[swift-dev] Breaking change in lexing operators next to comments

[Jesse Rusak]

Hi all,

I’m investigating this bug: https://bugs.swift.org/browse/SR-186

Which appears to be a result of the fact that the logic that determines if an operator is prefix/postfix/binary does not treat comments as whitespace. So, for example:

/* comment */!foo

does not lex as expected because the “!" thinks it has an something on both sides and so is treated as a binary operator. 

Fixing this (by treating comments as whitespace here) will break existing code which relies on the current behavior, such as:

foo/* comment */!

which currently treats the “!” as a postfix operator but will change to binary. I expect these cases would be rare (maybe in some generated code?), but the results might be pretty confusing. 

Any objections to fixing this or other thoughts? 

Thanks,
Jesse
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