`best_blame_constraint`: avoid blaming assignments without user-provided types

14 files changed, 63 insertions, 57 deletions

diff --git a/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.32bit.mir b/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.32bit.mir
index 35e44b2314a..7f4a2bbbb5c 100644
--- a/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.32bit.mir
+++ b/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.32bit.mir
@@ -17,8 +17,8 @@
 | '?2 live at {bb1[0]}
 | '?3 live at {bb1[1..=3]}
 | '?4 live at {bb1[4..=7], bb2[0..=2]}
-| '?2: '?3 due to Assignment at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
-| '?3: '?4 due to Assignment at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
+| '?2: '?3 due to Assignment { has_interesting_ty: false } at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
+| '?3: '?4 due to Assignment { has_interesting_ty: false } at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
 |
 | Borrows
 | bw0: issued at bb1[0] in '?2
diff --git a/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.64bit.mir b/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.64bit.mir
index 6d415f42d06..1d80df76b3f 100644
--- a/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.64bit.mir
+++ b/tests/mir-opt/nll/region_subtyping_basic.main.nll.0.64bit.mir
@@ -17,8 +17,8 @@
 | '?2 live at {bb1[0]}
 | '?3 live at {bb1[1..=3]}
 | '?4 live at {bb1[4..=7], bb2[0..=2]}
-| '?2: '?3 due to Assignment at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
-| '?3: '?4 due to Assignment at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
+| '?2: '?3 due to Assignment { has_interesting_ty: false } at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
+| '?3: '?4 due to Assignment { has_interesting_ty: false } at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
 |
 | Borrows
 | bw0: issued at bb1[0] in '?2
diff --git a/tests/mir-opt/storage_ranges.main.nll.0.mir b/tests/mir-opt/storage_ranges.main.nll.0.mir
index ae8cd0c894d..291e3bbc873 100644
--- a/tests/mir-opt/storage_ranges.main.nll.0.mir
+++ b/tests/mir-opt/storage_ranges.main.nll.0.mir
@@ -15,7 +15,7 @@
 | '?1 live at {bb0[0..=22]}
 | '?2 live at {bb0[10]}
 | '?3 live at {bb0[11]}
-| '?2: '?3 due to Assignment at Single(bb0[10]) ($DIR/storage_ranges.rs:7:17: 7:25 (#0)
+| '?2: '?3 due to Assignment { has_interesting_ty: false } at Single(bb0[10]) ($DIR/storage_ranges.rs:7:17: 7:25 (#0)
 |
 | Borrows
 | bw0: issued at bb0[10] in '?2
diff --git a/tests/ui/fn/fn_def_coercion.rs b/tests/ui/fn/fn_def_coercion.rs
index 31c8fa41de1..313be6f28cd 100644
--- a/tests/ui/fn/fn_def_coercion.rs
+++ b/tests/ui/fn/fn_def_coercion.rs
@@ -46,12 +46,12 @@ fn j<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
 
 fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
     let x = match true {
-        true => foo::<&'c ()>, //~ ERROR lifetime may not live long enough
+        true => foo::<&'c ()>,
         false => foo::<&'a ()>, //~ ERROR lifetime may not live long enough
     };
 
     x(a);
-    x(b);
+    x(b); //~ ERROR lifetime may not live long enough
     x(c);
 }
 
diff --git a/tests/ui/fn/fn_def_coercion.stderr b/tests/ui/fn/fn_def_coercion.stderr
index c2776887b79..ec4a1bde7fd 100644
--- a/tests/ui/fn/fn_def_coercion.stderr
+++ b/tests/ui/fn/fn_def_coercion.stderr
@@ -6,9 +6,9 @@ LL | fn f<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      |
    |      lifetime `'a` defined here
 LL |     let mut x = foo::<&'a ()>;
-   |                 ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
+   |                 ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
    |
-   = help: consider adding the following bound: `'b: 'a`
+   = help: consider adding the following bound: `'a: 'b`
    = note: requirement occurs because of a function pointer to `foo`
    = note: the function `foo` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -22,9 +22,9 @@ LL | fn f<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      lifetime `'a` defined here
 LL |     let mut x = foo::<&'a ()>;
 LL |     x = foo::<&'b ()>;
-   |     ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
+   |     ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
    |
-   = help: consider adding the following bound: `'a: 'b`
+   = help: consider adding the following bound: `'b: 'a`
    = note: requirement occurs because of a function pointer to `foo`
    = note: the function `foo` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -53,9 +53,9 @@ LL | fn i<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      lifetime `'a` defined here
 LL |     let mut x = foo::<&'c ()>;
 LL |     x = foo::<&'b ()>;
-   |     ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
+   |     ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
    |
-   = help: consider adding the following bound: `'a: 'b`
+   = help: consider adding the following bound: `'b: 'a`
    = note: requirement occurs because of a function pointer to `foo`
    = note: the function `foo` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -69,9 +69,9 @@ LL | fn i<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      lifetime `'a` defined here
 ...
 LL |     x = foo::<&'a ()>;
-   |     ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
+   |     ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
    |
-   = help: consider adding the following bound: `'b: 'a`
+   = help: consider adding the following bound: `'a: 'b`
    = note: requirement occurs because of a function pointer to `foo`
    = note: the function `foo` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -89,9 +89,9 @@ LL | fn j<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      lifetime `'a` defined here
 LL |     let x = match true {
 LL |         true => foo::<&'b ()>,
-   |                 ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
+   |                 ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
    |
-   = help: consider adding the following bound: `'a: 'b`
+   = help: consider adding the following bound: `'b: 'a`
    = note: requirement occurs because of a function pointer to `foo`
    = note: the function `foo` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -105,9 +105,9 @@ LL | fn j<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      lifetime `'a` defined here
 ...
 LL |         false => foo::<&'a ()>,
-   |                  ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
+   |                  ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
    |
-   = help: consider adding the following bound: `'b: 'a`
+   = help: consider adding the following bound: `'a: 'b`
    = note: requirement occurs because of a function pointer to `foo`
    = note: the function `foo` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -117,15 +117,15 @@ help: `'a` and `'b` must be the same: replace one with the other
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: lifetime may not live long enough
-  --> $DIR/fn_def_coercion.rs:49:17
+  --> $DIR/fn_def_coercion.rs:50:18
    |
 LL | fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      --      -- lifetime `'c` defined here
    |      |
    |      lifetime `'a` defined here
-LL |     let x = match true {
-LL |         true => foo::<&'c ()>,
-   |                 ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'c`
+...
+LL |         false => foo::<&'a ()>,
+   |                  ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'c`
    |
    = help: consider adding the following bound: `'a: 'c`
    = note: requirement occurs because of a function pointer to `foo`
@@ -133,20 +133,17 @@ LL |         true => foo::<&'c ()>,
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 error: lifetime may not live long enough
-  --> $DIR/fn_def_coercion.rs:50:18
+  --> $DIR/fn_def_coercion.rs:54:5
    |
 LL | fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
    |      --  -- lifetime `'b` defined here
    |      |
    |      lifetime `'a` defined here
 ...
-LL |         false => foo::<&'a ()>,
-   |                  ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
+LL |     x(b);
+   |     ^^^^ argument requires that `'b` must outlive `'a`
    |
    = help: consider adding the following bound: `'b: 'a`
-   = note: requirement occurs because of a function pointer to `foo`
-   = note: the function `foo` is invariant over the parameter `T`
-   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
 help: the following changes may resolve your lifetime errors
    |
diff --git a/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.rs b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.rs
index 66e6eb91a22..09ee9accccd 100644
--- a/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.rs
+++ b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.rs
@@ -1,6 +1,6 @@
 fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
-    //~^ ERROR lifetime may not live long enough
     *v = x;
+    //~^ ERROR lifetime may not live long enough
 }
 
 fn main() { }
diff --git a/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
index e7cab52084d..30083b5ef54 100644
--- a/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
+++ b/tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
@@ -1,15 +1,13 @@
 error: lifetime may not live long enough
-  --> $DIR/ex3-both-anon-regions-2.rs:1:14
+  --> $DIR/ex3-both-anon-regions-2.rs:2:5
    |
 LL | fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
-   |              ^^^^^^^^^            -             - let's call the lifetime of this reference `'1`
-   |              |                    |
-   |              |                    let's call the lifetime of this reference `'2`
-   |              assignment requires that `'1` must outlive `'2`
+   |                                   -             - let's call the lifetime of this reference `'1`
+   |                                   |
+   |                                   let's call the lifetime of this reference `'2`
+LL |     *v = x;
+   |     ^^^^^^ assignment requires that `'1` must outlive `'2`
    |
-   = note: requirement occurs because of a mutable reference to `&u8`
-   = note: mutable references are invariant over their type parameter
-   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 help: consider introducing a named lifetime parameter
    |
 LL | fn foo<'a>(&mut (ref mut v, w): &mut (&'a u8, &u8), x: &'a u8) {
diff --git a/tests/ui/match/match-ref-mut-invariance.stderr b/tests/ui/match/match-ref-mut-invariance.stderr
index 93844d34b41..b9878a19532 100644
--- a/tests/ui/match/match-ref-mut-invariance.stderr
+++ b/tests/ui/match/match-ref-mut-invariance.stderr
@@ -1,12 +1,12 @@
 error: lifetime may not live long enough
-  --> $DIR/match-ref-mut-invariance.rs:10:24
+  --> $DIR/match-ref-mut-invariance.rs:10:9
    |
 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 }
-   |                        ^^^^^^^^^ assignment requires that `'a` must outlive `'b`
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ method was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
    |
    = help: consider adding the following bound: `'a: 'b`
    = note: requirement occurs because of a mutable reference to `&i32`
diff --git a/tests/ui/match/match-ref-mut-let-invariance.rs b/tests/ui/match/match-ref-mut-let-invariance.rs
index 2c1f865b6d7..a33be09ac8b 100644
--- a/tests/ui/match/match-ref-mut-let-invariance.rs
+++ b/tests/ui/match/match-ref-mut-let-invariance.rs
@@ -8,8 +8,8 @@ struct S<'b>(&'b i32);
 impl<'b> S<'b> {
     fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
         let ref mut x = self.0;
-        //~^ ERROR lifetime may not live long enough
         x
+        //~^ ERROR lifetime may not live long enough
     }
 }
 
diff --git a/tests/ui/match/match-ref-mut-let-invariance.stderr b/tests/ui/match/match-ref-mut-let-invariance.stderr
index 3c5d73bb4f7..27968239a8e 100644
--- a/tests/ui/match/match-ref-mut-let-invariance.stderr
+++ b/tests/ui/match/match-ref-mut-let-invariance.stderr
@@ -1,12 +1,13 @@
 error: lifetime may not live long enough
-  --> $DIR/match-ref-mut-let-invariance.rs:10:13
+  --> $DIR/match-ref-mut-let-invariance.rs:11:9
    |
 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;
-   |             ^^^^^^^^^ assignment requires that `'a` must outlive `'b`
+LL |         x
+   |         ^ method was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
    |
    = help: consider adding the following bound: `'a: 'b`
    = note: requirement occurs because of a mutable reference to `&i32`
diff --git a/tests/ui/nll/user-annotations/adt-tuple-struct-calls.stderr b/tests/ui/nll/user-annotations/adt-tuple-struct-calls.stderr
index 1478ad1431b..2084697e7e2 100644
--- a/tests/ui/nll/user-annotations/adt-tuple-struct-calls.stderr
+++ b/tests/ui/nll/user-annotations/adt-tuple-struct-calls.stderr
@@ -4,9 +4,11 @@ error[E0597]: `c` does not live long enough
 LL |     let c = 66;
    |         - binding `c` declared here
 LL |     let f = SomeStruct::<&'static u32>;
-   |             -------------------------- assignment requires that `c` is borrowed for `'static`
 LL |     f(&c);
-   |       ^^ borrowed value does not live long enough
+   |     --^^-
+   |     | |
+   |     | borrowed value does not live long enough
+   |     argument requires that `c` is borrowed for `'static`
 LL | }
    | - `c` dropped here while still borrowed
 
@@ -18,9 +20,11 @@ LL | fn annot_reference_named_lifetime<'a>(_d: &'a u32) {
 LL |     let c = 66;
    |         - binding `c` declared here
 LL |     let f = SomeStruct::<&'a u32>;
-   |             --------------------- assignment requires that `c` is borrowed for `'a`
 LL |     f(&c);
-   |       ^^ borrowed value does not live long enough
+   |     --^^-
+   |     | |
+   |     | borrowed value does not live long enough
+   |     argument requires that `c` is borrowed for `'a`
 LL | }
    | - `c` dropped here while still borrowed
 
@@ -33,9 +37,11 @@ LL |     let _closure = || {
 LL |         let c = 66;
    |             - binding `c` declared here
 LL |         let f = SomeStruct::<&'a u32>;
-   |                 --------------------- assignment requires that `c` is borrowed for `'a`
 LL |         f(&c);
-   |           ^^ borrowed value does not live long enough
+   |         --^^-
+   |         | |
+   |         | borrowed value does not live long enough
+   |         argument requires that `c` is borrowed for `'a`
 LL |     };
    |     - `c` dropped here while still borrowed
 
diff --git a/tests/ui/nll/user-annotations/method-ufcs-1.stderr b/tests/ui/nll/user-annotations/method-ufcs-1.stderr
index 087e270c70f..c42ea0172cf 100644
--- a/tests/ui/nll/user-annotations/method-ufcs-1.stderr
+++ b/tests/ui/nll/user-annotations/method-ufcs-1.stderr
@@ -4,10 +4,11 @@ error[E0597]: `a` does not live long enough
 LL |     let a = 22;
    |         - binding `a` declared here
 ...
-LL |     let x = <&'static u32 as Bazoom<_>>::method;
-   |             ----------------------------------- assignment requires that `a` is borrowed for `'static`
 LL |     x(&a, b, c);
-   |       ^^ borrowed value does not live long enough
+   |     --^^-------
+   |     | |
+   |     | borrowed value does not live long enough
+   |     argument requires that `a` is borrowed for `'static`
 LL | }
    | - `a` dropped here while still borrowed
 
diff --git a/tests/ui/nll/user-annotations/method-ufcs-2.stderr b/tests/ui/nll/user-annotations/method-ufcs-2.stderr
index c89bed3b1b1..287337c7d52 100644
--- a/tests/ui/nll/user-annotations/method-ufcs-2.stderr
+++ b/tests/ui/nll/user-annotations/method-ufcs-2.stderr
@@ -4,10 +4,11 @@ error[E0597]: `a` does not live long enough
 LL |     let a = 22;
    |         - binding `a` declared here
 ...
-LL |     let x = <&'static u32 as Bazoom<_>>::method;
-   |             ----------------------------------- assignment requires that `a` is borrowed for `'static`
 LL |     x(&a, b, c);
-   |       ^^ borrowed value does not live long enough
+   |     --^^-------
+   |     | |
+   |     | borrowed value does not live long enough
+   |     argument requires that `a` is borrowed for `'static`
 LL | }
    | - `a` dropped here while still borrowed
 
diff --git a/tests/ui/nll/user-annotations/promoted-annotation.stderr b/tests/ui/nll/user-annotations/promoted-annotation.stderr
index ca99e531870..39993475796 100644
--- a/tests/ui/nll/user-annotations/promoted-annotation.stderr
+++ b/tests/ui/nll/user-annotations/promoted-annotation.stderr
@@ -6,9 +6,11 @@ LL | fn foo<'a>() {
 LL |     let x = 0;
    |         - binding `x` declared here
 LL |     let f = &drop::<&'a i32>;
-   |             ---------------- assignment requires that `x` is borrowed for `'a`
 LL |     f(&x);
-   |       ^^ borrowed value does not live long enough
+   |     --^^-
+   |     | |
+   |     | borrowed value does not live long enough
+   |     argument requires that `x` is borrowed for `'a`
 LL |
 LL | }
    | - `x` dropped here while still borrowed