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use approx. bounds to decide whether to add outlives obligations

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Before, if we had a projection like `<T as Foo<'0>>::Bar: 'x` and a
where clause like `<T as Foo<'a>>::Bar: 'a`, we considered those to
have nothing to do with one another. Therefore, we would use the
"overconstrained" path of adding `T: 'x` and `'0: 'x` requirements. We
now do a "fuzzy" match where we erase regions first and hence we see
the env bound `'a`.
This commit is contained in:
Niko Matsakis 2018-09-17 14:00:33 -04:00
parent 4b193cb92a
commit 689b791422
4 changed files with 24 additions and 30 deletions
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3
src/test/ui/nll/ty-outlives/projection-one-region-closure.rs
View file

@ -85,8 +85,7 @@ where
// can do better here with a more involved verification step.
with_signature(cell, t, |cell, t| require(cell, t));
//~^ ERROR the parameter type `T` may not live long enough
//~| ERROR
//~^ ERROR
}
#[rustc_regions]

26
src/test/ui/nll/ty-outlives/projection-one-region-closure.stderr
View file

@ -119,8 +119,7 @@ LL | with_signature(cell, t, |cell, t| require(cell, t));
extern "rust-call" fn((std::cell::Cell<&'_#3r ()>, T))
]
= note: number of external vids: 4
= note: where T: '_#3r
= note: where '_#2r: '_#3r
= note: where <T as Anything<ReClosureBound('_#2r)>>::AssocType: '_#3r
note: No external requirements
--> $DIR/projection-one-region-closure.rs:72:1
@ -130,7 +129,7 @@ LL | | where
LL | | T: Anything<'b>,
LL | | T::AssocType: 'a,
... |
LL | | //~| ERROR
LL | | //~^ ERROR
LL | | }
| |_^
|
@ -140,27 +139,16 @@ LL | | }
T
]
error[E0309]: the parameter type `T` may not live long enough
error[E0309]: the associated type `<T as Anything<'_#5r>>::AssocType` may not live long enough
--> $DIR/projection-one-region-closure.rs:87:29
|
LL | with_signature(cell, t, |cell, t| require(cell, t));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider adding an explicit lifetime bound `T: ReEarlyBound(0, 'a)`...
error: unsatisfied lifetime constraints
--> $DIR/projection-one-region-closure.rs:87:29
|
LL | fn projection_outlives<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
...
LL | with_signature(cell, t, |cell, t| require(cell, t));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ closure body requires that `'b` must outlive `'a`
= help: consider adding an explicit lifetime bound `<T as Anything<'_#5r>>::AssocType: ReEarlyBound(0, 'a)`...
note: External requirements
--> $DIR/projection-one-region-closure.rs:99:29
--> $DIR/projection-one-region-closure.rs:98:29
|
LL | with_signature(cell, t, |cell, t| require(cell, t));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -177,7 +165,7 @@ LL | with_signature(cell, t, |cell, t| require(cell, t));
= note: where '_#2r: '_#3r
note: No external requirements
--> $DIR/projection-one-region-closure.rs:93:1
--> $DIR/projection-one-region-closure.rs:92:1
|
LL | / fn elements_outlive<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
LL | | where
@ -194,6 +182,6 @@ LL | | }
T
]
error: aborting due to 6 previous errors
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0309`.

14
src/test/ui/nll/ty-outlives/projection-one-region-trait-bound-closure.stderr
View file

@ -101,7 +101,7 @@ LL | with_signature(cell, t, |cell, t| require(cell, t));
extern "rust-call" fn((std::cell::Cell<&'_#3r ()>, T))
]
= note: number of external vids: 4
= note: where '_#2r: '_#3r
= note: where <T as Anything<ReClosureBound('_#2r)>>::AssocType: '_#3r
note: No external requirements
--> $DIR/projection-one-region-trait-bound-closure.rs:62:1
@ -121,16 +121,13 @@ LL | | }
T
]
error: unsatisfied lifetime constraints
error[E0309]: the associated type `<T as Anything<'_#5r>>::AssocType` may not live long enough
--> $DIR/projection-one-region-trait-bound-closure.rs:77:29
|
LL | fn projection_outlives<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
...
LL | with_signature(cell, t, |cell, t| require(cell, t));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ closure body requires that `'b` must outlive `'a`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider adding an explicit lifetime bound `<T as Anything<'_#5r>>::AssocType: ReEarlyBound(0, 'a)`...
note: External requirements
--> $DIR/projection-one-region-trait-bound-closure.rs:87:29
@ -200,3 +197,4 @@ LL | | }
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0309`.