' Licensed to the .NET Foundation under one or more agreements.
' The .NET Foundation licenses this file to you under the MIT license.
' See the LICENSE file in the project root for more information.
 
Imports System.Collections.Immutable
Imports Microsoft.CodeAnalysis.Collections
Imports Microsoft.CodeAnalysis.ExpressionEvaluator
Imports Microsoft.CodeAnalysis.PooledObjects
Imports Microsoft.CodeAnalysis.VisualBasic.Symbols
 
Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
 
    Friend NotInheritable Class LocalDeclarationRewriter
 
        Friend Shared Function Rewrite(compilation As VisualBasicCompilation, container As EENamedTypeSymbol, block As BoundBlock) As BoundBlock
            Dim locals = PooledHashSet(Of LocalSymbol).GetInstance()
            Dim walker As New LocalDeclarationWalker(locals)
            walker.Visit(block)
 
            If locals.Count > 0 Then
                Dim syntax = block.Syntax
                Dim builder = ArrayBuilder(Of BoundStatement).GetInstance()
                For Each local In locals
                    builder.Add(GenerateCreateVariableStatement(compilation, container, syntax, local))
                Next
                builder.AddRange(block.Statements)
                block = New BoundBlock(syntax, block.StatementListSyntax, block.Locals, builder.ToImmutableAndFree())
            End If
 
            locals.Free()
            Return block
        End Function
 
        ' Find all implicitly declared locals.
        Private NotInheritable Class LocalDeclarationWalker
            Inherits BoundTreeWalkerWithStackGuardWithoutRecursionOnTheLeftOfBinaryOperator
 
            Private ReadOnly _locals As HashSet(Of LocalSymbol)
 
            Friend Sub New(locals As HashSet(Of LocalSymbol))
                _locals = locals
            End Sub
 
            Public Overrides Function VisitLocal(node As BoundLocal) As BoundNode
                Dim local = node.LocalSymbol
                If local.DeclarationKind = LocalDeclarationKind.ImplicitVariable Then
                    _locals.Add(local)
                End If
                Return node
            End Function
 
        End Class
 
        Private Shared Function GenerateCreateVariableStatement(
            compilation As VisualBasicCompilation,
            container As EENamedTypeSymbol,
            syntax As SyntaxNode,
            local As LocalSymbol) As BoundStatement
 
            Dim typeType = compilation.GetWellKnownType(WellKnownType.System_Type)
            Dim stringType = compilation.GetSpecialType(SpecialType.System_String)
            Dim guidType = compilation.GetWellKnownType(WellKnownType.System_Guid)
            Dim byteArrayType = ArrayTypeSymbol.CreateVBArray(
                compilation.GetSpecialType(SpecialType.System_Byte),
                ImmutableArray(Of CustomModifier).Empty,
                rank:=1,
                compilation:=compilation)
 
            ' CreateVariable(type As Type, name As String)
            Dim method = PlaceholderLocalSymbol.GetIntrinsicMethod(compilation, ExpressionCompilerConstants.CreateVariableMethodName)
            Dim type = New BoundGetType(syntax, New BoundTypeExpression(syntax, local.Type),
                                        DirectCast(compilation.GetWellKnownTypeMember(WellKnownMember.System_Type__GetTypeFromHandle), MethodSymbol),
                                        typeType)
            Dim name = New BoundLiteral(syntax, ConstantValue.Create(local.Name), stringType)
            Dim customTypeInfoPayloadId = New BoundObjectCreationExpression(syntax, Nothing, ImmutableArray(Of BoundExpression).Empty, Nothing, guidType)
            Dim customTypeInfoPayload = New BoundLiteral(syntax, ConstantValue.Null, byteArrayType)
            Dim expr = New BoundCall(
                syntax,
                method,
                methodGroupOpt:=Nothing,
                receiverOpt:=Nothing,
                arguments:=ImmutableArray.Create(Of BoundExpression)(type, name, customTypeInfoPayloadId, customTypeInfoPayload),
                constantValueOpt:=Nothing,
                suppressObjectClone:=False,
                type:=method.ReturnType)
            Return New BoundExpressionStatement(syntax, expr).MakeCompilerGenerated()
        End Function
 
    End Class
 
End Namespace