Steps:
npm install
npm run lint
This will fail with:
element-repro-typescript-issue (master) $ npm run lint
> lint
> vue-tsc --noEmit --diagnostics
node_modules/element-ui/types/element-ui.d.ts:310:60 - error TS2344: Type 'D' does not satisfy the constraint 'TreeData'.
310 export class Tree<K = any, D = TreeData> extends ElTree<K, D> {}
~
node_modules/element-ui/types/element-ui.d.ts:310:28
310 export class Tree<K = any, D = TreeData> extends ElTree<K, D> {}
~~~~~~~~~~~~
This type parameter might need an `extends TreeData` constraint.
Found 1 error in node_modules/element-ui/types/element-ui.d.ts:310
Files: 108
Lines: 30293
Identifiers: 46614
Symbols: 37072
Types: 14589
Instantiations: 5419
Memory used: 186490K
I/O read: 0.00s
I/O write: 0.00s
Parse time: 0.00s
Bind time: 0.00s
Check time: 0.00s
Emit time: 0.00s
Total time: 0.00s
Based on 'element-starter'