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Merge pull request #82477 from dalexeev/gds-covariance-and-contravariance

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GDScript: Add return type covariance and parameter type contravariance
This commit is contained in:
Yuri Sizov 2023-09-28 20:04:37 +02:00
commit b25f1f9c79
19 changed files with 169 additions and 4 deletions
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35
modules/gdscript/gdscript_analyzer.cpp
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@ -1671,15 +1671,42 @@ void GDScriptAnalyzer::resolve_function_signature(GDScriptParser::FunctionNode *
StringName native_base;
if (!p_is_lambda && get_function_signature(p_function, false, base_type, function_name, parent_return_type, parameters_types, default_par_count, method_flags, &native_base)) {
bool valid = p_function->is_static == method_flags.has_flag(METHOD_FLAG_STATIC);
valid = valid && parent_return_type == p_function->get_datatype();
if (p_function->return_type != nullptr) {
// Check return type covariance.
GDScriptParser::DataType return_type = p_function->get_datatype();
if (return_type.is_variant()) {
// `is_type_compatible()` returns `true` if one of the types is `Variant`.
// Don't allow an explicitly specified `Variant` if the parent return type is narrower.
valid = valid && parent_return_type.is_variant();
} else if (return_type.kind == GDScriptParser::DataType::BUILTIN && return_type.builtin_type == Variant::NIL) {
// `is_type_compatible()` returns `true` if target is an `Object` and source is `null`.
// Don't allow `void` if the parent return type is a hard non-`void` type.
if (parent_return_type.is_hard_type() && !(parent_return_type.kind == GDScriptParser::DataType::BUILTIN && parent_return_type.builtin_type == Variant::NIL)) {
valid = false;
}
} else {
valid = valid && is_type_compatible(parent_return_type, return_type);
}
}
int par_count_diff = p_function->parameters.size() - parameters_types.size();
valid = valid && par_count_diff >= 0;
valid = valid && default_value_count >= default_par_count + par_count_diff;
int i = 0;
for (const GDScriptParser::DataType &par_type : parameters_types) {
valid = valid && par_type == p_function->parameters[i++]->get_datatype();
if (valid) {
int i = 0;
for (const GDScriptParser::DataType &parent_par_type : parameters_types) {
// Check parameter type contravariance.
GDScriptParser::DataType current_par_type = p_function->parameters[i++]->get_datatype();
if (parent_par_type.is_variant() && parent_par_type.is_hard_type()) {
// `is_type_compatible()` returns `true` if one of the types is `Variant`.
// Don't allow narrowing a hard `Variant`.
valid = valid && current_par_type.is_variant();
} else {
valid = valid && is_type_compatible(current_par_type, parent_par_type);
}
}
}
if (!valid) {