[IOperation] Differing variable declaration in Blocks loops between C# and VB

[333fred]

C# Code:

for (int i = 0; i < 5; i++)
{
}

Resulting IOp Tree:

IForLoopStatement (LoopKind.For) (OperationKind.LoopStatement)
  Condition: IBinaryOperatorExpression (BinaryOperationKind.IntegerLessThan) (OperationKind.BinaryOperatorExpression, Type: System.Boolean)
      Left: ILocalReferenceExpression: i (OperationKind.LocalReferenceExpression, Type: System.Int32)
      Right: ILiteralExpression (Text: 5) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 5)
  Local_1: System.Int32 i
  Before: IVariableDeclarationStatement (1 variables) (OperationKind.VariableDeclarationStatement)
      IVariableDeclaration: System.Int32 i (OperationKind.VariableDeclaration)
        Initializer: ILiteralExpression (Text: 0) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 0)
  AtLoopBottom: IExpressionStatement (OperationKind.ExpressionStatement)
      IIncrementExpression (UnaryOperandKind.IntegerPostfixIncrement) (BinaryOperationKind.IntegerAdd) (OperationKind.IncrementExpression, Type: System.Int32)
        Left: ILocalReferenceExpression: i (OperationKind.LocalReferenceExpression, Type: System.Int32)
        Right: ILiteralExpression (OperationKind.LiteralExpression, Type: System.Int32, Constant: 1)
  IBlockStatement (0 statements) (OperationKind.BlockStatement)

Visual Basic code:

For i As Integer = 1 To 5
Next

Resulting IOp Tree:

IForLoopStatement (LoopKind.For) (OperationKind.LoopStatement)
  Condition: IBinaryOperatorExpression (BinaryOperationKind.IntegerLessThanOrEqual) (OperationKind.BinaryOperatorExpression, Type: System.Boolean)
      Left: ILocalReferenceExpression: i (OperationKind.LocalReferenceExpression, Type: System.Int32)
      Right: ILiteralExpression (Text: 5) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 5)
  Before: IExpressionStatement (OperationKind.ExpressionStatement)
      IAssignmentExpression (OperationKind.AssignmentExpression, Type: System.Int32)
        Left: ILocalReferenceExpression: i (OperationKind.LocalReferenceExpression, Type: System.Int32)
        Right: ILiteralExpression (Text: 1) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 1)
  AtLoopBottom: IExpressionStatement (OperationKind.ExpressionStatement)
      ICompoundAssignmentExpression (BinaryOperationKind.IntegerAdd) (OperationKind.CompoundAssignmentExpression, Type: System.Int32)
        Left: ILocalReferenceExpression: i (OperationKind.LocalReferenceExpression, Type: System.Int32)
        Right: IConversionExpression (ConversionKind.Basic, Explicit) (OperationKind.ConversionExpression, Type: System.Int32, Constant: 1)
            ILiteralExpression (OperationKind.LiteralExpression, Type: System.Int32, Constant: 1)
  IBlockStatement (0 statements) (OperationKind.BlockStatement)

There are a few differences here.

1. There's no IVariableDeclaration(Statement) in VB. In fact, there doesn't appear to be any variable declarations in the accessible IOperation statements for VB.
2. There's some inconsistency with getting access to the IForLoopStatement. Both languages have, syntax-wise, a ForStatement construct. In C#, this refers to the entire block. In VB, this refers just to the For i As Integer = 1 To 5 section, and is enclosed by a ForBlock construct. You can't get access to the IForLoopStatement from the ForStatement, only the ForBlock. While I can understand the difference between the languages here, perhaps we should allow getting the IForLoopStatement from the ForStatement in VB.

[333fred]

@dotnet/analyzer-ioperation

[333fred]

This issue also affects If Then Else loops as well. FYI @jinujoseph

[CyrusNajmabadi]

While I can understand the difference between the languages here, perhaps we should allow getting the IForLoopStatement from the ForStatement in VB.

VB statement/block handling has always been a bit baroque. We'll likely want to make an decision here across all VB statements. I view that as orthogonal to any other issues we find with individual elements.

[jinujoseph]

While I can understand the difference between the languages here, perhaps we should allow getting the IForLoopStatement from the ForStatement in VB.

Design Decision:
We will not allow for this. It means you have a situation where two syntax nodes in a language will point to the same IOPeration. Then the IOperation's '.Syntax' will not poitn back at one of these. That violates a previous design decision.

For now, let's keep things similar between the languages. We'll only support getting the Operation on the VB block, and not on hte header statement.

[jinujoseph]

There's no IVariableDeclaration(Statement) in VB. In fact, there doesn't appear to be any variable declarations in the accessible IOperation statements for VB.

This should be fixed by whoever works on these constructs. Any declared variables should show up in the operation tree somehow.

[jinujoseph]

this should be fixed as per our new design forloops