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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.
// See the LICENSE file in the project root for more information.
#nullable disable
using System;
using System.Collections.Generic;
using Microsoft.CodeAnalysis.ErrorReporting;
namespace Microsoft.CodeAnalysis.ExtractMethod;
internal class ExtractMethodMatrix
{
private static readonly Dictionary<Key, VariableStyle> s_matrix;
static ExtractMethodMatrix()
{
s_matrix = [];
BuildMatrix();
}
public static bool TryGetVariableStyle(
bool bestEffort,
bool dataFlowIn,
bool dataFlowOut,
bool alwaysAssigned,
bool variableDeclared,
bool readInside,
bool writtenInside,
bool readOutside,
bool writtenOutside,
bool unsafeAddressTaken,
out VariableStyle variableStyle)
{
// bug # 12258, 12114
// use "out" if "&" is taken for the variable
if (unsafeAddressTaken)
{
variableStyle = VariableStyle.Out;
return true;
}
var key = new Key(
dataFlowIn,
dataFlowOut,
alwaysAssigned,
variableDeclared,
readInside,
writtenInside,
readOutside,
writtenOutside);
// special cases
if (!s_matrix.ContainsKey(key))
{
// Interesting case. Due to things like constant analysis there can be regions that
// the compiler considers data not to flow in (because analysis proves that that
// path will never be taken). However, the variable can still be read/written inside
// the region. For purposes of extract method, we check for this case, and we
// pretend it's as if data flowed into the region.
if (!dataFlowIn && (readInside || writtenInside))
{
key = new Key(true, dataFlowOut, alwaysAssigned, variableDeclared, readInside, writtenInside, readOutside, writtenOutside);
}
// another interesting case (bug # 10875)
// basically, it can happen in malformed code where a variable is not properly assigned but used outside of the selection + unreachable code region
// for such cases, treat it like "MoveOut"
if (!dataFlowOut && !alwaysAssigned && variableDeclared && !writtenInside && readOutside)
{
key = new Key(dataFlowIn, /*dataFlowOut*/ true, alwaysAssigned, variableDeclared, readInside, writtenInside, readOutside, writtenOutside);
}
// interesting case in invalid code (bug #19136)
// variable is passed by reference, and another argument is an out variable with the same name
if (dataFlowIn && variableDeclared)
{
key = new Key(/*dataFlowIn:*/ false, dataFlowOut, alwaysAssigned, variableDeclared, readInside, writtenInside, readOutside, writtenOutside);
}
}
if (s_matrix.TryGetValue(key, out variableStyle))
{
return true;
}
if (bestEffort)
{
// In best effort mode, even though we didn't know precisely what to do, we still
// allow the user to keep going, assuming that this variable is a very basic one.
variableStyle = VariableStyle.InputOnly;
return true;
}
// Some combination we didn't anticipate. Can't do anything here. Log the issue
// and bail out.
FatalError.ReportAndCatch(new Exception($"extract method encountered unknown states: {key.ToString()}"), ErrorSeverity.Critical);
return false;
}
private static void BuildMatrix()
{
// meaning of each boolean values (total of 69 different cases)
// data flowin/data flow out/always assigned/variable declared/ read inside/written inside/read outside/written outside
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: false, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: false, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.MoveIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.SplitIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: false, readOutside: false, writtenOutside: true), VariableStyle.MoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: false, readOutside: true, writtenOutside: true), VariableStyle.MoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.None);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: false, readOutside: false, writtenOutside: false), VariableStyle.None);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: false, readOutside: false, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: false, readOutside: true, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.None);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: false, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.MoveIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: false, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.SplitIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.SplitIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.SplitIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: false, readOutside: false, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: false, readOutside: true, writtenOutside: true), VariableStyle.Ref);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.MoveIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.SplitIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.SplitIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.SplitIn);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: true, readInside: false, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.None);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: true, readInside: false, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: true, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: true, readInside: true, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.None);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: true, readInside: true, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: false, alwaysAssigned: true, variableDeclared: true, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.SplitOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.Ref);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.Ref);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.Ref);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.Ref);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: false, readOutside: true, writtenOutside: false), VariableStyle.NotUsed);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: false, readOutside: true, writtenOutside: true), VariableStyle.NotUsed);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: false, readOutside: true, writtenOutside: false), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: false, readOutside: true, writtenOutside: true), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: false, variableDeclared: true, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.Out);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.Out);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.Out);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.Out);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: true, readInside: false, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: true, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: true, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: false, dataFlowOut: true, alwaysAssigned: true, variableDeclared: true, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.OutWithMoveOut);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: false, readOutside: false, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: false, readOutside: false, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: false, readOutside: true, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: false, readOutside: true, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: false, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: false, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.InputOnly);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: true, alwaysAssigned: false, variableDeclared: false, readInside: false, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.Ref);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: true, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.OutWithErrorInput);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: true, alwaysAssigned: false, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.Ref);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: true, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: false), VariableStyle.OutWithErrorInput);
s_matrix.Add(new Key(dataFlowIn: true, dataFlowOut: true, alwaysAssigned: true, variableDeclared: false, readInside: true, writtenInside: true, readOutside: true, writtenOutside: true), VariableStyle.Ref);
}
private readonly struct Key : IEquatable<Key>
{
public bool DataFlowIn { get; }
public bool DataFlowOut { get; }
public bool AlwaysAssigned { get; }
public bool VariableDeclared { get; }
public bool ReadInside { get; }
public bool WrittenInside { get; }
public bool ReadOutside { get; }
public bool WrittenOutside { get; }
public Key(
bool dataFlowIn,
bool dataFlowOut,
bool alwaysAssigned,
bool variableDeclared,
bool readInside,
bool writtenInside,
bool readOutside,
bool writtenOutside)
: this()
{
DataFlowIn = dataFlowIn;
DataFlowOut = dataFlowOut;
AlwaysAssigned = alwaysAssigned;
VariableDeclared = variableDeclared;
ReadInside = readInside;
WrittenInside = writtenInside;
ReadOutside = readOutside;
WrittenOutside = writtenOutside;
}
public bool Equals(Key key)
{
return DataFlowIn == key.DataFlowIn &&
DataFlowOut == key.DataFlowOut &&
AlwaysAssigned == key.AlwaysAssigned &&
VariableDeclared == key.VariableDeclared &&
ReadInside == key.ReadInside &&
WrittenInside == key.WrittenInside &&
ReadOutside == key.ReadOutside &&
WrittenOutside == key.WrittenOutside;
}
public override bool Equals(object obj)
{
if (obj is Key key)
{
return Equals(key);
}
return false;
}
public override int GetHashCode()
{
var hashCode = 0;
hashCode = DataFlowIn ? 1 << 7 | hashCode : hashCode;
hashCode = DataFlowOut ? 1 << 6 | hashCode : hashCode;
hashCode = AlwaysAssigned ? 1 << 5 | hashCode : hashCode;
hashCode = VariableDeclared ? 1 << 4 | hashCode : hashCode;
hashCode = ReadInside ? 1 << 3 | hashCode : hashCode;
hashCode = WrittenInside ? 1 << 2 | hashCode : hashCode;
hashCode = ReadOutside ? 1 << 1 | hashCode : hashCode;
hashCode = WrittenOutside ? 1 << 0 | hashCode : hashCode;
return hashCode;
}
public override string ToString() => GetHashCode().ToString("X");
}
}
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