Print blocked statement to avoid dangling else even when it would be parsed correctly

[dwRchyngqxs]

The dangling else is a grammar ambiguity, as such sv2v should always avoid generating it. It is already done for statements, but only in the case where the else is attached to the outside if, not the inside it (common way to parse the dangling else).

Summary of changes: Removed begin/end block when the inner is a DoWhile because that would already enclose the else. Dangling else check passes through attributes (bug-fix). Dangling else check passes through most control flow structures instead of always enclosing inside begin/end. Added test case.

[zachjs]

Thank you very much for finding the issue with statement attributes and sharing this PR! The changes WRT the control flow constructs seem reasonable too. I simplified the test you wrote a bit, but it looks great overall.

Can you elaborate on the ambiguity you perceive? All three of IEEE 1364-2001, 1364-2005, and 1800-2017 all state:

Because the else part of an if-else is optional, there can be confusion when an else is omitted from a nested if sequence. This is resolved by always associating the else with the closest previous if that lacks an else.

I'm not opposed to making this change, but I'm wondering if you have a particular downstream tool or use case in mind given that it would indeed be parsed correctly either way.

[dwRchyngqxs]

The grammar is ambiguous, the standard states how to solve this ambiguity. Even though the standard states how to solve the ambiguity I wouldn't rely on downstream tools parsing a dangling else correctly. I don't have any tool in mind that doesn't parse it correctly, and even if I did, a bug in another tool wouldn't justify this change. In my mind there are 2 justifications:

• To not print Verilog that might trigger a bug in another tool.
• To print in an unambiguous way an incorrect code that someone might have written without being aware of the dangling else issue. If something goes wrong (and it will because the two ways of parsing the grammar ambiguity aren't equivalent), it will be easier for that person to understand the issue with a block than an indentation level.