diff --git a/compiler/rustc_error_codes/src/error_codes.rs b/compiler/rustc_error_codes/src/error_codes.rs
index 61a177f291ba0..b33667501cd02 100644
--- a/compiler/rustc_error_codes/src/error_codes.rs
+++ b/compiler/rustc_error_codes/src/error_codes.rs
@@ -374,7 +374,6 @@ E0633: include_str!("./error_codes/E0633.md"),
 E0634: include_str!("./error_codes/E0634.md"),
 E0635: include_str!("./error_codes/E0635.md"),
 E0636: include_str!("./error_codes/E0636.md"),
-E0637: include_str!("./error_codes/E0637.md"),
 E0638: include_str!("./error_codes/E0638.md"),
 E0639: include_str!("./error_codes/E0639.md"),
 E0641: include_str!("./error_codes/E0641.md"),
@@ -632,6 +631,7 @@ E0787: include_str!("./error_codes/E0787.md"),
 //  E0629, // missing 'feature' (rustc_const_unstable)
 //  E0630, // rustc_const_unstable attribute must be paired with stable/unstable
            // attribute
+//  E0637, // merged into E0106
     E0640, // infer outlives requirements
 //  E0645, // trait aliases not finished
 //  E0694, // an unknown tool name found in scoped attributes
diff --git a/compiler/rustc_error_codes/src/error_codes/E0637.md b/compiler/rustc_error_codes/src/error_codes/E0637.md
index 62d5565df2798..d5ed38c2939f9 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0637.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0637.md
@@ -1,9 +1,11 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 `'_` lifetime name or `&T` without an explicit lifetime name has been used
 on illegal place.
 
 Erroneous code example:
 
-```compile_fail,E0106,E0637
+```compile_fail,E0106
 fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str {
                      //^^ `'_` is a reserved lifetime name
     if str1.len() > str2.len() {
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 723e66e9ef618..4f27ff7f4aa67 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -224,11 +224,6 @@ enum LifetimeRibKind {
     /// For **Deprecated** cases, report an error.
     AnonymousCreateParameter(NodeId),
 
-    /// Give a hard error when either `&` or `'_` is written. Used to
-    /// rule out things like `where T: Foo<'_>`. Does not imply an
-    /// error on default object bounds (e.g., `Box<dyn Foo>`).
-    AnonymousReportError,
-
     /// Pass responsibility to `resolve_lifetime` code for all cases.
     AnonymousPassThrough(NodeId),
 }
@@ -881,40 +876,38 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
         debug!("visit_where_predicate {:?}", p);
         let previous_value =
             replace(&mut self.diagnostic_metadata.current_where_predicate, Some(p));
-        self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
-            if let WherePredicate::BoundPredicate(WhereBoundPredicate {
-                ref bounded_ty,
-                ref bounds,
-                ref bound_generic_params,
-                span: predicate_span,
-                ..
-            }) = p
-            {
-                let span = if bound_generic_params.is_empty() {
-                    predicate_span.shrink_to_lo()
-                } else {
-                    *predicate_span
-                };
-                this.with_generic_param_rib(
-                    &bound_generic_params,
-                    NormalRibKind,
-                    LifetimeRibKind::Generics {
-                        parent: bounded_ty.id,
-                        kind: LifetimeBinderKind::WhereBound,
-                        span,
-                    },
-                    |this| {
-                        this.visit_generic_param_vec(&bound_generic_params, false);
-                        this.visit_ty(bounded_ty);
-                        for bound in bounds {
-                            this.visit_param_bound(bound, BoundKind::Bound)
-                        }
-                    },
-                );
+        if let WherePredicate::BoundPredicate(WhereBoundPredicate {
+            ref bounded_ty,
+            ref bounds,
+            ref bound_generic_params,
+            span: predicate_span,
+            ..
+        }) = p
+        {
+            let span = if bound_generic_params.is_empty() {
+                predicate_span.shrink_to_lo()
             } else {
-                visit::walk_where_predicate(this, p);
-            }
-        });
+                *predicate_span
+            };
+            self.with_generic_param_rib(
+                &bound_generic_params,
+                NormalRibKind,
+                LifetimeRibKind::Generics {
+                    parent: bounded_ty.id,
+                    kind: LifetimeBinderKind::WhereBound,
+                    span,
+                },
+                |this| {
+                    this.visit_generic_param_vec(&bound_generic_params, false);
+                    this.visit_ty(bounded_ty);
+                    for bound in bounds {
+                        this.visit_param_bound(bound, BoundKind::Bound)
+                    }
+                },
+            );
+        } else {
+            visit::walk_where_predicate(self, p);
+        }
         self.diagnostic_metadata.current_where_predicate = previous_value;
     }
 
@@ -1093,62 +1086,56 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
             forward_ty_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err);
         }
 
-        self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
-            for param in params {
-                match param.kind {
-                    GenericParamKind::Lifetime => {
-                        for bound in &param.bounds {
-                            this.visit_param_bound(bound, BoundKind::Bound);
-                        }
+        for param in params {
+            match param.kind {
+                GenericParamKind::Lifetime => {
+                    for bound in &param.bounds {
+                        self.visit_param_bound(bound, BoundKind::Bound);
+                    }
+                }
+                GenericParamKind::Type { ref default } => {
+                    for bound in &param.bounds {
+                        self.visit_param_bound(bound, BoundKind::Bound);
                     }
-                    GenericParamKind::Type { ref default } => {
-                        for bound in &param.bounds {
-                            this.visit_param_bound(bound, BoundKind::Bound);
-                        }
-
-                        if let Some(ref ty) = default {
-                            this.ribs[TypeNS].push(forward_ty_ban_rib);
-                            this.ribs[ValueNS].push(forward_const_ban_rib);
-                            this.visit_ty(ty);
-                            forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
-                            forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
-                        }
 
-                        // Allow all following defaults to refer to this type parameter.
-                        forward_ty_ban_rib
-                            .bindings
-                            .remove(&Ident::with_dummy_span(param.ident.name));
+                    if let Some(ref ty) = default {
+                        self.ribs[TypeNS].push(forward_ty_ban_rib);
+                        self.ribs[ValueNS].push(forward_const_ban_rib);
+                        self.visit_ty(ty);
+                        forward_const_ban_rib = self.ribs[ValueNS].pop().unwrap();
+                        forward_ty_ban_rib = self.ribs[TypeNS].pop().unwrap();
                     }
-                    GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
-                        // Const parameters can't have param bounds.
-                        assert!(param.bounds.is_empty());
-
-                        this.ribs[TypeNS].push(Rib::new(ConstParamTyRibKind));
-                        this.ribs[ValueNS].push(Rib::new(ConstParamTyRibKind));
-                        this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
-                            this.visit_ty(ty)
-                        });
-                        this.ribs[TypeNS].pop().unwrap();
-                        this.ribs[ValueNS].pop().unwrap();
-
-                        if let Some(ref expr) = default {
-                            this.ribs[TypeNS].push(forward_ty_ban_rib);
-                            this.ribs[ValueNS].push(forward_const_ban_rib);
-                            this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
-                                this.resolve_anon_const(expr, IsRepeatExpr::No)
-                            });
-                            forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
-                            forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
-                        }
 
-                        // Allow all following defaults to refer to this const parameter.
-                        forward_const_ban_rib
-                            .bindings
-                            .remove(&Ident::with_dummy_span(param.ident.name));
+                    // Allow all following defaults to refer to this type parameter.
+                    forward_ty_ban_rib.bindings.remove(&Ident::with_dummy_span(param.ident.name));
+                }
+                GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
+                    // Const parameters can't have param bounds.
+                    assert!(param.bounds.is_empty());
+
+                    self.ribs[TypeNS].push(Rib::new(ConstParamTyRibKind));
+                    self.ribs[ValueNS].push(Rib::new(ConstParamTyRibKind));
+                    self.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| this.visit_ty(ty));
+                    self.ribs[TypeNS].pop().unwrap();
+                    self.ribs[ValueNS].pop().unwrap();
+
+                    if let Some(ref expr) = default {
+                        self.ribs[TypeNS].push(forward_ty_ban_rib);
+                        self.ribs[ValueNS].push(forward_const_ban_rib);
+                        self.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
+                            this.resolve_anon_const(expr, IsRepeatExpr::No)
+                        });
+                        forward_const_ban_rib = self.ribs[ValueNS].pop().unwrap();
+                        forward_ty_ban_rib = self.ribs[TypeNS].pop().unwrap();
                     }
+
+                    // Allow all following defaults to refer to this const parameter.
+                    forward_const_ban_rib
+                        .bindings
+                        .remove(&Ident::with_dummy_span(param.ident.name));
                 }
             }
-        })
+        }
     }
 
     #[tracing::instrument(level = "debug", skip(self, work))]
@@ -1226,28 +1213,6 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                     self.create_fresh_lifetime(lifetime.id, lifetime.ident, item_node_id);
                     return;
                 }
-                LifetimeRibKind::AnonymousReportError => {
-                    let (msg, note) = if elided {
-                        (
-                            "`&` without an explicit lifetime name cannot be used here",
-                            "explicit lifetime name needed here",
-                        )
-                    } else {
-                        ("`'_` cannot be used here", "`'_` is a reserved lifetime name")
-                    };
-                    rustc_errors::struct_span_err!(
-                        self.r.session,
-                        lifetime.ident.span,
-                        E0637,
-                        "{}",
-                        msg,
-                    )
-                    .span_label(lifetime.ident.span, note)
-                    .emit();
-
-                    self.record_lifetime_res(lifetime.id, LifetimeRes::Error);
-                    return;
-                }
                 LifetimeRibKind::AnonymousPassThrough(node_id) => {
                     self.record_lifetime_res(
                         lifetime.id,
@@ -1372,7 +1337,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                         res = LifetimeRes::Anonymous { binder, elided: true };
                         break;
                     }
-                    LifetimeRibKind::AnonymousReportError | LifetimeRibKind::Item => {
+                    LifetimeRibKind::Item => {
                         // FIXME(cjgillot) This resolution is wrong, but this does not matter
                         // since these cases are erroneous anyway.  Lifetime resolution should
                         // emit a "missing lifetime specifier" diagnostic.
@@ -2028,28 +1993,28 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         self.with_generic_param_rib(&generics.params, ItemRibKind(HasGenericParams::Yes), LifetimeRibKind::Generics { span: generics.span, parent: item_id, kind: LifetimeBinderKind::ImplBlock }, |this| {
             // Dummy self type for better errors if `Self` is used in the trait path.
             this.with_self_rib(Res::SelfTy { trait_: None, alias_to: None }, |this| {
-                this.with_lifetime_rib(LifetimeRibKind::AnonymousCreateParameter(item_id), |this| {
-                    // Resolve the trait reference, if necessary.
-                    this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
-                        let item_def_id = this.r.local_def_id(item_id);
-
-                        // Register the trait definitions from here.
-                        if let Some(trait_id) = trait_id {
-                            this.r.trait_impls.entry(trait_id).or_default().push(item_def_id);
-                        }
+                // Resolve the trait reference, if necessary.
+                this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
+                    let item_def_id = this.r.local_def_id(item_id);
+
+                    // Register the trait definitions from here.
+                    if let Some(trait_id) = trait_id {
+                        this.r.trait_impls.entry(trait_id).or_default().push(item_def_id);
+                    }
 
-                        let item_def_id = item_def_id.to_def_id();
-                        let res =
-                            Res::SelfTy { trait_: trait_id, alias_to: Some((item_def_id, false)) };
-                        this.with_self_rib(res, |this| {
+                    let item_def_id = item_def_id.to_def_id();
+                    let res =
+                        Res::SelfTy { trait_: trait_id, alias_to: Some((item_def_id, false)) };
+                    this.with_self_rib(res, |this| {
+                        // Resolve the generic parameters.
+                        this.visit_generics(generics);
+                        this.with_lifetime_rib(LifetimeRibKind::AnonymousCreateParameter(item_id), |this| {
                             if let Some(trait_ref) = opt_trait_reference.as_ref() {
                                 // Resolve type arguments in the trait path.
                                 visit::walk_trait_ref(this, trait_ref);
                             }
                             // Resolve the self type.
                             this.visit_ty(self_type);
-                            // Resolve the generic parameters.
-                            this.visit_generics(generics);
 
                             // Resolve the items within the impl.
                             this.with_lifetime_rib(LifetimeRibKind::AnonymousPassThrough(item_id),
diff --git a/src/test/ui/const-generics/const-param-elided-lifetime.full.stderr b/src/test/ui/const-generics/const-param-elided-lifetime.full.stderr
index d6753a74f8574..2ff6a36b282b7 100644
--- a/src/test/ui/const-generics/const-param-elided-lifetime.full.stderr
+++ b/src/test/ui/const-generics/const-param-elided-lifetime.full.stderr
@@ -1,33 +1,58 @@
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/const-param-elided-lifetime.rs:9:19
    |
 LL | struct A<const N: &u8>;
-   |                   ^ explicit lifetime name needed here
+   |                   ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | struct A<'a, const N: &'a u8>;
+   |          +++           ++
 
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/const-param-elided-lifetime.rs:14:15
    |
 LL | impl<const N: &u8> A<N> {
-   |               ^ explicit lifetime name needed here
+   |               ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | impl<'a, const N: &'a u8> A<N> {
+   |      +++           ++
 
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/const-param-elided-lifetime.rs:17:21
+error[E0106]: missing lifetime specifier
+  --> $DIR/const-param-elided-lifetime.rs:16:21
    |
 LL |     fn foo<const M: &u8>(&self) {}
-   |                     ^ explicit lifetime name needed here
+   |                     ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn foo<'a, const M: &'a u8>(&self) {}
+   |            +++           ++
 
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/const-param-elided-lifetime.rs:22:15
+error[E0106]: missing lifetime specifier
+  --> $DIR/const-param-elided-lifetime.rs:20:15
    |
 LL | impl<const N: &u8> B for A<N> {}
-   |               ^ explicit lifetime name needed here
+   |               ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | impl<'a, const N: &'a u8> B for A<N> {}
+   |      +++           ++
 
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/const-param-elided-lifetime.rs:26:17
+error[E0106]: missing lifetime specifier
+  --> $DIR/const-param-elided-lifetime.rs:23:17
    |
 LL | fn bar<const N: &u8>() {}
-   |                 ^ explicit lifetime name needed here
+   |                 ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn bar<'a, const N: &'a u8>() {}
+   |        +++           ++
 
 error: aborting due to 5 previous errors
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/const-generics/const-param-elided-lifetime.min.stderr b/src/test/ui/const-generics/const-param-elided-lifetime.min.stderr
index 48d85e7ff64ec..2ff6a36b282b7 100644
--- a/src/test/ui/const-generics/const-param-elided-lifetime.min.stderr
+++ b/src/test/ui/const-generics/const-param-elided-lifetime.min.stderr
@@ -1,78 +1,58 @@
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/const-param-elided-lifetime.rs:9:19
    |
 LL | struct A<const N: &u8>;
-   |                   ^ explicit lifetime name needed here
-
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/const-param-elided-lifetime.rs:14:15
-   |
-LL | impl<const N: &u8> A<N> {
-   |               ^ explicit lifetime name needed here
-
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/const-param-elided-lifetime.rs:17:21
-   |
-LL |     fn foo<const M: &u8>(&self) {}
-   |                     ^ explicit lifetime name needed here
-
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/const-param-elided-lifetime.rs:22:15
-   |
-LL | impl<const N: &u8> B for A<N> {}
-   |               ^ explicit lifetime name needed here
-
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/const-param-elided-lifetime.rs:26:17
-   |
-LL | fn bar<const N: &u8>() {}
-   |                 ^ explicit lifetime name needed here
-
-error: `&'static u8` is forbidden as the type of a const generic parameter
-  --> $DIR/const-param-elided-lifetime.rs:9:19
+   |                   ^ expected named lifetime parameter
    |
-LL | struct A<const N: &u8>;
-   |                   ^^^
+help: consider introducing a named lifetime parameter
    |
-   = note: the only supported types are integers, `bool` and `char`
-   = help: more complex types are supported with `#![feature(adt_const_params)]`
+LL | struct A<'a, const N: &'a u8>;
+   |          +++           ++
 
-error: `&'static u8` is forbidden as the type of a const generic parameter
+error[E0106]: missing lifetime specifier
   --> $DIR/const-param-elided-lifetime.rs:14:15
    |
 LL | impl<const N: &u8> A<N> {
-   |               ^^^
+   |               ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
    |
-   = note: the only supported types are integers, `bool` and `char`
-   = help: more complex types are supported with `#![feature(adt_const_params)]`
+LL | impl<'a, const N: &'a u8> A<N> {
+   |      +++           ++
 
-error: `&'static u8` is forbidden as the type of a const generic parameter
-  --> $DIR/const-param-elided-lifetime.rs:17:21
+error[E0106]: missing lifetime specifier
+  --> $DIR/const-param-elided-lifetime.rs:16:21
    |
 LL |     fn foo<const M: &u8>(&self) {}
-   |                     ^^^
+   |                     ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
    |
-   = note: the only supported types are integers, `bool` and `char`
-   = help: more complex types are supported with `#![feature(adt_const_params)]`
+LL |     fn foo<'a, const M: &'a u8>(&self) {}
+   |            +++           ++
 
-error: `&'static u8` is forbidden as the type of a const generic parameter
-  --> $DIR/const-param-elided-lifetime.rs:22:15
+error[E0106]: missing lifetime specifier
+  --> $DIR/const-param-elided-lifetime.rs:20:15
    |
 LL | impl<const N: &u8> B for A<N> {}
-   |               ^^^
+   |               ^ expected named lifetime parameter
    |
-   = note: the only supported types are integers, `bool` and `char`
-   = help: more complex types are supported with `#![feature(adt_const_params)]`
+help: consider introducing a named lifetime parameter
+   |
+LL | impl<'a, const N: &'a u8> B for A<N> {}
+   |      +++           ++
 
-error: `&'static u8` is forbidden as the type of a const generic parameter
-  --> $DIR/const-param-elided-lifetime.rs:26:17
+error[E0106]: missing lifetime specifier
+  --> $DIR/const-param-elided-lifetime.rs:23:17
    |
 LL | fn bar<const N: &u8>() {}
-   |                 ^^^
+   |                 ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
    |
-   = note: the only supported types are integers, `bool` and `char`
-   = help: more complex types are supported with `#![feature(adt_const_params)]`
+LL | fn bar<'a, const N: &'a u8>() {}
+   |        +++           ++
 
-error: aborting due to 10 previous errors
+error: aborting due to 5 previous errors
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/const-generics/const-param-elided-lifetime.rs b/src/test/ui/const-generics/const-param-elided-lifetime.rs
index 487b82dbf4ac4..1685eca426bdc 100644
--- a/src/test/ui/const-generics/const-param-elided-lifetime.rs
+++ b/src/test/ui/const-generics/const-param-elided-lifetime.rs
@@ -7,24 +7,20 @@
 #![cfg_attr(full, allow(incomplete_features))]
 
 struct A<const N: &u8>;
-//~^ ERROR `&` without an explicit lifetime name cannot be used here
-//[min]~^^ ERROR `&'static u8` is forbidden
+//~^ ERROR missing lifetime specifier [E0106]
+
 trait B {}
 
 impl<const N: &u8> A<N> {
-//~^ ERROR `&` without an explicit lifetime name cannot be used here
-//[min]~^^ ERROR `&'static u8` is forbidden
+//~^ ERROR missing lifetime specifier [E0106]
     fn foo<const M: &u8>(&self) {}
-    //~^ ERROR `&` without an explicit lifetime name cannot be used here
-    //[min]~^^ ERROR `&'static u8` is forbidden
+    //~^ ERROR missing lifetime specifier [E0106]
 }
 
 impl<const N: &u8> B for A<N> {}
-//~^ ERROR `&` without an explicit lifetime name cannot be used here
-//[min]~^^ ERROR `&'static u8` is forbidden
+//~^ ERROR missing lifetime specifier [E0106]
 
 fn bar<const N: &u8>() {}
-//~^ ERROR `&` without an explicit lifetime name cannot be used here
-//[min]~^^ ERROR `&'static u8` is forbidden
+//~^ ERROR missing lifetime specifier [E0106]
 
 fn main() {}
diff --git a/src/test/ui/error-codes/E0637.rs b/src/test/ui/error-codes/E0637.rs
deleted file mode 100644
index 382ce3ed01f34..0000000000000
--- a/src/test/ui/error-codes/E0637.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str {
-    //~^ ERROR: `'_` cannot be used here [E0637]
-    //~| ERROR: missing lifetime specifier
-    if str1.len() > str2.len() {
-        str1
-    } else {
-        str2
-    }
-}
-
-fn and_without_explicit_lifetime<T>()
-where
-    T: Into<&u32>, //~ ERROR: `&` without an explicit lifetime name cannot be used here [E0637]
-{
-}
-
-fn main() {}
diff --git a/src/test/ui/error-codes/E0637.stderr b/src/test/ui/error-codes/E0637.stderr
deleted file mode 100644
index 87aaba65a73ad..0000000000000
--- a/src/test/ui/error-codes/E0637.stderr
+++ /dev/null
@@ -1,28 +0,0 @@
-error[E0637]: `'_` cannot be used here
-  --> $DIR/E0637.rs:1:24
-   |
-LL | fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str {
-   |                        ^^ `'_` is a reserved lifetime name
-
-error[E0637]: `&` without an explicit lifetime name cannot be used here
-  --> $DIR/E0637.rs:13:13
-   |
-LL |     T: Into<&u32>,
-   |             ^ explicit lifetime name needed here
-
-error[E0106]: missing lifetime specifier
-  --> $DIR/E0637.rs:1:62
-   |
-LL | fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str {
-   |                                  -------        -------      ^^ expected named lifetime parameter
-   |
-   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `str1` or `str2`
-help: consider introducing a named lifetime parameter
-   |
-LL | fn underscore_lifetime<'a, '_>(str1: &'a str, str2: &'a str) -> &'a str {
-   |                        +++            ~~             ~~          ~~
-
-error: aborting due to 3 previous errors
-
-Some errors have detailed explanations: E0106, E0637.
-For more information about an error, try `rustc --explain E0106`.
diff --git a/src/test/ui/functions-closures/fn-help-with-err-generic-is-not-function.stderr b/src/test/ui/functions-closures/fn-help-with-err-generic-is-not-function.stderr
index 26bdf460f5e4d..3a0df04e40ff3 100644
--- a/src/test/ui/functions-closures/fn-help-with-err-generic-is-not-function.stderr
+++ b/src/test/ui/functions-closures/fn-help-with-err-generic-is-not-function.stderr
@@ -1,3 +1,9 @@
+error[E0412]: cannot find type `T` in this scope
+  --> $DIR/fn-help-with-err-generic-is-not-function.rs:7:5
+   |
+LL |     T: Copy,
+   |     ^ not found in this scope
+
 error[E0412]: cannot find type `T` in this scope
   --> $DIR/fn-help-with-err-generic-is-not-function.rs:2:13
    |
@@ -6,12 +12,6 @@ LL | impl Struct<T>
    |     |
    |     help: you might be missing a type parameter: `<T>`
 
-error[E0412]: cannot find type `T` in this scope
-  --> $DIR/fn-help-with-err-generic-is-not-function.rs:7:5
-   |
-LL |     T: Copy,
-   |     ^ not found in this scope
-
 error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0412`.
diff --git a/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs
index 54b483f53d4cb..1d1696fb20dcd 100644
--- a/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs
+++ b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs
@@ -3,7 +3,7 @@
 struct Nested<K>(K);
 
 fn should_error<T>() where T : Into<&u32> {}
-//~^ ERROR `&` without an explicit lifetime name cannot be used here [E0637]
+//~^ ERROR missing lifetime specifier [E0106]
 
 trait X<'a, K: 'a> {
     fn foo<'b, L: X<&'b Nested<K>>>();
diff --git a/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr
index 270d6b8e18e22..7ff45025b6b57 100644
--- a/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr
+++ b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr
@@ -1,8 +1,13 @@
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/issue-65285-incorrect-explicit-lifetime-name-needed.rs:5:37
    |
 LL | fn should_error<T>() where T : Into<&u32> {}
-   |                                     ^ explicit lifetime name needed here
+   |                                     ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn should_error<'a, T>() where T : Into<&'a u32> {}
+   |                 +++                      ++
 
 error[E0106]: missing lifetime specifier
   --> $DIR/issue-65285-incorrect-explicit-lifetime-name-needed.rs:13:17
@@ -35,5 +40,4 @@ LL |     fn foo<'b, L: X<'lifetime, &'b Nested<K>>>();
 
 error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0106, E0637.
-For more information about an error, try `rustc --explain E0106`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/impl-header-lifetime-elision/trait-elided.rs b/src/test/ui/impl-header-lifetime-elision/trait-elided.rs
index c3e76d9cb5a03..a5c25917b7b29 100644
--- a/src/test/ui/impl-header-lifetime-elision/trait-elided.rs
+++ b/src/test/ui/impl-header-lifetime-elision/trait-elided.rs
@@ -3,6 +3,6 @@
 trait MyTrait<'a> {}
 
 impl MyTrait for u32 {}
-//~^ ERROR implicit elided lifetime not allowed here
+//~^ ERROR missing lifetime specifier [E0106]
 
 fn main() {}
diff --git a/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr b/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr
index 412bba6be7167..219a892102f59 100644
--- a/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr
+++ b/src/test/ui/impl-header-lifetime-elision/trait-elided.stderr
@@ -1,15 +1,14 @@
-error[E0726]: implicit elided lifetime not allowed here
+error[E0106]: missing lifetime specifier
   --> $DIR/trait-elided.rs:5:6
    |
 LL | impl MyTrait for u32 {}
-   |      ^^^^^^^ expected lifetime parameter
+   |      ^^^^^^^ expected named lifetime parameter
    |
-   = note: assuming a `'static` lifetime...
-help: indicate the anonymous lifetime
+help: consider introducing a named lifetime parameter
    |
-LL | impl MyTrait<'_> for u32 {}
-   |             ++++
+LL | impl<'a> MyTrait<'a> for u32 {}
+   |     ++++ ~~~~~~~~~~~
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0726`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/issues/issue-10412.rs b/src/test/ui/issues/issue-10412.rs
index 0de170161b514..682975abbae88 100644
--- a/src/test/ui/issues/issue-10412.rs
+++ b/src/test/ui/issues/issue-10412.rs
@@ -7,8 +7,7 @@ trait Serializable<'self, T> {
 impl<'self> Serializable<str> for &'self str {
     //~^ ERROR lifetimes cannot use keyword names
     //~| ERROR lifetimes cannot use keyword names
-    //~| ERROR implicit elided lifetime not allowed here
-    //~| ERROR the size for values of type `str` cannot be known at compilation time [E0277]
+    //~| ERROR missing lifetime specifier [E0106]
     fn serialize(val: &'self str) -> Vec<u8> {
         //~^ ERROR lifetimes cannot use keyword names
         vec![1]
diff --git a/src/test/ui/issues/issue-10412.stderr b/src/test/ui/issues/issue-10412.stderr
index 46b9fd541adfa..16a344ae4b093 100644
--- a/src/test/ui/issues/issue-10412.stderr
+++ b/src/test/ui/issues/issue-10412.stderr
@@ -29,47 +29,28 @@ LL | impl<'self> Serializable<str> for &'self str {
    |                                    ^^^^^
 
 error: lifetimes cannot use keyword names
-  --> $DIR/issue-10412.rs:12:24
+  --> $DIR/issue-10412.rs:11:24
    |
 LL |     fn serialize(val: &'self str) -> Vec<u8> {
    |                        ^^^^^
 
 error: lifetimes cannot use keyword names
-  --> $DIR/issue-10412.rs:16:37
+  --> $DIR/issue-10412.rs:15:37
    |
 LL |     fn deserialize(repr: &[u8]) -> &'self str {
    |                                     ^^^^^
 
-error[E0726]: implicit elided lifetime not allowed here
-  --> $DIR/issue-10412.rs:7:13
+error[E0106]: missing lifetime specifier
+  --> $DIR/issue-10412.rs:7:26
    |
 LL | impl<'self> Serializable<str> for &'self str {
-   |             ^^^^^^^^^^^^^^^^^ expected lifetime parameter
+   |                          ^ expected named lifetime parameter
    |
-   = note: assuming a `'static` lifetime...
-help: indicate the anonymous lifetime
+help: consider using the `'self` lifetime
    |
-LL | impl<'self> Serializable<'_, str> for &'self str {
-   |                          +++
+LL | impl<'self> Serializable<'self, str> for &'self str {
+   |                          ++++++
 
-error[E0277]: the size for values of type `str` cannot be known at compilation time
-  --> $DIR/issue-10412.rs:7:13
-   |
-LL | impl<'self> Serializable<str> for &'self str {
-   |             ^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `str`
-note: required by a bound in `Serializable`
-  --> $DIR/issue-10412.rs:1:27
-   |
-LL | trait Serializable<'self, T> {
-   |                           ^ required by this bound in `Serializable`
-help: consider relaxing the implicit `Sized` restriction
-   |
-LL | trait Serializable<'self, T: ?Sized> {
-   |                            ++++++++
-
-error: aborting due to 9 previous errors
+error: aborting due to 8 previous errors
 
-Some errors have detailed explanations: E0277, E0726.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/in-binder.stderr b/src/test/ui/underscore-lifetime/in-binder.stderr
index fcd7eddb57605..1b936dd9aec2f 100644
--- a/src/test/ui/underscore-lifetime/in-binder.stderr
+++ b/src/test/ui/underscore-lifetime/in-binder.stderr
@@ -36,4 +36,3 @@ LL | fn foo<'_>() {
 
 error: aborting due to 6 previous errors
 
-For more information about this error, try `rustc --explain E0637`.
diff --git a/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr b/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr
index 22bf1fdba326f..6628e0ca7566d 100644
--- a/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr
+++ b/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr
@@ -47,5 +47,4 @@ LL | fn foo2<'a>(_: &'a u8, y: &'a u8) -> &'a u8 { y }
 
 error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0106, E0637.
-For more information about an error, try `rustc --explain E0106`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/underscore-outlives-bounds.rs b/src/test/ui/underscore-lifetime/underscore-outlives-bounds.rs
index 567cc7a3f5fa3..1c158e839a2b8 100644
--- a/src/test/ui/underscore-lifetime/underscore-outlives-bounds.rs
+++ b/src/test/ui/underscore-lifetime/underscore-outlives-bounds.rs
@@ -4,5 +4,5 @@
 // #54902
 
 trait Foo<'a> {}
-impl<'b: '_> Foo<'b> for i32 {} //~ ERROR `'_` cannot be used here
+impl<'b: '_> Foo<'b> for i32 {} //~ ERROR missing lifetime specifier [E0106]
 fn main() { }
diff --git a/src/test/ui/underscore-lifetime/underscore-outlives-bounds.stderr b/src/test/ui/underscore-lifetime/underscore-outlives-bounds.stderr
index 4b38a26f957f9..eab8826677736 100644
--- a/src/test/ui/underscore-lifetime/underscore-outlives-bounds.stderr
+++ b/src/test/ui/underscore-lifetime/underscore-outlives-bounds.stderr
@@ -1,9 +1,14 @@
-error[E0637]: `'_` cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/underscore-outlives-bounds.rs:7:10
    |
 LL | impl<'b: '_> Foo<'b> for i32 {}
-   |          ^^ `'_` is a reserved lifetime name
+   |          ^^ expected named lifetime parameter
+   |
+help: consider using the `'b` lifetime
+   |
+LL | impl<'b: 'b> Foo<'b> for i32 {}
+   |          ~~
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rs b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rs
index 43de30944cacb..ac18823187939 100644
--- a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rs
+++ b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rs
@@ -11,8 +11,7 @@ struct Foo<T> {
 impl<T> Foo<T>
 where
     T: WithType<&u32>
-//[rust2015]~^ ERROR `&` without an explicit lifetime name cannot be used here
-//[rust2018]~^^ ERROR `&` without an explicit lifetime name cannot be used here
+//[rust2015,rust2018]~^ ERROR missing lifetime specifier [E0106]
 { }
 
 fn main() {}
diff --git a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2015.stderr b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2015.stderr
index fe726cb49c737..0fd55fe9d5731 100644
--- a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2015.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2015.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-inherent-impl-ampersand.rs:13:17
    |
 LL |     T: WithType<&u32>
-   |                 ^ explicit lifetime name needed here
+   |                 ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo<T>
+LL | where
+LL ~     T: WithType<&'a u32>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2018.stderr b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2018.stderr
index fe726cb49c737..0fd55fe9d5731 100644
--- a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2018.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-ampersand.rust2018.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-inherent-impl-ampersand.rs:13:17
    |
 LL |     T: WithType<&u32>
-   |                 ^ explicit lifetime name needed here
+   |                 ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo<T>
+LL | where
+LL ~     T: WithType<&'a u32>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rs b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rs
index 38189816da849..091a3c265a1a4 100644
--- a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rs
+++ b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rs
@@ -11,7 +11,7 @@ struct Foo<T> {
 impl<T> Foo<T>
 where
     T: WithRegion<'_>
-//[rust2015,rust2018]~^ ERROR `'_` cannot be used here
+//[rust2015,rust2018]~^ ERROR missing lifetime specifier [E0106]
 { }
 
 fn main() {}
diff --git a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2015.stderr b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2015.stderr
index 95939fd6b7e03..12dd418a81fc9 100644
--- a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2015.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2015.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `'_` cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-inherent-impl-underscore.rs:13:19
    |
 LL |     T: WithRegion<'_>
-   |                   ^^ `'_` is a reserved lifetime name
+   |                   ^^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo<T>
+LL | where
+LL ~     T: WithRegion<'a>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2018.stderr b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2018.stderr
index 95939fd6b7e03..12dd418a81fc9 100644
--- a/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2018.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-inherent-impl-underscore.rust2018.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `'_` cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-inherent-impl-underscore.rs:13:19
    |
 LL |     T: WithRegion<'_>
-   |                   ^^ `'_` is a reserved lifetime name
+   |                   ^^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo<T>
+LL | where
+LL ~     T: WithRegion<'a>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rs b/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rs
index 09e5bbd846d6c..3d231ec8d83db 100644
--- a/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rs
+++ b/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rs
@@ -9,7 +9,7 @@ trait Foo { }
 impl<T> Foo for Vec<T>
 where
     T: WithType<&u32>
-//[rust2015,rust2018]~^ ERROR `&` without an explicit lifetime name cannot be used here
+//[rust2015,rust2018]~^ ERROR missing lifetime specifier [E0106]
 { }
 
 fn main() {}
diff --git a/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2015.stderr b/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2015.stderr
index fbd14de21078b..bcc86f306555c 100644
--- a/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2015.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2015.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-trait-impl-region.rs:11:17
    |
 LL |     T: WithType<&u32>
-   |                 ^ explicit lifetime name needed here
+   |                 ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo for Vec<T>
+LL | where
+LL ~     T: WithType<&'a u32>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2018.stderr b/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2018.stderr
index fbd14de21078b..bcc86f306555c 100644
--- a/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2018.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-trait-impl-region.rust2018.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `&` without an explicit lifetime name cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-trait-impl-region.rs:11:17
    |
 LL |     T: WithType<&u32>
-   |                 ^ explicit lifetime name needed here
+   |                 ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo for Vec<T>
+LL | where
+LL ~     T: WithType<&'a u32>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rs b/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rs
index 371d2e4ba43ac..87adbcdfdd810 100644
--- a/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rs
+++ b/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rs
@@ -9,7 +9,7 @@ trait Foo { }
 impl<T> Foo for Vec<T>
 where
     T: WithRegion<'_>
-//[rust2015,rust2018]~^ ERROR `'_` cannot be used here
+//[rust2015,rust2018]~^ ERROR missing lifetime specifier [E0106]
 { }
 
 fn main() {}
diff --git a/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2015.stderr b/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2015.stderr
index 92caff0dcde99..9a0f3bf6f0064 100644
--- a/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2015.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2015.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `'_` cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-trait-impl-underscore.rs:11:19
    |
 LL |     T: WithRegion<'_>
-   |                   ^^ `'_` is a reserved lifetime name
+   |                   ^^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo for Vec<T>
+LL | where
+LL ~     T: WithRegion<'a>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2018.stderr b/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2018.stderr
index 92caff0dcde99..9a0f3bf6f0064 100644
--- a/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2018.stderr
+++ b/src/test/ui/underscore-lifetime/where-clause-trait-impl-underscore.rust2018.stderr
@@ -1,9 +1,16 @@
-error[E0637]: `'_` cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clause-trait-impl-underscore.rs:11:19
    |
 LL |     T: WithRegion<'_>
-   |                   ^^ `'_` is a reserved lifetime name
+   |                   ^^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ impl<'a, T> Foo for Vec<T>
+LL | where
+LL ~     T: WithRegion<'a>
+   |
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/underscore-lifetime/where-clauses.rs b/src/test/ui/underscore-lifetime/where-clauses.rs
index ee6823b804782..648e4ff794c5e 100644
--- a/src/test/ui/underscore-lifetime/where-clauses.rs
+++ b/src/test/ui/underscore-lifetime/where-clauses.rs
@@ -1,7 +1,7 @@
 trait Foo<'a> {}
 
-impl<'b: '_> Foo<'b> for i32 {} //~ ERROR `'_` cannot be used here
+impl<'b: '_> Foo<'b> for i32 {} //~ ERROR missing lifetime specifier [E0106]
 
-impl<T: '_> Foo<'static> for Vec<T> {} //~ ERROR `'_` cannot be used here
+impl<T: '_> Foo<'static> for Vec<T> {} //~ ERROR missing lifetime specifier [E0106]
 
 fn main() { }
diff --git a/src/test/ui/underscore-lifetime/where-clauses.stderr b/src/test/ui/underscore-lifetime/where-clauses.stderr
index 1a3ea4af7e12e..e54735d4840be 100644
--- a/src/test/ui/underscore-lifetime/where-clauses.stderr
+++ b/src/test/ui/underscore-lifetime/where-clauses.stderr
@@ -1,15 +1,25 @@
-error[E0637]: `'_` cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clauses.rs:3:10
    |
 LL | impl<'b: '_> Foo<'b> for i32 {}
-   |          ^^ `'_` is a reserved lifetime name
+   |          ^^ expected named lifetime parameter
+   |
+help: consider using the `'b` lifetime
+   |
+LL | impl<'b: 'b> Foo<'b> for i32 {}
+   |          ~~
 
-error[E0637]: `'_` cannot be used here
+error[E0106]: missing lifetime specifier
   --> $DIR/where-clauses.rs:5:9
    |
 LL | impl<T: '_> Foo<'static> for Vec<T> {}
-   |         ^^ `'_` is a reserved lifetime name
+   |         ^^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | impl<'a, T: 'a> Foo<'static> for Vec<T> {}
+   |      +++    ~~
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0637`.
+For more information about this error, try `rustc --explain E0106`.