TypeScript Version: 3.3.3 to Nightly

Search Terms:

• Boolean
• Iteration
• Inference

Code

let value = false;

['a', 'b', 'c'].forEach(str => {
  if (str === 'b') {
    value = true;
  }
})

console.log(value)

Expected behavior: Type inspection (mouse on variable) should say that value type is a boolean as the variable can clearly take both true and false values.

Actual behavior: It says value can only be false, even after conditionnaly set value to true.

Playground Link: https://www.typescriptlang.org/play?ts=4.0.2#code/DYUwLgBAbghsCuIIF4IDM4GcQG4BQeA2gOQzEA0ExARhVQMbEC6AdGgPYBOAojPQBYAKTGE4oAfBADeeCBACWaCMNEpkqGsQCU02XOhxEKCKMT45AXzwWtBeuwB2mdqBbB2Ac0GwEIW0A

Related Issues: Not found, let me know if there is already one.