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When compiling a pattern match like ``` [] -> .. [_] -> .. [_, ..] -> .. ``` to a decision tree, we must make sure that the last test (len >= 1) does not touch the branch reached by the second test (len == 1). It is enough to ban (len >=) tests from ever touching exact-sized list patterns, because a spread test (len >=) can never reach an exact-sized test. On the other hand, an exact-sized test can reach a spread pattern, because in ``` [_, _] -> .. [..] -> .. ``` the last branch generates tests for patterns `[]` and `[_]`, and we would like those patterns to be covered by the spread test (len >= 0)! Closes #4685
57 lines
2.1 KiB
Text
57 lines
2.1 KiB
Text
procedure Test.0 ():
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let Test.31 : Int1 = false;
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let Test.32 : Int1 = true;
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let Test.1 : List Int1 = Array [Test.31, Test.32];
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joinpoint Test.9:
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let Test.8 : Str = "E";
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ret Test.8;
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in
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let Test.28 : U64 = lowlevel ListLen Test.1;
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let Test.29 : U64 = 0i64;
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let Test.30 : Int1 = lowlevel Eq Test.28 Test.29;
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if Test.30 then
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dec Test.1;
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let Test.4 : Str = "A";
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ret Test.4;
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else
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let Test.25 : U64 = lowlevel ListLen Test.1;
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let Test.26 : U64 = 1i64;
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let Test.27 : Int1 = lowlevel Eq Test.25 Test.26;
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if Test.27 then
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let Test.10 : U64 = 0i64;
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let Test.11 : Int1 = lowlevel ListGetUnsafe Test.1 Test.10;
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dec Test.1;
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let Test.12 : Int1 = false;
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let Test.13 : Int1 = lowlevel Eq Test.12 Test.11;
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if Test.13 then
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let Test.5 : Str = "B";
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ret Test.5;
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else
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jump Test.9;
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else
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let Test.22 : U64 = lowlevel ListLen Test.1;
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let Test.23 : U64 = 2i64;
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let Test.24 : Int1 = lowlevel NumGte Test.22 Test.23;
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if Test.24 then
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let Test.18 : U64 = 0i64;
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let Test.19 : Int1 = lowlevel ListGetUnsafe Test.1 Test.18;
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let Test.20 : Int1 = false;
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let Test.21 : Int1 = lowlevel Eq Test.20 Test.19;
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if Test.21 then
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let Test.14 : U64 = 1i64;
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let Test.15 : Int1 = lowlevel ListGetUnsafe Test.1 Test.14;
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dec Test.1;
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let Test.16 : Int1 = false;
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let Test.17 : Int1 = lowlevel Eq Test.16 Test.15;
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if Test.17 then
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let Test.6 : Str = "C";
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ret Test.6;
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else
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let Test.7 : Str = "D";
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ret Test.7;
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else
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dec Test.1;
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jump Test.9;
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else
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dec Test.1;
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jump Test.9;
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