vfmt: support inline comments before fields in struct initializations

vlib/v/ast/ast.v

@@ -211,11 +211,12 @@ pub mut:
 
 pub struct StructInit {
 pub:
-	pos      token.Position
-	is_short bool
+	pos          token.Position
+	is_short     bool
+	pre_comments []Comment
 pub mut:
-	typ      table.Type
-	fields   []StructInitField
+	typ          table.Type
+	fields       []StructInitField
 }
 
 // import statement

vlib/v/fmt/fmt.v

@@ -1806,6 +1806,11 @@ pub fn (mut f Fmt) struct_init(it ast.StructInit) {
 		} else {
 			f.writeln('$name{')
 		}
+		f.comments(it.pre_comments, {
+			inline: true
+			has_nl: true
+			level: .indent
+		})
 		f.indent++
 		for field in it.fields {
 			f.write('$field.name: ')

vlib/v/fmt/tests/struct_init_with_comments_keep.vv

@@ -0,0 +1,20 @@
+module abcde
+
+pub struct Builder {
+pub mut:
+	// TODO
+	buf          []byte
+	str_calls    int
+	len          int
+	initial_size int = 1
+}
+
+pub fn new_builder(initial_size int) Builder {
+	return Builder{
+		// buf: make(0, initial_size)
+		buf: []byte{cap: initial_size}
+		str_calls: 0 // after str_calls
+		len: 0 // after len
+		initial_size: initial_size // final
+	}
+}

vlib/v/parser/struct.v

@@ -299,6 +299,7 @@ fn (mut p Parser) struct_init(short_syntax bool) ast.StructInit {
 	if !short_syntax {
 		p.check(.lcbr)
 	}
+	pre_comments := p.eat_comments()
 	mut fields := []ast.StructInitField{}
 	mut i := 0
 	no_keys := p.peek_tok.kind != .colon && p.tok.kind != .rcbr // `Vec{a,b,c}
@@ -354,6 +355,7 @@ fn (mut p Parser) struct_init(short_syntax bool) ast.StructInit {
 			len: last_pos.pos - first_pos.pos + last_pos.len
 		}
 		is_short: no_keys
+		pre_comments: pre_comments
 	}
 	return node
 }