49 lines
1.1 KiB
Rust
49 lines
1.1 KiB
Rust
// Test cyclic detector when using trait instances.
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enum Tree = TreeR;
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type TreeR = @{
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mut left: option<Tree>,
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mut right: option<Tree>,
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val: to_str
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};
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trait to_str {
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fn to_str() -> ~str;
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}
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impl <T: to_str> of to_str for option<T> {
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fn to_str() -> ~str {
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match self {
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none => { ~"none" }
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some(t) => { ~"some(" + t.to_str() + ~")" }
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}
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}
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}
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impl of to_str for int {
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fn to_str() -> ~str { int::str(self) }
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}
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impl of to_str for Tree {
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fn to_str() -> ~str {
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let l = self.left, r = self.right;
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fmt!{"[%s, %s, %s]", self.val.to_str(),
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l.to_str(), r.to_str()}
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}
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}
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fn foo<T: to_str>(x: T) -> ~str { x.to_str() }
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fn main() {
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let t1 = Tree(@{mut left: none,
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mut right: none,
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val: 1 as to_str });
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let t2 = Tree(@{mut left: some(t1),
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mut right: some(t1),
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val: 2 as to_str });
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let expected = ~"[2, some([1, none, none]), some([1, none, none])]";
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assert t2.to_str() == expected;
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assert foo(t2 as to_str) == expected;
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t1.left = some(t2); // create cycle
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}
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