mixin-diff.patch

diff --git a/src/material/core/common-behaviors/tabindex.ts b/src/material/core/common-behaviors/tabindex.ts
index b5788d46c..3be2d0193 100644
--- a/src/material/core/common-behaviors/tabindex.ts
+++ b/src/material/core/common-behaviors/tabindex.ts
@@ -23,10 +23,15 @@ export interface HasTabIndex {
 /** @docs-private */
 export type HasTabIndexCtor = Constructor<HasTabIndex>;
 
+// Needs JSDOC
+type LooseConstructor<T> = Function & { prototype: T };
+
 /** Mixin to augment a directive with a `tabIndex` property. */
-export function mixinTabIndex<T extends Constructor<CanDisable>>(base: T, defaultTabIndex = 0)
-    : HasTabIndexCtor & T {
-  return class extends base {
+export function mixinTabIndex<T extends LooseConstructor<CanDisable>>(
+    base: T, defaultTabIndex = 0): HasTabIndexCtor & T {
+  // Note: We cast `base` to `unknown` and then `Constructor`. It could be an abstract class,
+  // but given we `extend` it from another class, we can assume a constructor being accessible.
+  abstract class Mixin extends (base as unknown as Constructor<CanDisable>) {
     private _tabIndex: number = defaultTabIndex;
     defaultTabIndex = defaultTabIndex;
 
@@ -39,5 +44,10 @@ export function mixinTabIndex<T extends Constructor<CanDisable>>(base: T, defaul
     constructor(...args: any[]) {
       super(...args);
     }
-  };
+  }
+
+  // Since we don't directly extend from `base` with it's original types, and we instruct
+  // TypeScript that `T` actually is instantiatable through `new`, the types don't overlap.
+  // This is a limitation in TS as abstract classes cannot be typed properly dynamically.
+  return Mixin as unknown as T & Constructor<HasTabIndex>;
 }
diff --git a/src/material/radio/radio.ts b/src/material/radio/radio.ts
index c54097c17..fee3d61f9 100644
--- a/src/material/radio/radio.ts
+++ b/src/material/radio/radio.ts
@@ -334,11 +334,11 @@ export class MatRadioGroup extends _MatRadioGroupBase<MatRadioButton> {
 
 // Boilerplate for applying mixins to MatRadioButton.
 /** @docs-private */
-class MatRadioButtonBase {
+abstract class MatRadioButtonBase {
   // Since the disabled property is manually defined for the MatRadioButton and isn't set up in
   // the mixin base class. To be able to use the tabindex mixin, a disabled property must be
   // defined to properly work.
-  disabled: boolean;
+  abstract disabled: boolean;
 
   constructor(public _elementRef: ElementRef) {}
 }