Callable type anntoation written apart of assignment causes false positive typecheck result.

A bugreport, mypy version is 0.761, python version is 3.7.3

This is a case where expected incapatible types, because i declared that foo's input type is float, and attempting to call it with str, but typechecking passed successful.

from typing import Callable

def bar(x):  return 5

foo : Callable[[float],int]
foo = bar

foo("test")

mypy this_file.py
Mypy's output:

Success: no issues found in 1 source file

A case with type annotation written with assignment wont give false positive result:

from typing import Callable

def bar(x):  return 5

foo : Callable[[float],int] = bar

foo("test")

mypy this_file.py
Mypy's output:

this_file.py:7: error: Argument 1 has incompatible type "str"; expected "float"
Found 1 error in 1 file (checked 1 source file)

I wasnt found other cases excluding cases with Callable type.

For example with Tuples type anntoation written apart of assignment all working fine:

from typing import Tuple

foo : Tuple[str,int]
foo = (1,3)

mypy this_file.py
Mypy's output:

this_file.py:4: error: Incompatible types in assignment (expression has type "Tuple[int, int]", variable has type "Tuple[str, int]")
Found 1 error in 1 file (checked 1 source file)

Reproduce the two Callable examples with mypy 0.761 and Python 3.7.3, then compare the separate declaration and assignment path with the combined form. Trace the Callable handling in the type checker and add a regression test that expects an incompatible argument-type error for the separate declaration case.