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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Dynamic.Utils;
using System.Linq.Expressions;
using System.Linq.Expressions.Compiler;
using static System.Linq.Expressions.CachedReflectionInfo;
namespace System.Runtime.CompilerServices
{
public partial class RuntimeOps
{
/// <summary>
/// Quotes the provided expression tree.
/// </summary>
/// <param name="expression">The expression to quote.</param>
/// <param name="hoistedLocals">The hoisted local state provided by the compiler.</param>
/// <param name="locals">The actual hoisted local values.</param>
/// <returns>The quoted expression.</returns>
[Obsolete("RuntimeOps has been deprecated and is not supported.", true), EditorBrowsable(EditorBrowsableState.Never)]
[return: NotNullIfNotNull(nameof(expression))]
public static Expression? Quote(Expression? expression, object hoistedLocals, object[] locals)
{
Debug.Assert(hoistedLocals != null && locals != null);
var quoter = new ExpressionQuoter((HoistedLocals)hoistedLocals, locals);
return quoter.Visit(expression);
}
/// <summary>
/// Combines two runtime variable lists and returns a new list.
/// </summary>
/// <param name="first">The first list.</param>
/// <param name="second">The second list.</param>
/// <param name="indexes">The index array indicating which list to get variables from.</param>
/// <returns>The merged runtime variables.</returns>
[Obsolete("RuntimeOps has been deprecated and is not supported.", true), EditorBrowsable(EditorBrowsableState.Never)]
public static IRuntimeVariables MergeRuntimeVariables(IRuntimeVariables first, IRuntimeVariables second, int[] indexes)
{
return new MergedRuntimeVariables(first, second, indexes);
}
// Modifies a quoted Expression instance by changing hoisted variables and
// parameters into hoisted local references. The variable's StrongBox is
// burned as a constant, and all hoisted variables/parameters are rewritten
// as indexing expressions.
//
// The behavior of Quote is intended to be like C# and VB expression quoting
private sealed class ExpressionQuoter : ExpressionVisitor
{
private readonly HoistedLocals _scope;
private readonly object[] _locals;
// A stack of variables that are defined in nested scopes. We search
// this first when resolving a variable in case a nested scope shadows
// one of our variable instances.
private readonly Stack<HashSet<ParameterExpression>> _shadowedVars = new Stack<HashSet<ParameterExpression>>();
internal ExpressionQuoter(HoistedLocals scope, object[] locals)
{
_scope = scope;
_locals = locals;
}
protected internal override Expression VisitLambda<T>(Expression<T> node)
{
if (node.ParameterCount > 0)
{
var parameters = new HashSet<ParameterExpression>();
for (int i = 0, n = node.ParameterCount; i < n; i++)
{
parameters.Add(node.GetParameter(i));
}
_shadowedVars.Push(parameters);
}
Expression b = Visit(node.Body);
if (node.ParameterCount > 0)
{
_shadowedVars.Pop();
}
if (b == node.Body)
{
return node;
}
return node.Rewrite(b, parameters: null);
}
protected internal override Expression VisitBlock(BlockExpression node)
{
if (node.Variables.Count > 0)
{
_shadowedVars.Push(new HashSet<ParameterExpression>(node.Variables));
}
Expression[]? b = ExpressionVisitorUtils.VisitBlockExpressions(this, node);
if (node.Variables.Count > 0)
{
_shadowedVars.Pop();
}
if (b == null)
{
return node;
}
return node.Rewrite(node.Variables, b);
}
protected override CatchBlock VisitCatchBlock(CatchBlock node)
{
if (node.Variable != null)
{
_shadowedVars.Push(new HashSet<ParameterExpression> { node.Variable });
}
Expression b = Visit(node.Body);
Expression? f = Visit(node.Filter);
if (node.Variable != null)
{
_shadowedVars.Pop();
}
if (b == node.Body && f == node.Filter)
{
return node;
}
return Expression.MakeCatchBlock(node.Test, node.Variable, b, f);
}
protected internal override Expression VisitRuntimeVariables(RuntimeVariablesExpression node)
{
int count = node.Variables.Count;
var boxes = new List<IStrongBox>();
var vars = new List<ParameterExpression>();
var indexes = new int[count];
for (int i = 0; i < indexes.Length; i++)
{
IStrongBox? box = GetBox(node.Variables[i]);
if (box == null)
{
indexes[i] = vars.Count;
vars.Add(node.Variables[i]);
}
else
{
indexes[i] = -1 - boxes.Count;
boxes.Add(box);
}
}
// No variables were rewritten. Just return the original node
if (boxes.Count == 0)
{
return node;
}
ConstantExpression boxesConst = Expression.Constant(new RuntimeVariables(boxes.ToArray()), typeof(IRuntimeVariables));
// All of them were rewritten. Just return the array as a constant
if (vars.Count == 0)
{
return boxesConst;
}
// Otherwise, we need to return an object that merges them
return Expression.Call(
RuntimeOps_MergeRuntimeVariables,
Expression.RuntimeVariables(new TrueReadOnlyCollection<ParameterExpression>(vars.ToArray())),
boxesConst,
Expression.Constant(indexes)
);
}
protected internal override Expression VisitParameter(ParameterExpression node)
{
IStrongBox? box = GetBox(node);
if (box == null)
{
return node;
}
return Utils.GetStrongBoxValueField(Expression.Constant(box));
}
private IStrongBox? GetBox(ParameterExpression variable)
{
// Skip variables that are shadowed by a nested scope/lambda
foreach (HashSet<ParameterExpression> hidden in _shadowedVars)
{
if (hidden.Contains(variable))
{
return null;
}
}
HoistedLocals? scope = _scope;
object[] locals = _locals;
while (true)
{
int hoistIndex;
if (scope.Indexes.TryGetValue(variable, out hoistIndex))
{
return (IStrongBox)locals[hoistIndex];
}
scope = scope.Parent;
if (scope == null)
{
break;
}
locals = HoistedLocals.GetParent(locals);
}
// Unbound variable: an error should've been thrown already
// from VariableBinder
throw ContractUtils.Unreachable;
}
}
}
}
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