type/prefer-reduce-type-parameter

Prefer Array#reduce type parameters over default-value assertions.

Applies to: Type information in Vue SFC scripts and templates, for the constructs shown below.

This rule reads type information from your TypeScript project (tsconfig.json), so the configuration sets typeAware: true. typeAware does not turn on opt-in rules by itself.

Bad

The initial value is asserted as number[] instead of using the reduce type parameter.

<script setup lang="ts">
const numbers = [1, 2, 3];
const collected = numbers.reduce((all, n) => [...all, n], [] as number[]);
</script>

Good

reduce<number[]> states the accumulator type without asserting the initial array.

<script setup lang="ts">
const numbers = [1, 2, 3];
const collected = numbers.reduce<number[]>((all, n) => [...all, n], []);
</script>

Configuration (Vite+)

import { defineConfig } from "@vizejs/vite-plugin/vite-plus";

export default defineConfig({}).withVue({
  linter: {
    "preset": "incremental",
    "rules": {
      "type/prefer-reduce-type-parameter": "warn"
    },
    "typeAware": true
  },
});

Then run vp run lint.

Related

• Type and script rules
• All rules
• Source code