Caching of initializeMemberResolvers seems to cause a bug

For contracts that contain both a .cdc source file, with Cadence code,
and with some functions being implemented natively, the GetMembers()
does not return the natively implemented members.

runtime/sema/type.go

@@ -4262,7 +4262,11 @@ func (t *CompositeType) GetMembers() map[string]MemberResolver {
 }
 
 func (t *CompositeType) initializeMemberResolvers() {
-	t.memberResolversOnce.Do(func() {
+	t.memberResolversOnce.Do(t.initializerMemberResolversFunc())
+}
+
+func (t *CompositeType) initializerMemberResolversFunc() func() {
+	return func() {
 		memberResolvers := MembersMapAsResolvers(t.Members)
 
 		// Check conformances.
@@ -4281,7 +4285,13 @@ func (t *CompositeType) initializeMemberResolvers() {
 			})
 
 		t.memberResolvers = withBuiltinMembers(t, memberResolvers)
-	})
+	}
+}
+
+func (t *CompositeType) ResolveMembers() {
+	if t.Members.Len() != len(t.GetMembers()) {
+		t.initializerMemberResolversFunc()()
+	}
 }
 
 func (t *CompositeType) FieldPosition(name string, declaration ast.CompositeLikeDeclaration) ast.Position {

runtime/stdlib/test_contract.go

@@ -1193,6 +1193,7 @@ func newTestContractType() *TestContractType {
 	ty.expectFailureFunction = newTestTypeExpectFailureFunction(
 		expectFailureFunctionType,
 	)
+	compositeType.ResolveMembers()
 
 	return ty
 }