Prevent import loops

[mbenke]

Importing the file with the same name leads to bad loop and consequently OOM.

We should probably record the files being processed (including the main file) and error out in case of loop.

[cameel]

Just for the record: this is actually allowed in Classic Solidity and works fine. It can be used as a workaround for namespacing things, though not sure how widespread that is in the wild.

[mbenke]

But I guess the Classic Solidity compiler does not loop on import loops :)

[mbenke]

@cameel oh and I mean "foo.sol" importing itself, not importing "foo.sol" twice in different places. Sorry if the decription isn't clear.

[cameel]

But I guess the Classic Solidity compiler does not loop on import loops :)

Yes, of course :) But it also does not error out on them unless there's an actual circular dependency between definitions within the files, not just imports.

I mean "foo.sol" importing itself, not importing "foo.sol" twice in different places

solc actually allows foo.sol to import itself. You can do weird things like this:

foo.sol:

import "foo.sol";
import "foo.sol" as M;
import {M as N} from "foo.sol";

enum E {A, B, C}

function f(E e1, M.E e2, N.M.E e3) {}

I mean, whether this is a good thing and has to be supported is another matter. Just wanted to make it clear that currently it is.