Copy type definition from local variables/methods in class definitions

[khukri]

It would be nice to be able to "self reference" local methods and variables/fields so that you can write the type definition once and refer to it elsewhere in the class definition.

If that's not easily doable, an informative error message would be preferable over a stack trace :-)

class A:
int b
void init(A self, A.b b):
print(b + 2)

Expected output:
b is defined as int, the print statement outputs the sum of b + 2.

Received output:

Traceback (most recent call last):
File "../../mypy-py/mypy.py", line 138, in
main()
File "../../mypy-py/mypy.py", line 52, in main
True)
File "/home/toor/mypydev/mypy-py/build.py", line 99, in build
return manager.process(UnprocessedFile(info, program_text))
File "/home/toor/mypydev/mypy-py/build.py", line 180, in process
next.process()
File "/home/toor/mypydev/mypy-py/build.py", line 516, in process
self.sem_analyzer().visit_file(self.tree, self.tree.path)
File "/home/toor/mypydev/mypy-py/semanal.py", line 170, in visit_file
d.accept(self)
File "/home/toor/mypydev/mypy-py/nodes.py", line 321, in accept
return visitor.visit_type_def(self)
File "/home/toor/mypydev/mypy-py/semanal.py", line 281, in visit_type_def
defn.defs.accept(self)
File "/home/toor/mypydev/mypy-py/nodes.py", line 386, in accept
return visitor.visit_block(self)
File "/home/toor/mypydev/mypy-py/semanal.py", line 351, in visit_block
s.accept(self)
File "/home/toor/mypydev/mypy-py/nodes.py", line 255, in accept
return visitor.visit_func_def(self)
File "/home/toor/mypydev/mypy-py/semanal.py", line 188, in visit_func_def
self.analyse_function(defn)
File "/home/toor/mypydev/mypy-py/semanal.py", line 209, in analyse_function
defn.typ.accept(self)
File "/home/toor/mypydev/mypy-py/nodes.py", line 907, in accept
return visitor.visit_annotation(self)
File "/home/toor/mypydev/mypy-py/semanal.py", line 300, in visit_annotation
ann.typ = self.anal_type(ann.typ)
File "/home/toor/mypydev/mypy-py/semanal.py", line 382, in anal_type
return t.accept(a)
File "/home/toor/mypydev/mypy-py/mtypes.py", line 208, in accept
return visitor.visit_callable(self)
File "/home/toor/mypydev/mypy-py/typeanal.py", line 81, in visit_callable
res = Callable(self.anal_array(t.arg_types),
File "/home/toor/mypydev/mypy-py/typeanal.py", line 98, in anal_array
res.append(t.accept(self))
File "/home/toor/mypydev/mypy-py/mtypes.py", line 38, in accept
return visitor.visit_unbound_type(self)
File "/home/toor/mypydev/mypy-py/typeanal.py", line 20, in visit_unbound_type
sym = self.lookup(t.name, t)
File "/home/toor/mypydev/mypy-py/semanal.py", line 704, in lookup_qualified
n = (n.node).names.get(parts[i], None)
AttributeError: 'TypeInfo' object has no attribute 'names'

[JukkaL]

Thanks for reporting the bug!

Yeah, that sucks. It's on the unsupported feature list in the wiki, but at least there should be a proper error message.

[JukkaL]

Fixed in the git repo: there is now an error message indicating that class attribute are not supported yet.

However, the original example will not be valid mypy, since A.x refers to the value of A.x, not the type of A.x. So you have to say void __init__(self, int b): (note also that the type of self is inferred). The declaration of b in the body of class A is optional, though.