cgen: fix multi return assignment with option (#17676)

vlib/v/gen/c/assign.v

@@ -174,7 +174,7 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 	if return_type != ast.void_type && return_type != 0 {
 		sym := g.table.sym(return_type)
 		if sym.kind == .multi_return {
-			g.gen_multi_return_assign(node, return_type)
+			g.gen_multi_return_assign(node, return_type, sym)
 			return
 		}
 	}
@@ -668,7 +668,7 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 	}
 }
 
-fn (mut g Gen) gen_multi_return_assign(node &ast.AssignStmt, return_type ast.Type) {
+fn (mut g Gen) gen_multi_return_assign(node &ast.AssignStmt, return_type ast.Type, return_sym ast.TypeSymbol) {
 	// multi return
 	// TODO Handle in if_expr
 	mr_var_name := 'mr_${node.pos.pos}'
@@ -681,6 +681,7 @@ fn (mut g Gen) gen_multi_return_assign(node &ast.AssignStmt, return_type ast.Typ
 	g.write('${mr_styp} ${mr_var_name} = ')
 	g.expr(node.right[0])
 	g.writeln(';')
+	mr_types := (return_sym.info as ast.MultiReturn).types
 	for i, lx in node.left {
 		mut is_auto_heap := false
 		mut ident := ast.Ident{
@@ -702,8 +703,26 @@ fn (mut g Gen) gen_multi_return_assign(node &ast.AssignStmt, return_type ast.Typ
 		if lx.is_auto_deref_var() {
 			g.write('*')
 		}
-		g.expr(lx)
 		noscan := if is_auto_heap { g.check_noscan(return_type) } else { '' }
+		if node.left_types[i].has_flag(.option) {
+			base_typ := g.base_type(node.left_types[i])
+			tmp_var := if is_auto_heap {
+				'HEAP${noscan}(${styp}, ${mr_var_name}.arg${i})'
+			} else if is_option {
+				'(*((${g.base_type(return_type)}*)${mr_var_name}.data)).arg${i}'
+			} else {
+				'${mr_var_name}.arg${i}'
+			}
+			if mr_types[i].has_flag(.option) {
+				g.expr(lx)
+				g.write(' = ${tmp_var};')
+			} else {
+				g.write('_option_ok(&(${base_typ}[]) { ${tmp_var} }, (${option_name}*)(&')
+				g.expr(lx)
+				g.writeln('), sizeof(${base_typ}));')
+			}
+		} else {
+			g.expr(lx)
 			if g.is_arraymap_set {
 				if is_auto_heap {
 					g.writeln('HEAP${noscan}(${styp}, ${mr_var_name}.arg${i}) });')
@@ -722,6 +741,7 @@ fn (mut g Gen) gen_multi_return_assign(node &ast.AssignStmt, return_type ast.Typ
 				}
 			}
 		}
+	}
 	if g.is_arraymap_set {
 		g.is_arraymap_set = false
 	}

vlib/v/tests/option_multi_ret_test.v

@@ -0,0 +1,41 @@
+struct Test {
+mut:
+	a ?int
+	b ?string
+	c ?[]int
+}
+
+fn mr_1() (?int, string, []int) {
+	return 456, 'foo', [1]
+}
+
+fn mr_2() (?int, string, []int) {
+	return none, 'zoo', [99]
+}
+
+fn mr_3() ([]?int, ?int) {
+	return [?int(456)], none
+}
+
+fn test_mr_first_option() {
+	mut t := Test{}
+	t.a, t.b, t.c = mr_1()
+	assert t.a? == 456
+	assert t.b? == 'foo'
+	assert t.c? == [1]
+}
+
+fn test_mr_first_option_none() {
+	mut t := Test{}
+	t.a, t.b, t.c = mr_2()
+	assert t.a == none
+	assert t.b? == 'zoo'
+	assert t.c? == [99]
+}
+
+fn test_mr_first_option_array() {
+	a, b := mr_3()
+	t := a[0]
+	assert t? == 456
+	assert b == none
+}