Assignment allowed to invalid variables in contract body

[pdaian]

• viper Version: 0.0.2
• pyethereum Version: 2.1.0
• OS: linux
• Python Version (python --version): 3.6

What's your issue about?

It appears that some programs parse which perhaps should not, including assigning to a global-style declaration in function bodies. These programs then behave unexpectedly. Below is a minimal example:

from ethereum.tools import tester as t
from ethereum.slogging import configure_logging

#configure_logging(':trace')
s = t.Chain()
from viper import com
piler

code = """
def foo() -> num:
    q:num = 1
    return q

def foo2() -> num:
    q = 1
    return q
"""

t.languages['viper'] = compiler.Compiler() 

c = s.contract(code, language='viper')

print(c.foo())  # Should not parse? returns 0
print(c.foo2()) # Should return 1; returns 1

This bug was discovered by Yi Zhang of the KEVM project. (@yzhang90)

How can it be fixed?

Make parsing consistent with what is specified in the old README.

Specifically, the offending statement can parse under these top-level rules:

 <varname> = <type>
        OR <var> = <expr>

with "q:num" being neither a valid varname or var (assuming varnames cannot contain colons, which would be sane).

Parsing should therefore likely fail in this case.

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[DavidKnott]

@pdaian Thanks for making an issue, I'll look into it right away!

[pdaian]

Interestingly enough the following works as tested, as spotted by @yzhang90

def foo() -> num:
    p:{x:num, y:num}
    p.x = 2
    p.y = 3
    return p.y

[jacqueswww]

@pdaian @yzhang90 good catch ! 🐟