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Fix extra warning for unused local function #47473

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merged 3 commits into from
Sep 9, 2020
Merged

Fix extra warning for unused local function #47473

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a728766
Fix extra warning for unused local function
Youssef1313 Sep 4, 2020
acd14f2
Update CodeGenLocalFunctionTests.cs
RikkiGibson Sep 5, 2020
4622a98
Update LocalFunctions.cs
RikkiGibson Sep 5, 2020
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2 changes: 1 addition & 1 deletion src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1180,7 +1180,7 @@ public override BoundNode VisitCall(BoundCall node)
VisitReceiverBeforeCall(node.ReceiverOpt, node.Method);
VisitArgumentsBeforeCall(node.Arguments, node.ArgumentRefKindsOpt);

if (!callsAreOmitted && node.Method?.OriginalDefinition is LocalFunctionSymbol localFunc)
if (node.Method?.OriginalDefinition is LocalFunctionSymbol localFunc)
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Since node is actually a BoundCall, then we already know the local function is used. We want to visit it regardless it's conditionally omitted or not.

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I worry that this change may be unsound (allowing accessing an unassigned variable). Please add a test for:

public class C 
{
    public void M() 
    {
        int i;
        local();
        i.ToString();
        
        [Conditional("DEBUG")]
        void local()
        {
           i = 1;   
        }
    }
}

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It will be good to add this test. I believe it will produce the desired error on i.ToString() because we reset the definite assignment state after visiting the call when callsAreOmitted is true.

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@RikkiGibson RikkiGibson Sep 7, 2020 •
edited
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Oh wait. I forgot that we disallow non-static local functions from having ConditionalAttribute at all. We have specified that a local function must be static in order to be conditional.

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we disallow non-static local functions from having ConditionalAttribute at all.

That saved some extra debugging 😄

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@jcouv Please take another look at your convenience. I do not think there is a supported scenario involving capturing variables in a conditional local function.

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Sounds good. That's great.
Can we update the test (LocalFunction_ConditionalAttributeDisallowed). We should be able to remove the #pragma warning.

{
VisitLocalFunctionUse(localFunc, node.Syntax, isCall: true);
}
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7 changes: 2 additions & 5 deletions src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenLocalFunctionTests.cs
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Expand Up @@ -5511,7 +5511,7 @@ static void validate(ModuleSymbol module)
}

[Fact]
public void StaticLocalFunction_ConditionalAttribute_Unreferenced()
public void StaticLocalFunction_ConditionalAttribute_NoUnreferencedWarning()
{
var source = @"
using System.Diagnostics;
Expand All @@ -5531,10 +5531,7 @@ static void local1()
}
}
";
CreateCompilation(source, parseOptions: TestOptions.Regular9).VerifyDiagnostics(
// (12,21): warning CS8321: The local function 'local1' is declared but never used
// static void local1()
Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "local1").WithArguments("local1").WithLocation(12, 21));
CreateCompilation(source, parseOptions: TestOptions.Regular9).VerifyDiagnostics();

CreateCompilation(source, parseOptions: TestOptions.Regular9.WithPreprocessorSymbols("DEBUG")).VerifyDiagnostics();
}
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