Right now theparent property is optional on all AST nodes.
However in reality, it's always defined on all AST nodes, except forProgram, where it is missing.

This leads to a bunch of unnecessary ifs/optional chains/"trust me it's right" assertions, all of which "harm" the type safety, or are impossible to get coverage on (leading to istanbul ignore statements):

// this shouldn't happen, checking just in case/* istanbul ignore if */if(node.parent){// ...}// selector asserts this is correctconstparent=node.parentasTSESTree.VariableDeclaration;if(node.parent?.type===AST_NODE_TYPES.VariableDeclaration){// ...}

There is an issue with this, however.
typescript-estree does not assign the parent property; this is done by ESLint as it traverses the AST at lint time.

So there are two solutions I can see:

1. changetypescript-estree so that it sets theparent appropriately.
2. create a separate set of types for use within plugins, which correctly type theparent property.

As an aside, doing this would unlock a really awesome benefit wherein we could make all the types generic, allowing you to specify the expected parent type ahead of time:

interfaceBaseNode<TParentextendsNode=Node>{// ...parent:TParent;}interfaceVariableDeclarator<TParentextendsNode=Node>extendsBaseNode<TParent>{}interfaceProgramextendsBaseNode{parent?:never;}

This would be great for things like return values of functions which explicitly check parent types, and for eslint selectors that explicitly state the tree structure (VariableDeclaration > VariableDeclarator).