fix lint errors

Author: vursen

packages/combo-box/src/vaadin-combo-box-light-mixin.js

@@ -99,17 +99,6 @@ export const ComboBoxLightMixin = (superClass) =>
       });
     }
 
-    /**
-     * Returns true if the current input value satisfies all constraints (if any).
-     * @return {boolean}
-     */
-    checkValidity() {
-      if (this.inputElement && this.inputElement.validate) {
-        return this.inputElement.validate();
-      }
-      return super.checkValidity();
-    }
-
     /**
      * @protected
      * @override

packages/date-picker/src/vaadin-date-picker-mixin.js

@@ -624,13 +624,8 @@ export const DatePickerMixin = (subclass) =>
         !this._selectedDate || dateAllowed(this._selectedDate, this._minDate, this._maxDate, this.isDateDisabled);
 
       let inputValidity = true;
-      if (this.inputElement) {
-        if (this.inputElement.checkValidity) {
-          inputValidity = this.inputElement.checkValidity();
-        } else if (this.inputElement.validate) {
-          // Iron-form-elements have the validate API
-          inputValidity = this.inputElement.validate();
-        }
+      if (this.inputElement && this.inputElement.checkValidity) {
+        inputValidity = this.inputElement.checkValidity();
       }
 
       return inputValid && isDateValid && inputValidity;

packages/login/src/vaadin-login-form-mixin.js

@@ -50,7 +50,12 @@ export const LoginFormMixin = (superClass) =>
       const userName = this.$.vaadinLoginUsername;
       const password = this.$.vaadinLoginPassword;
 
-      if (this.disabled || !(userName.validate() && password.validate())) {
+      // eslint-disable-next-line no-restricted-syntax
+      userName.validate();
+      // eslint-disable-next-line no-restricted-syntax
+      password.validate();
+
+      if (this.disabled || userName.invalid || password.invalid) {
         return;
       }
 
@@ -114,6 +119,7 @@ export const LoginFormMixin = (superClass) =>
         const { currentTarget: inputActive } = e;
         const nextInput =
           inputActive.id === 'vaadinLoginUsername' ? this.$.vaadinLoginPassword : this.$.vaadinLoginUsername;
+        // eslint-disable-next-line no-restricted-syntax
         if (inputActive.validate()) {
           if (nextInput.checkValidity()) {
             this.submit();