ty::FnUnboxedClosureKind) |
Unboxed(ty::FnMutUnboxedClosureKind) => ast::Many,
Unboxed(ty::FnOnceUnboxedClosureKind) => ast::Once
}
}
}
#[deriving(Clone, PartialEq, Show)]
pub struct CopiedUpvar {
pub upvar_id: ast::NodeId,
pub kind: CopiedUpvarKind,
pub capturing_proc: ast::NodeId,
pub struct Upvar {
pub id: ty::UpvarId,
// Unboxed closure kinds are used even for old-style closures for simplicity
pub kind: ty::UnboxedClosureKind,
// Is this from an unboxed closure? Used only for diagnostics.
pub is_unboxed: bool
}
// different kinds of pointers:
@ -154,6 +138,18 @@ pub enum MutabilityCategory {
McInherited, // Inherited from the fact that owner is mutable.
}
// A note about the provenance of a `cmt`. This is used for
// special-case handling of upvars such as mutability inference.
// Upvar categorization can generate a variable number of nested
// derefs. The note allows detecting them without deep pattern
// matching on the categorization.
#[deriving(Clone, PartialEq, Show)]
pub enum Note {
NoteClosureEnv(ty::UpvarId), // Deref through closure env
NoteUpvarRef(ty::UpvarId), // Deref through by-ref upvar
NoteNone // Nothing special
}
// `cmt`: "Category, Mutability, and Type".
//
// a complete categorization of a value indicating where it originated
@ -174,7 +170,8 @@ pub struct cmt_ {
pub span: Span, // span of same expr/pat
pub cat: categorization, // categorization of expr
pub mutbl: MutabilityCategory, // mutability of expr as lvalue
pub ty: ty::t // type of the expr (*see WARNING above*)
pub ty: ty::t, // type of the expr (*see WARNING above*)
pub note: Note, // Note about the provenance of this cmt
}
pub type cmt = Rc<cmt_>;
@ -560,7 +557,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span:span,
cat:cat_static_item,
mutbl: McImmutable,
ty:expr_ty
ty:expr_ty,
note: NoteNone
}))
}
@ -570,7 +568,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span:span,
cat:cat_static_item,
mutbl: if mutbl { McDeclared } else { McImmutable},
ty:expr_ty
ty:expr_ty,
note: NoteNone
}))
}
@ -578,55 +577,29 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
let ty = if_ok!(self.node_ty(fn_node_id));
match ty::get(ty).sty {
ty::ty_closure(ref closure_ty) => {
// Decide whether to use implicit reference or by copy/move
// capture for the upvar. This, combined with the onceness,
// determines whether the closure can move out of it.
let var_is_refd = match (closure_ty.store, closure_ty.onceness) {
// Many-shot stack closures can never move out.
(ty::RegionTraitStore(..), ast::Many) => true,
// 1-shot stack closures can move out.
(ty::RegionTraitStore(..), ast::Once) => false,
// Heap closures always capture by copy/move, and can
// move out if they are once.
(ty::UniqTraitStore, _) => false,
};
if var_is_refd {
self.cat_upvar(id, span, var_id, fn_node_id, None)
} else {
Ok(Rc::new(cmt_ {
id:id,
span:span,
cat:cat_copied_upvar(CopiedUpvar {
upvar_id: var_id,
kind: Boxed(closure_ty.onceness),
capturing_proc: fn_node_id,
}),
mutbl: MutabilityCategory::from_local(self.tcx(), var_id),
ty:expr_ty
}))
// Translate old closure type info into unboxed
// closure kind/capture mode
let (mode, kind) = match (closure_ty.store, closure_ty.onceness) {
// stack closure
(ty::RegionTraitStore(..), ast::Many) => {
(ast::CaptureByRef, ty::FnMutUnboxedClosureKind)
}
// proc or once closure
(_, ast::Once) => {
(ast::CaptureByValue, ty::FnOnceUnboxedClosureKind)
}
// There should be no such old closure type
(ty::UniqTraitStore, ast::Many) => {
self.tcx().sess.span_bug(span, "Impossible closure type");
}
};
self.cat_upvar(id, span, var_id, fn_node_id, kind, mode, false)
}
ty::ty_unboxed_closure(closure_id, _) => {
let unboxed_closures = self.typer
.unboxed_closures()
.borrow();
let unboxed_closures = self.typer.unboxed_closures().borrow();
let kind = unboxed_closures.get(&closure_id).kind;
if self.typer.capture_mode(fn_node_id) == ast::CaptureByRef {
self.cat_upvar(id, span, var_id, fn_node_id, Some(kind))
} else {
Ok(Rc::new(cmt_ {
id: id,
span: span,
cat: cat_copied_upvar(CopiedUpvar {
upvar_id: var_id,
kind: Unboxed(kind),
capturing_proc: fn_node_id,
}),
mutbl: MutabilityCategory::from_local(self.tcx(), var_id),
ty: expr_ty
}))
}
let mode = self.typer.capture_mode(fn_node_id);
self.cat_upvar(id, span, var_id, fn_node_id, kind, mode, true)
}
_ => {
self.tcx().sess.span_bug(
@ -644,61 +617,171 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span: span,
cat: cat_local(vid),
mutbl: MutabilityCategory::from_local(self.tcx(), vid),
ty: expr_ty
ty: expr_ty,
note: NoteNone
}))
}
}
}
// Categorize an upvar, complete with invisible derefs of closure
// environment and upvar reference as appropriate.
fn cat_upvar(&self,
id: ast::NodeId,
span: Span,
var_id: ast::NodeId,
fn_node_id: ast::NodeId,
kind: Option<ty::UnboxedClosureKind>)
kind: ty::UnboxedClosureKind,
mode: ast::CaptureClause,
is_unboxed: bool)
-> McResult<cmt> {
/*!
* Upvars through a closure are in fact indirect
* references. That is, when a closure refers to a
* variable from a parent stack frame like `x = 10`,
* that is equivalent to `*x_ = 10` where `x_` is a
* borrowed pointer (`&mut x`) created when the closure
* was created and store in the environment. This
* equivalence is expose in the mem-categorization.
*/
// An upvar can have up to 3 components. The base is a
// `cat_upvar`. Next, we add a deref through the implicit
// environment pointer with an anonymous free region 'env and
// appropriate borrow kind for closure kinds that take self by
// reference. Finally, if the upvar was captured
// by-reference, we add a deref through that reference. The
// region of this reference is an inference variable 'up that
// was previously generated and recorded in the upvar borrow
// map. The borrow kind bk is inferred by based on how the
// upvar is used.
//
// This results in the following table for concrete closure
// types:
//
// | move | ref
// ---------------+----------------------+-------------------------------
// Fn | copied -> &'env | upvar -> &'env -> &'up bk
// FnMut | copied -> &'env mut | upvar -> &'env mut -> &'up bk
// FnOnce | copied | upvar -> &'up bk
// old stack | N/A | upvar -> &'env mut -> &'up bk
// old proc/once | copied | N/A
let upvar_id = ty::UpvarId { var_id: var_id,
closure_expr_id: fn_node_id };
let upvar_borrow = self.typer.upvar_borrow(upvar_id);
// Do we need to deref through an env reference?
let has_env_deref = kind != ty::FnOnceUnboxedClosureKind;
// Mutability of original variable itself
let var_mutbl = MutabilityCategory::from_local(self.tcx(), var_id);
// Mutability of environment dereference
let env_mutbl = match kind {
ty::FnOnceUnboxedClosureKind => var_mutbl,
ty::FnMutUnboxedClosureKind => McInherited,
ty::FnUnboxedClosureKind => McImmutable
};
// Look up the node ID of the closure body so we can construct
// a free region within it
let fn_body_id = {
let fn_expr = match self.tcx().map.find(fn_node_id) {
Some(ast_map::NodeExpr(e)) => e,
_ => unreachable!()
};
match fn_expr.node {
ast::ExprFnBlock(_, _, ref body) |
ast::ExprProc(_, ref body) |
ast::ExprUnboxedFn(_, _, _, ref body) => body.id,
_ => unreachable!()
}
};
// Region of environment pointer
let env_region = ty::ReFree(ty::FreeRegion {
scope_id: fn_body_id,
bound_region: ty::BrEnv
});
let env_ptr = BorrowedPtr(if env_mutbl.is_mutable() {
ty::MutBorrow
} else {
ty::ImmBorrow
}, env_region);
let var_ty = if_ok!(self.node_ty(var_id));
// We can't actually represent the types of all upvars
// as user-describable types, since upvars support const
// and unique-imm borrows! Therefore, we cheat, and just
// give err type. Nobody should be inspecting this type anyhow.
let upvar_ty = ty::mk_err();
let base_cmt = Rc::new(cmt_ {
// First, switch by capture mode
Ok(match mode {
ast::CaptureByValue => {
let mut base = cmt_ {
id: id,
span: span,
cat:cat_upvar(upvar_id, upvar_borrow, kind),
mutbl:McImmutable,
ty:upvar_ty,
});
cat: cat_upvar(Upvar {
id: upvar_id,
kind: kind,
is_unboxed: is_unboxed
}),
mutbl: var_mutbl,
ty: var_ty,
note: NoteNone
};
if has_env_deref {
// We need to add the env deref. This means that
// the above is actually immutable and has a ref
// type. However, nothing should actually look at
// the type, so we can get away with stuffing a
// `ty_err` in there instead of bothering to
// construct a proper one.
base.mutbl = McImmutable;
base.ty = ty::mk_err();
Rc::new(cmt_ {
id: id,
span: span,
cat: cat_deref(Rc::new(base), 0, env_ptr),
mutbl: env_mutbl,
ty: var_ty,
note: NoteClosureEnv(upvar_id)
})
} else {
Rc::new(base)
}
},
ast::CaptureByRef => {
// The type here is actually a ref (or ref of a ref),
// but we can again get away with not constructing one
// properly since it will never be used.
let mut base = cmt_ {
id: id,
span: span,
cat: cat_upvar(Upvar {
id: upvar_id,
kind: kind,
is_unboxed: is_unboxed
}),
mutbl: McImmutable,
ty: ty::mk_err(),
note: NoteNone
};
// As in the by-value case, add env deref if needed
if has_env_deref {
base = cmt_ {
id: id,
span: span,
cat: cat_deref(Rc::new(base), 0, env_ptr),
mutbl: env_mutbl,
ty: ty::mk_err(),
note: NoteClosureEnv(upvar_id)
};
}
// Look up upvar borrow so we can get its region
let upvar_borrow = self.typer.upvar_borrow(upvar_id);
let ptr = BorrowedPtr(upvar_borrow.kind, upvar_borrow.region);
let deref_cmt = Rc::new(cmt_ {
Rc::new(cmt_ {
id: id,
span: span,
cat:cat_deref(base_cmt, 0, ptr),
cat: cat_deref(Rc::new(base), 0, ptr),
mutbl: MutabilityCategory::from_borrow_kind(upvar_borrow.kind),
ty: var_ty,
});
Ok(deref_cmt)
note: NoteUpvarRef(upvar_id)
})
}
})
}
pub fn cat_rvalue_node(&self,
@ -729,7 +812,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span:span,
cat:cat_rvalue(temp_scope),
mutbl:McDeclared,
ty:expr_ty
ty:expr_ty,
note: NoteNone
})
}
@ -744,7 +828,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span: node.span(),
mutbl: base_cmt.mutbl.inherit(),
cat: cat_interior(base_cmt, InteriorField(NamedField(f_name.name))),
ty: f_ty
ty: f_ty,
note: NoteNone
})
}
@ -759,7 +844,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span: node.span(),
mutbl: base_cmt.mutbl.inherit(),
cat: cat_interior(base_cmt, InteriorField(PositionalField(f_idx))),
ty: f_ty
ty: f_ty,
note: NoteNone
})
}
@ -834,7 +920,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span: node.span(),
cat: cat,
mutbl: m,
ty: deref_ty
ty: deref_ty,
note: NoteNone
})
}
@ -895,7 +982,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span:elt.span(),
cat:cat_interior(of_cmt, InteriorElement(element_kind(vec_ty))),
mutbl:mutbl,
ty:element_ty
ty:element_ty,
note: NoteNone
})
}
}
@ -921,7 +1009,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
ty: match ty::deref(base_cmt.ty, false) {
Some(mt) => mt.ty,
None => self.tcx().sess.bug("Found non-derefable type")
}
},
note: NoteNone
})
}
@ -988,7 +1077,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span: node.span(),
mutbl: base_cmt.mutbl.inherit(),
cat: cat_interior(base_cmt, interior),
ty: interior_ty
ty: interior_ty,
note: NoteNone
})
}
@ -1002,7 +1092,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
span: node.span(),
mutbl: base_cmt.mutbl.inherit(),
cat: cat_downcast(base_cmt),
ty: downcast_ty
ty: downcast_ty,
note: NoteNone
})
}
@ -1184,13 +1275,26 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
}
pub fn cmt_to_string(&self, cmt: &cmt_) -> String {
fn upvar_to_string(upvar: &Upvar, is_copy: bool) -> String {
if upvar.is_unboxed {
let kind = match upvar.kind {
ty::FnUnboxedClosureKind => "Fn",
ty::FnMutUnboxedClosureKind => "FnMut",
ty::FnOnceUnboxedClosureKind => "FnOnce"
};
format!("captured outer variable in an `{}` closure", kind)
} else {
(match (upvar.kind, is_copy) {
(ty::FnOnceUnboxedClosureKind, true) => "captured outer variable in a proc",
_ => "captured outer variable"
}).to_string()
}
}
match cmt.cat {
cat_static_item => {
"static item".to_string()
}
cat_copied_upvar(_) => {
"captured outer variable in a proc".to_string()
}
cat_rvalue(..) => {
"non-lvalue".to_string()
}
@ -1202,12 +1306,14 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
_ => "local variable".to_string()
}
}
cat_deref(ref base, _, pk) => {
match base.cat {
cat_upvar(..) => {
"captured outer variable".to_string()
cat_deref(_, _, pk) => {
let upvar = cmt.upvar();
match upvar.as_ref().map(|i| &i.cat) {
Some(&cat_upvar(ref var)) => {
upvar_to_string(var, false)
}
_ => {
Some(_) => unreachable!(),
None => {
match pk {
Implicit(..) => {
"dereference (dereference is implicit, due to indexing)".to_string()
@ -1230,8 +1336,8 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
cat_interior(_, InteriorElement(OtherElement)) => {
"indexed content".to_string()
}
cat_upvar(..) => {
"captured outer variable".to_string()
cat_upvar(ref var) => {
upvar_to_string(var, true)
}
cat_discr(ref cmt, _) => {
self.cmt_to_string(&**cmt)
@ -1250,7 +1356,7 @@ pub enum InteriorSafety {
pub enum AliasableReason {
AliasableBorrowed,
AliasableClosure(ast::NodeId), // Aliasable due to capture by unboxed closure expr
AliasableClosure(ast::NodeId), // Aliasable due to capture Fn closure env
AliasableOther,
AliasableStatic(InteriorSafety),
AliasableStaticMut(InteriorSafety),
@ -1265,7 +1371,6 @@ impl cmt_ {
match self.cat {
cat_rvalue(..) |
cat_static_item |
cat_copied_upvar(..) |
cat_local(..) |
cat_deref(_, _, UnsafePtr(..)) |
cat_deref(_, _, BorrowedPtr(..)) |
@ -1307,27 +1412,11 @@ impl cmt_ {
cat_rvalue(..) |
cat_local(..) |
cat_upvar(..) |
cat_deref(_, _, UnsafePtr(..)) => { // yes, it's aliasable, but...
None
}
cat_copied_upvar(CopiedUpvar {kind: kind, capturing_proc: id, ..}) => {
match kind {
Boxed(ast::Once) |
Unboxed(ty::FnOnceUnboxedClosureKind) |
Unboxed(ty::FnMutUnboxedClosureKind) => None,
Boxed(_) => Some(AliasableOther),
Unboxed(_) => Some(AliasableClosure(id))
}
}
cat_upvar(ty::UpvarId { closure_expr_id: id, .. }, _,
Some(ty::FnUnboxedClosureKind)) => {
Some(AliasableClosure(id))
}
cat_upvar(..) => None,
cat_static_item(..) => {
let int_safe = if ty::type_interior_is_unsafe(ctxt, self.ty) {
InteriorUnsafe
@ -1342,14 +1431,37 @@ impl cmt_ {
}
}
cat_deref(_, _, BorrowedPtr(ty::ImmBorrow, _)) |
cat_deref(_, _, Implicit(ty::ImmBorrow, _)) => {
Some(AliasableBorrowed)
cat_deref(ref base, _, BorrowedPtr(ty::ImmBorrow, _)) |
cat_deref(ref base, _, Implicit(ty::ImmBorrow, _)) => {
match base.cat {
cat_upvar(Upvar{ id, .. }) => Some(AliasableClosure(id.closure_expr_id)),
_ => Some(AliasableBorrowed)
}
}
}
}
// Digs down through one or two layers of deref and grabs the cmt
// for the upvar if a note indicates there is one.
pub fn upvar(&self) -> Option<cmt> {
match self.note {
NoteClosureEnv(..) | NoteUpvarRef(..) => {
Some(match self.cat {
cat_deref(ref inner, _, _) => {
match inner.cat {
cat_deref(ref inner, _, _) => inner.clone(),
cat_upvar(..) => inner.clone(),
_ => unreachable!()
}
}
_ => unreachable!()
})
}
NoteNone => None
}
}
}
impl Repr for cmt_ {
fn repr(&self, tcx: &ty::ctxt) -> String {
format!("{{{} id:{} m:{} ty:{}}}",
@ -1365,7 +1477,6 @@ impl Repr for categorization {
match *self {
cat_static_item |
cat_rvalue(..) |
cat_copied_upvar(..) |
cat_local(..) |
cat_upvar(..) => {
format!("{}", *self)

2
src/librustc/middle/trans/_match.rs
View File

@ -1270,7 +1270,7 @@ impl euv::Delegate for ReassignmentChecker {
fn mutate(&mut self, _: ast::NodeId, _: Span, cmt: mc::cmt, _: euv::MutateMode) {
match cmt.cat {
mc::cat_copied_upvar(mc::CopiedUpvar { upvar_id: vid, .. }) |
mc::cat_upvar(mc::Upvar { id: ty::UpvarId { var_id: vid, .. }, .. }) |
mc::cat_local(vid) => self.reassigned = self.node == vid,
_ => {}
}

4
src/librustc/middle/ty.rs
View File

@ -863,6 +863,10 @@ pub enum BoundRegion {
/// Fresh bound identifiers created during GLB computations.
BrFresh(uint),
// Anonymous region for the implicit env pointer parameter
// to a closure
BrEnv
}
mod primitives {

146
src/librustc/middle/typeck/check/regionck.rs
View File

@ -140,7 +140,9 @@ use syntax::codemap::Span;
use syntax::visit;
use syntax::visit::Visitor;
use std::cell::RefCell;
use std::cell::{RefCell};
use std::collections::HashMap;
use std::collections::hashmap::{Vacant, Occupied};
///////////////////////////////////////////////////////////////////////////
// PUBLIC ENTRY POINTS
@ -211,6 +213,19 @@ macro_rules! ignore_err(
)
)
// Stores parameters for a potential call to link_region()
// to perform if an upvar reference is marked unique/mutable after
// it has already been processed before.
struct MaybeLink {
span: Span,
borrow_region: ty::Region,
borrow_kind: ty::BorrowKind,
borrow_cmt: mc::cmt
}
// A map associating an upvar ID to a vector of the above
type MaybeLinkMap = RefCell<HashMap<ty::UpvarId, Vec<MaybeLink>>>;
pub struct Rcx<'a, 'tcx: 'a> {
fcx: &'a FnCtxt<'a, 'tcx>,
@ -218,6 +233,10 @@ pub struct Rcx<'a, 'tcx: 'a> {
// id of innermost fn or loop
repeating_scope: ast::NodeId,
// Possible region links we will establish if an upvar
// turns out to be unique/mutable
maybe_links: MaybeLinkMap
}
fn region_of_def(fcx: &FnCtxt, def: def::Def) -> ty::Region {
@ -250,7 +269,8 @@ impl<'a, 'tcx> Rcx<'a, 'tcx> {
initial_repeating_scope: ast::NodeId) -> Rcx<'a, 'tcx> {
Rcx { fcx: fcx,
repeating_scope: initial_repeating_scope,
region_param_pairs: Vec::new() }
region_param_pairs: Vec::new(),
maybe_links: RefCell::new(HashMap::new()) }
}
pub fn tcx(&self) -> &'a ty::ctxt<'tcx> {
@ -848,14 +868,13 @@ fn check_expr_fn_block(rcx: &mut Rcx,
});
}
ty::ty_unboxed_closure(_, region) => {
let bounds = ty::region_existential_bound(region);
if tcx.capture_modes.borrow().get_copy(&expr.id) == ast::CaptureByRef {
ty::with_freevars(tcx, expr.id, |freevars| {
if !freevars.is_empty() {
// Variables being referenced must be constrained and registered
// in the upvar borrow map
constrain_free_variables_in_by_ref_closure(
rcx, bounds.region_bound, expr, freevars);
rcx, region, expr, freevars);
}
})
}
@ -1463,7 +1482,8 @@ fn link_region(rcx: &Rcx,
mc::BorrowedPtr(ref_kind, ref_region)) => {
match link_reborrowed_region(rcx, span,
borrow_region, borrow_kind,
ref_cmt, ref_region, ref_kind) {
ref_cmt, ref_region, ref_kind,
borrow_cmt.note) {
Some((c, k)) => {
borrow_cmt = c;
borrow_kind = k;
@ -1486,9 +1506,8 @@ fn link_region(rcx: &Rcx,
mc::cat_deref(_, _, mc::UnsafePtr(..)) |
mc::cat_static_item |
mc::cat_copied_upvar(..) |
mc::cat_local(..) |
mc::cat_upvar(..) |
mc::cat_local(..) |
mc::cat_rvalue(..) => {
// These are all "base cases" with independent lifetimes
// that are not subject to inference
@ -1504,7 +1523,8 @@ fn link_reborrowed_region(rcx: &Rcx,
borrow_kind: ty::BorrowKind,
ref_cmt: mc::cmt,
ref_region: ty::Region,
ref_kind: ty::BorrowKind)
mut ref_kind: ty::BorrowKind,
note: mc::Note)
-> Option<(mc::cmt, ty::BorrowKind)>
{
/*!
@ -1550,9 +1570,12 @@ fn link_reborrowed_region(rcx: &Rcx,
* recurse and process `ref_cmt` (see case 2 above).
*/
// Detect references to an upvar `x`:
let cause = match ref_cmt.cat {
mc::cat_upvar(ref upvar_id, _, _) => {
// Possible upvar ID we may need later to create an entry in the
// maybe link map.
// Detect by-ref upvar `x`:
let cause = match note {
mc::NoteUpvarRef(ref upvar_id) => {
let mut upvar_borrow_map =
rcx.fcx.inh.upvar_borrow_map.borrow_mut();
match upvar_borrow_map.find_mut(upvar_id) {
@ -1560,10 +1583,15 @@ fn link_reborrowed_region(rcx: &Rcx,
// Adjust mutability that we infer for the upvar
// so it can accommodate being borrowed with
// mutability `kind`:
adjust_upvar_borrow_kind_for_loan(*upvar_id,
adjust_upvar_borrow_kind_for_loan(rcx,
*upvar_id,
upvar_borrow,
borrow_kind);
// The mutability of the upvar may have been modified
// by the above adjustment, so update our local variable.
ref_kind = upvar_borrow.kind;
infer::ReborrowUpvar(span, *upvar_id)
}
None => {
@ -1575,7 +1603,12 @@ fn link_reborrowed_region(rcx: &Rcx,
}
}
}
mc::NoteClosureEnv(ref upvar_id) => {
// We don't have any mutability changes to propagate, but
// we do want to note that an upvar reborrow caused this
// link
infer::ReborrowUpvar(span, *upvar_id)
}
_ => {
infer::Reborrow(span)
}
@ -1586,6 +1619,21 @@ fn link_reborrowed_region(rcx: &Rcx,
ref_region.repr(rcx.tcx()));
rcx.fcx.mk_subr(cause, borrow_region, ref_region);
// If we end up needing to recurse and establish a region link
// with `ref_cmt`, calculate what borrow kind we will end up
// needing. This will be used below.
//
// One interesting twist is that we can weaken the borrow kind
// when we recurse: to reborrow an `&mut` referent as mutable,
// borrowck requires a unique path to the `&mut` reference but not
// necessarily a *mutable* path.
let new_borrow_kind = match borrow_kind {
ty::ImmBorrow =>
ty::ImmBorrow,
ty::MutBorrow | ty::UniqueImmBorrow =>
ty::UniqueImmBorrow
};
// Decide whether we need to recurse and link any regions within
// the `ref_cmt`. This is concerned for the case where the value
// being reborrowed is in fact a borrowed pointer found within
@ -1624,23 +1672,36 @@ fn link_reborrowed_region(rcx: &Rcx,
// else the user is borrowed imm memory as mut memory,
// which means they'll get an error downstream in borrowck
// anyhow.)
//
// If mutability was inferred from an upvar, we may be
// forced to revisit this decision later if processing
// another borrow or nested closure ends up coverting the
// upvar borrow kind to mutable/unique. Record the
// information needed to perform the recursive link in the
// maybe link map.
match note {
mc::NoteUpvarRef(upvar_id) => {
let link = MaybeLink {
span: span,
borrow_region: borrow_region,
borrow_kind: new_borrow_kind,
borrow_cmt: ref_cmt
};
match rcx.maybe_links.borrow_mut().entry(upvar_id) {
Vacant(entry) => { entry.set(vec![link]); }
Occupied(entry) => { entry.into_mut().push(link); }
}
},
_ => {}
}
return None;
}
ty::MutBorrow | ty::UniqueImmBorrow => {
// The reference being reborrowed is either an `&mut T` or
// `&uniq T`. This is the case where recursion is needed.
//
// One interesting twist is that we can weaken the borrow
// kind when we recurse: to reborrow an `&mut` referent as
// mutable, borrowck requires a unique path to the `&mut`
// reference but not necessarily a *mutable* path.
let new_borrow_kind = match borrow_kind {
ty::ImmBorrow =>
ty::ImmBorrow,
ty::MutBorrow | ty::UniqueImmBorrow =>
ty::UniqueImmBorrow
};
return Some((ref_cmt, new_borrow_kind));
}
}
@ -1685,8 +1746,8 @@ fn adjust_upvar_borrow_kind_for_mut(rcx: &Rcx,
mc::cat_deref(base, _, mc::BorrowedPtr(..)) |
mc::cat_deref(base, _, mc::Implicit(..)) => {
match base.cat {
mc::cat_upvar(ref upvar_id, _, _) => {
match cmt.note {
mc::NoteUpvarRef(ref upvar_id) => {
// if this is an implicit deref of an
// upvar, then we need to modify the
// borrow_kind of the upvar to make sure it
@ -1694,7 +1755,7 @@ fn adjust_upvar_borrow_kind_for_mut(rcx: &Rcx,
let mut upvar_borrow_map =
rcx.fcx.inh.upvar_borrow_map.borrow_mut();
let ub = upvar_borrow_map.get_mut(upvar_id);
return adjust_upvar_borrow_kind(*upvar_id, ub, ty::MutBorrow);
return adjust_upvar_borrow_kind(rcx, *upvar_id, ub, ty::MutBorrow);
}
_ => {}
@ -1710,7 +1771,6 @@ fn adjust_upvar_borrow_kind_for_mut(rcx: &Rcx,
mc::cat_deref(_, _, mc::UnsafePtr(..)) |
mc::cat_static_item |
mc::cat_rvalue(_) |
mc::cat_copied_upvar(_) |
mc::cat_local(_) |
mc::cat_upvar(..) => {
return;
@ -1738,15 +1798,15 @@ fn adjust_upvar_borrow_kind_for_unique(rcx: &Rcx, cmt: mc::cmt) {
mc::cat_deref(base, _, mc::BorrowedPtr(..)) |
mc::cat_deref(base, _, mc::Implicit(..)) => {
match base.cat {
mc::cat_upvar(ref upvar_id, _, _) => {
match cmt.note {
mc::NoteUpvarRef(ref upvar_id) => {
// if this is an implicit deref of an
// upvar, then we need to modify the
// borrow_kind of the upvar to make sure it
// is inferred to unique if necessary
let mut ub = rcx.fcx.inh.upvar_borrow_map.borrow_mut();
let ub = ub.get_mut(upvar_id);
return adjust_upvar_borrow_kind(*upvar_id, ub, ty::UniqueImmBorrow);
return adjust_upvar_borrow_kind(rcx, *upvar_id, ub, ty::UniqueImmBorrow);
}
_ => {}
@ -1760,7 +1820,6 @@ fn adjust_upvar_borrow_kind_for_unique(rcx: &Rcx, cmt: mc::cmt) {
mc::cat_deref(_, _, mc::UnsafePtr(..)) |
mc::cat_static_item |
mc::cat_rvalue(_) |
mc::cat_copied_upvar(_) |
mc::cat_local(_) |
mc::cat_upvar(..) => {
return;
@ -1786,22 +1845,24 @@ fn link_upvar_borrow_kind_for_nested_closures(rcx: &mut Rcx,
let inner_borrow = upvar_borrow_map.get_copy(&inner_upvar_id);
match upvar_borrow_map.find_mut(&outer_upvar_id) {
Some(outer_borrow) => {
adjust_upvar_borrow_kind(outer_upvar_id, outer_borrow, inner_borrow.kind);
adjust_upvar_borrow_kind(rcx, outer_upvar_id, outer_borrow, inner_borrow.kind);
}
None => { /* outer closure is not a stack closure */ }
}
}
fn adjust_upvar_borrow_kind_for_loan(upvar_id: ty::UpvarId,
fn adjust_upvar_borrow_kind_for_loan(rcx: &Rcx,
upvar_id: ty::UpvarId,
upvar_borrow: &mut ty::UpvarBorrow,
kind: ty::BorrowKind) {
debug!("adjust_upvar_borrow_kind_for_loan: upvar_id={} kind={} -> {}",
upvar_id, upvar_borrow.kind, kind);
adjust_upvar_borrow_kind(upvar_id, upvar_borrow, kind)
adjust_upvar_borrow_kind(rcx, upvar_id, upvar_borrow, kind)
}
fn adjust_upvar_borrow_kind(upvar_id: ty::UpvarId,
fn adjust_upvar_borrow_kind(rcx: &Rcx,
upvar_id: ty::UpvarId,
upvar_borrow: &mut ty::UpvarBorrow,
kind: ty::BorrowKind) {
/*!
@ -1821,6 +1882,19 @@ fn adjust_upvar_borrow_kind(upvar_id: ty::UpvarId,
(ty::ImmBorrow, ty::MutBorrow) |
(ty::UniqueImmBorrow, ty::MutBorrow) => {
upvar_borrow.kind = kind;
// Check if there are any region links we now need to
// establish due to adjusting the borrow kind of the upvar
match rcx.maybe_links.borrow_mut().entry(upvar_id) {
Occupied(entry) => {
for MaybeLink { span, borrow_region,
borrow_kind, borrow_cmt } in entry.take().into_iter()
{
link_region(rcx, span, borrow_region, borrow_kind, borrow_cmt);
}
}
Vacant(_) => {}
}
}
// Take LHS:
(ty::ImmBorrow, ty::ImmBorrow) |

6
src/librustc/util/ppaux.rs
View File

@ -15,7 +15,7 @@ use middle::subst;
use middle::ty::{BoundRegion, BrAnon, BrNamed};
use middle::ty::{ReEarlyBound, BrFresh, ctxt};
use middle::ty::{ReFree, ReScope, ReInfer, ReStatic, Region, ReEmpty};
use middle::ty::{ReSkolemized, ReVar};
use middle::ty::{ReSkolemized, ReVar, BrEnv};
use middle::ty::{mt, t, ParamTy};
use middle::ty::{ty_bool, ty_char, ty_bot, ty_struct, ty_enum};
use middle::ty::{ty_err, ty_str, ty_vec, ty_float, ty_bare_fn, ty_closure};
@ -183,8 +183,7 @@ pub fn bound_region_to_string(cx: &ctxt,
BrNamed(_, name) => {
format!("{}{}{}", prefix, token::get_name(name), space_str)
}
BrAnon(_) => prefix.to_string(),
BrFresh(_) => prefix.to_string(),
BrAnon(_) | BrFresh(_) | BrEnv => prefix.to_string()
}
}
@ -769,6 +768,7 @@ impl Repr for ty::BoundRegion {
format!("BrNamed({}, {})", id.repr(tcx), token::get_name(name))
}
ty::BrFresh(id) => format!("BrFresh({})", id),
ty::BrEnv => "BrEnv".to_string()
}
}
}