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[Tolk] Nullable types T? and null safety

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This commit introduces nullable types `T?` that are
distinct from non-nullable `T`.
Example: `int?` (int or null) and `int` are different now.
Previously, `null` could be assigned to any primitive type.
Now, it can be assigned only to `T?`.

A non-null assertion operator `!` was also introduced,
similar to `!` in TypeScript and `!!` in Kotlin.

If `int?` still occupies 1 stack slot, `(int,int)?` and
other nullable tensors occupy N+1 slots, the last for
"null precedence". `v == null` actually compares that slot.
Assigning `(int,int)` to `(int,int)?` implicitly creates
a null presence slot. Assigning `null` to `(int,int)?` widens
this null value to 3 slots. This is called "type transitioning".

All stdlib functions prototypes have been updated to reflect
whether they return/accept a nullable or a strict value.

This commit also contains refactoring from `const FunctionData*`
to `FunctionPtr` and similar.
This commit is contained in:
tolk-vm 2025-02-24 20:13:36 +03:00
parent 1389ff6789
commit f3e620f48c
No known key found for this signature in database
GPG key ID: 7905DD7FE0324B12
62 changed files with 2031 additions and 702 deletions
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28
tolk/pipe-check-rvalue-lvalue.cpp
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@ -37,7 +37,7 @@ static void fire_error_cannot_be_used_as_lvalue(AnyV v, const std::string& detai
}
GNU_ATTRIBUTE_NORETURN GNU_ATTRIBUTE_COLD
static void fire_error_modifying_immutable_variable(AnyExprV v, const LocalVarData* var_ref) {
static void fire_error_modifying_immutable_variable(AnyExprV v, LocalVarPtr var_ref) {
if (var_ref->param_idx == 0 && var_ref->name == "self") {
v->error("modifying `self`, which is immutable by default; probably, you want to declare `mutate self`");
} else {
@ -47,7 +47,7 @@ static void fire_error_modifying_immutable_variable(AnyExprV v, const LocalVarDa
// validate a function used as rvalue, like `var cb = f`
// it's not a generic function (ensured earlier at type inferring) and has some more restrictions
static void validate_function_used_as_noncall(AnyExprV v, const FunctionData* fun_ref) {
static void validate_function_used_as_noncall(AnyExprV v, FunctionPtr fun_ref) {
if (!fun_ref->arg_order.empty() || !fun_ref->ret_order.empty()) {
v->error("saving `" + fun_ref->name + "` into a variable will most likely lead to invalid usage, since it changes the order of variables on the stack");
}
@ -97,6 +97,18 @@ class CheckRValueLvalueVisitor final : public ASTVisitorFunctionBody {
parent::visit(v->get_expr());
}
void visit(V<ast_not_null_operator> v) override {
// if `x!` is lvalue, then `x` is also lvalue, so check that `x` is ok
parent::visit(v->get_expr());
}
void visit(V<ast_is_null_check> v) override {
if (v->is_lvalue) {
fire_error_cannot_be_used_as_lvalue(v, v->is_negated ? "operator !=" : "operator ==");
}
parent::visit(v->get_expr());
}
void visit(V<ast_int_const> v) override {
if (v->is_lvalue) {
fire_error_cannot_be_used_as_lvalue(v, "literal");
@ -124,7 +136,7 @@ class CheckRValueLvalueVisitor final : public ASTVisitorFunctionBody {
void visit(V<ast_dot_access> v) override {
// a reference to a method used as rvalue, like `var v = t.tupleAt`
if (v->is_rvalue && v->is_target_fun_ref()) {
validate_function_used_as_noncall(v, std::get<const FunctionData*>(v->target));
validate_function_used_as_noncall(v, std::get<FunctionPtr>(v->target));
}
}
@ -158,17 +170,17 @@ class CheckRValueLvalueVisitor final : public ASTVisitorFunctionBody {
void visit(V<ast_reference> v) override {
if (v->is_lvalue) {
tolk_assert(v->sym);
if (const auto* var_ref = v->sym->try_as<LocalVarData>(); var_ref && var_ref->is_immutable()) {
if (LocalVarPtr var_ref = v->sym->try_as<LocalVarPtr>(); var_ref && var_ref->is_immutable()) {
fire_error_modifying_immutable_variable(v, var_ref);
} else if (v->sym->try_as<GlobalConstData>()) {
} else if (v->sym->try_as<GlobalConstPtr>()) {
v->error("modifying immutable constant");
} else if (v->sym->try_as<FunctionData>()) {
} else if (v->sym->try_as<FunctionPtr>()) {
v->error("function can't be used as lvalue");
}
}
// a reference to a function used as rvalue, like `var v = someFunction`
if (const FunctionData* fun_ref = v->sym->try_as<FunctionData>(); fun_ref && v->is_rvalue) {
if (FunctionPtr fun_ref = v->sym->try_as<FunctionPtr>(); fun_ref && v->is_rvalue) {
validate_function_used_as_noncall(v, fun_ref);
}
}
@ -186,7 +198,7 @@ class CheckRValueLvalueVisitor final : public ASTVisitorFunctionBody {
}
public:
bool should_visit_function(const FunctionData* fun_ref) override {
bool should_visit_function(FunctionPtr fun_ref) override {
return fun_ref->is_code_function() && !fun_ref->is_generic_function();
}
};