Change wording for lifetime suggestion for opaque types from `constraint` to `bound`

src/librustc/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -54,7 +54,7 @@ pub(super) fn try_report_static_impl_trait(&self) -> Option<ErrorReported> {
                             err.span_suggestion(
                                 fn_return_span,
                                 &format!(
-                                    "you can add a constraint to the return type to make it last \
+                                    "you can add a bound to the return type to make it last \
                                  less than `'static` and match {}",
                                     lifetime,
                                 ),

src/librustc_mir/borrow_check/diagnostics/explain_borrow.rs

@@ -238,7 +238,7 @@ pub(in crate::borrow_check) fn add_lifetime_bound_suggestion_to_diagnostic<'tcx>
                     err.span_suggestion(
                         span,
                         &format!(
-                            "you can add a constraint to the {}to make it last less than \
+                            "you can add a bound to the {}to make it last less than \
                              `'static` and match `{}`",
                             category.description(),
                             region_name,

src/librustc_mir/borrow_check/diagnostics/region_errors.rs

@@ -840,7 +840,7 @@ fn add_static_impl_trait_suggestion(
                             span,
                             &format!(
                                 "to allow this `impl Trait` to capture borrowed data with lifetime \
-                                 `{}`, add `{}` as a constraint",
+                                 `{}`, add `{}` as a bound",
                                 fr_name, suggestable_fr_name,
                             ),
                             format!("{} + {}", snippet, suggestable_fr_name),

src/test/ui/impl-trait/does-not-live-long-enough.stderr

@@ -11,7 +11,7 @@ LL |
 LL |     }
    |     - `prefix` dropped here while still borrowed
    |
-help: you can add a constraint to the opaque type to make it last less than `'static` and match `'a`
+help: you can add a bound to the opaque type to make it last less than `'static` and match `'a`
    |
 LL |     fn started_with<'a>(&'a self, prefix: &'a str) -> impl Iterator<Item=&'a str> + 'a {
    |                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/impl-trait/multiple-lifetimes/error-handling.stderr

@@ -5,7 +5,7 @@ LL | fn foo<'a, 'b, 'c>(x: &'static i32, mut y: &'a i32) -> E<'b, 'c> {
    |        -- lifetime `'a` defined here                   ^^^^^^^^^ opaque type requires that `'a` must outlive `'static`
    |
    = help: consider replacing `'a` with `'static`
-help: to allow this `impl Trait` to capture borrowed data with lifetime `'a`, add `'a` as a constraint
+help: to allow this `impl Trait` to capture borrowed data with lifetime `'a`, add `'a` as a bound
    |
 LL | type E<'a, 'b> = impl Sized; + 'a
    |

src/test/ui/impl-trait/must_outlive_least_region_or_bound.nll.stderr

@@ -6,7 +6,7 @@ LL | fn elided(x: &i32) -> impl Copy { x }
    |              |
    |              let's call the lifetime of this reference `'1`
    |
-help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a constraint
+help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a bound
    |
 LL | fn elided(x: &i32) -> impl Copy + '_ { x }
    |                       ^^^^^^^^^^^^^^
@@ -20,7 +20,7 @@ LL | fn explicit<'a>(x: &'a i32) -> impl Copy { x }
    |             lifetime `'a` defined here
    |
    = help: consider replacing `'a` with `'static`
-help: to allow this `impl Trait` to capture borrowed data with lifetime `'a`, add `'a` as a constraint
+help: to allow this `impl Trait` to capture borrowed data with lifetime `'a`, add `'a` as a bound
    |
 LL | fn explicit<'a>(x: &'a i32) -> impl Copy + 'a { x }
    |                                ^^^^^^^^^^^^^^

src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr

@@ -11,7 +11,7 @@ note: ...can't outlive the anonymous lifetime #1 defined on the function body at
    |
 LL | fn elided(x: &i32) -> impl Copy { x }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-help: you can add a constraint to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the function body at 3:1
+help: you can add a bound to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the function body at 3:1
    |
 LL | fn elided(x: &i32) -> impl Copy + '_ { x }
    |                       ^^^^^^^^^^^^^^
@@ -29,7 +29,7 @@ note: ...can't outlive the lifetime `'a` as defined on the function body at 6:13
    |
 LL | fn explicit<'a>(x: &'a i32) -> impl Copy { x }
    |             ^^
-help: you can add a constraint to the return type to make it last less than `'static` and match the lifetime `'a` as defined on the function body at 6:13
+help: you can add a bound to the return type to make it last less than `'static` and match the lifetime `'a` as defined on the function body at 6:13
    |
 LL | fn explicit<'a>(x: &'a i32) -> impl Copy + 'a { x }
    |                                ^^^^^^^^^^^^^^
@@ -47,7 +47,7 @@ note: ...can't outlive the lifetime `'a` as defined on the function body at 12:1
    |
 LL | fn with_bound<'a>(x: &'a i32) -> impl LifetimeTrait<'a> + 'static { x }
    |               ^^
-help: you can add a constraint to the return type to make it last less than `'static` and match the lifetime `'a` as defined on the function body at 12:15
+help: you can add a bound to the return type to make it last less than `'static` and match the lifetime `'a` as defined on the function body at 12:15
    |
 LL | fn with_bound<'a>(x: &'a i32) -> impl LifetimeTrait<'a> + 'static + 'a { x }
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/impl-trait/static-return-lifetime-infered.nll.stderr

@@ -6,7 +6,7 @@ LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> {
    |                         |
    |                         let's call the lifetime of this reference `'1`
    |
-help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a constraint
+help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a bound
    |
 LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> + '_ {
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -20,7 +20,7 @@ LL |     fn iter_values<'a>(&'a self) -> impl Iterator<Item=u32> {
    |                    lifetime `'a` defined here
    |
    = help: consider replacing `'a` with `'static`
-help: to allow this `impl Trait` to capture borrowed data with lifetime `'a`, add `'a` as a constraint
+help: to allow this `impl Trait` to capture borrowed data with lifetime `'a`, add `'a` as a bound
    |
 LL |     fn iter_values<'a>(&'a self) -> impl Iterator<Item=u32> + 'a {
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/impl-trait/static-return-lifetime-infered.stderr

@@ -15,7 +15,7 @@ LL | /     fn iter_values_anon(&self) -> impl Iterator<Item=u32> {
 LL | |         self.x.iter().map(|a| a.0)
 LL | |     }
    | |_____^
-help: you can add a constraint to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the method body at 6:5
+help: you can add a bound to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the method body at 6:5
    |
 LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> + '_ {
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -35,7 +35,7 @@ note: ...can't outlive the lifetime `'a` as defined on the method body at 10:20
    |
 LL |     fn iter_values<'a>(&'a self) -> impl Iterator<Item=u32> {
    |                    ^^
-help: you can add a constraint to the return type to make it last less than `'static` and match the lifetime `'a` as defined on the method body at 10:20
+help: you can add a bound to the return type to make it last less than `'static` and match the lifetime `'a` as defined on the method body at 10:20
    |
 LL |     fn iter_values<'a>(&'a self) -> impl Iterator<Item=u32> + 'a {
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait-async.nll.stderr

@@ -6,7 +6,7 @@ LL |     async fn f(self: Pin<&Self>) -> impl Clone { self }
    |                          |
    |                          let's call the lifetime of this reference `'1`
    |
-help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a constraint
+help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a bound
    |
 LL |     async fn f(self: Pin<&Self>) -> impl Clone + '_ { self }
    |                                     ^^^^^^^^^^^^^^^

src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait.nll.stderr

@@ -6,7 +6,7 @@ LL |     fn f(self: Pin<&Self>) -> impl Clone { self }
    |                    |
    |                    let's call the lifetime of this reference `'1`
    |
-help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a constraint
+help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a bound
    |
 LL |     fn f(self: Pin<&Self>) -> impl Clone + '_ { self }
    |                               ^^^^^^^^^^^^^^^

src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait.stderr

@@ -11,7 +11,7 @@ note: ...can't outlive the anonymous lifetime #1 defined on the method body at 8
    |
 LL |     fn f(self: Pin<&Self>) -> impl Clone { self }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-help: you can add a constraint to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the method body at 8:5
+help: you can add a bound to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the method body at 8:5
    |
 LL |     fn f(self: Pin<&Self>) -> impl Clone + '_ { self }
    |                               ^^^^^^^^^^^^^^^