diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index 0daeb0c4ddb45..5c7079e3c245e 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -3056,7 +3056,7 @@ ERROR(duplicate_inheritance,none,
 WARNING(duplicate_anyobject_class_inheritance,none,
   "redundant inheritance from 'AnyObject' and Swift 3 'class' keyword", ())
 ERROR(inheritance_from_protocol_with_superclass,none,
-  "inheritance from class-constrained protocol composition type %0", (Type))
+  "cannot inherit from class-constrained protocol composition type %0", (Type))
 WARNING(anyobject_class_inheritance_deprecated,Deprecation,
   "using 'class' keyword to define a class-constrained protocol is deprecated; "
   "use 'AnyObject' instead", ())
@@ -3065,7 +3065,7 @@ ERROR(multiple_inheritance,none,
 ERROR(inheritance_from_non_protocol_or_class,none,
   "inheritance from non-protocol, non-class type %0", (Type))
 ERROR(inheritance_from_non_protocol,none,
-  "inheritance from non-protocol type %0", (Type))
+  "cannot inherit from non-protocol type %0", (Type))
 ERROR(inheritance_from_anyobject,none,
   "only protocols can inherit from 'AnyObject'", ())
 ERROR(inheritance_from_parameterized_protocol,none,
diff --git a/test/Generics/inheritance.swift b/test/Generics/inheritance.swift
index ebfd77736f1d5..9226c91524df0 100644
--- a/test/Generics/inheritance.swift
+++ b/test/Generics/inheritance.swift
@@ -55,7 +55,7 @@ func testGenericInherit() {
 }
 
 
-struct SS<T> : T { } // expected-error{{inheritance from non-protocol type 'T'}}
+struct SS<T> : T { } // expected-error{{cannot inherit from non-protocol type 'T'}}
 enum SE<T> : T { case X } // expected-error{{raw type 'T' is not expressible by a string, integer, or floating-point literal}} // expected-error {{SE<T>' declares raw type 'T', but does not conform to RawRepresentable and conformance could not be synthesized}} expected-error{{RawRepresentable conformance cannot be synthesized because raw type 'T' is not Equatable}} 
 
 // Also need Equatable for init?(RawValue)
diff --git a/test/Sema/moveonly_restrictions.swift b/test/Sema/moveonly_restrictions.swift
index b77e22c482c1c..2de1ae0061207 100644
--- a/test/Sema/moveonly_restrictions.swift
+++ b/test/Sema/moveonly_restrictions.swift
@@ -185,7 +185,7 @@ extension ProtocolCheckMoveOnlyEnum : Any {}
 
 extension ProtocolCheckMoveOnlyEnum : AnyHashable {}
 // expected-error@-1 {{move-only enum 'ProtocolCheckMoveOnlyEnum' cannot conform to 'AnyHashable'}}
-// expected-error@-2 {{inheritance from non-protocol type 'AnyHashable'}}
+// expected-error@-2 {{cannot inherit from non-protocol type 'AnyHashable'}}
 
 // But a normal extension is ok.
 extension ProtocolCheckMoveOnlyKlass {}
diff --git a/test/decl/enum/enumtest.swift b/test/decl/enum/enumtest.swift
index 6f7d02e597998..b870ec87952dc 100644
--- a/test/decl/enum/enumtest.swift
+++ b/test/decl/enum/enumtest.swift
@@ -446,7 +446,7 @@ class C {}
 protocol P {}
 
 enum E : C & P {}
-// expected-error@-1 {{inheritance from class-constrained protocol composition type 'C & P'}}
+// expected-error@-1 {{cannot inherit from class-constrained protocol composition type 'C & P'}}
 
 // https://github.com/apple/swift/issues/53923
 
diff --git a/test/decl/inherit/inherit.swift b/test/decl/inherit/inherit.swift
index c97a04e3ec41c..c1a3557b7694d 100644
--- a/test/decl/inherit/inherit.swift
+++ b/test/decl/inherit/inherit.swift
@@ -30,13 +30,13 @@ class D3 : Any, A { } // expected-error{{superclass 'A' must appear first in the
 class D4 : P & P1, A { } // expected-error{{superclass 'A' must appear first in the inheritance clause}}{{18-21=}}{{12-12=A, }}
 
 // Struct inheriting a class
-struct S : A { } // expected-error{{inheritance from non-protocol type 'A'}}
+struct S : A { } // expected-error{{cannot inherit from non-protocol type 'A'}}
 
 // Protocol inheriting a class
 protocol Q : A { }
 
 // Extension inheriting a class
-extension C : A { } // expected-error{{inheritance from non-protocol type 'A'}}
+extension C : A { } // expected-error{{cannot inherit from non-protocol type 'A'}}
 
 // Keywords in inheritance clauses
 struct S2 : struct { } // expected-error{{expected type}}
diff --git a/test/decl/protocol/protocol_with_superclass_objc.swift b/test/decl/protocol/protocol_with_superclass_objc.swift
index 1d5a20d507789..3d59ac9c785c0 100644
--- a/test/decl/protocol/protocol_with_superclass_objc.swift
+++ b/test/decl/protocol/protocol_with_superclass_objc.swift
@@ -3,14 +3,14 @@
 class Base {}
 
 @objc protocol Protocol1 : Base {}
-// expected-error@-1 {{inheritance from non-protocol type 'Base'}}
+// expected-error@-1 {{cannot inherit from non-protocol type 'Base'}}
 
 @objc protocol OtherProtocol {}
 
 typealias Composition = OtherProtocol & Base
 
 @objc protocol Protocol2 : Composition {}
-// expected-error@-1 {{inheritance from class-constrained protocol composition type 'Composition' (aka 'Base & OtherProtocol')}}
+// expected-error@-1 {{cannot inherit from class-constrained protocol composition type 'Composition' (aka 'Base & OtherProtocol')}}
 
 @objc protocol Protocol3 : OtherProtocol & Base {}
-// expected-error@-1 {{inheritance from class-constrained protocol composition type 'Base & OtherProtocol'}}
+// expected-error@-1 {{cannot inherit from class-constrained protocol composition type 'Base & OtherProtocol'}}
diff --git a/test/type/explicit_existential.swift b/test/type/explicit_existential.swift
index e4693ec1f2c4d..af9a3c0e20100 100644
--- a/test/type/explicit_existential.swift
+++ b/test/type/explicit_existential.swift
@@ -255,7 +255,7 @@ func testExistentialAlias(x: Existential, y: any Constraint) {}
 // Reject explicit existential types in inheritance clauses
 protocol Empty {}
 
-struct S : any Empty {} // expected-error {{inheritance from non-protocol type 'any Empty'}}
+struct S : any Empty {} // expected-error {{cannot inherit from non-protocol type 'any Empty'}}
 class C : any Empty {} // expected-error {{inheritance from non-protocol, non-class type 'any Empty'}}
 
 // FIXME: Diagnostics are not great in the enum case because we confuse this with a raw type
@@ -353,4 +353,4 @@ var example1: any (any IteratorProtocol) = 5 // expected-error{{redundant 'any'
 protocol PP {}
 struct A : PP {}
 let _: any PP = A() // Ok
-let _: any (any PP) = A() // expected-error{{redundant 'any' in type 'any (any PP)'}} {{8-12=}}
\ No newline at end of file
+let _: any (any PP) = A() // expected-error{{redundant 'any' in type 'any (any PP)'}} {{8-12=}}
diff --git a/test/type/explicit_existential_swift6.swift b/test/type/explicit_existential_swift6.swift
index 8e28dd8dc72f2..ce317bb4dc55a 100644
--- a/test/type/explicit_existential_swift6.swift
+++ b/test/type/explicit_existential_swift6.swift
@@ -285,7 +285,7 @@ func testExistentialAlias(x: Existential, y: any Constraint) {}
 // Reject explicit existential types in inheritance clauses
 protocol Empty {}
 
-struct S : any Empty {} // expected-error {{inheritance from non-protocol type 'any Empty'}}
+struct S : any Empty {} // expected-error {{cannot inherit from non-protocol type 'any Empty'}}
 class C : any Empty {} // expected-error {{inheritance from non-protocol, non-class type 'any Empty'}}
 
 // FIXME: Diagnostics are not great in the enum case because we confuse this with a raw type
diff --git a/test/type/implicit_some/explicit_existential.swift b/test/type/implicit_some/explicit_existential.swift
index 0355b29a254ac..9a04481efcca8 100644
--- a/test/type/implicit_some/explicit_existential.swift
+++ b/test/type/implicit_some/explicit_existential.swift
@@ -225,7 +225,7 @@ func testExistentialAlias(x: Existential, y: any Constraint) {}
 // Reject explicit existential types in inheritance clauses
 protocol Empty {}
 
-struct S : any Empty {} // expected-error {{inheritance from non-protocol type 'any Empty'}}
+struct S : any Empty {} // expected-error {{cannot inherit from non-protocol type 'any Empty'}}
 class C : any Empty {} // expected-error {{inheritance from non-protocol, non-class type 'any Empty'}}
 
 // FIXME: Diagnostics are not great in the enum case because we confuse this with a raw type