sail -fmt is confused about trailing comments

[arichardson]

From formatting the sail-cheri-riscv model:

 /* Cheri PCC helpers */
-
 function min_instruction_bytes () -> CapAddrInt = {
-  if   (~ (sys_enable_writable_misa ())) & (~ (sys_enable_rvc ()))
-  then 4  /* RVC is hardwired to be disabled */
-  else 2  /* RVC is active or it could become active */
+    if ~(sys_enable_writable_misa()) & ~(sys_enable_rvc()) then {
+        4
+    } else {
+        /* RVC is hardwired to be disabled */
+        2
+    }/* RVC is active or it could become active */
 }

Would it be possible to keep trailing comments associated with the same AST node even when inserting braces?

[Alasdair]

Yes, the problem here is we don't have locations for the if, then and else tokens in the syntax tree so it's hard to place the comments precisely. I need to add those and probably for some other keywords and delimiters.

[Alasdair]

The second comment /* RVC is active or it could become active */ is going to be hard to place correctly for an if-statement without braces, unless we try to do something clever using the indentation level of the comment, because it's hard to reliably distinguish

if   (~ (sys_enable_writable_misa ())) & (~ (sys_enable_rvc ()))
then 4  /* RVC is hardwired to be disabled */
else 2
/* RVC is active or it could become active */

Peter suggested some syntax for forcing comments to be attached in a specific direction, something like (making syntax up on the spot): /*< comment */ or /*> comment */

[arichardson]

I'd be fine to require braces for if statements with comments. In that case the comment would remain within the braces right? It's just because there weren't any initially? Doxygen uses /**< to place documentation after members: https://www.doxygen.nl/manual/docblocks.html (Putting documentation after members)

[Alasdair]

If you have braces it should work fine:

function foo() = {
    if cond
    then 2 /* comment 1 */
    else { 3 /* comment 2 */ }
}

will become:

function foo () = {
    if cond then {
        2/* comment 1 */
    } else {
        3/* comment 2 */
    }
}

The awkward lack of spaces between the numbers and the comments is also a known problem right now. I'll need some kind of pass that re-lexes the formatted source and adjusts the spaces in front of comments to fix it properly.