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narrowing an undefined | A property not working anymore #10169
Description
nightly build August 5, 2016
function noUnnecessaryTypeAnnotations(node: ts.Node, checker: ts.TypeChecker): Issue | void {
if (isVariableDeclaration(node)) {
if (node.initializer !== undefined && node.type !== undefined) {
node.initializer; // <-- expected: Expression; actual: Expression | undefined
}
}
}
Activity
ahejlsberg commentedon Aug 5, 2016
The issue here is that the checker thinks
node.type !== undefinedmight be a discriminant type guard, so it resets other type guards for properties of the formnode.xxx. A workaround would be to reverse the two type guards (but of course you'll then have the same problem fornode.type).