Rollup merge of #90667 - rukai:improve_static_lifetime_diagnostics, r=estebank

Improve diagnostics when a static lifetime is expected

Makes progress towards https://github.com/rust-lang/rust/issues/90600

The diagnostics here were previously entirely removed due to giving a misleading suggestion but if we instead provide an informative label in that same location it should better help the user understand the situation.

I included the example from the issue as it demonstrates an area where the diagnostics are still lacking.
Happy to remove that if its just adding noise atm.

26 files changed, 269 insertions, 176 deletions

diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
index 0878f8550da..eb1c80ecb01 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
@@ -3,8 +3,6 @@
 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
-use rustc_hir::intravisit::Visitor;
-use rustc_hir::FnRetTy;
 use rustc_middle::ty;
 
 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
@@ -48,19 +46,24 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             return None; // inapplicable
         };
 
+        // Suggesting to add a `'static` lifetime to a parameter is nearly always incorrect,
+        // and can steer users down the wrong path.
+        if *named == ty::ReStatic {
+            return None;
+        }
+
         debug!("try_report_named_anon_conflict: named = {:?}", named);
         debug!("try_report_named_anon_conflict: anon_param_info = {:?}", anon_param_info);
         debug!("try_report_named_anon_conflict: region_info = {:?}", region_info);
 
-        let (param, new_ty, new_ty_span, br, is_first, scope_def_id, is_impl_item) = (
-            anon_param_info.param,
-            anon_param_info.param_ty,
-            anon_param_info.param_ty_span,
-            anon_param_info.bound_region,
-            anon_param_info.is_first,
-            region_info.def_id,
-            region_info.is_impl_item,
-        );
+        let param = anon_param_info.param;
+        let new_ty = anon_param_info.param_ty;
+        let new_ty_span = anon_param_info.param_ty_span;
+        let br = anon_param_info.bound_region;
+        let is_first = anon_param_info.is_first;
+        let scope_def_id = region_info.def_id;
+        let is_impl_item = region_info.is_impl_item;
+
         match br {
             ty::BrAnon(_) => {}
             _ => {
@@ -75,26 +78,10 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             return None;
         }
 
-        if let Some((_, fndecl)) = find_anon_type(self.tcx(), anon, &br) {
-            if self.is_self_anon(is_first, scope_def_id) {
-                return None;
-            }
-
-            if let FnRetTy::Return(ty) = &fndecl.output {
-                let mut v = ty::TraitObjectVisitor(vec![], self.tcx().hir());
-                v.visit_ty(ty);
-
-                debug!("try_report_named_anon_conflict: ret ty {:?}", ty);
-                if sub == &ty::ReStatic
-                    && v.0.into_iter().any(|t| t.span.desugaring_kind().is_none())
-                {
-                    // If the failure is due to a `'static` requirement coming from a `dyn` or
-                    // `impl` Trait that *isn't* caused by `async fn` desugaring, handle this case
-                    // better in `static_impl_trait`.
-                    debug!("try_report_named_anon_conflict: impl Trait + 'static");
-                    return None;
-                }
-            }
+        if find_anon_type(self.tcx(), anon, &br).is_some()
+            && self.is_self_anon(is_first, scope_def_id)
+        {
+            return None;
         }
 
         let (error_var, span_label_var) = match param.pat.simple_ident() {
@@ -114,16 +101,12 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         );
 
         diag.span_label(span, format!("lifetime `{}` required", named));
-        // Suggesting `'static` is nearly always incorrect, and can steer users
-        // down the wrong path.
-        if *named != ty::ReStatic {
-            diag.span_suggestion(
-                new_ty_span,
-                &format!("add explicit lifetime `{}` to {}", named, span_label_var),
-                new_ty.to_string(),
-                Applicability::Unspecified,
-            );
-        }
+        diag.span_suggestion(
+            new_ty_span,
+            &format!("add explicit lifetime `{}` to {}", named, span_label_var),
+            new_ty.to_string(),
+            Applicability::Unspecified,
+        );
 
         Some(diag)
     }
diff --git a/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.nll.stderr b/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.nll.stderr
index e7d9664ec50..af3810e91ae 100644
--- a/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.nll.stderr
+++ b/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.nll.stderr
@@ -1,11 +1,18 @@
-error[E0621]: explicit lifetime required in the type of `x`
+error[E0521]: borrowed data escapes outside of function
   --> $DIR/closure-bounds-static-cant-capture-borrowed.rs:5:5
    |
+LL |   fn foo(x: &()) {
+   |          -  - let's call the lifetime of this reference `'1`
+   |          |
+   |          `x` is a reference that is only valid in the function body
 LL | /     bar(|| {
 LL | |
 LL | |         let _ = x;
 LL | |     })
-   | |______^ lifetime `'static` required
+   | |      ^
+   | |      |
+   | |______`x` escapes the function body here
+   |        argument requires that `'1` must outlive `'static`
 
 error[E0373]: closure may outlive the current function, but it borrows `x`, which is owned by the current function
   --> $DIR/closure-bounds-static-cant-capture-borrowed.rs:5:9
@@ -31,5 +38,5 @@ LL |     bar(move || {
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0373, E0621.
+Some errors have detailed explanations: E0373, E0521.
 For more information about an error, try `rustc --explain E0373`.
diff --git a/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.rs b/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.rs
index 4fa5d54431c..cbdc8b7deef 100644
--- a/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.rs
+++ b/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.rs
@@ -3,7 +3,7 @@ fn bar<F>(blk: F) where F: FnOnce() + 'static {
 
 fn foo(x: &()) {
     bar(|| {
-        //~^ ERROR explicit lifetime required in the type of `x` [E0621]
+        //~^ ERROR `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
         let _ = x;
     })
 }
diff --git a/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.stderr b/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.stderr
index a9add6184f1..d761abdfc6a 100644
--- a/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.stderr
+++ b/src/test/ui/closures/closure-bounds-static-cant-capture-borrowed.stderr
@@ -1,9 +1,21 @@
-error[E0621]: explicit lifetime required in the type of `x`
+error[E0759]: `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/closure-bounds-static-cant-capture-borrowed.rs:5:9
+   |
+LL |   fn foo(x: &()) {
+   |             --- this data with an anonymous lifetime `'_`...
+LL |       bar(|| {
+   |  _________^
+LL | |
+LL | |         let _ = x;
+LL | |     })
+   | |_____^ ...is captured here...
+   |
+note: ...and is required to live as long as `'static` here
   --> $DIR/closure-bounds-static-cant-capture-borrowed.rs:5:5
    |
 LL |     bar(|| {
-   |     ^^^ lifetime `'static` required
+   |     ^^^
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0621`.
+For more information about this error, try `rustc --explain E0759`.
diff --git a/src/test/ui/generator/generator-region-requirements.nll.stderr b/src/test/ui/generator/generator-region-requirements.nll.stderr
new file mode 100644
index 00000000000..b4530cfda2b
--- /dev/null
+++ b/src/test/ui/generator/generator-region-requirements.nll.stderr
@@ -0,0 +1,11 @@
+error: lifetime may not live long enough
+  --> $DIR/generator-region-requirements.rs:13:51
+   |
+LL | fn dangle(x: &mut i32) -> &'static mut i32 {
+   |              - let's call the lifetime of this reference `'1`
+...
+LL |             GeneratorState::Complete(c) => return c,
+   |                                                   ^ returning this value requires that `'1` must outlive `'static`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/generator/generator-region-requirements.rs b/src/test/ui/generator/generator-region-requirements.rs
index 5f0a6bb09b7..cec68509a66 100644
--- a/src/test/ui/generator/generator-region-requirements.rs
+++ b/src/test/ui/generator/generator-region-requirements.rs
@@ -6,11 +6,11 @@ fn dangle(x: &mut i32) -> &'static mut i32 {
     let mut g = || {
         yield;
         x
+        //~^ ERROR `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
     };
     loop {
         match Pin::new(&mut g).resume(()) {
             GeneratorState::Complete(c) => return c,
-            //~^ ERROR explicit lifetime required
             GeneratorState::Yielded(_) => (),
         }
     }
diff --git a/src/test/ui/generator/generator-region-requirements.stderr b/src/test/ui/generator/generator-region-requirements.stderr
index de90a599e76..b6b9db22426 100644
--- a/src/test/ui/generator/generator-region-requirements.stderr
+++ b/src/test/ui/generator/generator-region-requirements.stderr
@@ -1,9 +1,15 @@
-error[E0621]: explicit lifetime required in the type of `x`
-  --> $DIR/generator-region-requirements.rs:12:51
+error[E0759]: `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/generator-region-requirements.rs:8:9
    |
+LL | fn dangle(x: &mut i32) -> &'static mut i32 {
+   |              -------- this data with an anonymous lifetime `'_`...
+...
+LL |         x
+   |         ^ ...is captured here...
+...
 LL |             GeneratorState::Complete(c) => return c,
-   |                                                   ^ lifetime `'static` required
+   |                                                   - ...and is required to live as long as `'static` here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0621`.
+For more information about this error, try `rustc --explain E0759`.
diff --git a/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.nll.stderr b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.nll.stderr
new file mode 100644
index 00000000000..4620aa34e84
--- /dev/null
+++ b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.nll.stderr
@@ -0,0 +1,26 @@
+error: lifetime may not live long enough
+  --> $DIR/projection-type-lifetime-mismatch.rs:17:5
+   |
+LL | fn f(x: &impl for<'a> X<Y<'a> = &'a ()>) -> &'static () {
+   |         - let's call the lifetime of this reference `'1`
+LL |     x.m()
+   |     ^^^^^ returning this value requires that `'1` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/projection-type-lifetime-mismatch.rs:22:5
+   |
+LL | fn g<T: for<'a> X<Y<'a> = &'a ()>>(x: &T) -> &'static () {
+   |                                       - let's call the lifetime of this reference `'1`
+LL |     x.m()
+   |     ^^^^^ returning this value requires that `'1` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/projection-type-lifetime-mismatch.rs:27:5
+   |
+LL | fn h(x: &()) -> &'static () {
+   |         - let's call the lifetime of this reference `'1`
+LL |     x.m()
+   |     ^^^^^ returning this value requires that `'1` must outlive `'static`
+
+error: aborting due to 3 previous errors
+
diff --git a/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.rs b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.rs
index bcbcfc18996..9b04fe23320 100644
--- a/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.rs
+++ b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.rs
@@ -15,17 +15,17 @@ impl X for () {
 
 fn f(x: &impl for<'a> X<Y<'a> = &'a ()>) -> &'static () {
     x.m()
-    //~^ ERROR explicit lifetime required
+    //~^ ERROR `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
 }
 
 fn g<T: for<'a> X<Y<'a> = &'a ()>>(x: &T) -> &'static () {
     x.m()
-    //~^ ERROR explicit lifetime required
+    //~^ ERROR `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
 }
 
 fn h(x: &()) -> &'static () {
     x.m()
-    //~^ ERROR explicit lifetime required
+    //~^ ERROR `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
 }
 
 fn main() {
diff --git a/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr
index 315bef16c5f..1ffd205652f 100644
--- a/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr
+++ b/src/test/ui/generic-associated-types/projection-type-lifetime-mismatch.stderr
@@ -1,21 +1,27 @@
-error[E0621]: explicit lifetime required in the type of `x`
-  --> $DIR/projection-type-lifetime-mismatch.rs:17:5
+error[E0759]: `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/projection-type-lifetime-mismatch.rs:17:7
    |
+LL | fn f(x: &impl for<'a> X<Y<'a> = &'a ()>) -> &'static () {
+   |         ------------------------------- this data with an anonymous lifetime `'_`...
 LL |     x.m()
-   |     ^^^^^ lifetime `'static` required
+   |     --^-- ...is captured and required to live as long as `'static` here
 
-error[E0621]: explicit lifetime required in the type of `x`
-  --> $DIR/projection-type-lifetime-mismatch.rs:22:5
+error[E0759]: `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/projection-type-lifetime-mismatch.rs:22:7
    |
+LL | fn g<T: for<'a> X<Y<'a> = &'a ()>>(x: &T) -> &'static () {
+   |                                       -- this data with an anonymous lifetime `'_`...
 LL |     x.m()
-   |     ^^^^^ lifetime `'static` required
+   |     --^-- ...is captured and required to live as long as `'static` here
 
-error[E0621]: explicit lifetime required in the type of `x`
-  --> $DIR/projection-type-lifetime-mismatch.rs:27:5
+error[E0759]: `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/projection-type-lifetime-mismatch.rs:27:7
    |
+LL | fn h(x: &()) -> &'static () {
+   |         --- this data with an anonymous lifetime `'_`...
 LL |     x.m()
-   |     ^^^^^ lifetime `'static` required
+   |     --^-- ...is captured and required to live as long as `'static` here
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0621`.
+For more information about this error, try `rustc --explain E0759`.
diff --git a/src/test/ui/issues/issue-46983.nll.stderr b/src/test/ui/issues/issue-46983.nll.stderr
new file mode 100644
index 00000000000..38a219bbd7b
--- /dev/null
+++ b/src/test/ui/issues/issue-46983.nll.stderr
@@ -0,0 +1,10 @@
+error: lifetime may not live long enough
+  --> $DIR/issue-46983.rs:2:5
+   |
+LL | fn foo(x: &u32) -> &'static u32 {
+   |           - let's call the lifetime of this reference `'1`
+LL |     &*x
+   |     ^^^ returning this value requires that `'1` must outlive `'static`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/issues/issue-46983.rs b/src/test/ui/issues/issue-46983.rs
index c1fd7729bde..87ed8928944 100644
--- a/src/test/ui/issues/issue-46983.rs
+++ b/src/test/ui/issues/issue-46983.rs
@@ -1,6 +1,6 @@
 fn foo(x: &u32) -> &'static u32 {
     &*x
-    //~^ ERROR explicit lifetime required in the type of `x` [E0621]
+    //~^ ERROR `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
 }
 
 fn main() {}
diff --git a/src/test/ui/issues/issue-46983.stderr b/src/test/ui/issues/issue-46983.stderr
index d328329edad..77fb130f519 100644
--- a/src/test/ui/issues/issue-46983.stderr
+++ b/src/test/ui/issues/issue-46983.stderr
@@ -1,9 +1,11 @@
-error[E0621]: explicit lifetime required in the type of `x`
+error[E0759]: `x` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
   --> $DIR/issue-46983.rs:2:5
    |
+LL | fn foo(x: &u32) -> &'static u32 {
+   |           ---- this data with an anonymous lifetime `'_`...
 LL |     &*x
-   |     ^^^ lifetime `'static` required
+   |     ^^^ ...is captured and required to live as long as `'static` here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0621`.
+For more information about this error, try `rustc --explain E0759`.
diff --git a/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.nll.stderr b/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.nll.stderr
new file mode 100644
index 00000000000..99e1e7217b4
--- /dev/null
+++ b/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.nll.stderr
@@ -0,0 +1,24 @@
+error[E0597]: `foo` does not live long enough
+  --> $DIR/issue-90600-expected-return-static-indirect.rs:7:32
+   |
+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 | }
+   | - `foo` dropped here while still borrowed
+
+error: lifetime may not live long enough
+  --> $DIR/issue-90600-expected-return-static-indirect.rs:9:16
+   |
+LL | fn inner(mut foo: &[u8]) {
+   |                   - let's call the lifetime of this reference `'1`
+...
+LL |     let read = &refcell as &RefCell<dyn Read>;
+   |                ^^^^^^^^ cast requires that `'1` must outlive `'static`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0597`.
diff --git a/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.rs b/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.rs
new file mode 100644
index 00000000000..39996bbf43b
--- /dev/null
+++ b/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.rs
@@ -0,0 +1,14 @@
+use std::cell::RefCell;
+use std::io::Read;
+
+fn main() {}
+
+fn inner(mut foo: &[u8]) {
+    let refcell = RefCell::new(&mut foo);
+    //~^ ERROR `foo` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
+    let read = &refcell as &RefCell<dyn Read>;
+
+    read_thing(read);
+}
+
+fn read_thing(refcell: &RefCell<dyn Read>) {}
diff --git a/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr b/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
new file mode 100644
index 00000000000..3f65d3af725
--- /dev/null
+++ b/src/test/ui/lifetimes/issue-90600-expected-return-static-indirect.stderr
@@ -0,0 +1,14 @@
+error[E0759]: `foo` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/issue-90600-expected-return-static-indirect.rs:7:32
+   |
+LL | fn inner(mut foo: &[u8]) {
+   |                   ----- this data with an anonymous lifetime `'_`...
+LL |     let refcell = RefCell::new(&mut foo);
+   |                                ^^^^^^^^ ...is captured here...
+...
+LL |     read_thing(read);
+   |                ---- ...and is required to live as long as `'static` here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0759`.
diff --git a/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.rs b/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.rs
index ac2943fc3a5..c8f226f5238 100644
--- a/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.rs
+++ b/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.rs
@@ -7,7 +7,7 @@
 
 fn foo(x: &u32) -> &'static u32 {
     &*x
-        //~^ ERROR explicit lifetime required in the type of `x`
+    //~^ ERROR lifetime may not live long enough
 }
 
 fn main() { }
diff --git a/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.stderr b/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.stderr
index 4c302d935db..7034492cee0 100644
--- a/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.stderr
+++ b/src/test/ui/nll/closure-requirements/region-lbr-anon-does-not-outlive-static.stderr
@@ -1,9 +1,10 @@
-error[E0621]: explicit lifetime required in the type of `x`
+error: lifetime may not live long enough
   --> $DIR/region-lbr-anon-does-not-outlive-static.rs:9:5
    |
+LL | fn foo(x: &u32) -> &'static u32 {
+   |           - let's call the lifetime of this reference `'1`
 LL |     &*x
-   |     ^^^ lifetime `ReStatic` required
+   |     ^^^ returning this value requires that `'1` must outlive `'static`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0621`.
diff --git a/src/test/ui/nll/guarantor-issue-46974.rs b/src/test/ui/nll/guarantor-issue-46974.rs
index d0af468cff6..87ed0e642e9 100644
--- a/src/test/ui/nll/guarantor-issue-46974.rs
+++ b/src/test/ui/nll/guarantor-issue-46974.rs
@@ -12,7 +12,7 @@ fn foo(s: &mut (i32,)) -> i32 {
 
 fn bar(s: &Box<(i32,)>) -> &'static i32 {
     // FIXME(#46983): error message should be better
-    &s.0 //~ ERROR explicit lifetime required in the type of `s` [E0621]
+    &s.0 //~ ERROR lifetime may not live long enough
 }
 
 fn main() {
diff --git a/src/test/ui/nll/guarantor-issue-46974.stderr b/src/test/ui/nll/guarantor-issue-46974.stderr
index eabc3105c02..8245aadf826 100644
--- a/src/test/ui/nll/guarantor-issue-46974.stderr
+++ b/src/test/ui/nll/guarantor-issue-46974.stderr
@@ -9,13 +9,15 @@ LL |     *s = (2,);
 LL |     *x
    |     -- borrow later used here
 
-error[E0621]: explicit lifetime required in the type of `s`
+error: lifetime may not live long enough
   --> $DIR/guarantor-issue-46974.rs:15:5
    |
+LL | fn bar(s: &Box<(i32,)>) -> &'static i32 {
+   |           - let's call the lifetime of this reference `'1`
+LL |     // FIXME(#46983): error message should be better
 LL |     &s.0
-   |     ^^^^ lifetime `'static` required
+   |     ^^^^ returning this value requires that `'1` must outlive `'static`
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0506, E0621.
-For more information about an error, try `rustc --explain E0506`.
+For more information about this error, try `rustc --explain E0506`.
diff --git a/src/test/ui/regions/regions-static-bound.ll.nll.stderr b/src/test/ui/regions/regions-static-bound.ll.nll.stderr
deleted file mode 100644
index d6cec03e0ff..00000000000
--- a/src/test/ui/regions/regions-static-bound.ll.nll.stderr
+++ /dev/null
@@ -1,28 +0,0 @@
-error: lifetime may not live long enough
-  --> $DIR/regions-static-bound.rs:9:5
-   |
-LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
-   |                        -- lifetime `'a` defined here
-LL |     t //[ll]~ ERROR E0312
-   |     ^ returning this value requires that `'a` must outlive `'static`
-
-error[E0621]: explicit lifetime required in the type of `u`
-  --> $DIR/regions-static-bound.rs:14:5
-   |
-LL | fn error(u: &(), v: &()) {
-   |             --- help: add explicit lifetime `'static` to the type of `u`: `&'static ()`
-LL |     static_id(&u); //[ll]~ ERROR explicit lifetime required in the type of `u` [E0621]
-   |     ^^^^^^^^^^^^^ lifetime `'static` required
-
-error[E0621]: explicit lifetime required in the type of `v`
-  --> $DIR/regions-static-bound.rs:16:5
-   |
-LL | fn error(u: &(), v: &()) {
-   |                     --- help: add explicit lifetime `'static` to the type of `v`: `&'static ()`
-...
-LL |     static_id_indirect(&v); //[ll]~ ERROR explicit lifetime required in the type of `v` [E0621]
-   |     ^^^^^^^^^^^^^^^^^^^^^^ lifetime `'static` required
-
-error: aborting due to 3 previous errors
-
-For more information about this error, try `rustc --explain E0621`.
diff --git a/src/test/ui/regions/regions-static-bound.migrate.nll.stderr b/src/test/ui/regions/regions-static-bound.migrate.nll.stderr
deleted file mode 100644
index a280c6f0a02..00000000000
--- a/src/test/ui/regions/regions-static-bound.migrate.nll.stderr
+++ /dev/null
@@ -1,23 +0,0 @@
-error: lifetime may not live long enough
-  --> $DIR/regions-static-bound.rs:9:5
-   |
-LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
-   |                        -- lifetime `'a` defined here
-LL |     t
-   |     ^ returning this value requires that `'a` must outlive `'static`
-
-error[E0621]: explicit lifetime required in the type of `u`
-  --> $DIR/regions-static-bound.rs:14:5
-   |
-LL |     static_id(&u);
-   |     ^^^^^^^^^^^^^ lifetime `'static` required
-
-error[E0621]: explicit lifetime required in the type of `v`
-  --> $DIR/regions-static-bound.rs:16:5
-   |
-LL |     static_id_indirect(&v);
-   |     ^^^^^^^^^^^^^^^^^^^^^^ lifetime `'static` required
-
-error: aborting due to 3 previous errors
-
-For more information about this error, try `rustc --explain E0621`.
diff --git a/src/test/ui/regions/regions-static-bound.migrate.stderr b/src/test/ui/regions/regions-static-bound.migrate.stderr
deleted file mode 100644
index 8f11e148220..00000000000
--- a/src/test/ui/regions/regions-static-bound.migrate.stderr
+++ /dev/null
@@ -1,29 +0,0 @@
-error[E0312]: lifetime of reference outlives lifetime of borrowed content...
-  --> $DIR/regions-static-bound.rs:9:5
-   |
-LL |     t
-   |     ^
-   |
-   = note: ...the reference is valid for the static lifetime...
-note: ...but the borrowed content is only valid for the lifetime `'a` as defined here
-  --> $DIR/regions-static-bound.rs:8:24
-   |
-LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
-   |                        ^^
-
-error[E0621]: explicit lifetime required in the type of `u`
-  --> $DIR/regions-static-bound.rs:14:5
-   |
-LL |     static_id(&u);
-   |     ^^^^^^^^^ lifetime `'static` required
-
-error[E0621]: explicit lifetime required in the type of `v`
-  --> $DIR/regions-static-bound.rs:16:5
-   |
-LL |     static_id_indirect(&v);
-   |     ^^^^^^^^^^^^^^^^^^ lifetime `'static` required
-
-error: aborting due to 3 previous errors
-
-Some errors have detailed explanations: E0312, E0621.
-For more information about an error, try `rustc --explain E0312`.
diff --git a/src/test/ui/regions/regions-static-bound.nll.stderr b/src/test/ui/regions/regions-static-bound.nll.stderr
index a280c6f0a02..699638c7ef9 100644
--- a/src/test/ui/regions/regions-static-bound.nll.stderr
+++ b/src/test/ui/regions/regions-static-bound.nll.stderr
@@ -1,23 +1,38 @@
 error: lifetime may not live long enough
-  --> $DIR/regions-static-bound.rs:9:5
+  --> $DIR/regions-static-bound.rs:6:5
    |
 LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
    |                        -- lifetime `'a` defined here
 LL |     t
    |     ^ returning this value requires that `'a` must outlive `'static`
 
-error[E0621]: explicit lifetime required in the type of `u`
-  --> $DIR/regions-static-bound.rs:14:5
+error[E0521]: borrowed data escapes outside of function
+  --> $DIR/regions-static-bound.rs:10:5
    |
+LL | fn error(u: &(), v: &()) {
+   |          -  - let's call the lifetime of this reference `'1`
+   |          |
+   |          `u` is a reference that is only valid in the function body
 LL |     static_id(&u);
-   |     ^^^^^^^^^^^^^ lifetime `'static` required
+   |     ^^^^^^^^^^^^^
+   |     |
+   |     `u` escapes the function body here
+   |     argument requires that `'1` must outlive `'static`
 
-error[E0621]: explicit lifetime required in the type of `v`
-  --> $DIR/regions-static-bound.rs:16:5
+error[E0521]: borrowed data escapes outside of function
+  --> $DIR/regions-static-bound.rs:11:5
    |
+LL | fn error(u: &(), v: &()) {
+   |                  -  - let's call the lifetime of this reference `'2`
+   |                  |
+   |                  `v` is a reference that is only valid in the function body
+LL |     static_id(&u);
 LL |     static_id_indirect(&v);
-   |     ^^^^^^^^^^^^^^^^^^^^^^ lifetime `'static` required
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     `v` escapes the function body here
+   |     argument requires that `'2` must outlive `'static`
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0621`.
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/regions/regions-static-bound.rs b/src/test/ui/regions/regions-static-bound.rs
index 1db54881d3e..a977a8b36d0 100644
--- a/src/test/ui/regions/regions-static-bound.rs
+++ b/src/test/ui/regions/regions-static-bound.rs
@@ -1,20 +1,14 @@
-// revisions: migrate nll
-//[nll] compile-flags:-Zborrowck=mir
-
 fn static_id<'a,'b>(t: &'a ()) -> &'static ()
     where 'a: 'static { t }
 fn static_id_indirect<'a,'b>(t: &'a ()) -> &'static ()
     where 'a: 'b, 'b: 'static { t }
 fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
-    t //[migrate]~ ERROR E0312
-        //[nll]~^ ERROR lifetime may not live long enough
+    t //~ ERROR E0312
 }
 
 fn error(u: &(), v: &()) {
-    static_id(&u); //[migrate]~ ERROR explicit lifetime required in the type of `u` [E0621]
-    //[nll]~^ ERROR explicit lifetime required in the type of `u` [E0621]
-    static_id_indirect(&v); //[migrate]~ ERROR explicit lifetime required in the type of `v` [E0621]
-    //[nll]~^ ERROR explicit lifetime required in the type of `v` [E0621]
+    static_id(&u); //~ ERROR `u` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
+    static_id_indirect(&v); //~ ERROR `v` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement [E0759]
 }
 
 fn main() {}
diff --git a/src/test/ui/regions/regions-static-bound.stderr b/src/test/ui/regions/regions-static-bound.stderr
new file mode 100644
index 00000000000..51fe16ca9da
--- /dev/null
+++ b/src/test/ui/regions/regions-static-bound.stderr
@@ -0,0 +1,46 @@
+error[E0312]: lifetime of reference outlives lifetime of borrowed content...
+  --> $DIR/regions-static-bound.rs:6:5
+   |
+LL |     t
+   |     ^
+   |
+   = note: ...the reference is valid for the static lifetime...
+note: ...but the borrowed content is only valid for the lifetime `'a` as defined here
+  --> $DIR/regions-static-bound.rs:5:24
+   |
+LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
+   |                        ^^
+
+error[E0759]: `u` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/regions-static-bound.rs:10:5
+   |
+LL | fn error(u: &(), v: &()) {
+   |             --- this data with an anonymous lifetime `'_`...
+LL |     static_id(&u);
+   |     ^^^^^^^^^ -- ...is captured here...
+   |
+note: ...and is required to live as long as `'static` here
+  --> $DIR/regions-static-bound.rs:10:5
+   |
+LL |     static_id(&u);
+   |     ^^^^^^^^^
+
+error[E0759]: `v` has an anonymous lifetime `'_` but it needs to satisfy a `'static` lifetime requirement
+  --> $DIR/regions-static-bound.rs:11:5
+   |
+LL | fn error(u: &(), v: &()) {
+   |                     --- this data with an anonymous lifetime `'_`...
+LL |     static_id(&u);
+LL |     static_id_indirect(&v);
+   |     ^^^^^^^^^^^^^^^^^^ -- ...is captured here...
+   |
+note: ...and is required to live as long as `'static` here
+  --> $DIR/regions-static-bound.rs:11:5
+   |
+LL |     static_id_indirect(&v);
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0312, E0759.
+For more information about an error, try `rustc --explain E0312`.