internal ListCSharpPattern(CSharpObjectPatternInfo info, LambdaExpression lengthAccess, LambdaExpression indexerAccess, ReadOnlyCollection <CSharpPattern> patterns)
: base(info)
{
LengthAccess = lengthAccess;
IndexerAccess = indexerAccess;
Patterns = patterns;
}
internal RecursiveCSharpPattern(CSharpObjectPatternInfo info, Type type, MethodInfo deconstructMethod, ReadOnlyCollection <PositionalCSharpSubpattern> deconstruction, ReadOnlyCollection <PropertyCSharpSubpattern> properties)
: base(info)
{
Type = type;
DeconstructMethod = deconstructMethod;
Deconstruction = deconstruction;
Properties = properties;
}
/// <summary>
/// Creates a pattern that always matches and assigns the input to a variable.
/// </summary>
/// <param name="info">Type information about the pattern.</param>
/// <returns>A <see cref="DiscardCSharpPattern" /> that represents a pattern that always matches.</returns>
public static VarCSharpPattern Var(CSharpObjectPatternInfo info)
{
RequiresNotNull(info, nameof(info));
if (info.Info.InputType != info.Info.NarrowedType)
{
throw Error.PatternInputAndNarrowedTypeShouldMatch(nameof(CSharpPatternType.Var));
}
if (info.Variable != null && info.Variable.Type != info.Info.NarrowedType)
{
throw Error.CannotAssignPatternResultToVariable(info.Variable.Type, info.Info.NarrowedType);
}
return(new VarCSharpPattern(info));
}
/// <summary>
/// Creates a positional pattern that matches on components of an object.
/// </summary>
/// <param name="info">Type information about the pattern.</param>
/// <param name="type">The type to check for.</param>
/// <param name="deconstructMethod">The method used to deconstruct an object into its components for use with positional subpatterns.</param>
/// <param name="deconstruction">The property subpatterns to apply.</param>
/// <returns>A <see cref="IPositionalCSharpPattern" /> representing a positional pattern.</returns>
public static IPositionalCSharpPattern Positional(CSharpObjectPatternInfo info, Type type, MethodInfo deconstructMethod, IEnumerable <PositionalCSharpSubpattern> deconstruction)
{
RequiresNotNull(info, nameof(info));
if (deconstructMethod == null && info.Variable == null && type == null)
{
var narrowedType = info.Info.NarrowedType;
if (!IsTupleType(narrowedType))
{
return(ITuple(deconstruction));
}
}
return(Recursive(info, type, deconstructMethod, deconstruction, properties: null));
}
// REVIEW: Type cannot be nullable.
/// <summary>
/// Creates a pattern that checks convertibility to a type and assigns to a variable.
/// </summary>
/// <param name="info">Type information about the pattern.</param>
/// <param name="type">The type to check for.</param>
/// <returns>A <see cref="DeclarationCSharpPattern" /> that represents a pattern that checks convertibility to a type and assigns to a variable.</returns>
public static DeclarationCSharpPattern Declaration(CSharpObjectPatternInfo info, Type type)
{
RequiresNotNull(info, nameof(info));
RequiresNotNull(type, nameof(type));
ValidatePatternType(type);
var variableType = info.Variable?.Type;
if (variableType != null)
{
RequiresCompatiblePatternTypes(type, variableType);
if (variableType != info.Info.NarrowedType)
{
throw Error.CannotAssignPatternResultToVariable(variableType, info.Info.NarrowedType);
}
}
return(new DeclarationCSharpPattern(info, type));
}
/// <summary>
/// Creates a list pattern.
/// </summary>
/// <param name="info">Type information about the pattern.</param>
/// <param name="lengthAccess">The <see cref="LambdaExpression"/> representing the expression used to retrieve the collection's length or element count.</param>
/// <param name="indexerAccess">The <see cref="LambdaExpression"/> representing the indexer access used to retrieve an element from the collection.</param>
/// <param name="patterns">The list of <see cref="CSharpPattern"/> patterns to apply to the elements of the collection, optionally containing a slice pattern.</param>
/// <returns>A <see cref="ListCSharpPattern" /> representing a list pattern.</returns>
public static ListCSharpPattern List(CSharpObjectPatternInfo info, LambdaExpression lengthAccess, LambdaExpression indexerAccess, IEnumerable <CSharpPattern> patterns)
{
RequiresNotNull(info, nameof(info));
var nonNullInputType = info.Info.InputType.GetNonNullableType();
var collectionType = info.Info.NarrowedType;
if (!AreEquivalent(nonNullInputType, collectionType))
{
throw Error.ListPatternInputTypeInvalid(nonNullInputType, collectionType);
}
RequiresCanRead(lengthAccess, nameof(lengthAccess));
if (lengthAccess.Parameters.Count != 1)
{
throw Error.LengthAccessShouldHaveOneParameter();
}
if (!AreEquivalent(lengthAccess.Parameters[0].Type, collectionType))
{
throw Error.LengthAccessParameterShouldHaveCollectionType(collectionType);
}
if (lengthAccess.ReturnType != typeof(int))
{
throw Error.LengthAccessShouldReturnInt32();
}
RequiresCanRead(indexerAccess, nameof(indexerAccess));
if (indexerAccess.Parameters.Count != 2)
{
throw Error.IndexerAccessShouldHaveTwoParameters();
}
if (!AreEquivalent(indexerAccess.Parameters[0].Type, collectionType))
{
throw Error.IndexerAccessFirstParameterShouldHaveCollectionType(collectionType);
}
if (indexerAccess.Parameters[1].Type != typeof(Index))
{
throw Error.IndexerAccessSecondParameterInvalidType(typeof(Index));
}
var elementType = indexerAccess.ReturnType;
if (elementType == typeof(void))
{
throw Error.ElementTypeCannotBeVoid();
}
var patternsList = patterns.ToArray();
RequiresNotNullItems(patternsList, nameof(patterns));
var hasSlice = false;
for (int i = 0, n = patternsList.Length; i < n; i++)
{
var pattern = patternsList[i];
if (pattern.PatternType == CSharpPatternType.Slice)
{
if (hasSlice)
{
throw Error.MoreThanOneSlicePattern();
}
hasSlice = true;
RequiresCompatiblePatternTypes(collectionType, ref patternsList[i]);
}
else
{
RequiresCompatiblePatternTypes(elementType, ref patternsList[i]);
}
}
return(new ListCSharpPattern(info, lengthAccess, indexerAccess, new TrueReadOnlyCollection <CSharpPattern>(patternsList)));
}
/// <summary> /// Creates a list pattern. /// </summary> /// <param name="info">Type information about the pattern.</param> /// <param name="lengthAccess">The <see cref="LambdaExpression"/> representing the expression used to retrieve the collection's length or element count.</param> /// <param name="indexerAccess">The <see cref="LambdaExpression"/> representing the indexer access used to retrieve an element from the collection.</param> /// <param name="patterns">The list of <see cref="CSharpPattern"/> patterns to apply to the elements of the collection, optionally containing a slice pattern.</param> /// <returns>A <see cref="ListCSharpPattern" /> representing a list pattern.</returns> public static ListCSharpPattern List(CSharpObjectPatternInfo info, LambdaExpression lengthAccess, LambdaExpression indexerAccess, params CSharpPattern[] patterns) => List(info, lengthAccess, indexerAccess, (IEnumerable <CSharpPattern>)patterns);
/// <summary>
/// Creates a recursive pattern that can perform positional matching and/or matching on properties.
/// </summary>
/// <param name="info">Type information about the pattern.</param>
/// <param name="type">The type to check for.</param>
/// <param name="deconstructMethod">The method used to deconstruct an object into its components for use with positional subpatterns.</param>
/// <param name="deconstruction">The positional subpatterns to apply to the components of the object.</param>
/// <param name="properties">The property subpatterns to apply.</param>
/// <returns>A <see cref="RecursiveCSharpPattern" /> representing a recursive pattern.</returns>
public static RecursiveCSharpPattern Recursive(CSharpObjectPatternInfo info, Type type, MethodInfo deconstructMethod, IEnumerable <PositionalCSharpSubpattern> deconstruction, IEnumerable <PropertyCSharpSubpattern> properties)
{
if (info == null)
{
// NB: We could arguably attempt to infer the type from the other parameters but that's a bit too implicit.
RequiresNotNull(type, nameof(type));
info = ObjectPatternInfo(PatternInfo(typeof(object), type), variable: null);
}
else
{
if (info.Variable != null)
{
RequiresCompatiblePatternTypes(info.Info.NarrowedType, info.Variable.Type);
}
}
var narrowedType = info.Info.NarrowedType;
var deconstructionCollection = deconstruction.ToReadOnly();
var propertiesCollection = properties.ToReadOnly();
var objParam = Expression.Parameter(narrowedType); // NB: Utility to utilize some expression factories to expedite some checks.
// REVIEW: Reordering of positional matches with names (for tuple elements or deconstruction out parameters) is not supported.
validateType();
validatePositional();
validateProperties();
return(new RecursiveCSharpPattern(info, type, deconstructMethod, deconstructionCollection, propertiesCollection));
void validateType()
{
if (type != null)
{
ValidatePatternType(type);
var variableType = info.Variable?.Type;
if (variableType != null)
{
RequiresCompatiblePatternTypes(type, variableType);
if (variableType != narrowedType)
{
throw Error.CannotAssignPatternResultToVariable(variableType, narrowedType);
}
}
}
}
void validatePositional()
{
if (deconstructionCollection.Count > 0)
{
foreach (var positionalPattern in deconstructionCollection)
{
RequiresNotNull(positionalPattern, nameof(deconstruction));
}
if (deconstructMethod != null)
{
validateWithDeconstructMethod();
}
else if (IsTupleType(narrowedType))
{
validateWithTupleType();
}
else
{
throw Error.InvalidPositionalPattern();
}
void validateWithDeconstructMethod()
{
ValidateMethodInfo(deconstructMethod);
if (deconstructMethod.ReturnType != typeof(void))
{
throw Error.DeconstructShouldReturnVoid(deconstructMethod);
}
var parameters = deconstructMethod.GetParametersCached();
if (deconstructMethod.IsStatic)
{
if (parameters.Length == 0)
{
throw Error.DeconstructExtensionMethodMissingThis(deconstructMethod);
}
ValidateOneArgument(deconstructMethod, ExpressionType.Call, objParam, parameters[0]);
parameters = parameters.RemoveFirst();
}
else
{
ValidateCallInstanceType(narrowedType, deconstructMethod);
}
var arity = parameters.Length;
checkArity(arity);
var parameterToPattern = new Dictionary <ParameterInfo, PositionalCSharpSubpattern>();
foreach (var positionalPattern in deconstructionCollection)
{
if (positionalPattern.Field != null)
{
throw Error.PositionalPatternWithDeconstructMethodCannotSpecifyField();
}
var parameter = positionalPattern.Parameter;
if (parameter != null)
{
if (parameter.Member != deconstructMethod)
{
throw Error.PositionalPatternParameterIsNotDeclaredOnDeconstructMethod(parameter, deconstructMethod);
}
if (parameterToPattern.ContainsKey(parameter))
{
throw Error.PositionalPatternParameterShouldOnlyBeUsedOnce(parameter);
}
parameterToPattern.Add(parameter, positionalPattern);
}
}
var bindByParameter = parameterToPattern.Count > 0;
if (bindByParameter && parameterToPattern.Count != arity)
{
throw Error.PositionalPatternWithDeconstructMethodShouldSpecifyAllParameters();
}
PositionalCSharpSubpattern getPositionalPattern(ParameterInfo parameter, int index) => bindByParameter
? parameterToPattern[parameter]
: deconstructionCollection[index];
for (var i = 0; i < arity; i++)
{
var parameter = parameters[i];
if (!parameter.IsOut)
{
throw Error.DeconstructParameterShouldBeOut(parameter, deconstructMethod);
}
var pattern = getPositionalPattern(parameter, i).Pattern;
var parameterType = parameter.ParameterType.GetElementType();
// REVIEW: Can we loosen the type checking here (assignment compatibility) or trigger ChangeType?
RequiresCompatiblePatternTypes(pattern.InputType, parameterType);
}
}
void validateWithTupleType()
{
var arity = GetTupleArity(narrowedType);
checkArity(arity);
var byIndexCount = 0;
var indexToPattern = new PositionalCSharpSubpattern[arity];
foreach (var positionalPattern in deconstructionCollection)
{
if (positionalPattern.Parameter != null)
{
throw Error.PositionalPatternWithTupleCannotSpecifyParameter();
}
if (positionalPattern.Field != null)
{
var index = positionalPattern.Field.Index;
if (index < 0 || index >= arity)
{
throw Error.PositionalPatternTupleIndexOutOfRange(index, arity);
}
if (indexToPattern[index] != null)
{
throw Error.PositionalPatternTupleIndexShouldOnlyBeUsedOnce(index);
}
indexToPattern[index] = positionalPattern;
byIndexCount++;
}
}
var bindByIndex = byIndexCount > 0;
if (bindByIndex && byIndexCount != arity)
{
throw Error.PositionalPatternWithTupleShouldSpecifyAllIndices();
}
PositionalCSharpSubpattern getPositionalPattern(int index) => bindByIndex
? indexToPattern[index]
: deconstructionCollection[index];
var elementTypes = GetTupleComponentTypes(narrowedType).ToReadOnly();
for (var i = 0; i < arity; i++)
{
var elementType = elementTypes[i];
var pattern = getPositionalPattern(i).Pattern;
// REVIEW: Can we loosen the type checking here (assignment compatibility) or trigger ChangeType?
RequiresCompatiblePatternTypes(pattern.InputType, elementType);
}
}
void checkArity(int arity)
{
if (arity != deconstructionCollection.Count)
{
throw Error.InvalidPositionalPatternCount(narrowedType);
}
}
}
}
void validateProperties()
{
foreach (var propertyPattern in propertiesCollection)
{
RequiresNotNull(propertyPattern, nameof(properties));
var member = findTopMostMember(propertyPattern.Member);
if (member.Member != null)
{
// TODO: Inline the check.
_ = Expression.MakeMemberAccess(objParam, member.Member);
}
else
{
// TODO: Inline the check.
_ = Helpers.GetTupleItemAccess(objParam, member.TupleField.Index);
}
}
/// <summary> /// Creates a property pattern that matches on properties. /// </summary> /// <param name="info">Type information about the pattern.</param> /// <param name="type">The type to check for.</param> /// <param name="properties">The property subpatterns to apply.</param> /// <returns>A <see cref="RecursiveCSharpPattern" /> representing a property pattern.</returns> public static RecursiveCSharpPattern Property(CSharpObjectPatternInfo info, Type type, IEnumerable <PropertyCSharpSubpattern> properties) => Recursive(info, type, deconstructMethod: null, deconstruction: null, properties);
/// <summary> /// Creates a property pattern that matches on properties. /// </summary> /// <param name="info">Type information about the pattern.</param> /// <param name="type">The type to check for.</param> /// <param name="properties">The property subpatterns to apply.</param> /// <returns>A <see cref="RecursiveCSharpPattern" /> representing a property pattern.</returns> public static RecursiveCSharpPattern Property(CSharpObjectPatternInfo info, Type type, params PropertyCSharpSubpattern[] properties) => Property(info, type, (IEnumerable <PropertyCSharpSubpattern>)properties);
//
// TODO: Add more convenience overloads for positional recursive patterns.
//
// - Should it find Deconstruct instance methods if unspecified?
// - This will require to find types from PositionalCSharpSubpattern.Pattern.InputType to do overload resolution for the out parameters.
//
/// <summary>
/// Creates a positional pattern that matches on components of an object.
/// </summary>
/// <param name="info">Type information about the pattern.</param>
/// <param name="type">The type to check for.</param>
/// <param name="deconstructMethod">The method used to deconstruct an object into its components for use with positional subpatterns.</param>
/// <param name="deconstruction">The property subpatterns to apply.</param>
/// <returns>A <see cref="IPositionalCSharpPattern" /> representing a positional pattern.</returns>
public static IPositionalCSharpPattern Positional(CSharpObjectPatternInfo info, Type type, MethodInfo deconstructMethod, params PositionalCSharpSubpattern[] deconstruction) => Positional(info, type, deconstructMethod, (IEnumerable <PositionalCSharpSubpattern>)deconstruction);
internal CSharpObjectPattern(CSharpObjectPatternInfo info)
: base(info.Info)
{
_objectInfo = info;
}
internal VarCSharpPattern(CSharpObjectPatternInfo info)
: base(info)
{
}
internal DeclarationCSharpPattern(CSharpObjectPatternInfo info, Type type)
: base(info)
{
Type = type;
}