mirror of
https://github.com/ton-blockchain/ton
synced 2025-03-09 15:40:10 +00:00
7bcb8b895f
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.
28 lines
742 B
Text
28 lines
742 B
Text
fun getNullableInt(): int? { return null; }
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fun main() {
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var c: int? = 6;
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__expect_type(c, "int");
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if (c == null) {}
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var d: int? = c;
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if (((d)) != null && tupleSize(createEmptyTuple())) {}
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var e: int? = getNullableInt();
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if (e != null) {
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return true;
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}
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__expect_type(e, "null");
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null == e;
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return null != null;
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}
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/**
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@testcase | 0 | | 0
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@stderr warning: variable `c` of type `int` is always not null, this condition is always false
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@stderr warning: variable `d` of type `int` is always not null, this condition is always true
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@stderr warning: variable `e` is always null, this condition is always true
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@stderr warning: expression is always null, this condition is always false
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*/
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