[BUG] Contract after simple expression function fails

[JohelEGP]

It works with an extra ;, if the expression function has a compound-statement, or with a statement in-between.

Minimal reproducer (https://godbolt.org/z/TfajzxMT1):

main: () = {
  :() = 1;
  [[assert: 1]]
}

Commands:

cppfront x.cpp2

Expected result: The same as any of the first two workarounds above.

Actual result and error:

main.cpp2(3,4): error: subscript expression [ ] must not be empty (if you were trying to name a C-style array type, use 'std::array' instead) (at '[')

[filipsajdak]

This is all about this:

cppfront/source/parse.h

Lines 3858 to 3873 in f83ca9b

	if (
	semicolon_required
	&& (done() || curr().type() != lexeme::Semicolon)
	&& peek(-1)->type() != lexeme::Semicolon
	// this last peek(-1)-condition is a hack (? or is it just
	// maybe elegant? I'm torn) so that code like
	//
	// callback := :(inout x:_) = x += "suffix"; ;
	//
	// doesn't need the redundant semicolon at the end of a decl...
	// there's probably a cleaner way to do it, but this works and
	// it doesn't destabilize any regression tests
	)
	{
	return {};
	}

[filipsajdak]

I have a fix for that. No impact on regression tests. Last tests are running and will push it.

[filipsajdak]

@JohelEGP fix: #359