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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
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62 changed files with 2031 additions and 702 deletions
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9
crypto/smartcont/tolk-stdlib/lisp-lists.tolk
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@ -14,17 +14,18 @@ fun createEmptyList(): tuple
/// Adds an element to the beginning of lisp-style list.
/// Note, that it does not mutate the list: instead, it returns a new one (it's a lisp pattern).
@pure
fun listPrepend<X>(head: X, tail: tuple): tuple
fun listPrepend<X>(head: X, tail: tuple?): tuple
asm "CONS";
/// Extracts the head and the tail of lisp-style list.
@pure
fun listSplit<X>(list: tuple): (X, tuple)
fun listSplit<X>(list: tuple): (X, tuple?)
asm "UNCONS";
/// Extracts the tail and the head of lisp-style list.
/// After extracting the last element, tuple is assigned to null.
@pure
fun listNext<X>(mutate self: tuple): X
fun listNext<X>(mutate self: tuple?): X
asm( -> 1 0) "UNCONS";
/// Returns the head of lisp-style list.
@ -34,5 +35,5 @@ fun listGetHead<X>(list: tuple): X
/// Returns the tail of lisp-style list.
@pure
fun listGetTail(list: tuple): tuple
fun listGetTail(list: tuple): tuple?
asm "CDR";