TypeScript error: Property does not exist on type 'never'

What causes this error

never represents a type that TypeScript believes is impossible to reach. It shows up most often when a series of if/else or switch branches, combined with type guards, has (in TypeScript's view) eliminated every member of a union type — leaving nothing left, so any property access is flagged.

The Fix

type Shape = { kind: 'circle'; radius: number } | { kind: 'square'; side: number };

function area(shape: Shape) {
  if (shape.kind === 'circle') {
    return Math.PI * shape.radius ** 2;
  }
  if (shape.kind === 'square') {
    return shape.side ** 2;
  }
  // shape is narrowed to `never` here — correct, since both cases are handled
}

// If you see this error unexpectedly, check for a typo in a discriminant
// check (e.g. comparing shape.kind === 'circl' by mistake), which makes
// TypeScript think that branch is unreachable.

Common causes / variations

• A typo in a string literal comparison used as a type guard
• An exhaustive switch where a new union member was added to the type but not handled in the switch
• Merging two functions with incompatible parameter types, collapsing the parameter type to never

Related errors

See also: Object is possibly 'null'.