Fix AST construction for chained post incr/decr operators

Observe that instructions such as
``
a++ ++;
``
are not allowed, but this could generate a crash and not a clean error message

src/language/ASTBuilder.cpp

@@ -99,14 +99,24 @@ struct ASTBuilder::simplify_unary : parse_tree::apply<ASTBuilder::simplify_unary
         n = std::move(unary_operator);
         n->remove_content();
         transform(n, st...);
-      } else if (n->children[1]->is<language::post_minusminus>() or n->children[1]->is<language::post_plusplus>()) {
-        n->remove_content();
-        auto expression     = std::move(n->children[0]);
-        auto unary_operator = std::move(n->children[1]);
-        unary_operator->children.emplace_back(std::move(expression));
+      }
+    }
+
+    if (n->is<language::unary_expression>()) {
+      size_t child_nb = n->children.size();
+      if (child_nb > 1) {
+        if (n->children[child_nb - 1]->is<language::post_minusminus>() or
+            n->children[child_nb - 1]->is<language::post_plusplus>()) {
+          auto unary_operator = std::move(n->children[child_nb - 1]);
+          n->children.pop_back();
+
+          unary_operator->remove_content();
+          unary_operator->children.emplace_back(std::move(n));
+
           n = std::move(unary_operator);
           n->remove_content();
-        transform(n, st...);
+          transform(n->children[0], st...);
+        }
       }
     }
   }
@@ -203,8 +213,8 @@ struct ASTBuilder::simplify_stream_statement : parse_tree::apply<ASTBuilder::sim
 };
 
 template <typename Rule>
-using selector =
-  parse_tree::selector<Rule,
+using selector = parse_tree::selector<
+  Rule,
   parse_tree::store_content::on<import_instruction,
                                 module_name,
                                 true_kw,
@@ -233,7 +243,8 @@ using selector =
                                 for_statement,
                                 break_kw,
                                 continue_kw>,
-                       ASTBuilder::rearrange::on<logical_or, logical_and, bitwise_xor, equality, compare, sum, product, affectation, expression>,
+  ASTBuilder::rearrange::
+    on<logical_or, logical_and, bitwise_xor, equality, compare, sum, product, affectation, expression>,
   ASTBuilder::simplify_unary::
     on<unary_minus, unary_plus, unary_not, function_evaluation, type_expression, unary_expression>,
   parse_tree::remove_content::on<plus_op,