A tuple containing a spread not at the trailing edge has its minimum length calculated incorrectly

Bug Report

🔎 Search Terms

• tuple
• spread

🕗 Version & Regression Information

It happens in v4.9.5, no idea about other versions.

⏯ Playground Link

https://www.typescriptlang.org/play?jsx=0#code/C4TwDgpgBAYgcgRigHgCoD4oF4oAoB0hAhgE4DmAzgFxQXAkCWAdmQNoC6AlNpqgNwAoAaEiw4AJhQZseKIXylKNVgGMA9kwoBXALYQAJjTqMWAGjmEyJNVrDVa9Zm3bnmYLcCOOzUZvogAHl4mZOxQ3Fi8ggLqmsBQAGZMCDTwCMhMugBGECSYOLhQROZZ4TxQAAzRsXSJTOKpEhnZufmyxVClEZhVQA

💻 Code

type FN1 <T> = (...args: string[]) => T;

type FN2 <T> = ( ...args: [consumed: string, ...groups: string[], input: string, index: string] ) => T;

const fn1: FN1<number> = ( a, b ) => 0;

const fn2: FN2<number> = ( a, b ) => 0;

🙁 Actual behavior

TS complains about my fn2, with the following error:

Type '(a: string, b: string) => number' is not assignable to type 'FN2<number>'.
  Types of parameters 'b' and 'groups' are incompatible.
    Type '[...groups: string[], input: string, index: string]' is not assignable to type '[b: string]'.
      Source has 2 element(s) but target allows only 1.(2322)

If I'm interpreting it correctly it is saying like "hey you defined two arguments, but maybe this tuple only has one item in it.

🙂 Expected behavior

If I'm interpreting the error correctly then the error is wrong because there's no scenario where that tuple has just one item in it, minimum it will always have 3.

Reproduisez le problème dans le TypeScript Playground lié en utilisant les types tuple et fonction de l’issue. Suivez le calcul par le compilateur de la longueur minimale des tuples pour les spreads situés à des positions non finales. Le travail est considéré comme terminé lorsque l’exemple n’indique plus que le tuple source peut ne contenir qu’un seul élément, tout en conservant le comportement de diagnostic existant pour les tuples réellement trop courts.