Tuple should be readonly by default

Any tuples can mutate, this entails incorrect typing

TypeScript Version: 4.1.0-dev.20200828

Search Terms:
"readonly tuple"
"immutable tuple"

Code

const exampleSort: [number, string] = [2, '1'];

exampleSort.sort();

exampleSort // Type: [number, string], RealType: [string, number]

const exampleSplice: [number, string] = [2, '1'];

exampleSplice.splice(0, 1);

exampleSplice // Type: [number, string], RealType: [string]

Expected behavior:

const exampleSort: [number, string] = [2, '1'];

// Property 'sort' does not exist on type '[number, string]'.(2339)
exampleSort.sort();

const exampleSplice: [number, string] = [2, '1'];

// Property 'splice' does not exist on type '[number, string]'.(2339)
exampleSplice.splice(0, 1);

Actual behavior:

const exampleSort: [number, string] = [2, '1'];

exampleSort.sort();

const exampleSplice: [number, string] = [2, '1'];

exampleSplice.splice(0, 1);

Playground Link: https://www.typescriptlang.org/play?ts=4.1.0-dev.20200828#code/MYewdgzgLgBApgDwIYFsAOAbOBlEAnKALhgG0wBXFAIzjwBoZo8BLMAcwF0YBeUgJgYByAIyCOAbgBQkxKkw58UAHQRFACgCUUmcnRZcBGAHojMACoBPNHGJlKNeoygt2HBgCU4SDJeu2mrGwMFNS0HNKgkLCyejiYzMA2pCEODAGuPPxCohLSMfLY8YkqRXBqAAwMwlp5ugWlxqa+SXahjumcHl4+Vi0d4dKSQA

Related Issues:

まず、リンクされた TypeScript Playground でタプルの例を再現し、報告された型を sort と splice による実行時の変更と比較します。コンパイラーがタプルと配列の可変性をどのように扱うかを追跡します。これらの操作に対して期待される診断が表示され、タプルの有効な使用を壊さなければ完了です。