TS2339: Property 'tooltip' does not exist on type '{ label: string; } | { label: string; tooltip: string; }'.

[retorquere]

TypeScript Version: [email protected]

Code

const cells = [
  { label: '1' },
  { label: '2', tooltip: '2' },
  { label: '3', tooltip: '3' },
  { label: '4' },
  { label: '5' },
  { label: '6' },
]
for (const cell of cells) {
  if (cell.tooltip) console.log(cell.tooltip)
}

Expected behavior:
That this compiles without error; the error message seems to indicate TS sees a call to cell.tooltip as valid but then forbids it in the second part of the error message.

Actual behavior:

tt.ts(10,12): error TS2339: Property 'tooltip' does not exist on type '{ label: string; } | { label: string; tooltip: string; }'.
  Property 'tooltip' does not exist on type '{ label: string; }'.
tt.ts(10,38): error TS2339: Property 'tooltip' does not exist on type '{ label: string; } | { label: string; tooltip: string; }'.
  Property 'tooltip' does not exist on type '{ label: string; }'.

[DanielRosenwasser]

Looks like a duplicate of #1260. You can get around this with a user-defined type guard or a type-assertion.

[retorquere]

I eyed that issue but couldn't make out whether it was the same problem; If it's a dup feel free to close. The suggestions in #1260 do allow compilation, but is this issue planned for a fix in a 2.x release? #1260 has been open for a while.

[ajafff]

The easy fix for your problem is a type annotation:

const cells: {label: string, tooltip?: string} = [
  { label: '1' },
  { label: '2', tooltip: '2' },
  { label: '3', tooltip: '3' },
  { label: '4' },
  { label: '5' },
  { label: '6' },
]

[retorquere]

Yeah, that's what I settled on in the end.

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.