cgen: fix cross assign for functions (#5734)

vlib/v/gen/cgen.v

@@ -1132,8 +1132,26 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 		for i, left in assign_stmt.left {
 			match left {
 				ast.Ident {
-					styp := g.typ(assign_stmt.left_types[i])
-					g.writeln('$styp _var_$left.pos.pos = $left.name;')
+					var_type := assign_stmt.left_types[i]
+					left_sym := g.table.get_type_symbol(var_type)
+					if left_sym.kind == .function {
+						func := left_sym.info as table.FnType
+						ret_styp := g.typ(func.func.return_type)
+						g.write('$ret_styp (*_var_$left.pos.pos) (')
+						arg_len := func.func.args.len
+						for j, arg in func.func.args {
+							arg_type := g.table.get_type_symbol(arg.typ)
+							g.write('${arg_type.str()} ${arg.name}')
+							if j < arg_len - 1 {
+								g.write(', ')
+							}
+						}
+						g.writeln(') = $left.name;')
+					}
+					else {
+						styp := g.typ(var_type)
+						g.writeln('$styp _var_$left.pos.pos = $left.name;')
+					}
 				}
 				ast.IndexExpr {
 					sym := g.table.get_type_symbol(left.left_type)

vlib/v/tests/fn_cross_assign_test.v

@@ -0,0 +1,69 @@
+
+fn cross_assign_anon_fn_one (a int, b bool) string {
+	return 'one'
+}
+
+fn cross_assign_anon_fn_two (a int, b bool) string {
+	return 'two'
+}
+
+fn cross_assign_anon_fn_three() (string, string) {
+	return 'three', 'three'
+}
+
+fn cross_assign_anon_fn_four() (string, string) {
+	return 'four', 'four'
+}
+
+fn cross_assign_anon_fn_five(a ...int) string {
+	return 'five'
+}
+
+fn cross_assign_anon_fn_six(a ...int) string {
+	return 'six'
+}
+
+fn cross_assign_anon_fn_seven (a int, b bool) string {
+	return 'seven'
+}
+
+fn cross_assign_anon_fn_eight (a int, b bool) string {
+	return 'eight'
+}
+
+fn test_cross_assign_anon_fn() {
+	mut one := cross_assign_anon_fn_one
+	mut two := cross_assign_anon_fn_two
+	one, two = two, one
+	foo := two(0, true) + one(0, true)
+	assert foo == 'onetwo'
+	
+	mut three := cross_assign_anon_fn_three
+	mut four := cross_assign_anon_fn_four
+	three, four = four, three
+	mut foo2, mut foo3 := four()
+	foo4, foo5 := three()
+	foo2 += foo4
+	foo3 += foo5
+	assert foo2 == 'threefour'
+	assert foo3 == 'threefour'
+	
+	mut five := cross_assign_anon_fn_five
+	mut six := cross_assign_anon_fn_six
+	five, six = six, five
+	foo6 := six(1, 2, 3) + five(1, 2, 3)
+	assert foo6 == 'fivesix'
+	
+	one, two, three, four, five, six = two, one, four, three, six, five
+	mut foo7, _ := three()
+	foo8, _ := four()
+	foo7 += foo8
+	foo9 := one(0, true) + two(0, true) + foo7 + five(1, 2, 3) + six(1, 2, 3)
+	assert foo9 == 'onetwothreefourfivesix'
+	
+	mut seven := cross_assign_anon_fn_seven
+	mut eight := cross_assign_anon_fn_eight
+	one, two, seven, eight = two, seven, eight, one
+	foo10 := one(0, true) + two(0, true) + seven(0, true) + eight(0, true)
+	assert foo10 == 'twoseveneightone'
+}