Extension based GetEnumerator does not report default argument in ControlFlowGraph

[chsienki]

The following test fails because the IInvocationOperation does not report the default arguments. It should work for params too.

        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
        [Fact, WorkItem(17602, "https://github.com/dotnet/roslyn/issues/17602")]
        public void ForEachFlow_ViaExtensionMethod_WithDefaultParameters()
        {
            var source = @"
using System.Collections.Generic;
class Program
{
    static void Main()
    /*<bind>*/{
        foreach (var value in new Program())
        {
            System.Console.WriteLine(value);
        }
    }/*</bind>*/
}

static class Extensions
{
    public static IEnumerator<string> GetEnumerator(this Program p, int a = 3, bool b = true) => throw null;
}
";
            var expectedDiagnostics = DiagnosticDescription.None;

            var expectedFlowGraph = @"
Block[B0] - Entry
    Statements (0)
    Next (Regular) Block[B1]
        Entering: {R1}
.locals {R1}
{
    CaptureIds: [0]
    Block[B1] - Block
        Predecessors: [B0]
        Statements (1)
            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'new Program()')
              Value: 
                IInvocationOperation (System.Collections.Generic.IEnumerator<System.String> Extensions.GetEnumerator(this Program p, [System.Int32 a = 3], [System.Boolean b = true])) (OperationKind.Invocation, Type: System.Collections.Generic.IEnumerator<System.String>, IsImplicit) (Syntax: 'new Program()')
                  Instance Receiver: 
                    null
                  Arguments(1):
                      IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: p) (OperationKind.Argument, Type: null, IsImplicit) (Syntax: 'new Program()')
                        IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: Program, IsImplicit) (Syntax: 'new Program()')
                          Conversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                            (Identity)
                          Operand: 
                            IObjectCreationOperation (Constructor: Program..ctor()) (OperationKind.ObjectCreation, Type: Program) (Syntax: 'new Program()')
                              Arguments(0)
                              Initializer: 
                                null
                        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                      IArgumentOperation (ArgumentKind.DefaultValue, Matching Parameter: a) (OperationKind.Argument, Type: null, IsImplicit) (Syntax: 'new Program()')
                        IILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 3, IsImplicit) (Syntax: 'new Program()')
                        IInConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                        IOutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                      IArgumentOperation (ArgumentKind.DefaultValue, Matching Parameter: b) (OperationKind.Argument, Type: null, IsImplicit) (Syntax: 'new Program()')
                        IILiteralOperation (OperationKind.Literal, Type: System.Boolean, Constant: True, IsImplicit) (Syntax: 'new Program()')
                        IInConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                        IOutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
        Next (Regular) Block[B2]
            Entering: {R2} {R3}
    .try {R2, R3}
    {
        Block[B2] - Block
            Predecessors: [B1] [B3]
            Statements (0)
            Jump if False (Regular) to Block[B7]
                IInvocationOperation (virtual System.Boolean System.Collections.IEnumerator.MoveNext()) (OperationKind.Invocation, Type: System.Boolean, IsImplicit) (Syntax: 'new Program()')
                  Instance Receiver: 
                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Collections.Generic.IEnumerator<System.String>, IsImplicit) (Syntax: 'new Program()')
                  Arguments(0)
                Finalizing: {R5}
                Leaving: {R3} {R2} {R1}
            Next (Regular) Block[B3]
                Entering: {R4}
        .locals {R4}
        {
            Locals: [System.String value]
            Block[B3] - Block
                Predecessors: [B2]
                Statements (2)
                    ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: null, IsImplicit) (Syntax: 'var')
                      Left: 
                        ILocalReferenceOperation: value (IsDeclaration: True) (OperationKind.LocalReference, Type: System.String, IsImplicit) (Syntax: 'var')
                      Right: 
                        IPropertyReferenceOperation: System.String System.Collections.Generic.IEnumerator<System.String>.Current { get; } (OperationKind.PropertyReference, Type: System.String, IsImplicit) (Syntax: 'var')
                          Instance Receiver: 
                            IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Collections.Generic.IEnumerator<System.String>, IsImplicit) (Syntax: 'new Program()')
                    IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'System.Cons ... ine(value);')
                      Expression: 
                        IInvocationOperation (void System.Console.WriteLine(System.String value)) (OperationKind.Invocation, Type: System.Void) (Syntax: 'System.Cons ... Line(value)')
                          Instance Receiver: 
                            null
                          Arguments(1):
                              IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: value) (OperationKind.Argument, Type: null) (Syntax: 'value')
                                ILocalReferenceOperation: value (OperationKind.LocalReference, Type: System.String) (Syntax: 'value')
                                InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                                OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                Next (Regular) Block[B2]
                    Leaving: {R4}
        }
    }
    .finally {R5}
    {
        Block[B4] - Block
            Predecessors (0)
            Statements (0)
            Jump if True (Regular) to Block[B6]
                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'new Program()')
                  Operand: 
                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Collections.Generic.IEnumerator<System.String>, IsImplicit) (Syntax: 'new Program()')
            Next (Regular) Block[B5]
        Block[B5] - Block
            Predecessors: [B4]
            Statements (1)
                IInvocationOperation (virtual void System.IDisposable.Dispose()) (OperationKind.Invocation, Type: System.Void, IsImplicit) (Syntax: 'new Program()')
                  Instance Receiver: 
                    IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.IDisposable, IsImplicit) (Syntax: 'new Program()')
                      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: True, IsUserDefined: False) (MethodSymbol: null)
                        (ImplicitReference)
                      Operand: 
                        IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Collections.Generic.IEnumerator<System.String>, IsImplicit) (Syntax: 'new Program()')
                  Arguments(0)
            Next (Regular) Block[B6]
        Block[B6] - Block
            Predecessors: [B4] [B5]
            Statements (0)
            Next (StructuredExceptionHandling) Block[null]
    }
}
Block[B7] - Exit
    Predecessors: [B2]
    Statements (0)";

            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(source, expectedFlowGraph, expectedDiagnostics, parseOptions: TestOptions.Regular9);
        }

[chsienki]

/cc @333fred @AlekseyTs I found this when working on #49481

[333fred]

Yep, this is one of the bugs I've fixed in my test hook pr.