Type inference not works inside function while works well on params

[k8w]

TypeScript Version: 3.5.3

Search Terms: Type inference function

Code

interface ValueType {
    a: { a: string };
    b: { b: string };
    c: { c: string };
}

function setValue<T extends keyof ValueType>(key: T, value: ValueType[T]) {
    if (key === 'a') {
        console.log(value.a);
    }
}

Expected behavior:
Compile succ

Actual behavior:
test.ts:9:27 - error TS2339: Property 'a' does not exist on type 'ValueType[T]'.
9 console.log(value.a);

Playground Link:

Related Issues:
#31904

[Succubussix]

interface ValueType {
    a: { a: string };
    b: { b: string };
    c: { c: string };
}

function setProperty<T, K extends keyof T>(obj: T, key: K, value: ValueType) {
    // obj[key] = value;
    if (key === 'a') {
        console.log(value.);
    }
}

i think this is what you are trying to do ?

nvm

[jack-williams]

Duplicate of #13995.

[RyanCavanaugh]

This is a correct error. A legal call to this function is

setValue<"a" | "b">("a", { b: "" } );

[k8w]

@RyanCavanaugh @Dj-jom2x
setValue("a", { b: "" }); is not a legal call.

It would get error as expect

error TS2345: Argument of type '{ b: string; }' is not assignable to parameter of type '{ a: string; }'.
Object literal may only specify known properties, and 'b' does not exist in type '{ a: string; }'.

What I try to achieve is to let key and value match.

The issue is:

1. Type inference works well on function call params checking
2. But it do not works inside the function