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Auto merge of #56722 - Aaron1011:fix/blanket-eval-overflow, r=nikomatsakis

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Fix stack overflow when finding blanket impls

Currently, SelectionContext tries to prevent stack overflow by keeping
track of the current recursion depth. However, this depth tracking is
only used when performing normal section (which includes confirmation).
No such tracking is performed for evaluate_obligation_recursively, which
can allow a stack overflow to occur.

To fix this, this commit tracks the current predicate evaluation depth.
This is done separately from the existing obligation depth tracking:
an obligation overflow can occur across multiple calls to 'select' (e.g.
when fulfilling a trait), while a predicate evaluation overflow can only
happen as a result of a deep recursive call stack.

Fixes #56701

I've re-used `tcx.sess.recursion_limit` when checking for predication evaluation overflows. This is such a weird corner case that I don't believe it's necessary to have a separate setting controlling the maximum depth.
This commit is contained in:
bors 2019-01-19 05:05:48 +00:00
commit af73e64423
9 changed files with 117 additions and 38 deletions
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2
src/test/run-pass/weird-exprs.rs
View file

@ -4,7 +4,7 @@
#![allow(unused_parens)]
// compile-flags: -Z borrowck=compare
#![recursion_limit = "128"]
#![recursion_limit = "256"]
use std::cell::Cell;
use std::mem::swap;

34
src/test/rustdoc/issue-56701.rs Normal file
View file

@ -0,0 +1,34 @@
// This shouldn't cause a stack overflow when rustdoc is run
use std::ops::Deref;
use std::ops::DerefMut;
pub trait SimpleTrait {
type SimpleT;
}
impl<Inner: SimpleTrait, Outer: Deref<Target = Inner>> SimpleTrait for Outer {
type SimpleT = Inner::SimpleT;
}
pub trait AnotherTrait {
type AnotherT;
}
impl<T, Simple: SimpleTrait<SimpleT = Vec<T>>> AnotherTrait for Simple {
type AnotherT = T;
}
pub struct Unrelated<Inner, UnrelatedT: DerefMut<Target = Vec<Inner>>>(UnrelatedT);
impl<Inner, UnrelatedT: DerefMut<Target = Vec<Inner>>> Deref for Unrelated<Inner, UnrelatedT> {
type Target = Vec<Inner>;
fn deref(&self) -> &Self::Target {
&self.0
}
}
pub fn main() { }

3
src/test/ui/did_you_mean/recursion_limit.stderr
View file

@ -1,11 +1,10 @@
error[E0275]: overflow evaluating the requirement `K: std::marker::Send`
error[E0275]: overflow evaluating the requirement `J: std::marker::Send`
--> $DIR/recursion_limit.rs:34:5
|
LL | is_send::<A>(); //~ ERROR overflow evaluating the requirement
| ^^^^^^^^^^^^
|
= help: consider adding a `#![recursion_limit="20"]` attribute to your crate
= note: required because it appears within the type `J`
= note: required because it appears within the type `I`
= note: required because it appears within the type `H`
= note: required because it appears within the type `G`

4
src/test/ui/error-codes/E0055.rs
View file

@ -1,4 +1,4 @@
#![recursion_limit="2"]
#![recursion_limit="5"]
struct Foo;
impl Foo {
@ -7,7 +7,7 @@ impl Foo {
fn main() {
let foo = Foo;
let ref_foo = &&Foo;
let ref_foo = &&&&&Foo;
ref_foo.foo();
//~^ ERROR E0055
}

2
src/test/ui/error-codes/E0055.stderr
View file

@ -4,7 +4,7 @@ error[E0055]: reached the recursion limit while auto-dereferencing `Foo`
LL | ref_foo.foo();
| ^^^ deref recursion limit reached
|
= help: consider adding a `#![recursion_limit="4"]` attribute to your crate
= help: consider adding a `#![recursion_limit="10"]` attribute to your crate
error: aborting due to previous error

3
src/test/ui/error-codes/E0275.stderr
View file

@ -1,11 +1,10 @@
error[E0275]: overflow evaluating the requirement `Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>: std::marker::Sized`
error[E0275]: overflow evaluating the requirement `Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>: Foo`
--> $DIR/E0275.rs:5:1
|
LL | impl<T> Foo for T where Bar<T>: Foo {} //~ ERROR E0275
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider adding a `#![recursion_limit="128"]` attribute to your crate
= note: required because of the requirements on the impl of `Foo` for `Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
= note: required because of the requirements on the impl of `Foo` for `Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
= note: required because of the requirements on the impl of `Foo` for `Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
= note: required because of the requirements on the impl of `Foo` for `Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<Bar<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`

3
src/test/ui/issues/issue-20413.stderr
View file

@ -6,7 +6,7 @@ LL | struct NoData<T>;
|
= help: consider removing `T` or using a marker such as `std::marker::PhantomData`
error[E0275]: overflow evaluating the requirement `NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>: std::marker::Sized`
error[E0275]: overflow evaluating the requirement `NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>: Foo`
--> $DIR/issue-20413.rs:8:1
|
LL | / impl<T> Foo for T where NoData<T>: Foo {
@ -18,7 +18,6 @@ LL | | }
| |_^
|
= help: consider adding a `#![recursion_limit="128"]` attribute to your crate
= note: required because of the requirements on the impl of `Foo` for `NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
= note: required because of the requirements on the impl of `Foo` for `NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
= note: required because of the requirements on the impl of `Foo` for `NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
= note: required because of the requirements on the impl of `Foo` for `NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<NoData<T>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`