When infer K type from value type, occured an error in generic T[K]

[HealGaren]

TypeScript Version: 3.9.2

Search Terms: ts type inference by value type, ts get property name from value type

Expected behavior:
this is an example code of typescriptlang.org : Distributive conditional types
I got K type that T[K] is Function. (following code:)

I expected TypeScript to be able to properly infer value type using this K type.
testForT1 and TestForGeneric should works fine.

Actual behavior:
I can't get V into the proper type using the K I got.
testForT1 function worked, but testForGeneric function occured that error.

Type 'T[{ [K in keyof T]: T[K] extends Function ? K : never; }[keyof T]]' is not assignable to type 'Function'.
  Type 'T[T[keyof T] extends Function ? keyof T : never]' is not assignable to type 'Function'.
    Type 'T[keyof T]' is not assignable to type 'Function'.
      Type 'T[string] | T[number] | T[symbol]' is not assignable to type 'Function'.
        Type 'T[string]' is not assignable to type 'Function'.(2322)

Related Issues:

Code

type FunctionPropertyNames<T> = {
  [K in keyof T]: T[K] extends Function ? K : never;
}[keyof T];
type FunctionProperties<T> = Pick<T, FunctionPropertyNames<T>>;

interface T1 {
    method(): string;
    method2(): number;
}

function testForT1(data: T1, key: FunctionPropertyNames<T1>): Function {
    return data[key];
}


function testForGeneric<T>(data: T, key: FunctionPropertyNames<T>): Function {
    return data[key];
}

Output

"use strict";
function testForI1(data, key) {
    return data[key];
}
function testForGeneric(data, key) {
    return data[key];
}

Compiler Options

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

[jack-williams]

Duplicate of #32550, and in particular see Ryan's comment.