Bug Report

🔎 Search Terms

empty intersections, never, return type

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about types.

⏯ Playground Link

strictNullChecks: false

strictNullChecks: true

💻 Code

type A = { p: "A" };
type B = { p: "B" };

function f1(): never {
  return;
}

function f2(): A & B {
  return;
}

function g1(): never {}

function g2(): A & B {}

🙁 Actual behavior

f1: Type 'undefined' is not assignable to type 'never'. (expected)
f2 w/ strictNullChecks: false: no error emitted
f2 w/ strictNullChecks: true: Type 'undefined' is not assignable to type 'never'. The intersection 'A & B' was reduced to 'never' because property 'p' has conflicting types in some constituents. (expected)

g1: A function returning 'never' cannot have a reachable end point. (expected)
g2: A function whose declared type is neither 'void' nor 'any' must return a value.

🙂 Expected behavior

f2 and g2 should generate the same errors as f1 and g1 respectively other than elaboration on empty intersection types.

Note: I was suggested to separate fix from #47751 and I'm ready to submit another PR if this is really a bug.