fmt: correct indent for StructDecl multi line default exprs (#8148)

vlib/v/fmt/fmt.v

@@ -687,6 +687,7 @@ pub fn (mut f Fmt) struct_decl(node ast.StructDecl) {
 	mut field_align_i := 0
 	mut comment_align_i := 0
 	mut default_expr_align_i := 0
+	mut inc_indent := false // for correct indents with multi line default exprs
 	for i, field in node.fields {
 		if i == node.mut_pos {
 			f.writeln('mut:')
@@ -738,7 +739,15 @@ pub fn (mut f Fmt) struct_decl(node ast.StructDecl) {
 			pad_len := align.max_attrs_len - attrs_len + align.max_type_len - field_types[i].len
 			f.write(strings.repeat(` `, pad_len))
 			f.write(' = ')
+			if !expr_is_single_line(field.default_expr) {
+				f.indent++
+				inc_indent = true
+			}
 			f.prefix_expr_cast_expr(field.default_expr)
+			if inc_indent {
+				f.indent--
+				inc_indent = false
+			}
 		}
 		// Handle comments after field type (same line)
 		if comm_idx < comments.len {
@@ -1007,6 +1016,11 @@ fn expr_is_single_line(expr ast.Expr) bool {
 				return false
 			}
 		}
+		ast.ArrayInit {
+			if expr.exprs.len > 0 {
+				return expr_is_single_line(expr.exprs[0])
+			}
+		}
 		else {}
 	}
 	return true

vlib/v/fmt/tests/struct_keep.vv

@@ -34,3 +34,13 @@ pub:
 	a int
 	b int
 }
+
+struct KeepMultiLineDefaultExprsIndent {
+	buttons []PeriodButton = [PeriodButton{
+		period: pr.Period.m1
+		text: 'M1'
+	}, PeriodButton{
+		period: pr.Period.m5
+		text: 'M5'
+	}]
+}