Multi-line comments cannot be nested

[jiribenes]

/*
  /*
  nested
  */
  comment
*/

returns:

[error] nested.effekt:5:3: Unexpected end of input
  comment
  ^^^^^^^

which implies that multi-line comments cannot be nested.

[dvdvgt]

Is there a practical use-case for nested comments to justify the implied lexer complexity by supporting it? Otherwise, I would just not support it and add a lexer error upon encountering a /* while already lexing a multiline comment.

[jiribenes]

TL;DR: No, not really.

The only use case I have is when my code looks like this:

def foo() = 42
def bar() = 100
/*
def baz() = 400
*/
def quux() = 1000

(with way larger, multiline functions) and I want to comment out the rest of the file except for foo, I do:

def foo() = 42
/* 
def bar() = 100
/*
def baz() = 400
*/
def quux() = 1000
*/

which then doesn't work.

[jiribenes]

But a few months ago, we were discussing that we might remove multiline comments anyways and instead add better support for singleline ones (see effekt-lang/effekt-vscode#19).

In fact, I was thinking about simplifying the language to remove all multiline tokens (we can hack around multiline strings, Zig-style), since that would make the lexer simpler and it would be super simple to do incremental compilation (since only the changed lines need to be re-lexed, re-parsed, ...).