ton/tolk-tester/tests/invalid-declaration-12.tolk

fun proxy(x: int) {
    return factorial(x);
}

fun factorial(x: int) {
    if (x <= 0) {
        return 1;
    }
    return x * proxy(x-1);
}

/**
@compilation_should_fail
@stderr could not infer return type of `factorial`, because it appears in a recursive call chain
@stderr fun factorial
 */
[Tolk] Rewrite the type system from Hindley-Milner to static typing FunC's (and Tolk's before this PR) type system is based on Hindley-Milner. This is a common approach for functional languages, where types are inferred from usage through unification. As a result, type declarations are not necessary: () f(a,b) { return a+b; } // a and b now int, since `+` (int, int) While this approach works for now, problems arise with the introduction of new types like bool, where `!x` must handle both int and bool. It will also become incompatible with int32 and other strict integers. This will clash with structure methods, struggle with proper generics, and become entirely impractical for union types. This PR completely rewrites the type system targeting the future. 1) type of any expression is inferred and never changed 2) this is available because dependent expressions already inferred 3) forall completely removed, generic functions introduced (they work like template functions actually, instantiated while inferring) 4) instantiation `<...>` syntax, example: `t.tupleAt<int>(0)` 5) `as` keyword, for example `t.tupleAt(0) as int` 6) methods binding is done along with type inferring, not before ("before", as worked previously, was always a wrong approach) 2024-12-30 15:31:27 +00:00			`fun proxy(x: int) {`
			`return factorial(x);`
			`}`

			`fun factorial(x: int) {`
			`if (x <= 0) {`
			`return 1;`
			`}`
			`return x * proxy(x-1);`
			`}`

			`/**`
			`@compilation_should_fail`
			@stderr could not infer return type of `factorial`, because it appears in a recursive call chain
			`@stderr fun factorial`
			`*/`