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Slice value is always assumed to be not null
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@alrz
alrz committed Oct 28, 2021
1 parent 64f4343 commit f975e80
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Showing 3 changed files with 122 additions and 77 deletions.
6 changes: 5 additions & 1 deletion src/Compilers/CSharp/Portable/Binder/DecisionDagBuilder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -421,8 +421,12 @@ private static void MakeCheckNotNull(
ArrayBuilder<Tests> tests)
{
// Add a null test if needed
if (input.Type.CanContainNull())
if (input.Type.CanContainNull() &&
// The slice value is assumed to be never null
input.Source is not BoundDagSliceEvaluation)
{
tests.Add(new Tests.One(new BoundDagNonNullTest(syntax, isExplicitTest, input)));
}
}

/// <summary>
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5 changes: 3 additions & 2 deletions src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTestBase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -441,12 +441,13 @@ protected static void AssertEmpty(SymbolInfo info)
Assert.Equal(CandidateReason.None, info.CandidateReason);
}

protected static void VerifyDecisionDagDump<T>(Compilation comp, string expectedDecisionDag)
[Conditional("DEBUG")]
protected static void VerifyDecisionDagDump<T>(Compilation comp, string expectedDecisionDag, int index = 0)
where T : CSharpSyntaxNode
{
#if DEBUG
var tree = comp.SyntaxTrees.First();
var node = tree.GetRoot().DescendantNodes().OfType<T>().First();
var node = tree.GetRoot().DescendantNodes().OfType<T>().ElementAt(index);
var model = (CSharpSemanticModel)comp.GetSemanticModel(tree);
var binder = model.GetEnclosingBinder(node.SpanStart);
var decisionDag = node switch
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188 changes: 114 additions & 74 deletions src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTests_ListPatterns.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3436,9 +3436,6 @@ public void M()
// Note: we don't try to explain nested slice patterns right now so all these just produce a fallback example
var compilation = CreateCompilation(new[] { source, TestSources.Index, TestSources.Range });
compilation.VerifyEmitDiagnostics(
// (20,18): warning CS8655: The switch expression does not handle some null inputs (it is not exhaustive). For example, the pattern '_' is not covered.
// _ = this switch // we didn't test for [.. null] but we're looking for an example with Length=1. // 1
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(20, 18),
// (27,18): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive). For example, the pattern '_' is not covered.
// _ = this switch // didn't test for [.. [not null]] // // 2
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithArguments("_").WithLocation(27, 18),
Expand All @@ -3451,9 +3448,6 @@ public void M()
// (46,18): warning CS8655: The switch expression does not handle some null inputs (it is not exhaustive). For example, the pattern '_' is not covered.
// _ = this switch // didn't test for [_, .. null, _, _, _] // we're trying to construct an example with Length=4, the slice may not be null // 5
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(46, 18),
// (52,18): warning CS8655: The switch expression does not handle some null inputs (it is not exhaustive). For example, the pattern '_' is not covered.
// _ = this switch // we should consider this switch exhaustive // 6
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(52, 18),
// (58,18): warning CS8655: The switch expression does not handle some null inputs (it is not exhaustive). For example, the pattern '_' is not covered.
// _ = this switch // didn't test for [_, .. [_, null], _] // 7
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(58, 18),
Expand All @@ -3462,10 +3456,7 @@ public void M()
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(64, 18),
// (70,18): warning CS8655: The switch expression does not handle some null inputs (it is not exhaustive). For example, the pattern '_' is not covered.
// _ = this switch // didn't test for [_, .. [_, null, _], _] // 9
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(70, 18),
// (76,18): warning CS8655: The switch expression does not handle some null inputs (it is not exhaustive). For example, the pattern '_' is not covered.
// _ = this switch // didn't test for [.. null, _] // we're trying to construct an example with Length=1 but a null slice // 10
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(76, 18)
Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustiveForNull, "switch").WithArguments("_").WithLocation(70, 18)
);
}

Expand Down Expand Up @@ -4840,46 +4831,72 @@ void Test(int[] a)
{ Length: not 1 } => 0,
[<0, ..] => 0,
[..[>= 0]] or [..null] => 1,
[_] => 2, // unreachable
[_] => 2, // unreachable 1
};
_ = a switch // exhaustive
_ = a switch
{
{ Length: not 1 } => 0,
[<0, ..] => 0,
[..[>= 0]] => 1,
[_] => 2,
[_] => 2, // unreachable 2
};
}
}" + TestSources.GetSubArray;
var comp = CreateCompilationWithIndexAndRange(src);
comp.VerifyEmitDiagnostics(
// (11,13): error CS8510: The pattern is unreachable. It has already been handled by a previous arm of the switch expression or it is impossible to match.
// [_] => 2, // unreachable
Diagnostic(ErrorCode.ERR_SwitchArmSubsumed, "[_]").WithLocation(11, 13));

VerifyDecisionDagDump<SwitchExpressionSyntax>(comp,
// (11,13): error CS8510: The pattern is unreachable. It has already been handled by a previous arm of the switch expression or it is impossible to match.
// [_] => 2, // unreachable
Diagnostic(ErrorCode.ERR_SwitchArmSubsumed, "[_]").WithLocation(11, 13),
// (18,13): error CS8510: The pattern is unreachable. It has already been handled by a previous arm of the switch expression or it is impossible to match.
// [_] => 2,
Diagnostic(ErrorCode.ERR_SwitchArmSubsumed, "[_]").WithLocation(18, 13)
);

@"[0]: t0 != null ? [1] : [13]
AssertEx.Multiple(
() => VerifyDecisionDagDump<SwitchExpressionSyntax>(comp,
@"[0]: t0 != null ? [1] : [12]
[1]: t1 = t0.Length; [2]
[2]: t1 == 1 ? [3] : [12]
[2]: t1 == 1 ? [3] : [11]
[3]: t2 = t0[0]; [4]
[4]: t2 < 0 ? [5] : [6]
[5]: leaf <arm> `[<0, ..] => 0`
[6]: t3 = DagSliceEvaluation(t0); [7]
[7]: t3 != null ? [8] : [11]
[8]: t4 = t3.Length; [9]
[9]: t5 = t3[0]; [10]
[10]: t5 <-- t2; [11]
[11]: leaf <arm> `[..[>= 0]] or [..null] => 1`
[12]: leaf <arm> `{ Length: not 1 } => 0`
[13]: leaf <default> `a switch
[7]: t4 = t3.Length; [8]
[8]: t5 = t3[0]; [9]
[9]: t5 <-- t2; [10]
[10]: leaf <arm> `[..[>= 0]] or [..null] => 1`
[11]: leaf <arm> `{ Length: not 1 } => 0`
[12]: leaf <default> `a switch
{
{ Length: not 1 } => 0,
[<0, ..] => 0,
[..[>= 0]] or [..null] => 1,
[_] => 2, // unreachable
[_] => 2, // unreachable 1
}`
");
", index: 0),

() => VerifyDecisionDagDump<SwitchExpressionSyntax>(comp,
@"[0]: t0 != null ? [1] : [12]
[1]: t1 = t0.Length; [2]
[2]: t1 == 1 ? [3] : [11]
[3]: t2 = t0[0]; [4]
[4]: t2 < 0 ? [5] : [6]
[5]: leaf <arm> `[<0, ..] => 0`
[6]: t3 = DagSliceEvaluation(t0); [7]
[7]: t4 = t3.Length; [8]
[8]: t5 = t3[0]; [9]
[9]: t5 <-- t2; [10]
[10]: leaf <arm> `[..[>= 0]] => 1`
[11]: leaf <arm> `{ Length: not 1 } => 0`
[12]: leaf <default> `a switch
{
{ Length: not 1 } => 0,
[<0, ..] => 0,
[..[>= 0]] => 1,
[_] => 2, // unreachable 2
}`
", index: 1)
);
}

[Fact]
Expand Down Expand Up @@ -5268,52 +5285,39 @@ class Derived : Base, I2
[Theory]
[CombinatorialData]
public void Subsumption_Slice_00(
[CombinatorialValues(
"[1,2,3]",
"[1,2,3,..[]]",
"[1,2,..[],3]",
"[1,..[],2,3]",
"[..[],1,2,3]",
"[1,..[2,3]]",
"[..[1,2],3]",
"[..[1,2,3]]",
"[..[..[1,2,3]]]",
"[..[1,2,3,..[]]]",
"[..[1,2,..[],3]]",
"[..[1,..[],2,3]]",
"[..[..[],1,2,3]]",
"[..[1,..[2,3]]]",
"[..[..[1,2],3]]",
"[1, ..[2], 3]",
"[1, ..[2, ..[3]]]",
"[1, ..[2, ..[], 3]]")]
string case1,
[CombinatorialValues(
"[1,2,3]",
"[1,2,3,..[]]",
"[1,2,..[],3]",
"[1,..[],2,3]",
"[..[],1,2,3]",
"[1,..[2,3]]",
"[..[1,2],3]",
"[..[1,2,3]]",
"[..[..[1,2,3]]]",
"[..[1,2,3,..[]]]",
"[..[1,2,..[],3]]",
"[..[1,..[],2,3]]",
"[..[..[],1,2,3]]",
"[..[1,..[2,3]]]",
"[..[..[1,2],3]]",
"[1, ..[2], 3]",
"[1, ..[2, ..[3]]]",
"[1, ..[2, ..[], 3]]")]
string case2)
[CombinatorialRange(0, 18)] int c1,
[CombinatorialRange(0, 18)] int c2,
[CombinatorialValues("System.Span<int>", "int[]")] string type)
{
var cases = new string[18]
{
"[1,2,3]",
"[1,2,3,..[]]",
"[1,2,..[],3]",
"[1,..[],2,3]",
"[..[],1,2,3]",
"[1,..[2,3]]",
"[..[1,2],3]",
"[..[1,2,3]]",
"[..[..[1,2,3]]]",
"[..[1,2,3,..[]]]",
"[..[1,2,..[],3]]",
"[..[1,..[],2,3]]",
"[..[..[],1,2,3]]",
"[..[1,..[2,3]]]",
"[..[..[1,2],3]]",
"[1, ..[2], 3]",
"[1, ..[2, ..[3]]]",
"[1, ..[2, ..[], 3]]"
};

var case1 = cases[c1];
var case2 = cases[c2];

var src = @"
using System;
class C
{
void Test(Span<int> a)
void Test(" + type + @" a)
{
switch (a)
{
Expand All @@ -5323,10 +5327,10 @@ void Test(Span<int> a)
}
}
}";
var comp = CreateCompilationWithIndexAndRangeAndSpan(src, parseOptions: TestOptions.RegularWithListPatterns);
var comp = CreateCompilationWithIndexAndRangeAndSpan(new[] { src, TestSources.GetSubArray }, parseOptions: TestOptions.RegularWithListPatterns);
comp.VerifyEmitDiagnostics(
// (10,18): error CS8120: The switch case is unreachable. It has already been handled by a previous case or it is impossible to match.
Diagnostic(ErrorCode.ERR_SwitchCaseSubsumed, case2).WithLocation(10, 18)
// (9,18): error CS8120: The switch case is unreachable. It has already been handled by a previous case or it is impossible to match.
Diagnostic(ErrorCode.ERR_SwitchCaseSubsumed, case2).WithLocation(9, 18)
);
}

Expand All @@ -5352,6 +5356,42 @@ public static void Test(System.Span<int> a)
Diagnostic(ErrorCode.ERR_SwitchCaseSubsumed, "[..[var v]]").WithLocation(9, 18));
}

[Fact]
public void Subsumption_Slice_02()
{
var source = @"
using System;
IOuter outer = null;
switch (outer)
{
case [..[..[10],20]]:
break;
case [..[10],20]: // 1
break;
}
interface IOuter
{
int Length { get; }
IInner Slice(int a, int b);
object this[int i] { get; }
}
interface IInner
{
int Count { get; }
IOuter this[Range r] { get; }
object this[Index i] { get; }
}
";
var comp = CreateCompilationWithIndexAndRangeAndSpan(new[] { source, TestSources.GetSubArray }, options: TestOptions.DebugExe);
comp.VerifyEmitDiagnostics(
// (9,10): error CS8120: The switch case is unreachable. It has already been handled by a previous case or it is impossible to match.
// case [..[10],20]: // 1
Diagnostic(ErrorCode.ERR_SwitchCaseSubsumed, "[..[10],20]").WithLocation(9, 10)
);
}

[Fact]
public void Exhaustiveness_01()
{
Expand Down

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