Feedback sought: Optional Braces

Language Design
318

To be clear, in my view blocks and definitions are two orthogonal things. I proposed = as the universal identifier for introducing definitions. For blocks, the examples I have seen so far fall under two categories: (1) those introduced by control words (if, while, etc.) which are well-defined already, and (2) arguments to functions.

For the latter, and again this is my personal view so very biased, parentheses are unambiguous. And if the language is powerful enough, they can be removed by introducing a combinator with the proper fixity. If I refer to the Scala rules for operator precedence and associativity, it looks like :| and |: would be good candidates.

To take @LPTK’s example:

def constrExpr(): Tree =
  if in.isNestedStart then
    atSpan(in.offset)(
      inBracesOrIndented (
        val stats = selfInvocation() ::
          if isStatSep then { in.nextToken(); blockStatSeq() }
          else Nil
        Block(stats, unitLiteral)
      )
    )
  else
    Block(selfInvocation() :: Nil, unitLiteral)

or

def constrExpr(): Tree =
  if in.isNestedStart then
    atSpan(in.offset) |:
      inBracesOrIndented |:
        val stats = selfInvocation() ::
          if isStatSep then { in.nextToken(); blockStatSeq() }
          else Nil
        Block(stats, unitLiteral)
  else
    Block(selfInvocation() :: Nil, unitLiteral)
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