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Fix region analysis of == containing ?. #53687

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merged 2 commits into from
Jun 8, 2021
Merged

Fix region analysis of == containing ?. #53687

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c828679
Fix region analysis of == containing ?.
RikkiGibson May 24, 2021
aad09e2
Inline local function
RikkiGibson Jun 3, 2021
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28 changes: 26 additions & 2 deletions src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2363,8 +2363,32 @@ protected virtual void VisitBinaryOperatorChildren(ArrayBuilder<BoundBinaryOpera
&& canLearnFromOperator(binary)
&& isKnownNullOrNotNull(binary.Right))
{
VisitRvalue(binary.Right);
Meet(ref stateWhenNotNull, ref State);
if (_nonMonotonicTransfer)
{
// In this very specific scenario, we need to do extra work to track unassignments for region analysis.
// See `AbstractFlowPass.VisitCatchBlockWithAnyTransferFunction` for a similar scenario in catch blocks.
Optional<TLocalState> oldState = NonMonotonicState;
NonMonotonicState = ReachableBottomState();

VisitRvalue(binary.Right);

var tempStateValue = NonMonotonicState.Value;
Join(ref stateWhenNotNull, ref tempStateValue);
if (oldState.HasValue)
{
var oldStateValue = oldState.Value;
Join(ref oldStateValue, ref tempStateValue);
oldState = oldStateValue;
}

NonMonotonicState = oldState;
}
else
{
VisitRvalue(binary.Right);
Meet(ref stateWhenNotNull, ref State);
}

var isNullConstant = binary.Right.ConstantValue?.IsNull == true;
SetConditionalState(isNullConstant == isEquals(binary)
? (State, stateWhenNotNull)
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70 changes: 70 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/FlowAnalysis/RegionAnalysisTests.cs
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Expand Up @@ -2546,6 +2546,76 @@ public string M()
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.CapturedOutside));
}

[Theory]
[InlineData("c?.M0(x = 0)")]
[InlineData("c!.M0(x = 0)")]
public void CondAccess_Equals_DataFlowsOut_01(string leftOperand)
{
var dataFlowAnalysis = CompileAndAnalyzeDataFlowExpression(@"
#nullable enable
class C
{
bool M0(object? obj) => false;

public static void M(C? c)
{
int x = 0;
if (" + leftOperand + @" == /*<bind>*/c!.M0(x = 0)/*</bind>*/)
{
x.ToString();
}

x.ToString();
}
}
");
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.VariablesDeclared));
Assert.Equal("x", GetSymbolNamesJoined(dataFlowAnalysis.AlwaysAssigned));
Assert.Equal("c", GetSymbolNamesJoined(dataFlowAnalysis.DataFlowsIn));
Assert.Equal("x", GetSymbolNamesJoined(dataFlowAnalysis.DataFlowsOut));
Assert.Equal("c", GetSymbolNamesJoined(dataFlowAnalysis.ReadInside));
Assert.Equal("c, x", GetSymbolNamesJoined(dataFlowAnalysis.ReadOutside));
Assert.Equal("x", GetSymbolNamesJoined(dataFlowAnalysis.WrittenInside));
Assert.Equal("c, x", GetSymbolNamesJoined(dataFlowAnalysis.WrittenOutside));
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@333fred 333fred Jun 3, 2021 •
edited
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c

Why is c considered written anywhere in this function? #Closed

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It appears that this is how parameters are handled in general. For example, the following test will pass in the main branch:

        [Fact]
        public void Test1()
        {
            var results = CompileAndAnalyzeDataFlowExpression(@"
class C
{
    static void M(int i)
    {
        System.Console.Write(/*<bind>*/i/*</bind>*/);
    }
}
");
            Assert.Equal("i", GetSymbolNamesJoined(results.WrittenOutside));
        }

My speculation is that it might be useful to model a parameter as having been "written" at the beginning of a method.

Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.Captured));
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.CapturedInside));
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.CapturedOutside));
}

[Theory]
[InlineData("c?.M0(x = 0)")]
[InlineData("c!.M0(x = 0)")]
public void CondAccess_Equals_DataFlowsOut_02(string leftOperand)
{
var dataFlowAnalysis = CompileAndAnalyzeDataFlowExpression(@"
#nullable enable
class C
{
bool M0(object? obj) => false;

public static void M(C? c)
{
int x = 0;
if (" + leftOperand + @" == /*<bind>*/c!.M0(x = 0)/*</bind>*/)
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This is the test case where behavior is affected by the implementation change. Without the change, we don't include x in the DataFlowsOut set in this scenario.

{
x.ToString();
}
}
}
");
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.VariablesDeclared));
Assert.Equal("x", GetSymbolNamesJoined(dataFlowAnalysis.AlwaysAssigned));
Assert.Equal("c", GetSymbolNamesJoined(dataFlowAnalysis.DataFlowsIn));
Assert.Equal("x", GetSymbolNamesJoined(dataFlowAnalysis.DataFlowsOut));
Assert.Equal("c", GetSymbolNamesJoined(dataFlowAnalysis.ReadInside));
Assert.Equal("c, x", GetSymbolNamesJoined(dataFlowAnalysis.ReadOutside));
Assert.Equal("x", GetSymbolNamesJoined(dataFlowAnalysis.WrittenInside));
Assert.Equal("c, x", GetSymbolNamesJoined(dataFlowAnalysis.WrittenOutside));
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.Captured));
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.CapturedInside));
Assert.Null(GetSymbolNamesJoined(dataFlowAnalysis.CapturedOutside));
}

#endregion

#region "Statements"
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