Exit statements with succeeding code not prevented in For loops.

[trocher]

Version Information

• vyper Version (output of vyper --version): 0.3.8+commit.ae7d6d28
• OS: OSX
• Python Version (output of python --version): 3.8.0

What's your issue about?

The compiler checks that there is no exit statements (Return, Selfdestruct, Raise) with succeeding code (that would not execute) including other exit statements.

As For loops are not checked for this matter by the compiler it is possible to compile exit statements with succeeding code.

For example, in the following, foo will fail to compile due to a StructureException (Exit statement with succeeding code) while bar would compile.

@external
def foo():
    if(True):
        return
        a:uint256 = 2

@external
def bar():
    for i in range(12):
        return
        a:uint256 = 2

How can it be fixed?

Adding a case to handle For statements in check_single_exit should be enough to fix the issue.