### Godot version

v4.0.rc1.official [8843d9ad3]

### System information

Lubuntu

### Issue description

You can't use + or += to mutate typed arrays.

It seems to be not correctly getting the type information from the second operand.

An erudite poster on the discord puts it differently:
> it's more like operator + doesn't retain Array typing
> the syntax for Array Concatenation via operators, but the idea gets across i think


The error you see is:
```Trying to assign an array of type "Array" to a variable of type "Array[int]".```


### Steps to reproduce

```
	var Alice: Array[int] = [1,2,3]
	var Bob: Array[int] = [4,5,6]
	Alice += Bob
```
This will crash with the above error message.

### Minimal reproduction project

[plus_syntax_broken_demo_project.zip](https://github.com/godotengine/godot/files/10694514/plus_syntax_broken_demo_project.zip)

current_enum = prev_enum;
					if (!member.enum_value.custom_value->is_constant) {
						push_error(R"(Enum values must be constant.)", member.enum_value.custom_value);
					} else if (member.enum_value.custom_value->reduced_value.get_type() != Variant::INT) {
						push_error(R"(Enum values must be integers.)", member.enum_value.custom_value);
					} else {
						member.enum_value.value = member.enum_value.custom_value->reduced_value;
						member.enum_value.resolved = true;
					}
				} else {
					check_class_member_name_conflict(p_class, member.enum_value.identifier->name, member.enum_value.parent_enum);
					if (member.enum_value.index > 0) {
						const GDScriptParser::EnumNode::Value &prev_value = member.enum_value.parent_enum->values[member.enum_value.index - 1];
						resolve_class_member(p_class, prev_value.identifier->name, member.enum_value.identifier);
						member.enum_value.value = prev_value.value + 1;
					} else {
						member.enum_value.value = 0;
					}
					member.enum_value.resolved = true;
				}
				
				member.enum_value.parent_enum->values.set(member.enum_value.index, member.enum_value);
				member.enum_value.identifier->set_datatype(make_enum_type(UNNAMED_ENUM, p_class->fqcn, false));
			} break;
			case GDScriptParser::ClassNode::Member::CLASS:
				check_class_member_name_conflict(p_class, member.m_class->identifier->name, member.m_class);
				
				if (!member.m_class->base_type.is_resolving()) {
					resolve_class_inheritance(member.m_class, p_source);
				}