Infer method argument types from interface.

[sinclairzx81]

Hi,

This has likely been asked before, and suspect there has probably been some consensus reached on the following. But curious with respect to the following implementation that seems to allow for breaking issues when not compiling in strict and Parameter 'x' implicitly has an 'any' type errors when compiling in strict when the type of x should be obvious.

interface IFoo {
    add(a: number, b: number): number
}
// class satisfies interface (non-strict)
class Foo implements IFoo {
   // can't `a` and `b` be inferred to be of type `number` ? 
   public add(a, b) {
        return a + b
    }
}

const foo = new Foo()
foo.add("hello", "world") // allowed (non-strict)

Are there any future plans to perhaps have TS statically resolve the arguments a and b when implementing from an interface in this way?

Many Thanks

[mattmccutchen]

Duplicate of #23911.

[sinclairzx81]

@mattmccutchen thanks will track there.