type inference issue with dynamic template literals

🔎 Search Terms

"template literals and type inference", "type inference with dynamic template literals"

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about it

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.4.5#code/C4TwDgpgBAgmCWUC8UDeAoKUDaBrCIAXFAAYAWEANpQPYB0AJKgM7ABO8AdgOYC+JAXWIAKACYBDYOOKooncQFsIxVhx5ReASmQA+KADca8Uel7p0lCMCgBXZhDYBJUSvZduyKAHJRIeQvgAYyhVdy9zAHoIqABRAA9FMEsARmIAERoIZk4vawB3GjZcOihQSCgAM0LSCBIoQPEc6wAjaC4KhzYIE0CaTlZSrOBU2ARPDCxscipaRlQ7B2d+IShoJD0JrHq+5hpLOlpuYQg6fwhNTA0AGlNI6PjEywAmYgB1QtxmdF7+62Ahl6jRAoTZTCjUeisSRBAD6oR4gmIaw2lywP12+0Ox1OinOl14NzM6CisQSCiSEAAzG8Pl90dY+p4ADwAaVWcX+nFEzCg+BANAqQJ0wkufOILJuWHEgWA8D6IgkUmIcHg2BZAm06wMRlEN01KKwJN2SighyCt3QfWE0whcwWTlE-Cuq10aEu6L2JyxJzOFy0QA

💻 Code

type Api = {
  [key: `hello.${string}`]: (data: { name: string }) => void
}

let userId: string = 'dynamic string'

// Example1: Doesn't work. type for `e` can't be inferred
const test1: Api = {
  [`hello.${userId}`]: e => {
    console.log(e.name)
  },
}

// Example2: Works
const test2: Api = {
  [`hello.static_string`]: e => {
    console.log(e.name)
  },
}

// Example3: Works
const on = <K extends keyof Api>(
  key: K,
  action: (data: Api[K]) => void,
) => {
  // some logic
}

on(`hello.${userId}`, e => {
  console.log(e.name)
})

🙁 Actual behavior

Example 1 doesn't work, while Example 2 and Example 3 works properly. The type for e can't be inferred

🙂 Expected behavior

To infer type of e in the Example 1.

Additional information about the issue

No response

Start with the linked TypeScript Playground and reproduce the contrast between the three examples, especially the contextual typing of the dynamic template-literal property in Example 1. Compare the inferred type of e with the static-key and generic-function cases; done means Example 1 infers e as the shown { name: string } parameter type.