Add support for switch with case statement instead of block statement

[xdufour]

As demonstrated by https://godbolt.org/z/zoh6c3Psq, a edge case for the syntax of the switch statement: https://learn.microsoft.com/en-us/cpp/c-language/switch-statement-c?view=msvc-170,

switch ( expression ) statement

where statement, although almost always a block-statement, isn't required to be one.

It can instead be a case statement, and even potentially multiple labelled statements, such that the resulting syntax is:

switch ( expression ) case constant-expression : statement

This PR adds support for this edge case in sh.c: comp_switch(), in order for the Godbolt snippet above to generate the following sh code and produce the expected output:

case 123 in
  123)
    printf "F"
  ;;
esac
case 456 in
  123|456)
    printf "E"
  ;;
esac

[laurenthuberdeau]

I think changing the switch parser so that it always produces a { node (i.e. wrap the result in new_ast2('{', child1, 0) if the node is not 0 and not of type { ) would be best. That way it would also work with the following switch statement (which prints nothing):

switch (456) {
  putchar('B');
}

[xdufour]

Fair enough - it does simplify this edge case down to the more typical syntax the parser would expect as well.

After a quick test, it doesn't seem to work per say with the given example:
tests/_sh/switch.c:112:0 Expected case in switch. Fallthrough is not supported.

However, gcc 14.2 emits a warning saying it is an unreachable statement that will never get executed - so I would think it is fine to enforce it as ill-formed?

[laurenthuberdeau]

Thanks for the PR!