external/ton
1
0
Fork 0
mirror of https://github.com/ton-blockchain/ton synced 2025-03-09 15:40:10 +00:00
Code Issues Releases Wiki Activity

[Tolk] Smart casts and control flow graph

Browse source 
With the introduction of nullable types, we want the
compiler to be smart in cases like
> if (x == null) return;
> // x is int now
or
> if (x == null) x = 0;
> // x is int now

These are called smart casts: when the type of variable
at particular usage might differ from its declaration.

Implementing smart casts is very challenging. They are based
on building control-flow graph and handling every AST vertex
with care. Actually, I represent cfg not a as a "graph with
edges". Instead, it's a "structured DFS" for the AST:
1) at every point of inferring, we have "current flow facts"
2) when we see an `if (...)`, we create two derived contexts
3) after `if`, finalize them at the end and unify
4) if we detect unreachable code, we mark that context
In other words, we get the effect of a CFG but in a more direct
approach. That's enough for AST-level data-flow.

Smart casts work for local variables and tensor/tuple indices.
Compilation errors have been reworked and now are more friendly.
There are also compilation warnings for always true/false
conditions inside if, assert, etc.
This commit is contained in:
tolk-vm 2025-02-24 20:14:16 +03:00
parent f3e620f48c
commit 7bcb8b895f
No known key found for this signature in database
GPG key ID: 7905DD7FE0324B12
47 changed files with 3057 additions and 833 deletions
Download patch file Download diff file Expand all files Collapse all files

27
tolk-tester/tests/null-keyword.tolk
View file

@ -26,7 +26,9 @@ fun test2(x: int?) {
if (null != x) {
var y: int? = null;
if (y != null) { return 10; }
return y;
if (10 < 20) { // always true at runtime (not at compile-time)
return y;
}
}
try {
return x! + 10; // will throw, since not a number
@ -45,14 +47,6 @@ fun test3(x: int) {
return myIsNull(x > 10 ? null : x);
}
fun getUntypedNull() {
var untyped: null = null;
if (true) {
return untyped;
}
return untyped;
}
@method_id(104)
fun test4(): null {
var (_, (_, untyped: null)) = (3, (createEmptyTuple, null));
@ -62,12 +56,6 @@ fun test4(): null {
return untyped;
}
@method_id(105)
fun test5() {
var n: slice? = getUntypedNull();
return !(null == n) ? n!.loadInt(32) : 100;
}
@method_id(107)
fun test7() {
var b = beginCell().storeMaybeRef(null) as builder?;
@ -85,6 +73,7 @@ fun test8() {
}
fun main() {
// the compiler optimizes this at compile-time
var i: int? = null;
if (i == null) {
return 1;
@ -99,7 +88,6 @@ fun main() {
@testcase | 103 | 5 | 5
@testcase | 103 | 15 | -1
@testcase | 104 | | (null)
@testcase | 105 | | 100
@testcase | 107 | | -11
@fif_codegen
"""
@ -127,12 +115,7 @@ fun main() {
"""
main PROC:<{
//
PUSHNULL // i
ISNULL // '2
IFJMP:<{ //
1 PUSHINT // '3=1
}> //
10 PUSHINT // '4=10
1 PUSHINT // '3=1
}>
"""