rust-lang · aliemjay · Jul 19, 2023
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -2233,10 +2233,21 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // is in the same SCC or something. In that case, find what
         // appears to be the most interesting point to report to the
         // user via an even more ad-hoc guess.
-        categorized_path.sort_by_key(|p| p.category);
+        categorized_path.sort_by_key(|p| {
+            let location = p.outlives_constraint.locations.from_location();
+            (
+                location.is_none()
+                    && matches!(
+                        p.category,
+                        ConstraintCategory::Return(_) | ConstraintCategory::OpaqueType
+                    ),
+                location,
+                std::cmp::Reverse(p.category),
+            )
+        });
         debug!("sorted_path={:#?}", categorized_path);
 
-        (categorized_path.remove(0), extra_info)
+        (categorized_path.pop().unwrap(), extra_info)
     }
 
     pub(crate) fn universe_info(&self, universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {

diff --git a/tests/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr b/tests/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr
@@ -1,13 +1,13 @@
 error: lifetime may not live long enough
-  --> $DIR/associated-types-project-from-hrtb-in-fn-body.rs:22:29
+  --> $DIR/associated-types-project-from-hrtb-in-fn-body.rs:22:40
    |
 LL | fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
    |        --  -- lifetime `'b` defined here
    |        |
    |        lifetime `'a` defined here
 ...
 LL |     let z: I::A = if cond { x } else { y };
-   |                             ^ assignment requires that `'a` must outlive `'b`
+   |                                        ^ assignment requires that `'a` must outlive `'b`
    |
    = help: consider adding the following bound: `'a: 'b`
 

diff --git a/tests/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr b/tests/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr
@@ -1,12 +1,12 @@
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-invariant.rs:40:13
+  --> $DIR/project-fn-ret-invariant.rs:41:13
    |
 LL | fn baz<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
    |        --  -- lifetime `'b` defined here
    |        |
    |        lifetime `'a` defined here
-LL |     let f = foo; // <-- No consistent type can be inferred for `f` here.
-LL |     let a = bar(f, x);
+...
+LL |     let b = bar(f, y);
    |             ^^^^^^^^^ argument requires that `'a` must outlive `'b`
    |
    = help: consider adding the following bound: `'a: 'b`
@@ -15,7 +15,7 @@ LL |     let a = bar(f, x);
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: lifetime may not live long enough
-  --> $DIR/project-fn-ret-invariant.rs:42:13
+  --> $DIR/project-fn-ret-invariant.rs:41:13
    |
 LL | fn baz<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
    |        --  -- lifetime `'b` defined here
@@ -26,8 +26,8 @@ LL |     let b = bar(f, y);
    |             ^^^^^^^^^ argument requires that `'b` must outlive `'a`
    |
    = help: consider adding the following bound: `'b: 'a`
-   = note: requirement occurs because of the type `Type<'_>`, which makes the generic argument `'_` invariant
-   = note: the struct `Type<'a>` is invariant over the parameter `'a`
+   = note: requirement occurs because of a function pointer to `foo`
+   = note: the function `foo` is invariant over the parameter `'a`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 help: `'a` and `'b` must be the same: replace one with the other

diff --git a/tests/ui/associated-types/cache/project-fn-ret-invariant.rs b/tests/ui/associated-types/cache/project-fn-ret-invariant.rs
@@ -38,9 +38,9 @@ fn baz<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
 fn baz<'a, 'b>(x: Type<'a>, y: Type<'b>) -> (Type<'a>, Type<'b>) {
     let f = foo; // <-- No consistent type can be inferred for `f` here.
     let a = bar(f, x);
-    //[oneuse]~^ ERROR lifetime may not live long enough
     let b = bar(f, y);
     //[oneuse]~^ ERROR lifetime may not live long enough
+    //[oneuse]~| ERROR lifetime may not live long enough
     (a, b)
 }
 

diff --git a/tests/ui/borrowck/issue-102209.stderr b/tests/ui/borrowck/issue-102209.stderr
@@ -1,22 +1,26 @@
 error: lifetime may not live long enough
-  --> $DIR/issue-102209.rs:10:29
+  --> $DIR/issue-102209.rs:10:15
    |
 LL | impl NfaBuilder<'_> {
    |                 -- lifetime `'2` appears in the `impl`'s self type
 LL |     pub fn with<R, F: FnOnce(NfaBuilder<'_>) -> R>(f: F) -> R {
 LL |         Brand::with(|brand| {
    |                      ----- has type `Brand<'1>`
 LL |             f(Self { brand: brand.lt })
-   |                             ^^^^^^^^ this usage requires that `'1` must outlive `'2`
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^ requires that `'1` must outlive `'2`
+   |
+   = note: requirement occurs because of the type `NfaBuilder<'_>`, which makes the generic argument `'_` invariant
+   = note: the struct `NfaBuilder<'brand>` is invariant over the parameter `'brand`
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: lifetime may not live long enough
-  --> $DIR/issue-102209.rs:10:29
+  --> $DIR/issue-102209.rs:10:15
    |
 LL | impl NfaBuilder<'_> {
    |                 -- lifetime `'1` appears in the `impl`'s self type
 ...
 LL |             f(Self { brand: brand.lt })
-   |                             ^^^^^^^^ this usage requires that `'1` must outlive `'static`
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^ requires that `'1` must outlive `'static`
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/borrowck/two-phase-surprise-no-conflict.stderr b/tests/ui/borrowck/two-phase-surprise-no-conflict.stderr
@@ -72,11 +72,11 @@ LL | fn register_plugins<'a>(mk_reg: impl Fn() -> &'a mut Registry<'a>) {
    |                     -- lifetime `'a` defined here
 ...
 LL |     reg.register_univ(Box::new(CapturePass::new(&reg.sess_mut)));
-   |     ^^^^^^^^^^^^^^^^^^-----------------------------------------^
-   |     |                 |                         |
-   |     |                 |                         immutable borrow occurs here
-   |     |                 cast requires that `reg.sess_mut` is borrowed for `'a`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-------------^^^
+   |     |                                           |
+   |     |                                           immutable borrow occurs here
    |     mutable borrow occurs here
+   |     argument requires that `reg.sess_mut` is borrowed for `'a`
 
 error[E0502]: cannot borrow `*reg` as mutable because it is also borrowed as immutable
   --> $DIR/two-phase-surprise-no-conflict.rs:144:5
@@ -114,11 +114,11 @@ LL | fn register_plugins<'a>(mk_reg: impl Fn() -> &'a mut Registry<'a>) {
    |                     -- lifetime `'a` defined here
 ...
 LL |     reg.register_univ(Box::new(CapturePass::new_mut(&mut reg.sess_mut)));
-   |     ^^^^^^^^^^^^^^^^^^-------------------------------------------------^
-   |     |                 |                             |
-   |     |                 |                             first mutable borrow occurs here
-   |     |                 cast requires that `reg.sess_mut` is borrowed for `'a`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-----------------^^^
+   |     |                                               |
+   |     |                                               first mutable borrow occurs here
    |     second mutable borrow occurs here
+   |     argument requires that `reg.sess_mut` is borrowed for `'a`
 
 error[E0499]: cannot borrow `reg.sess_mut` as mutable more than once at a time
   --> $DIR/two-phase-surprise-no-conflict.rs:158:53

diff --git a/tests/ui/c-variadic/variadic-ffi-4.stderr b/tests/ui/c-variadic/variadic-ffi-4.stderr
@@ -120,28 +120,28 @@ LL | }
    | - `ap1` dropped here while still borrowed
 
 error: lifetime may not live long enough
-  --> $DIR/variadic-ffi-4.rs:35:12
+  --> $DIR/variadic-ffi-4.rs:35:5
    |
 LL | pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
    |                                               -------                   ------- has type `VaListImpl<'2>`
    |                                               |
    |                                               has type `&mut VaListImpl<'1>`
 LL |     *ap0 = ap1.clone();
-   |            ^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |     ^^^^ assignment requires that `'1` must outlive `'2`
    |
    = note: requirement occurs because of the type `VaListImpl<'_>`, which makes the generic argument `'_` invariant
    = note: the struct `VaListImpl<'f>` is invariant over the parameter `'f`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: lifetime may not live long enough
-  --> $DIR/variadic-ffi-4.rs:35:12
+  --> $DIR/variadic-ffi-4.rs:35:5
    |
 LL | pub unsafe extern "C" fn no_escape5(_: usize, mut ap0: &mut VaListImpl, mut ap1: ...) {
    |                                               -------                   ------- has type `VaListImpl<'2>`
    |                                               |
    |                                               has type `&mut VaListImpl<'1>`
 LL |     *ap0 = ap1.clone();
-   |            ^^^^^^^^^^^ argument requires that `'2` must outlive `'1`
+   |     ^^^^ assignment requires that `'2` must outlive `'1`
    |
    = note: requirement occurs because of the type `VaListImpl<'_>`, which makes the generic argument `'_` invariant
    = note: the struct `VaListImpl<'f>` is invariant over the parameter `'f`

diff --git a/tests/ui/dropck/dropck_trait_cycle_checked.stderr b/tests/ui/dropck/dropck_trait_cycle_checked.stderr
@@ -2,33 +2,42 @@ error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:111:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |              -- binding `o2` declared here                          -------- cast requires that `o2` is borrowed for `'static`
+   |              -- binding `o2` declared here
 LL |     o1.set0(&o2);
    |             ^^^ borrowed value does not live long enough
 ...
+LL |     o3.set0(&o1);
+   |     ------------ argument requires that `o2` is borrowed for `'static`
+LL |     o3.set1(&o2);
 LL | }
    | - `o2` dropped here while still borrowed
 
 error[E0597]: `o3` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:112:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |                  -- binding `o3` declared here                      -------- cast requires that `o3` is borrowed for `'static`
+   |                  -- binding `o3` declared here
 LL |     o1.set0(&o2);
 LL |     o1.set1(&o3);
    |             ^^^ borrowed value does not live long enough
 ...
+LL |     o3.set0(&o1);
+   |     ------------ argument requires that `o3` is borrowed for `'static`
+LL |     o3.set1(&o2);
 LL | }
    | - `o3` dropped here while still borrowed
 
 error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:113:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |              -- binding `o2` declared here                                    -------- cast requires that `o2` is borrowed for `'static`
+   |              -- binding `o2` declared here
 ...
 LL |     o2.set0(&o2);
-   |             ^^^ borrowed value does not live long enough
+   |     --------^^^-
+   |     |       |
+   |     |       borrowed value does not live long enough
+   |     argument requires that `o2` is borrowed for `'static`
 ...
 LL | }
    | - `o2` dropped here while still borrowed
@@ -37,10 +46,13 @@ error[E0597]: `o3` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:114:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |                  -- binding `o3` declared here                                -------- cast requires that `o3` is borrowed for `'static`
+   |                  -- binding `o3` declared here
 ...
 LL |     o2.set1(&o3);
-   |             ^^^ borrowed value does not live long enough
+   |     --------^^^-
+   |     |       |
+   |     |       borrowed value does not live long enough
+   |     argument requires that `o3` is borrowed for `'static`
 ...
 LL | }
    | - `o3` dropped here while still borrowed
@@ -49,10 +61,13 @@ error[E0597]: `o1` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:115:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |          -- binding `o1` declared here                                                  -------- cast requires that `o1` is borrowed for `'static`
+   |          -- binding `o1` declared here
 ...
 LL |     o3.set0(&o1);
-   |             ^^^ borrowed value does not live long enough
+   |     --------^^^-
+   |     |       |
+   |     |       borrowed value does not live long enough
+   |     argument requires that `o1` is borrowed for `'static`
 LL |     o3.set1(&o2);
 LL | }
    | - `o1` dropped here while still borrowed
@@ -61,10 +76,13 @@ error[E0597]: `o2` does not live long enough
   --> $DIR/dropck_trait_cycle_checked.rs:116:13
    |
 LL |     let (o1, o2, o3): (Box<dyn Obj>, Box<dyn Obj>, Box<dyn Obj>) = (O::new(), O::new(), O::new());
-   |              -- binding `o2` declared here                                              -------- cast requires that `o2` is borrowed for `'static`
+   |              -- binding `o2` declared here
 ...
 LL |     o3.set1(&o2);
-   |             ^^^ borrowed value does not live long enough
+   |     --------^^^-
+   |     |       |
+   |     |       borrowed value does not live long enough
+   |     argument requires that `o2` is borrowed for `'static`
 LL | }
    | - `o2` dropped here while still borrowed
 

diff --git a/tests/ui/lifetimes/issue-69314.stderr b/tests/ui/lifetimes/issue-69314.stderr
@@ -17,8 +17,8 @@ LL |         let mut buf = [0; 512];
 LL |         let m2 = &buf[..];
    |                   ^^^ borrowed value does not live long enough
 LL |         let m = Self::g(m2).await;
-   |                 ----------- argument requires that `buf` is borrowed for `'static`
 LL |         Self::f2(m).await;
+   |         ----------- argument requires that `buf` is borrowed for `'static`
 LL |     }
    |     - `buf` dropped here while still borrowed
 

diff --git a/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.rs b/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.rs
@@ -7,9 +7,9 @@ fn inner(mut foo: &[u8]) {
     let refcell = RefCell::new(&mut foo);
     //~^ ERROR `foo` does not live long enough
     let read = &refcell as &RefCell<dyn Read>;
-    //~^ ERROR lifetime may not live long enough
 
     read_thing(read);
+    //~^ ERROR borrowed data escapes outside of function [E0521]
 }
 
 fn read_thing(refcell: &RefCell<dyn Read>) {}
diff --git a/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr b/tests/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
@@ -5,22 +5,32 @@ LL | fn inner(mut foo: &[u8]) {
    |          ------- binding `foo` declared here
 LL |     let refcell = RefCell::new(&mut foo);
    |                                ^^^^^^^^ borrowed value does not live long enough
-LL |
-LL |     let read = &refcell as &RefCell<dyn Read>;
-   |                -------- cast requires that `foo` is borrowed for `'static`
 ...
+LL |     read_thing(read);
+   |     ---------------- argument requires that `foo` is borrowed for `'static`
+LL |
 LL | }
    |  - `foo` dropped here while still borrowed
 
-error: lifetime may not live long enough
-  --> $DIR/issue-90600-expected-return-static-indirect.rs:9:16
+error[E0521]: borrowed data escapes outside of function
+  --> $DIR/issue-90600-expected-return-static-indirect.rs:11:5
    |
 LL | fn inner(mut foo: &[u8]) {
-   |                   - let's call the lifetime of this reference `'1`
+   |          -------  - let's call the lifetime of this reference `'1`
+   |          |
+   |          `foo` is a reference that is only valid in the function body
 ...
-LL |     let read = &refcell as &RefCell<dyn Read>;
-   |                ^^^^^^^^ cast requires that `'1` must outlive `'static`
+LL |     read_thing(read);
+   |     ^^^^^^^^^^^^^^^^
+   |     |
+   |     `foo` escapes the function body here
+   |     argument requires that `'1` must outlive `'static`
+   |
+   = note: requirement occurs because of the type `RefCell<(dyn std::io::Read + 'static)>`, which makes the generic argument `(dyn std::io::Read + 'static)` invariant
+   = note: the struct `RefCell<T>` is invariant over the parameter `T`
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0597`.
+Some errors have detailed explanations: E0521, E0597.
+For more information about an error, try `rustc --explain E0521`.
diff --git a/tests/ui/nll/blame-furthest-statement.rs b/tests/ui/nll/blame-furthest-statement.rs
@@ -0,0 +1,48 @@
+// Make sure we blame the furthest statment in lifetime errors.
+
+fn id<X>(x: X) -> X { x }
+fn relate<X>(_: &X, _: &X) {}
+struct Inv<'a>(*mut &'a u8);
+
+fn test_static(a: Inv<'_>, b: Inv<'static>) {
+    let a = id(a);
+    let b = id(b);
+    relate(&a, &b);
+    //~^ ERROR
+}
+
+fn test1(a: Inv<'_>, b: Inv<'_>) {
+    let a = id(a);
+    let b = id(b);
+    relate(&a, &b);
+    //~^ ERROR
+    //~| ERROR
+}
+
+fn test2(cond: bool, a: Inv<'_>, b: Inv<'_>) {
+    let mut x = None::<Inv<'_>>;
+    let mut y = None::<Inv<'_>>;
+    if cond {
+        relate(&x, &y);
+    } else {
+        x.replace(a);
+        y.replace(b);
+        //~^ ERROR
+        //~| ERROR
+    }
+}
+
+fn test3(cond: bool, a: Inv<'_>, b: Inv<'_>) {
+    let mut x = None::<Inv<'_>>;
+    let mut y = None::<Inv<'_>>;
+    if cond {
+        x.replace(a);
+        y.replace(b);
+    } else {
+        relate(&x, &y);
+        //~^ ERROR
+        //~| ERROR
+    }
+}
+
+fn main() {}