Remove IUnboundLambda

[mavasani]

1. Paste the following code in ETA:

using System;

class Program
{
    static void Main(string[] args)
    {
        var x = () => F();
    }

    static void F()
    {
    }
}

2. Display IOperation tree for the EqualsValueClauseSyntax. Note that we have no IOperations for code inside the lambda body.

IOperation tree for "= () => F()"

IVariableDeclarationStatement (1 variables) (OperationKind.VariableDeclarationStatement, IsInvalid)
  IVariableDeclaration: var x (OperationKind.VariableDeclaration)
    Initializer: IUnboundLambdaExpression (OperationKind.UnboundLambdaExpression, Type: null)

3. Display IOperation tree for the ParenthesizedLambdaExpressionSyntax.

IOperation tree for "() => F()"

ILambdaExpression (Signature: lambda expression) (OperationKind.LambdaExpression, Type: null)
  IBlockStatement (1 statements) (OperationKind.BlockStatement)
    IExpressionStatement (OperationKind.ExpressionStatement)
      IInvocationExpression (static void Program.F()) (OperationKind.InvocationExpression, Type: System.Void)

I expected the IOperation tree in 3. to be a sub-tree of IOperation tree of 2.

[mavasani]

Tagging @dotnet/analyzer-ioperation

[mavasani]

This might actually be a missing API issue. UnboundLambda generally contains a BoundLambda node within it for error recovery, we should probably expose it. @AlekseyTs your thoughts?

[AlekseyTs]

This might actually be a missing API issue. UnboundLambda generally contains a BoundLambda node within it for error recovery, we should probably expose it.

I think the IUnboundLambdaExpression should not be a part of the API.

[mavasani]

@jinujoseph @CyrusNajmabadi can we add this issue to the list of API discussions for next week?

[jinujoseph]

Design Team Decision

We are in agreement that IUnboundLambdaExpression should not be part of our API, it's not correct and appropriate. It would be great if we expose ILamda where we give the best effort to get the
Method symbol and the body.