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Auto merge of #53493 - matthewjasper:hair-spans, r=nikomatsakis

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Use smaller span for adjustments on block expressions

When returning a mutable reference don't use the entire body of the function as the span for the adjustments at the end.

The error [in this case](https://github.com/rust-lang/rust/compare/master...matthewjasper:hair-spans?expand=1#diff-ecef8b1f15622fb48a803c9b61605c78) is worse, but neither error message is really what we want. I have some ideas on how to get a better error message that will have to wait for a future PR.
This commit is contained in:
bors 2018-08-28 13:12:16 +00:00
commit ec4a752202
19 changed files with 143 additions and 184 deletions
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28
src/librustc_mir/hair/cx/expr.rs
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@ -78,7 +78,7 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
mut expr: Expr<'tcx>,
adjustment: &Adjustment<'tcx>)
-> Expr<'tcx> {
let Expr { temp_lifetime, span, .. } = expr;
let Expr { temp_lifetime, mut span, .. } = expr;
let kind = match adjustment.kind {
Adjust::ReifyFnPointer => {
ExprKind::ReifyFnPointer { source: expr.to_ref() }
@ -96,6 +96,25 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
ExprKind::Cast { source: expr.to_ref() }
}
Adjust::Deref(None) => {
// Adjust the span from the block, to the last expression of the
// block. This is a better span when returning a mutable reference
// with too short a lifetime. The error message will use the span
// from the assignment to the return place, which should only point
// at the returned value, not the entire function body.
//
// fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
// x
// // ^ error message points at this expression.
// }
//
// We don't need to do this adjustment in the next match arm since
// deref coercions always start with a built-in deref.
if let ExprKind::Block { body } = expr.kind {
if let Some(ref last_expr) = body.expr {
span = last_expr.span;
expr.span = span;
}
}
ExprKind::Deref { arg: expr.to_ref() }
}
Adjust::Deref(Some(deref)) => {
@ -180,6 +199,13 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
ExprKind::Use { source: cast_expr.to_ref() }
}
Adjust::Unsize => {
// See the above comment for Adjust::Deref
if let ExprKind::Block { body } = expr.kind {
if let Some(ref last_expr) = body.expr {
span = last_expr.span;
expr.span = span;
}
}
ExprKind::Unsize { source: expr.to_ref() }
}
};

1
src/test/ui/issues/issue-17718-const-bad-values.rs
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@ -15,6 +15,5 @@ static mut S: usize = 3;
const C2: &'static mut usize = unsafe { &mut S };
//~^ ERROR: constants cannot refer to statics
//~| ERROR: references in constants may only refer to immutable values
//~| ERROR: references in constants may only refer to immutable values
fn main() {}

8
src/test/ui/issues/issue-17718-const-bad-values.stderr
View File

@ -16,13 +16,7 @@ error[E0017]: references in constants may only refer to immutable values
LL | const C2: &'static mut usize = unsafe { &mut S };
| ^^^^^^ constants require immutable values
error[E0017]: references in constants may only refer to immutable values
--> $DIR/issue-17718-const-bad-values.rs:15:32
|
LL | const C2: &'static mut usize = unsafe { &mut S };
| ^^^^^^^^^^^^^^^^^ constants require immutable values
error: aborting due to 4 previous errors
error: aborting due to 3 previous errors
Some errors occurred: E0013, E0017.
For more information about an error, try `rustc --explain E0013`.

17
src/test/ui/issues/issue-46471-1.stderr
View File

@ -12,16 +12,13 @@ LL | }
error[E0597]: `z` does not live long enough (Mir)
--> $DIR/issue-46471-1.rs:16:9
|
LL | let y = {
| _____________-
LL | | let mut z = 0;
LL | | &mut z
| | ^^^^^^ borrowed value does not live long enough
LL | | };
| | -
| | |
| |_____`z` dropped here while still borrowed
| borrow later used here
LL | &mut z
| ^^^^^^
| |
| borrowed value does not live long enough
| borrow later used here
LL | };
| - `z` dropped here while still borrowed
error: aborting due to 2 previous errors

17
src/test/ui/match/match-ref-mut-invariance.nll.stderr
View File

@ -5,17 +5,14 @@ LL | match self.0 { ref mut x => x } //~ ERROR mismatched types
| ^
error: unsatisfied lifetime constraints
--> $DIR/match-ref-mut-invariance.rs:19:49
--> $DIR/match-ref-mut-invariance.rs:20:9
|
LL | impl<'b> S<'b> {
| -- lifetime `'b` defined here
LL | fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
| ____________--___________________________________^
| | |
| | lifetime `'a` defined here
LL | | match self.0 { ref mut x => x } //~ ERROR mismatched types
LL | | }
| |_____^ returning this value requires that `'a` must outlive `'b`
LL | impl<'b> S<'b> {
| -- lifetime `'b` defined here
LL | fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
| -- lifetime `'a` defined here
LL | match self.0 { ref mut x => x } //~ ERROR mismatched types
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'a` must outlive `'b`
error: aborting due to previous error

19
src/test/ui/match/match-ref-mut-let-invariance.nll.stderr
View File

@ -5,18 +5,15 @@ LL | x //~ ERROR mismatched types
| ^
error: unsatisfied lifetime constraints
--> $DIR/match-ref-mut-let-invariance.rs:19:49
--> $DIR/match-ref-mut-let-invariance.rs:21:9
|
LL | impl<'b> S<'b> {
| -- lifetime `'b` defined here
LL | fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
| ____________--___________________________________^
| | |
| | lifetime `'a` defined here
LL | | let ref mut x = self.0;
LL | | x //~ ERROR mismatched types
LL | | }
| |_____^ returning this value requires that `'a` must outlive `'b`
LL | impl<'b> S<'b> {
| -- lifetime `'b` defined here
LL | fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
| -- lifetime `'a` defined here
LL | let ref mut x = self.0;
LL | x //~ ERROR mismatched types
| ^ returning this value requires that `'a` must outlive `'b`
error: aborting due to previous error

4
src/test/ui/nll/mir_check_cast_unsize.rs
View File

@ -15,9 +15,9 @@
use std::fmt::Debug;
fn bar<'a>(x: &'a u32) -> &'static dyn Debug {
//~^ ERROR unsatisfied lifetime constraints
x
//~^ WARNING not reporting region error due to nll
//~^ ERROR unsatisfied lifetime constraints
//~| WARNING not reporting region error due to nll
}
fn main() {}

17
src/test/ui/nll/mir_check_cast_unsize.stderr
View File

@ -1,21 +1,16 @@
warning: not reporting region error due to nll
--> $DIR/mir_check_cast_unsize.rs:19:5
--> $DIR/mir_check_cast_unsize.rs:18:5
|
LL | x
| ^
error: unsatisfied lifetime constraints
--> $DIR/mir_check_cast_unsize.rs:17:46
--> $DIR/mir_check_cast_unsize.rs:18:5
|
LL | fn bar<'a>(x: &'a u32) -> &'static dyn Debug {
| ________--____________________________________^
| | |
| | lifetime `'a` defined here
LL | | //~^ ERROR unsatisfied lifetime constraints
LL | | x
LL | | //~^ WARNING not reporting region error due to nll
LL | | }
| |_^ returning this value requires that `'a` must outlive `'static`
LL | fn bar<'a>(x: &'a u32) -> &'static dyn Debug {
| -- lifetime `'a` defined here
LL | x
| ^ returning this value requires that `'a` must outlive `'static`
error: aborting due to previous error

21
src/test/ui/object-lifetime/object-lifetime-default-elision.nll.stderr
View File

@ -5,20 +5,15 @@ LL | ss
| ^^
error: unsatisfied lifetime constraints
--> $DIR/object-lifetime-default-elision.rs:64:53
--> $DIR/object-lifetime-default-elision.rs:81:5
|
LL | fn load3<'a,'b>(ss: &'a SomeTrait) -> &'b SomeTrait {
| __________--_--______________________________________^
| | | |
| | | lifetime `'b` defined here
| | lifetime `'a` defined here
LL | | // Under old rules, the fully elaborated types of input/output were:
LL | | //
LL | | // for<'a,'b,'c>fn(&'a (SomeTrait+'c)) -> &'b (SomeTrait+'a)
... |
LL | | //~| ERROR cannot infer
LL | | }
| |_^ returning this value requires that `'a` must outlive `'b`
LL | fn load3<'a,'b>(ss: &'a SomeTrait) -> &'b SomeTrait {
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
...
LL | ss
| ^^ returning this value requires that `'a` must outlive `'b`
error: aborting due to previous error

17
src/test/ui/object-lifetime/object-lifetime-default-from-box-error.nll.stderr
View File

@ -11,18 +11,13 @@ LL | ss.r = b; //~ ERROR 41:12: 41:13: explicit lifetime required in the typ
| ^
error[E0621]: explicit lifetime required in the type of `ss`
--> $DIR/object-lifetime-default-from-box-error.rs:24:48
--> $DIR/object-lifetime-default-from-box-error.rs:28:5
|
LL | fn load(ss: &mut SomeStruct) -> Box<SomeTrait> {
| _____________---------------____________________^
| | |
| | help: add explicit lifetime `'static` to the type of `ss`: `&mut SomeStruct<'static>`
LL | | // `Box<SomeTrait>` defaults to a `'static` bound, so this return
LL | | // is illegal.
LL | |
LL | | ss.r //~ ERROR explicit lifetime required in the type of `ss` [E0621]
LL | | }
| |_^ lifetime `'static` required
LL | fn load(ss: &mut SomeStruct) -> Box<SomeTrait> {
| --------------- help: add explicit lifetime `'static` to the type of `ss`: `&mut SomeStruct<'static>`
...
LL | ss.r //~ ERROR explicit lifetime required in the type of `ss` [E0621]
| ^^^^ lifetime `'static` required
error[E0507]: cannot move out of borrowed content
--> $DIR/object-lifetime-default-from-box-error.rs:28:5

48
src/test/ui/regions/region-object-lifetime-in-coercion.nll.stderr
View File

@ -31,43 +31,31 @@ LL | let x: Box<Foo + 'static> = Box::new(v);
| ^^^^^^^^^^^ lifetime `'static` required
error[E0621]: explicit lifetime required in the type of `v`
--> $DIR/region-object-lifetime-in-coercion.rs:23:38
--> $DIR/region-object-lifetime-in-coercion.rs:24:5
|
LL | fn b(v: &[u8]) -> Box<Foo + 'static> {
| _________-----________________________^
| | |
| | help: add explicit lifetime `'static` to the type of `v`: `&'static [u8]`
LL | | Box::new(v)
LL | | //~^ ERROR explicit lifetime required in the type of `v` [E0621]
LL | | }
| |_^ lifetime `'static` required
LL | fn b(v: &[u8]) -> Box<Foo + 'static> {
| ----- help: add explicit lifetime `'static` to the type of `v`: `&'static [u8]`
LL | Box::new(v)
| ^^^^^^^^^^^ lifetime `'static` required
error[E0621]: explicit lifetime required in the type of `v`
--> $DIR/region-object-lifetime-in-coercion.rs:28:28
--> $DIR/region-object-lifetime-in-coercion.rs:31:5
|
LL | fn c(v: &[u8]) -> Box<Foo> {
| _________-----______________^
| | |
| | help: add explicit lifetime `'static` to the type of `v`: `&'static [u8]`
LL | | // same as previous case due to RFC 599
LL | |
LL | | Box::new(v)
LL | | //~^ ERROR explicit lifetime required in the type of `v` [E0621]
LL | | }
| |_^ lifetime `'static` required
LL | fn c(v: &[u8]) -> Box<Foo> {
| ----- help: add explicit lifetime `'static` to the type of `v`: `&'static [u8]`
...
LL | Box::new(v)
| ^^^^^^^^^^^ lifetime `'static` required
error: unsatisfied lifetime constraints
--> $DIR/region-object-lifetime-in-coercion.rs:35:41
--> $DIR/region-object-lifetime-in-coercion.rs:36:5
|
LL | fn d<'a,'b>(v: &'a [u8]) -> Box<Foo+'b> {
| ______--_--______________________________^
| | | |
| | | lifetime `'b` defined here
| | lifetime `'a` defined here
LL | | Box::new(v)
LL | | //~^ ERROR cannot infer an appropriate lifetime due to conflicting
LL | | }
| |_^ returning this value requires that `'a` must outlive `'b`
LL | fn d<'a,'b>(v: &'a [u8]) -> Box<Foo+'b> {
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
LL | Box::new(v)
| ^^^^^^^^^^^ returning this value requires that `'a` must outlive `'b`
error: aborting due to 4 previous errors

13
src/test/ui/regions/regions-close-object-into-object-2.nll.stderr
View File

@ -5,15 +5,12 @@ LL | box B(&*v) as Box<X> //~ ERROR cannot infer
| ^^^
error: unsatisfied lifetime constraints
--> $DIR/regions-close-object-into-object-2.rs:19:57
--> $DIR/regions-close-object-into-object-2.rs:20:5
|
LL | fn g<'a, T: 'static>(v: Box<A<T>+'a>) -> Box<X+'static> {
| ______--_________________________________________________^
| | |
| | lifetime `'a` defined here
LL | | box B(&*v) as Box<X> //~ ERROR cannot infer
LL | | }
| |_^ returning this value requires that `'a` must outlive `'static`
LL | fn g<'a, T: 'static>(v: Box<A<T>+'a>) -> Box<X+'static> {
| -- lifetime `'a` defined here
LL | box B(&*v) as Box<X> //~ ERROR cannot infer
| ^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
error[E0597]: `*v` does not live long enough
--> $DIR/regions-close-object-into-object-2.rs:20:11

19
src/test/ui/regions/regions-close-object-into-object-4.nll.stderr
View File

@ -28,17 +28,6 @@ warning: not reporting region error due to nll
LL | box B(&*v) as Box<X> //~ ERROR cannot infer
| ^^^^^^^^^^
error: unsatisfied lifetime constraints
--> $DIR/regions-close-object-into-object-4.rs:19:51
|
LL | fn i<'a, T, U>(v: Box<A<U>+'a>) -> Box<X+'static> {
| ______--___________________________________________^
| | |
| | lifetime `'a` defined here
LL | | box B(&*v) as Box<X> //~ ERROR cannot infer
LL | | }
| |_^ returning this value requires that `'a` must outlive `'static`
error[E0310]: the parameter type `U` may not live long enough
--> $DIR/regions-close-object-into-object-4.rs:20:5
|
@ -47,6 +36,14 @@ LL | box B(&*v) as Box<X> //~ ERROR cannot infer
|
= help: consider adding an explicit lifetime bound `U: 'static`...
error: unsatisfied lifetime constraints
--> $DIR/regions-close-object-into-object-4.rs:20:5
|
LL | fn i<'a, T, U>(v: Box<A<U>+'a>) -> Box<X+'static> {
| -- lifetime `'a` defined here
LL | box B(&*v) as Box<X> //~ ERROR cannot infer
| ^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
error[E0310]: the parameter type `U` may not live long enough
--> $DIR/regions-close-object-into-object-4.rs:20:9
|

15
src/test/ui/regions/regions-proc-bound-capture.nll.stderr
View File

@ -5,16 +5,13 @@ LL | Box::new(move|| { *x }) //~ ERROR explicit lifetime required in the typ
| ^^^^^^^^^^^^^
error[E0621]: explicit lifetime required in the type of `x`
--> $DIR/regions-proc-bound-capture.rs:17:62
--> $DIR/regions-proc-bound-capture.rs:19:5
|
LL | fn static_proc(x: &isize) -> Box<FnMut()->(isize) + 'static> {
| ___________________------_____________________________________^
| | |
| | help: add explicit lifetime `'static` to the type of `x`: `&'static isize`
LL | | // This is illegal, because the region bound on `proc` is 'static.
LL | | Box::new(move|| { *x }) //~ ERROR explicit lifetime required in the type of `x` [E0621]
LL | | }
| |_^ lifetime `'static` required
LL | fn static_proc(x: &isize) -> Box<FnMut()->(isize) + 'static> {
| ------ help: add explicit lifetime `'static` to the type of `x`: `&'static isize`
LL | // This is illegal, because the region bound on `proc` is 'static.
LL | Box::new(move|| { *x }) //~ ERROR explicit lifetime required in the type of `x` [E0621]
| ^^^^^^^^^^^^^^^^^^^^^^^ lifetime `'static` required
error: aborting due to previous error

16
src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.nll.stderr
View File

@ -5,16 +5,14 @@ LL | &mut ***p //~ ERROR 14:5: 14:14: lifetime mismatch [E0623]
| ^^^^^^^^^
error: unsatisfied lifetime constraints
--> $DIR/regions-reborrow-from-shorter-mut-ref-mut-ref.rs:13:85
--> $DIR/regions-reborrow-from-shorter-mut-ref-mut-ref.rs:14:5
|
LL | fn copy_borrowed_ptr<'a, 'b, 'c>(p: &'a mut &'b mut &'c mut isize) -> &'b mut isize {
| ______________________--__--_________________________________________________________^
| | | |
| | | lifetime `'b` defined here
| | lifetime `'a` defined here
LL | | &mut ***p //~ ERROR 14:5: 14:14: lifetime mismatch [E0623]
LL | | }
| |_^ function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
LL | fn copy_borrowed_ptr<'a, 'b, 'c>(p: &'a mut &'b mut &'c mut isize) -> &'b mut isize {
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
LL | &mut ***p //~ ERROR 14:5: 14:14: lifetime mismatch [E0623]
| ^^^^^^^^^ function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
error: aborting due to previous error

16
src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.nll.stderr
View File

@ -5,16 +5,14 @@ LL | &mut **p //~ ERROR 16:5: 16:13: lifetime mismatch [E0623]
| ^^^^^^^^
error: unsatisfied lifetime constraints
--> $DIR/regions-reborrow-from-shorter-mut-ref.rs:15:73
--> $DIR/regions-reborrow-from-shorter-mut-ref.rs:16:5
|
LL | fn copy_borrowed_ptr<'a, 'b>(p: &'a mut &'b mut isize) -> &'b mut isize {
| ______________________--__--_____________________________________________^
| | | |
| | | lifetime `'b` defined here
| | lifetime `'a` defined here
LL | | &mut **p //~ ERROR 16:5: 16:13: lifetime mismatch [E0623]
LL | | }
| |_^ function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
LL | fn copy_borrowed_ptr<'a, 'b>(p: &'a mut &'b mut isize) -> &'b mut isize {
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
LL | &mut **p //~ ERROR 16:5: 16:13: lifetime mismatch [E0623]
| ^^^^^^^^ function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
error: aborting due to previous error

19
src/test/ui/regions/regions-trait-object-subtyping.nll.stderr
View File

@ -11,18 +11,15 @@ LL | x //~ ERROR mismatched types
| ^
error: unsatisfied lifetime constraints
--> $DIR/regions-trait-object-subtyping.rs:23:51
--> $DIR/regions-trait-object-subtyping.rs:25:5
|
LL | fn foo3<'a,'b>(x: &'a mut Dummy) -> &'b mut Dummy {
| _________--_--_____________________________________^
| | | |
| | | lifetime `'b` defined here
| | lifetime `'a` defined here
LL | | // Without knowing 'a:'b, we can't coerce
LL | | x //~ ERROR lifetime bound not satisfied
LL | | //~^ ERROR cannot infer an appropriate lifetime
LL | | }
| |_^ returning this value requires that `'a` must outlive `'b`
LL | fn foo3<'a,'b>(x: &'a mut Dummy) -> &'b mut Dummy {
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
LL | // Without knowing 'a:'b, we can't coerce
LL | x //~ ERROR lifetime bound not satisfied
| ^ returning this value requires that `'a` must outlive `'b`
error: unsatisfied lifetime constraints
--> $DIR/regions-trait-object-subtyping.rs:32:5

17
src/test/ui/span/regions-close-over-type-parameter-2.nll.stderr
View File

@ -1,17 +1,12 @@
error[E0597]: `tmp0` does not live long enough
--> $DIR/regions-close-over-type-parameter-2.rs:33:20
|
LL | let _ = {
| _____________-
LL | | let tmp0 = 3;
LL | | let tmp1 = &tmp0;
| | ^^^^^ borrowed value does not live long enough
LL | | repeater3(tmp1)
LL | | };
| | -
| | |
| |_____`tmp0` dropped here while still borrowed
| borrow later used here
LL | let tmp1 = &tmp0;
| ^^^^^ borrowed value does not live long enough
LL | repeater3(tmp1)
| --------------- borrow later used here
LL | };
| - `tmp0` dropped here while still borrowed
error: aborting due to previous error

15
src/test/ui/underscore-lifetime/dyn-trait-underscore.nll.stderr
View File

@ -23,16 +23,13 @@ LL | Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime
| ^^^^^^^^^^^^^^^^^^^^^^
error: unsatisfied lifetime constraints
--> $DIR/dyn-trait-underscore.rs:16:52
--> $DIR/dyn-trait-underscore.rs:18:5
|
LL | fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
| ________________-___________________________________^
| | |
| | let's call the lifetime of this reference `'1`
LL | | // ^^^^^^^^^^^^^^^^^^^^^ bound *here* defaults to `'static`
LL | | Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime
LL | | }
| |_^ returning this value requires that `'1` must outlive `'static`
LL | fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
| - let's call the lifetime of this reference `'1`
LL | // ^^^^^^^^^^^^^^^^^^^^^ bound *here* defaults to `'static`
LL | Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime
| ^^^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'1` must outlive `'static`
error: aborting due to previous error