cgen: fix complex map_fixed_array (#8209)

vlib/v/gen/cgen.v

@@ -1950,6 +1950,7 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 		right_sym := g.table.get_type_symbol(val_type)
 		is_fixed_array_copy := right_sym.kind == .array_fixed && val is ast.Ident
 		g.is_assign_lhs = true
+		g.assign_op = assign_stmt.op
 		if is_interface && right_sym.kind == .interface_ {
 			is_interface = false
 		}
@@ -1969,25 +1970,42 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 			if right.has_val {
 				for j, expr in right.exprs {
 					g.expr(left)
+					if g.is_array_set {
+						g.out.go_back(2)
+					} else {
 						g.write('[$j] = ')
+					}
 					g.expr(expr)
+					if g.is_array_set {
+						g.writeln(')')
+						g.is_array_set = false
+					} else {
 						g.writeln(';')
 					}
+				}
 			} else {
 				fixed_array := right_sym.info as table.ArrayFixed
 				for j in 0 .. fixed_array.size {
 					g.expr(left)
+					if g.is_array_set {
+						g.out.go_back(2)
+					} else {
 						g.write('[$j] = ')
+					}
 					if right.has_default {
 						g.expr(right.default_expr)
 					} else {
 						g.write(g.type_default(right.elem_type))
 					}
+					if g.is_array_set {
+						g.writeln(')')
+						g.is_array_set = false
+					} else {
 						g.writeln(';')
 					}
 				}
+			}
 		} else {
-			g.assign_op = assign_stmt.op
 			is_inside_ternary := g.inside_ternary != 0
 			cur_line := if is_inside_ternary && is_decl {
 				g.register_ternary_name(ident.name)

vlib/v/tests/map_complex_fixed_array_test.v

@@ -0,0 +1,10 @@
+fn foo(mut m map[string][1][2]map[string]int) {
+	m['foo'] = [[{'bar': 1}, {'baz':3}]!]!
+}
+
+fn test_complex_map_fixed_array() {
+	mut m := map[string][1][2]map[string]int
+	foo(mut m)
+	println(m)
+	assert '$m' == "{'foo': [[{'bar': 1}, {'baz': 3}]]}"
+}