a type var should always be used at least twice in a context to make sense.

I have "reactions", but I still don't have a good question,per se.

@staticmethoddeftarget[个:hasDOTtarget,归个:ast.expr|ast.Name|ast.Attribute|ast.Subscript](node:个)->归个:returnnode.target

Analytically, this makes sense, but as you pointed out, it needs to make sense within the specification. I think that this does not work because, in part, neither TypeVar ("ge" and "guige") is used more than once.

@staticmethoddeftarget[个:hasDOTtarget,归个:ast.expr|ast.Name|ast.Attribute|ast.Subscript](node:个)->归个:returncast(归个,node.target)

I don't think thecast is valid because I don'tfeel that the symbol is defined in the scope. But I don't know what scope the definition has: just the signature?

Ithink theoverload definitions have the desired effect of type narrowing, so Ithink the aboveTypeVar would be redundant anyway.

"used twice",TypeAlias, andTypeVar

This statement is triggering my spidey sense--about a union of types:

a type var should always be used at least twice in a context to make sense.

For example, take:

工=typing_TypeVar('工',bound=ast.expr,covariant=True)# "gong"...classGrab:@staticmethoddeftargetAttribute(action:Callable[[ast.Name],ast.Name] \|Callable[[ast.Name|ast.Attribute|ast.Subscript],ast.Name|ast.Attribute|ast.Subscript] \|Callable[[工],工])->Callable[[hasDOTtarget],hasDOTtarget]:defworkhorse(node:hasDOTtarget)->hasDOTtarget:setattr(node,'target',action(getattr(node,'target')))returnnodereturnworkhorse

I switched some annotations toTypeVar recently, and I'm not sure of their impact yet, but I am pretty sure it is not helping in this context. Because of what you wrote, I wonder ifhasDOTtarget is effectively acting as a type "widener" and saying the return is always a union of types. Until now, I guess I believed that if the "input" type wereast.Name and the annotation wasCallable[[hasDOTtarget], hasDOTtarget], then the type checker would treat the return asast.Name.

classThen:@staticmethoddefreplaceWith(this:归个)->Callable[[Any],归个]:returnlambda_replaceMe:this

The abovemight be working: as in, the type checkers are using this annotation to "transitively define" the type. "Transitive:" I have no idea what the correct term is, so I mean A = B, B = C, -> A = C.

Parentheses

the meaning of grouping parentheses is currently not defined in the typing spec

I hadn't considered that. I'll change that. Thank you.

I don't think thecast is valid because I don'tfeel that the symbol is defined in the scope. But I don't know what scope the definition has: just the signature?

Just one quick point: The scope of the type var is the whole function, but when I said "a type var should always be used at least twice in a context" I should have said "a type var should always be used at least twice in a signature" (which for classes includes the signature of its methods and attributes).

So the cast is not necessarily "wrong", but the type var is kind of redundant, because the following definition would basically be equivalent:

@staticmethoddeftarget(node:Any)->ast.expr|ast.Name|ast.Attribute|ast.Subscript:returncast(ast.expr|ast.Name|ast.Attribute|ast.Subscript,node.target)