Object spread works for unconstrained generic

TypeScript Version: 3.8.3

Search Terms:
generic
spread
unrestrained
unrestricted

Expected behavior:
The spread function should not compile because T is not constrained to a type that can be spread.

Actual behavior:
It compiles.

Related Issues:
https://github.com/microsoft/TypeScript/issues/30129
https://github.com/microsoft/TypeScript/pull/13288

Code

function spread<T>(t: T) {
  // This should not compile
  return { ...t };
}

// The type of `result` is `number` even though the value of `result` is `{}`
const result = spread(5);

"use strict";

function spread(t) {

    // This should not compile

    return Object.assign({}, t);

}

// Result is still a number when in reality it's {}

const result = spread(5);

{
  "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

Reproduce the behavior in the provided Playground link using TypeScript 3.8.3 and the listed compiler options. Read the related issue and pull request, then trace the compiler's handling of object spread for an unconstrained generic. Done means the sample is rejected as expected and the resulting type no longer incorrectly remains the argument type.