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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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80
tolk/type-system.h
View file

@ -50,6 +50,8 @@ class TypeData {
const uint64_t type_id;
// bits of flag_mask, to store often-used properties and return them without tree traversing
const int flags;
// how many slots on a stack this type occupies (calculated on creation), e.g. `int`=1, `(int,int)`=2, `(int,int)?`=3
const int width_on_stack;
friend class TypeDataTypeIdCalculation;
@ -60,9 +62,10 @@ protected:
flag_contains_unresolved_inside = 1 << 3,
};
explicit TypeData(uint64_t type_id, int flags_with_children)
explicit TypeData(uint64_t type_id, int flags_with_children, int width_on_stack)
: type_id(type_id)
, flags(flags_with_children) {
, flags(flags_with_children)
, width_on_stack(width_on_stack) {
}
public:
@ -74,6 +77,7 @@ public:
}
uint64_t get_type_id() const { return type_id; }
int get_width_on_stack() const { return width_on_stack; }
bool has_unknown_inside() const { return flags & flag_contains_unknown_inside; }
bool has_genericT_inside() const { return flags & flag_contains_genericT_inside; }
@ -86,6 +90,10 @@ public:
virtual bool can_rhs_be_assigned(TypePtr rhs) const = 0;
virtual bool can_be_casted_with_as_operator(TypePtr cast_to) const = 0;
virtual bool can_hold_tvm_null_instead() const {
return true;
}
virtual void traverse(const TraverserCallbackT& callback) const {
callback(this);
}
@ -93,17 +101,13 @@ public:
virtual TypePtr replace_children_custom(const ReplacerCallbackT& callback) const {
return callback(this);
}
virtual int calc_width_on_stack() const {
return 1;
}
};
/*
* `int` is TypeDataInt, representation of TVM int.
*/
class TypeDataInt final : public TypeData {
TypeDataInt() : TypeData(1ULL, 0) {}
TypeDataInt() : TypeData(1ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -121,7 +125,7 @@ public:
* From the type system point of view, int and bool are different, not-autocastable types.
*/
class TypeDataBool final : public TypeData {
TypeDataBool() : TypeData(2ULL, 0) {}
TypeDataBool() : TypeData(2ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -138,7 +142,7 @@ public:
* `cell` is TypeDataCell, representation of TVM cell.
*/
class TypeDataCell final : public TypeData {
TypeDataCell() : TypeData(3ULL, 0) {}
TypeDataCell() : TypeData(3ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -155,7 +159,7 @@ public:
* `slice` is TypeDataSlice, representation of TVM slice.
*/
class TypeDataSlice final : public TypeData {
TypeDataSlice() : TypeData(4ULL, 0) {}
TypeDataSlice() : TypeData(4ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -172,7 +176,7 @@ public:
* `builder` is TypeDataBuilder, representation of TVM builder.
*/
class TypeDataBuilder final : public TypeData {
TypeDataBuilder() : TypeData(5ULL, 0) {}
TypeDataBuilder() : TypeData(5ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -191,7 +195,7 @@ public:
* so getting its element results in TypeDataUnknown (which must be assigned/cast explicitly).
*/
class TypeDataTuple final : public TypeData {
TypeDataTuple() : TypeData(6ULL, 0) {}
TypeDataTuple() : TypeData(6ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -209,7 +213,7 @@ public:
* It's like "untyped callable", not compatible with other types.
*/
class TypeDataContinuation final : public TypeData {
TypeDataContinuation() : TypeData(7ULL, 0) {}
TypeDataContinuation() : TypeData(7ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -224,12 +228,12 @@ public:
/*
* `null` has TypeDataNullLiteral type.
* Currently, it can be assigned to int/slice/etc., but later Tolk will have T? types and null safety.
* It can be assigned only to nullable types (`int?`, etc.), to ensure null safety.
* Note, that `var i = null`, though valid (i would be constant null), fires an "always-null" compilation error
* (it's much better for user to see an error here than when he passes this variable somewhere).
*/
class TypeDataNullLiteral final : public TypeData {
TypeDataNullLiteral() : TypeData(8ULL, 0) {}
TypeDataNullLiteral() : TypeData(8ULL, 0, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -242,6 +246,30 @@ public:
bool can_be_casted_with_as_operator(TypePtr cast_to) const override;
};
/*
* `T?` is "nullable T".
* It can be converted to T either with ! (non-null assertion operator) or with smart casts.
*/
class TypeDataNullable final : public TypeData {
TypeDataNullable(uint64_t type_id, int children_flags, int width_on_stack, TypePtr inner)
: TypeData(type_id, children_flags, width_on_stack)
, inner(inner) {}
public:
const TypePtr inner;
static TypePtr create(TypePtr inner);
bool is_primitive_nullable() const { return get_width_on_stack() == 1 && inner->get_width_on_stack() == 1; }
std::string as_human_readable() const override;
bool can_rhs_be_assigned(TypePtr rhs) const override;
bool can_be_casted_with_as_operator(TypePtr cast_to) const override;
void traverse(const TraverserCallbackT& callback) const override;
TypePtr replace_children_custom(const ReplacerCallbackT& callback) const override;
bool can_hold_tvm_null_instead() const override;
};
/*
* `fun(int, int) -> void` is TypeDataFunCallable, think of is as a typed continuation.
* A type of function `fun f(x: int) { return x; }` is actually `fun(int) -> int`.
@ -249,7 +277,7 @@ public:
*/
class TypeDataFunCallable final : public TypeData {
TypeDataFunCallable(uint64_t type_id, int children_flags, std::vector<TypePtr>&& params_types, TypePtr return_type)
: TypeData(type_id, children_flags)
: TypeData(type_id, children_flags, 1)
, params_types(std::move(params_types))
, return_type(return_type) {}
@ -275,7 +303,7 @@ public:
*/
class TypeDataGenericT final : public TypeData {
TypeDataGenericT(uint64_t type_id, std::string&& nameT)
: TypeData(type_id, flag_contains_genericT_inside)
: TypeData(type_id, flag_contains_genericT_inside, -999999) // width undefined until instantiated
, nameT(std::move(nameT)) {}
public:
@ -286,7 +314,6 @@ public:
std::string as_human_readable() const override { return nameT; }
bool can_rhs_be_assigned(TypePtr rhs) const override;
bool can_be_casted_with_as_operator(TypePtr cast_to) const override;
int calc_width_on_stack() const override;
};
/*
@ -296,8 +323,8 @@ public:
* A tensor can be empty.
*/
class TypeDataTensor final : public TypeData {
TypeDataTensor(uint64_t type_id, int children_flags, std::vector<TypePtr>&& items)
: TypeData(type_id, children_flags)
TypeDataTensor(uint64_t type_id, int children_flags, int width_on_stack, std::vector<TypePtr>&& items)
: TypeData(type_id, children_flags, width_on_stack)
, items(std::move(items)) {}
public:
@ -312,7 +339,7 @@ public:
bool can_be_casted_with_as_operator(TypePtr cast_to) const override;
void traverse(const TraverserCallbackT& callback) const override;
TypePtr replace_children_custom(const ReplacerCallbackT& callback) const override;
int calc_width_on_stack() const override;
bool can_hold_tvm_null_instead() const override;
};
/*
@ -322,7 +349,7 @@ public:
*/
class TypeDataTypedTuple final : public TypeData {
TypeDataTypedTuple(uint64_t type_id, int children_flags, std::vector<TypePtr>&& items)
: TypeData(type_id, children_flags)
: TypeData(type_id, children_flags, 1)
, items(std::move(items)) {}
public:
@ -346,7 +373,7 @@ public:
* The only thing available to do with unknown is to cast it: `catch (excNo, arg) { var i = arg as int; }`
*/
class TypeDataUnknown final : public TypeData {
TypeDataUnknown() : TypeData(20ULL, flag_contains_unknown_inside) {}
TypeDataUnknown() : TypeData(20ULL, flag_contains_unknown_inside, 1) {}
static TypePtr singleton;
friend void type_system_init();
@ -367,7 +394,7 @@ public:
*/
class TypeDataUnresolved final : public TypeData {
TypeDataUnresolved(uint64_t type_id, std::string&& text, SrcLocation loc)
: TypeData(type_id, flag_contains_unresolved_inside)
: TypeData(type_id, flag_contains_unresolved_inside, -999999)
, text(std::move(text))
, loc(loc) {}
@ -380,7 +407,6 @@ public:
std::string as_human_readable() const override { return text + "*"; }
bool can_rhs_be_assigned(TypePtr rhs) const override;
bool can_be_casted_with_as_operator(TypePtr cast_to) const override;
int calc_width_on_stack() const override;
};
/*
@ -389,7 +415,7 @@ public:
* Empty tensor is not compatible with void, although at IR level they are similar, 0 stack slots.
*/
class TypeDataVoid final : public TypeData {
TypeDataVoid() : TypeData(10ULL, 0) {}
TypeDataVoid() : TypeData(10ULL, 0, 0) {}
static TypePtr singleton;
friend void type_system_init();
@ -400,7 +426,7 @@ public:
std::string as_human_readable() const override { return "void"; }
bool can_rhs_be_assigned(TypePtr rhs) const override;
bool can_be_casted_with_as_operator(TypePtr cast_to) const override;
int calc_width_on_stack() const override;
bool can_hold_tvm_null_instead() const override;
};