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Rollup merge of #22777 - pnkfelix:issue-22443, r=nikomatsakis

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Check for unbounded recursion during dropck.

Such recursion can be introduced by the erroneous use of non-regular types (aka types employing polymorphic recursion), which Rust does not support.

Fix #22443
This commit is contained in:
Manish Goregaokar 2015-03-02 03:53:48 +05:30
commit 85bdb31306
6 changed files with 300 additions and 25 deletions
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132
src/librustc_typeck/check/dropck.rs
View file

@ -14,8 +14,9 @@ use middle::infer;
use middle::region;
use middle::subst;
use middle::ty::{self, Ty};
use util::ppaux::{Repr};
use util::ppaux::{Repr, UserString};
use syntax::ast;
use syntax::codemap::Span;
pub fn check_safety_of_destructor_if_necessary<'a, 'tcx>(rcx: &mut Rcx<'a, 'tcx>,
@ -28,29 +29,98 @@ pub fn check_safety_of_destructor_if_necessary<'a, 'tcx>(rcx: &mut Rcx<'a, 'tcx>
// types that have been traversed so far by `traverse_type_if_unseen`
let mut breadcrumbs: Vec<Ty<'tcx>> = Vec::new();
iterate_over_potentially_unsafe_regions_in_type(
let result = iterate_over_potentially_unsafe_regions_in_type(
rcx,
&mut breadcrumbs,
TypeContext::Root,
typ,
span,
scope,
0,
0);
match result {
Ok(()) => {}
Err(Error::Overflow(ref ctxt, ref detected_on_typ)) => {
let tcx = rcx.tcx();
span_err!(tcx.sess, span, E0320,
"overflow while adding drop-check rules for {}",
typ.user_string(rcx.tcx()));
match *ctxt {
TypeContext::Root => {
// no need for an additional note if the overflow
// was somehow on the root.
}
TypeContext::EnumVariant { def_id, variant, arg_index } => {
// FIXME (pnkfelix): eventually lookup arg_name
// for the given index on struct variants.
span_note!(
rcx.tcx().sess,
span,
"overflowed on enum {} variant {} argument {} type: {}",
ty::item_path_str(tcx, def_id),
variant,
arg_index,
detected_on_typ.user_string(rcx.tcx()));
}
TypeContext::Struct { def_id, field } => {
span_note!(
rcx.tcx().sess,
span,
"overflowed on struct {} field {} type: {}",
ty::item_path_str(tcx, def_id),
field,
detected_on_typ.user_string(rcx.tcx()));
}
}
}
}
}
enum Error<'tcx> {
Overflow(TypeContext, ty::Ty<'tcx>),
}
enum TypeContext {
Root,
EnumVariant {
def_id: ast::DefId,
variant: ast::Name,
arg_index: usize,
},
Struct {
def_id: ast::DefId,
field: ast::Name,
}
}
// The `depth` counts the number of calls to this function;
// the `xref_depth` counts the subset of such calls that go
// across a `Box<T>` or `PhantomData<T>`.
fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
rcx: &mut Rcx<'a, 'tcx>,
breadcrumbs: &mut Vec<Ty<'tcx>>,
context: TypeContext,
ty_root: ty::Ty<'tcx>,
span: Span,
scope: region::CodeExtent,
depth: uint)
depth: uint,
xref_depth: uint) -> Result<(), Error<'tcx>>
{
// Issue #22443: Watch out for overflow. While we are careful to
// handle regular types properly, non-regular ones cause problems.
let recursion_limit = rcx.tcx().sess.recursion_limit.get();
if xref_depth >= recursion_limit {
return Err(Error::Overflow(context, ty_root))
}
let origin = || infer::SubregionOrigin::SafeDestructor(span);
let mut walker = ty_root.walk();
let opt_phantom_data_def_id = rcx.tcx().lang_items.phantom_data();
let destructor_for_type = rcx.tcx().destructor_for_type.borrow();
let xref_depth_orig = xref_depth;
while let Some(typ) = walker.next() {
// Avoid recursing forever.
if breadcrumbs.contains(&typ) {
@ -61,7 +131,8 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
// If we encounter `PhantomData<T>`, then we should replace it
// with `T`, the type it represents as owned by the
// surrounding context, before doing further analysis.
let typ = if let ty::ty_struct(struct_did, substs) = typ.sty {
let (typ, xref_depth) = match typ.sty {
ty::ty_struct(struct_did, substs) => {
if opt_phantom_data_def_id == Some(struct_did) {
let item_type = ty::lookup_item_type(rcx.tcx(), struct_did);
let tp_def = item_type.generics.types
@ -69,12 +140,24 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
let new_typ = substs.type_for_def(tp_def);
debug!("replacing phantom {} with {}",
typ.repr(rcx.tcx()), new_typ.repr(rcx.tcx()));
new_typ
(new_typ, xref_depth_orig + 1)
} else {
typ
(typ, xref_depth_orig)
}
}
// Note: When ty_uniq is removed from compiler, the
// definition of `Box<T>` must carry a PhantomData that
// puts us into the previous case.
ty::ty_uniq(new_typ) => {
debug!("replacing ty_uniq {} with {}",
typ.repr(rcx.tcx()), new_typ.repr(rcx.tcx()));
(new_typ, xref_depth_orig + 1)
}
_ => {
(typ, xref_depth_orig)
}
} else {
typ
};
let opt_type_did = match typ.sty {
@ -87,9 +170,9 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
opt_type_did.and_then(|did| destructor_for_type.get(&did));
debug!("iterate_over_potentially_unsafe_regions_in_type \
{}typ: {} scope: {:?} opt_dtor: {:?}",
{}typ: {} scope: {:?} opt_dtor: {:?} xref: {}",
(0..depth).map(|_| ' ').collect::<String>(),
typ.repr(rcx.tcx()), scope, opt_dtor);
typ.repr(rcx.tcx()), scope, opt_dtor, xref_depth);
// If `typ` has a destructor, then we must ensure that all
// borrowed data reachable via `typ` must outlive the parent
@ -228,6 +311,8 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
match typ.sty {
ty::ty_struct(struct_did, substs) => {
debug!("typ: {} is struct; traverse structure and not type-expression",
typ.repr(rcx.tcx()));
// Don't recurse; we extract type's substructure,
// so do not process subparts of type expression.
walker.skip_current_subtree();
@ -240,17 +325,24 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
struct_did,
field.id,
substs);
iterate_over_potentially_unsafe_regions_in_type(
try!(iterate_over_potentially_unsafe_regions_in_type(
rcx,
breadcrumbs,
TypeContext::Struct {
def_id: struct_did,
field: field.name,
},
field_type,
span,
scope,
depth+1)
depth+1,
xref_depth))
}
}
ty::ty_enum(enum_did, substs) => {
debug!("typ: {} is enum; traverse structure and not type-expression",
typ.repr(rcx.tcx()));
// Don't recurse; we extract type's substructure,
// so do not process subparts of type expression.
walker.skip_current_subtree();
@ -260,14 +352,20 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
enum_did,
substs);
for variant_info in all_variant_info.iter() {
for argument_type in variant_info.args.iter() {
iterate_over_potentially_unsafe_regions_in_type(
for (i, arg_type) in variant_info.args.iter().enumerate() {
try!(iterate_over_potentially_unsafe_regions_in_type(
rcx,
breadcrumbs,
*argument_type,
TypeContext::EnumVariant {
def_id: enum_did,
variant: variant_info.name,
arg_index: i,
},
*arg_type,
span,
scope,
depth+1)
depth+1,
xref_depth));
}
}
}
@ -290,4 +388,6 @@ fn iterate_over_potentially_unsafe_regions_in_type<'a, 'tcx>(
// is done.
}
}
return Ok(());
}

3
src/librustc_typeck/diagnostics.rs
View file

@ -174,7 +174,8 @@ register_diagnostics! {
E0249, // expected constant expr for array length
E0250, // expected constant expr for array length
E0318, // can't create default impls for traits outside their crates
E0319 // trait impls for defaulted traits allowed just for structs/enums
E0319, // trait impls for defaulted traits allowed just for structs/enums
E0320 // recursive overflow during dropck
}
__build_diagnostic_array! { DIAGNOSTICS }

37
src/test/compile-fail/dropck_no_diverge_on_nonregular_1.rs Normal file
View file

@ -0,0 +1,37 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Issue 22443: Reject code using non-regular types that would
// otherwise cause dropck to loop infinitely.
use std::marker::PhantomData;
struct Digit<T> {
elem: T
}
struct Node<T:'static> { m: PhantomData<&'static T> }
enum FingerTree<T:'static> {
Single(T),
// Bug report said Digit after Box would stack overflow (versus
// Digit before Box; see dropck_no_diverge_on_nonregular_2).
Deep(
Box<FingerTree<Node<T>>>,
Digit<T>,
)
}
fn main() {
let ft = //~ ERROR overflow while adding drop-check rules for FingerTree
FingerTree::Single(1);
//~^ ERROR overflow while adding drop-check rules for FingerTree
}

36
src/test/compile-fail/dropck_no_diverge_on_nonregular_2.rs Normal file
View file

@ -0,0 +1,36 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Issue 22443: Reject code using non-regular types that would
// otherwise cause dropck to loop infinitely.
use std::marker::PhantomData;
struct Digit<T> {
elem: T
}
struct Node<T:'static> { m: PhantomData<&'static T> }
enum FingerTree<T:'static> {
Single(T),
// Bug report said Digit before Box would infinite loop (versus
// Digit after Box; see dropck_no_diverge_on_nonregular_1).
Deep(
Digit<T>,
Box<FingerTree<Node<T>>>,
)
}
fn main() {
let ft = //~ ERROR overflow while adding drop-check rules for FingerTree
FingerTree::Single(1);
//~^ ERROR overflow while adding drop-check rules for FingerTree
}

46
src/test/compile-fail/dropck_no_diverge_on_nonregular_3.rs Normal file
View file

@ -0,0 +1,46 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Issue 22443: Reject code using non-regular types that would
// otherwise cause dropck to loop infinitely.
//
// This version is just checking that we still sanely handle a trivial
// wrapper around the non-regular type. (It also demonstrates how the
// error messages will report different types depending on which type
// dropck is analyzing.)
use std::marker::PhantomData;
struct Digit<T> {
elem: T
}
struct Node<T:'static> { m: PhantomData<&'static T> }
enum FingerTree<T:'static> {
Single(T),
// According to the bug report, Digit before Box would infinite loop.
Deep(
Digit<T>,
Box<FingerTree<Node<T>>>,
)
}
enum Wrapper<T:'static> {
Simple,
Other(FingerTree<T>),
}
fn main() {
let w = //~ ERROR overflow while adding drop-check rules for core::option
Some(Wrapper::Simple::<u32>);
//~^ ERROR overflow while adding drop-check rules for core::option::Option
//~| ERROR overflow while adding drop-check rules for Wrapper
}

55
src/test/run-pass/issue-22777.rs Normal file
View file

@ -0,0 +1,55 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// This test is reduced from libsyntax. It is just checking that we
// can successfully deal with a "deep" structure, which the drop-check
// was hitting a recursion limit on at one point.
#![allow(non_camel_case_types)]
pub fn noop_fold_impl_item() -> SmallVector<ImplItem> {
loop { }
}
pub struct SmallVector<T>(P<T>);
pub struct ImplItem(P<S01_Method>);
struct P<T>(Box<T>);
struct S01_Method(P<S02_Generics>);
struct S02_Generics(P<S03_TyParam>);
struct S03_TyParam(P<S04_TyParamBound>);
struct S04_TyParamBound(S05_PolyTraitRef);
struct S05_PolyTraitRef(S06_TraitRef);
struct S06_TraitRef(S07_Path);
struct S07_Path(Vec<S08_PathSegment>);
struct S08_PathSegment(S09_PathParameters);
struct S09_PathParameters(P<S10_ParenthesizedParameterData>);
struct S10_ParenthesizedParameterData(Option<P<S11_Ty>>);
struct S11_Ty(P<S12_Expr>);
struct S12_Expr(P<S13_Block>);
struct S13_Block(Vec<P<S14_Stmt>>);
struct S14_Stmt(P<S15_Decl>);
struct S15_Decl(P<S16_Local>);
struct S16_Local(P<S17_Pat>);
struct S17_Pat(P<S18_Mac>);
struct S18_Mac(Vec<P<S19_TokenTree>>);
struct S19_TokenTree(P<S20_Token>);
struct S20_Token(P<S21_Nonterminal>);
struct S21_Nonterminal(P<S22_Item>);
struct S22_Item(P<S23_EnumDef>);
struct S23_EnumDef(Vec<P<S24_Variant>>);
struct S24_Variant(P<S25_VariantKind>);
struct S25_VariantKind(P<S26_StructDef>);
struct S26_StructDef(Vec<P<S27_StructField>>);
struct S27_StructField(P<S28_StructFieldKind>);
struct S28_StructFieldKind;
pub fn main() {}