86175bea00
This PR informs the borrow inference that if an `Array` is borrowed and we index into it, the value we obtain is effectively a borrowed value as well. This helps improve the ABI of operations that recurse on linked structures containing arrays such as tries or persistent hash maps.
51 lines
1.5 KiB
Text
51 lines
1.5 KiB
Text
/-!
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This test asserts that the compiler is able to handle compilation of functions that recurse through
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nested arrays in a way that does not unnecessarily remove borrow annotations.
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-/
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inductive NAryTree where
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| tip (x : String)
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| node (ys : Array NAryTree)
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deriving Inhabited
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/--
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trace: [Compiler.explicitRc] size: 19
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def followPath @&tree @&path : obj :=
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cases tree : obj
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| NAryTree.tip =>
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cases path : obj
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| List.nil =>
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let x.1 := oproj[0] tree;
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inc x.1;
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return x.1
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| _ =>
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let _x.2 := instInhabitedNAryTree.default._closed_0;
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return _x.2
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| NAryTree.node =>
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cases path : obj
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| List.cons =>
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let ys.3 := oproj[0] tree;
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let head.4 := oproj[0] path;
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let tail.5 := oproj[1] path;
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let _x.6 := instInhabitedNAryTree.default;
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let _x.7 := Array.get!InternalBorrowed ◾ _x.6 ys.3 head.4;
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let _x.8 := followPath _x.7 tail.5;
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return _x.8
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| _ =>
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let _x.9 := instInhabitedNAryTree.default._closed_0;
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return _x.9
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[Compiler.explicitRc] size: 3
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def followPath._boxed tree path : obj :=
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let res := followPath tree path;
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dec path;
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dec tree;
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return res
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-/
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#guard_msgs in
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set_option trace.Compiler.explicitRc true in
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def followPath (tree : NAryTree) (path : List Nat) : String :=
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match tree, path with
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| .tip x, [] => x
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| .node ys, idx :: path => followPath ys[idx]! path
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| _, _ => default
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