问Python类型提示语法是如何/为什么工作的？

EN

def greeting(name: str) -> str:
    return 'Hello ' + name

print(greeting('Martin'))
print(greeting(1))

  File "test.py", line 1
    def greeting(name: str) -> str:
                     ^
SyntaxError: invalid syntax

Hello Martin
Traceback (most recent call last):
  File "test.py", line 5, in <module>
    print(greeting(1))
  File "test.py", line 2, in greeting
    return 'Hello ' + name
TypeError: Can't convert 'int' object to str implicitly

def greeting(name: str) -> int:
    return 'Hello ' + name

print(greeting('Martin'))

def aha(something):
    print("aha")
    return something+"!"

def greeting(name: aha, foo) -> int:
    return 'Hello ' + name + foo

print(greeting('Martin', 'ad'))