pyos
a9be27e330
Quick quiz:
Q: In a CFG, what does `a -> b -> c -> d` mean?
A: `a`, then `b`, then `c`, then `d`.
Q: In a CFG, what does `a -> b -> d; a -> c -> d` mean?
A: `a`, then `b` or `c`, then `d`.
Q: So how do you encode "a, then (b, then c) or (c, then b), then d`?
A: You can't.
Problem is, you need to, because that's what `a; run2({ b }, { c }); d`
does when `run2` has a contract that it calls both its lambda arguments
in-place: `shuffle(listOf(block1, block2)).forEach { it() }` is a
perfectly valid implementation for it, as little sense as that makes.
So that's what union nodes solve. When a node implements
`UnionNodeMarker`, its inputs are interpreted as "all visited in some
order" instead of the normal "one of the inputs is visited".
Currently this is used for data flow. It *should* also be used for
control flow, but it isn't. But it should be. But that's not so easy.
BTW, `try` exit is NOT a union node; although lambdas in one branch can
be completed according to types' of lambdas in another, data does not
flow between the branches anyway (since we don't know how much of the
`try` executed before jumping into `catch`, and `catch`es are mutually
exclusive) so a `try` expression is more like `when` than a function
call with called-in-place-exactly-once arguments. The fact that
`exitTryExpression` used `processUnionOfArguments` in a weird way
should've hinted at that, but now we know for certain.
128 lines
4.2 KiB
Plaintext
Vendored
128 lines
4.2 KiB
Plaintext
Vendored
digraph variableInitializedInTryBlock_kt {
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graph [nodesep=3]
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node [shape=box penwidth=2]
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edge [penwidth=2]
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subgraph cluster_0 {
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color=red
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0 [label="Enter function test" style="filled" fillcolor=red];
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subgraph cluster_1 {
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color=blue
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1 [label="Enter block"];
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2 [label="Variable declaration: lval b: R|kotlin/Boolean|"];
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subgraph cluster_2 {
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color=blue
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3 [label="Try expression enter"];
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subgraph cluster_3 {
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color=blue
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4 [label="Try main block enter"];
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subgraph cluster_4 {
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color=blue
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5 [label="Enter block"];
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6 [label="Function call: R|/getStringOrNull|()" style="filled" fillcolor=yellow];
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7 [label="Exit lhs of ?:"];
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8 [label="Enter rhs of ?:"];
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9 [label="Jump: ^test Unit"];
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10 [label="Stub" style="filled" fillcolor=gray];
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11 [label="Lhs of ?: is not null"];
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12 [label="Exit ?:"];
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13 [label="Variable declaration: lval s: R|kotlin/String|"];
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14 [label="Access variable R|<local>/s|"];
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15 [label="Access variable R|kotlin/String.length|"];
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16 [label="Const: Int(0)"];
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17 [label="Equality operator !="];
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18 [label="Assignment: R|<local>/b|"];
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19 [label="Exit block"];
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}
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20 [label="Try main block exit"];
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}
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subgraph cluster_5 {
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color=blue
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21 [label="Enter finally"];
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subgraph cluster_6 {
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color=blue
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22 [label="Enter block"];
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23 [label="Function call: R|/test|()" style="filled" fillcolor=yellow];
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24 [label="Exit block"];
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}
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25 [label="Exit finally"];
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}
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26 [label="Try expression exit"];
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}
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27 [label="Access variable R|<local>/b|"];
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28 [label="Function call: R|/takeBoolean|(...)" style="filled" fillcolor=yellow];
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29 [label="Exit block"];
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}
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30 [label="Exit function test" style="filled" fillcolor=red];
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}
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0 -> {1};
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1 -> {2};
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2 -> {3};
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3 -> {4};
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3 -> {21} [label=onUncaughtException];
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4 -> {5};
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5 -> {6};
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6 -> {7};
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7 -> {11 8};
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8 -> {9};
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9 -> {21} [label="return@/test"];
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9 -> {10} [style=dotted];
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10 -> {12} [style=dotted];
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11 -> {12};
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12 -> {13};
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13 -> {14};
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14 -> {15};
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15 -> {16};
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16 -> {17};
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17 -> {18};
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18 -> {19};
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19 -> {20};
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20 -> {21};
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21 -> {22};
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22 -> {23};
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23 -> {24};
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24 -> {25};
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25 -> {26};
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25 -> {30} [label="return@/test"];
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26 -> {27};
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27 -> {28};
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28 -> {29};
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29 -> {30};
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subgraph cluster_7 {
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color=red
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31 [label="Enter function takeBoolean" style="filled" fillcolor=red];
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subgraph cluster_8 {
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color=blue
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32 [label="Enter block"];
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33 [label="Exit block"];
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}
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34 [label="Exit function takeBoolean" style="filled" fillcolor=red];
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}
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31 -> {32};
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32 -> {33};
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33 -> {34};
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subgraph cluster_9 {
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color=red
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35 [label="Enter function getStringOrNull" style="filled" fillcolor=red];
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subgraph cluster_10 {
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color=blue
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36 [label="Enter block"];
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37 [label="Const: String(hello)"];
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38 [label="Jump: ^getStringOrNull String(hello)"];
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39 [label="Stub" style="filled" fillcolor=gray];
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40 [label="Exit block" style="filled" fillcolor=gray];
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}
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41 [label="Exit function getStringOrNull" style="filled" fillcolor=red];
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}
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35 -> {36};
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36 -> {37};
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37 -> {38};
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38 -> {41};
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38 -> {39} [style=dotted];
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39 -> {40} [style=dotted];
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40 -> {41} [style=dotted];
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}
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