Property 'clear' doesn't exist on type 'IonButtonAttributes'

Tried rebuilding the Ionic-Stencil HN app component by component, rewriting everything in order to grasp how it all works together, but after rewriting all the components and making sure that there are no typo errors in any of the files and importing the @ionic/core npm module, I have this errors:

[44:04.7]  @stencil/core v0.1.1-0 
[44:04.7]  build, app, dev mode, started ... 
[44:04.7]  compile started ... 
[44:09.7]  compile finished in 4.99 s 

[ ERROR ]  typescript: src/components/ask-page/ask-page.tsx, line: 52
           Property 'clear' does not exist on type 'IonButtonAttributes'. 

     L51:  onClick={() => this.back ()}
     L52:  clear
     L53:  color='primary'

[ ERROR ]  typescript: src/components/comments-page/comments-page.tsx, line: 43
           Property 'clear' does not exist on type 'IonButtonAttributes'. 

     L42:  <ion-buttons slot='end'>
     L43:    <ion-button class='close-button' clear onClick={() => this.close()}>
     L44:      <ion-icon slot='icon-only' name='close' style={{ fill: 'white' }} />

[ ERROR ]  typescript: src/components/ionic-hn/ionic-hn.tsx, line: 27
           Property 'clear' does not exist on type 'IonButtonAttributes'. 

     L26:  }}
     L27:  clear>
     L28:  News
[ ERROR ]  typescript: src/components/jobs-page/jobs-page.tsx, line: 67
           Property 'clear' does not exist on type 'IonButtonAttributes'. 

     L66:  <ion-buttons slot='end'>
     L67:  <ion-button onClick={() => this.forward()} clear color='primary'>
     L68:  Next

[ ERROR ]  typescript: src/components/news-page/news-page.tsx, line: 54
           Property 'clear' does not exist on type 'IonButtonAttributes'. 

     L53:  onClick={() => this.back()}
     L54:  clear
     L55:  color='primary'

[ ERROR ]  typescript: src/components/show-page/show-page.tsx, line: 54
           Property 'clear' does not exist on type 'IonButtonAttributes'. 

     L53:  onClick={() => this.back()}
     L54:  clear
     L55:  color='primary'

[44:09.8]  build failed, watching for changes... in 5.08 s 

There is apparently only one problem:

Property 'clear' does not exist on type 'IonButtonAttributes'.

What exactly is causing this? What am I missing?