fix[ux]: fix error message for common typo

[charles-cooper]

the staticall typo is very common, and was raising a hard-to-read error message from the python parser like "invalid syntax. Perhaps you forgot a comma?"

this commit adds it to the pre-parser, so we can raise an exception after we have successfully gone through the python parser and have the ability to add source info and a hint.

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[tserg]

I think a more scalable approach is to rely on the existing levenshtein utility. It currently raises a circular import, but I we can move vyper/semantics/analysis/levenshtein_utils.py to a top-level vyper/levenshtein_utils.py.

...

NAMESPACE = VYPER_CLASS_TYPES | CUSTOM_STATEMENT_TYPES | CUSTOM_EXPRESSION_TYPES

...

def pre_parse(...):
    ...
    try:
        ...
        for token in token_list:
            ...
            if typ == NAME:
                ...
                else:
                    from vyper.semantics.analysis.levenshtein_utils import _get_levenshtein_error_suggestions
                    hint = _get_levenshtein_error_suggestions(string, NAMESPACE, 0.3)
                    if hint != "":
                        raise SyntaxException("Possible typo", code, start[0], start[1], hint=hint)

[charles-cooper]

i don't think that's good, because

• the keyword might not be in the namespace (which could be addressed by hand-rolling the dict, i suppose)
• this is going to throw on all names (e.g. my_var: ...). we don't have enough info at this stage to determine whether we are parsing a keyword or any other name. we only have token info.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.46%. Comparing base (c32b9b4) to head (2eac70d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4363      +/-   ##
==========================================
- Coverage   91.23%   90.46%   -0.78%     
==========================================
  Files         112      112              
  Lines       16010    16012       +2     
  Branches     2697     2698       +1     
==========================================
- Hits        14607    14485     -122     
- Misses        968     1072     +104     
- Partials      435      455      +20     

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[pcaversaccio]

The test contract itself is incomplete. Can we make sure we unit test only the introduced change here?

A correct (i.e. compileable) Vyper contract would look like this

from ethereum.ercs import IERC20
from ethereum.ercs import IERC20Detailed


@external
def foo():
    extcall IERC20(msg.sender).transfer(
        msg.sender,
        convert(staticcall IERC20Detailed(msg.sender).decimals(), uint256),
    )

so we could have the following here:

from ethereum.ercs import IERC20
from ethereum.ercs import IERC20Detailed


@external
def foo():
    extcall IERC20(msg.sender).transfer(
        msg.sender,
        convert(staticall IERC20Detailed(msg.sender).decimals(), uint256),
    )

Another example with nested staticcall could be:

from ethereum.ercs import IERC20
from ethereum.ercs import IERC20Detailed


@view
def bar() -> uint256:
    return staticcall IERC20(msg.sender).balanceOf(
        convert(staticall IERC20Detailed(msg.sender).decimals(), address)
    )

In the last example, if you replace view with pure, it will raise the staticcall first instead of:

vyper.exceptions.StateAccessViolation: Cannot call a view function from a pure function

which is the expected behaviour IMO.

[pcaversaccio]

some other (not so common, but still) typos are:

• staticcal (that one we should probably also cover)
• statiiccall
• stacticall
• staticcal

[cyberthirst]

although I can imagine such mistakes being made, I don't like the idea that we would reserve 5 keywords just for error reporting (though I don't think such keywords would be used by users anyway)

[cyberthirst]

very unlikely.. but for completness

staticall: uint256

vyper.exceptions.SyntaxException: invalid syntax (<unknown>, line 1)

  line 1:10 
  ---> 1 staticall: uint256
  -----------------^
       2

or

def staticall():
    pass

yieds same the same ex

edit: added examples