cgen: fix map of complex array (#17660)

vlib/v/gen/c/cgen.v

@@ -123,6 +123,7 @@ mut:
 	inside_map_infix          bool // inside map<</+=/-= infix expr
 	inside_assign             bool
 	inside_map_index          bool
+	inside_array_index        bool
 	inside_opt_or_res         bool
 	inside_opt_data           bool
 	inside_if_option          bool

vlib/v/gen/c/index.v

@@ -202,7 +202,14 @@ fn (mut g Gen) index_of_array(node ast.IndexExpr, sym ast.TypeSymbol) {
 				g.write('&')
 			}
 		}
-		g.expr(node.left)
+		if node.left is ast.IndexExpr {
+			g.inside_array_index = true
+			g.expr(node.left)
+			g.inside_array_index = false
+		} else {
+			g.expr(node.left)
+		}
+
 		if node.left_type.has_flag(.shared_f) {
 			if left_is_ptr {
 				g.write('->val')
@@ -393,7 +400,7 @@ fn (mut g Gen) index_of_map(node ast.IndexExpr, sym ast.TypeSymbol) {
 			g.typ(elem_type.clear_flag(.option).clear_flag(.result))
 		}
 	}
-	get_and_set_types := elem_sym.kind in [.struct_, .map]
+	get_and_set_types := elem_sym.kind in [.struct_, .map, .array]
 	if g.is_assign_lhs && !g.is_arraymap_set && !get_and_set_types {
 		if g.assign_op == .assign || info.value_type == ast.string_type {
 			g.is_arraymap_set = true
@@ -434,6 +441,7 @@ fn (mut g Gen) index_of_map(node ast.IndexExpr, sym ast.TypeSymbol) {
 			g.write('${zero} })))')
 		}
 	} else if g.inside_map_postfix || g.inside_map_infix || g.inside_map_index
+		|| g.inside_array_index
 		|| (g.is_assign_lhs && !g.is_arraymap_set && get_and_set_types) {
 		zero := g.type_default(info.value_type)
 		if node.is_setter {

vlib/v/tests/map_complex_array_test.v

@@ -0,0 +1,19 @@
+struct Instr {
+mut:
+	a int
+	b int
+}
+
+fn test_map_complex_array() {
+	mut map1 := map[string][]&Instr{}
+	instr := &Instr{
+		a: 1
+		b: 2
+	}
+	arr := [instr]
+	map1['Hello'] = arr
+	map1['Hello'][0].a = 2
+	println(map1['Hello'][0].a)
+	assert map1['Hello'][0].a == 2
+	assert map1['Hello'][0].b == 2
+}