parser,fmt: handle array pre-comments separately from exprs (#8884)

vlib/v/ast/ast.v

@@ -942,6 +942,7 @@ pub:
 	elem_type_pos token.Position // `Type` in []Type{} position
 	exprs         []Expr      // `[expr, expr]` or `[expr]Type{}` for fixed array
 	ecmnts        [][]Comment // optional iembed comments after each expr
+	pre_cmnts     []Comment
 	is_fixed      bool
 	has_val       bool // fixed size literal `[expr, expr]!`
 	mod           string

vlib/v/fmt/fmt.v

@@ -1961,6 +1961,18 @@ pub fn (mut f Fmt) array_init(it ast.ArrayInit) {
 	mut inc_indent := false
 	mut last_line_nr := it.pos.line_nr // to have the same newlines between array elements
 	f.array_init_depth++
+	for i, c in it.pre_cmnts {
+		if c.pos.line_nr > last_line_nr {
+			f.writeln('')
+		} else if i > 0 {
+			f.write(' ')
+		}
+		f.comment(c, level: .indent, iembed: true)
+		last_line_nr = c.pos.last_line
+	}
+	if it.exprs.len == 0 && it.pre_cmnts.len > 0 && it.pre_cmnts[0].pos.line_nr != it.pos.line_nr {
+		f.writeln('')
+	}
 	for i, expr in it.exprs {
 		line_nr := expr.position().line_nr
 		if i == 0 {

vlib/v/fmt/tests/comments_embedded_keep.vv

@@ -6,7 +6,7 @@ fn only_comments_array() {
 		/* 4, */
 	]
 	arr2 := [
-		/* 1, */ /* 2, *//* 3, */
+		/* 1, */ /* 2, */ /* 3, */
 		/* 4, */
 	]
 }

vlib/v/parser/containers.v

@@ -16,6 +16,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 	mut elem_type_pos := first_pos
 	mut exprs := []ast.Expr{}
 	mut ecmnts := [][]ast.Comment{}
+	mut pre_cmnts := []ast.Comment{}
 	mut is_fixed := false
 	mut has_val := false
 	mut has_type := false
@@ -39,6 +40,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 		last_pos = p.tok.position()
 	} else {
 		// [1,2,3] or [const]byte
+		pre_cmnts = p.eat_comments({})
 		for i := 0; p.tok.kind !in [.rsbr, .eof]; i++ {
 			exprs << p.expr(0)
 			ecmnts << p.eat_comments({})
@@ -141,6 +143,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 		typ: array_type
 		exprs: exprs
 		ecmnts: ecmnts
+		pre_cmnts: pre_cmnts
 		pos: pos
 		elem_type_pos: elem_type_pos
 		has_len: has_len