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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.
using System;
using System.Collections.Immutable;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.PooledObjects;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.CSharp
{
partial class Binder
{
private BoundExpression BindIsPatternExpression(IsPatternExpressionSyntax node, BindingDiagnosticBag diagnostics)
{
MessageID.IDS_FeaturePatternMatching.CheckFeatureAvailability(diagnostics, node.IsKeyword);
BoundExpression expression = BindRValueWithoutTargetType(node.Expression, diagnostics);
bool hasErrors = IsOperandErrors(node, ref expression, diagnostics);
TypeSymbol? expressionType = expression.Type;
if (expressionType is null || expressionType.IsVoidType())
{
if (!hasErrors)
{
// value expected
diagnostics.Add(ErrorCode.ERR_BadPatternExpression, node.Expression.Location, expression.Display);
hasErrors = true;
}
expression = BadExpression(expression.Syntax, expression);
}
Debug.Assert(expression.Type is { });
BoundPattern pattern = BindPattern(node.Pattern, expression.Type, permitDesignations: true, hasErrors, diagnostics, underIsPattern: true);
hasErrors |= pattern.HasErrors;
return MakeIsPatternExpression(
node, expression, pattern, GetSpecialType(SpecialType.System_Boolean, diagnostics, node),
hasErrors, diagnostics);
}
private BoundExpression MakeIsPatternExpression(
SyntaxNode node,
BoundExpression expression,
BoundPattern pattern,
TypeSymbol boolType,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
// Note that these labels are for the convenience of the compilation of patterns, and are not necessarily emitted into the lowered code.
LabelSymbol whenTrueLabel = new GeneratedLabelSymbol("isPatternSuccess");
LabelSymbol whenFalseLabel = new GeneratedLabelSymbol("isPatternFailure");
bool negated = pattern.IsNegated(out var innerPattern);
BoundDecisionDag decisionDag = DecisionDagBuilder.CreateDecisionDagForIsPattern(
this.Compilation, pattern.Syntax, expression, innerPattern, whenTrueLabel: whenTrueLabel, whenFalseLabel: whenFalseLabel, diagnostics);
if (!hasErrors && getConstantResult(decisionDag, negated, whenTrueLabel, whenFalseLabel) is { } constantResult)
{
if (!constantResult)
{
Debug.Assert(expression.Type is object);
diagnostics.Add(ErrorCode.ERR_IsPatternImpossible, node.Location, expression.Type);
hasErrors = true;
}
else
{
switch (pattern)
{
case BoundConstantPattern _:
case BoundITuplePattern _:
// these patterns can fail in practice
throw ExceptionUtilities.Unreachable();
case BoundRelationalPattern _:
case BoundTypePattern _:
case BoundNegatedPattern _:
case BoundBinaryPattern _:
case BoundListPattern:
Debug.Assert(expression.Type is object);
diagnostics.Add(ErrorCode.WRN_IsPatternAlways, node.Location, expression.Type);
break;
case BoundDiscardPattern _:
// we do not give a warning on this because it is an existing scenario, and it should
// have been obvious in source that it would always match.
break;
case BoundDeclarationPattern _:
case BoundRecursivePattern _:
// We do not give a warning on these because people do this to give a name to a value
break;
}
}
}
else if (expression.ConstantValueOpt != null)
{
decisionDag = decisionDag.SimplifyDecisionDagIfConstantInput(expression);
if (!hasErrors && getConstantResult(decisionDag, negated, whenTrueLabel, whenFalseLabel) is { } simplifiedResult)
{
if (!simplifiedResult)
{
diagnostics.Add(ErrorCode.WRN_GivenExpressionNeverMatchesPattern, node.Location);
}
else
{
switch (pattern)
{
case BoundConstantPattern _:
diagnostics.Add(ErrorCode.WRN_GivenExpressionAlwaysMatchesConstant, node.Location);
break;
case BoundRelationalPattern _:
case BoundTypePattern _:
case BoundNegatedPattern _:
case BoundBinaryPattern _:
case BoundDiscardPattern _:
diagnostics.Add(ErrorCode.WRN_GivenExpressionAlwaysMatchesPattern, node.Location);
break;
}
}
}
}
// decisionDag, whenTrueLabel, and whenFalseLabel represent the decision DAG for the inner pattern,
// after removing any outer 'not's, so consumers will need to compensate for negated patterns.
return new BoundIsPatternExpression(
node, expression, pattern, negated, decisionDag, whenTrueLabel: whenTrueLabel, whenFalseLabel: whenFalseLabel, boolType, hasErrors);
static bool? getConstantResult(BoundDecisionDag decisionDag, bool negated, LabelSymbol whenTrueLabel, LabelSymbol whenFalseLabel)
{
if (!decisionDag.ReachableLabels.Contains(whenTrueLabel))
{
return negated;
}
else if (!decisionDag.ReachableLabels.Contains(whenFalseLabel))
{
return !negated;
}
return null;
}
}
private BoundExpression BindSwitchExpression(SwitchExpressionSyntax node, BindingDiagnosticBag diagnostics)
{
RoslynDebug.Assert(node is not null);
MessageID.IDS_FeatureRecursivePatterns.CheckFeatureAvailability(diagnostics, node.SwitchKeyword);
Binder? switchBinder = this.GetBinder(node);
RoslynDebug.Assert(switchBinder is { });
return switchBinder.BindSwitchExpressionCore(node, switchBinder, diagnostics);
}
internal virtual BoundExpression BindSwitchExpressionCore(
SwitchExpressionSyntax node,
Binder originalBinder,
BindingDiagnosticBag diagnostics)
{
RoslynDebug.Assert(this.Next is { });
return this.Next.BindSwitchExpressionCore(node, originalBinder, diagnostics);
}
internal BoundPattern BindPattern(
PatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics,
bool underIsPattern = false)
{
return node switch
{
DiscardPatternSyntax p => BindDiscardPattern(p, inputType, diagnostics),
DeclarationPatternSyntax p => BindDeclarationPattern(p, inputType, permitDesignations, hasErrors, diagnostics),
ConstantPatternSyntax p => BindConstantPatternWithFallbackToTypePattern(p, inputType, hasErrors, diagnostics),
RecursivePatternSyntax p => BindRecursivePattern(p, inputType, permitDesignations, hasErrors, diagnostics),
VarPatternSyntax p => BindVarPattern(p, inputType, permitDesignations, hasErrors, diagnostics),
ParenthesizedPatternSyntax p => BindParenthesizedPattern(p, inputType, permitDesignations, hasErrors, diagnostics, underIsPattern),
BinaryPatternSyntax p => BindBinaryPattern(p, inputType, permitDesignations, hasErrors, diagnostics),
UnaryPatternSyntax p => BindUnaryPattern(p, inputType, hasErrors, diagnostics, underIsPattern),
RelationalPatternSyntax p => BindRelationalPattern(p, inputType, hasErrors, diagnostics),
TypePatternSyntax p => BindTypePattern(p, inputType, hasErrors, diagnostics),
ListPatternSyntax p => BindListPattern(p, inputType, permitDesignations, hasErrors, diagnostics),
SlicePatternSyntax p => BindSlicePattern(p, inputType, permitDesignations, ref hasErrors, misplaced: true, diagnostics),
_ => throw ExceptionUtilities.UnexpectedValue(node.Kind()),
};
}
private BoundPattern BindParenthesizedPattern(
ParenthesizedPatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics,
bool underIsPattern)
{
MessageID.IDS_FeatureParenthesizedPattern.CheckFeatureAvailability(diagnostics, node.OpenParenToken);
return BindPattern(node.Pattern, inputType, permitDesignations, hasErrors, diagnostics, underIsPattern);
}
private BoundPattern BindSlicePattern(
SlicePatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
ref bool hasErrors,
bool misplaced,
BindingDiagnosticBag diagnostics)
{
if (misplaced && !hasErrors)
{
diagnostics.Add(ErrorCode.ERR_MisplacedSlicePattern, node.Location);
hasErrors = true;
}
BoundExpression? indexerAccess = null;
BoundPattern? pattern = null;
BoundSlicePatternReceiverPlaceholder? receiverPlaceholder = null;
BoundSlicePatternRangePlaceholder? argumentPlaceholder = null;
// We don't require the type to be sliceable if there's no subpattern.
if (node.Pattern is not null)
{
receiverPlaceholder = new BoundSlicePatternReceiverPlaceholder(node, inputType) { WasCompilerGenerated = true };
var systemRangeType = GetWellKnownType(WellKnownType.System_Range, diagnostics, node);
argumentPlaceholder = new BoundSlicePatternRangePlaceholder(node, systemRangeType) { WasCompilerGenerated = true };
TypeSymbol sliceType;
if (inputType.IsErrorType())
{
hasErrors = true;
sliceType = inputType;
}
else
{
var analyzedArguments = AnalyzedArguments.GetInstance();
analyzedArguments.Arguments.Add(argumentPlaceholder);
indexerAccess = BindElementAccessCore(node, receiverPlaceholder, analyzedArguments, diagnostics).MakeCompilerGenerated();
indexerAccess = CheckValue(indexerAccess, BindValueKind.RValue, diagnostics);
Debug.Assert(indexerAccess is BoundIndexerAccess or BoundImplicitIndexerAccess or BoundArrayAccess or BoundBadExpression or BoundDynamicIndexerAccess);
analyzedArguments.Free();
if (!systemRangeType.HasUseSiteError)
{
_ = GetWellKnownTypeMember(WellKnownMember.System_Range__ctor, diagnostics, syntax: node);
}
Debug.Assert(indexerAccess.Type is not null);
sliceType = indexerAccess.Type;
}
pattern = BindPattern(node.Pattern, sliceType, permitDesignations, hasErrors, diagnostics);
}
return new BoundSlicePattern(node, pattern, indexerAccess, receiverPlaceholder, argumentPlaceholder, inputType: inputType, narrowedType: inputType, hasErrors);
}
private ImmutableArray<BoundPattern> BindListPatternSubpatterns(
SeparatedSyntaxList<PatternSyntax> subpatterns,
TypeSymbol inputType,
TypeSymbol elementType,
bool permitDesignations,
ref bool hasErrors,
out bool sawSlice,
BindingDiagnosticBag diagnostics)
{
sawSlice = false;
var builder = ArrayBuilder<BoundPattern>.GetInstance(subpatterns.Count);
foreach (PatternSyntax pattern in subpatterns)
{
BoundPattern boundPattern;
if (pattern is SlicePatternSyntax slice)
{
boundPattern = BindSlicePattern(slice, inputType, permitDesignations, ref hasErrors, misplaced: sawSlice, diagnostics: diagnostics);
sawSlice = true;
}
else
{
boundPattern = BindPattern(pattern, elementType, permitDesignations, hasErrors, diagnostics);
}
builder.Add(boundPattern);
}
return builder.ToImmutableAndFree();
}
private BoundListPattern BindListPattern(
ListPatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
CheckFeatureAvailability(node, MessageID.IDS_FeatureListPattern, diagnostics);
TypeSymbol elementType;
BoundExpression? indexerAccess;
BoundExpression? lengthAccess;
TypeSymbol narrowedType = inputType.StrippedType();
BoundListPatternReceiverPlaceholder? receiverPlaceholder;
BoundListPatternIndexPlaceholder? argumentPlaceholder;
if (inputType.IsDynamic())
{
Error(diagnostics, ErrorCode.ERR_UnsupportedTypeForListPattern, node, inputType);
}
if (inputType.IsErrorType() || inputType.IsDynamic())
{
hasErrors = true;
elementType = inputType;
indexerAccess = null;
lengthAccess = null;
receiverPlaceholder = null;
argumentPlaceholder = null;
}
else
{
hasErrors |= !BindLengthAndIndexerForListPattern(node, narrowedType, diagnostics, out indexerAccess, out lengthAccess, out receiverPlaceholder, out argumentPlaceholder);
Debug.Assert(indexerAccess!.Type is not null);
elementType = indexerAccess.Type;
}
ImmutableArray<BoundPattern> subpatterns = BindListPatternSubpatterns(
node.Patterns, inputType: narrowedType, elementType: elementType,
permitDesignations, ref hasErrors, out bool sawSlice, diagnostics);
BindPatternDesignation(
node.Designation,
declType: TypeWithAnnotations.Create(narrowedType, NullableAnnotation.NotAnnotated),
permitDesignations, typeSyntax: null, diagnostics, ref hasErrors,
out Symbol? variableSymbol, out BoundExpression? variableAccess);
return new BoundListPattern(
syntax: node, subpatterns: subpatterns, hasSlice: sawSlice, lengthAccess: lengthAccess,
indexerAccess: indexerAccess, receiverPlaceholder, argumentPlaceholder, variable: variableSymbol,
variableAccess: variableAccess, inputType: inputType, narrowedType: narrowedType, hasErrors);
}
/// <summary>
/// Types which list-patterns can be used on (ie. countable and indexable ones) are assumed to have
/// non-negative lengths.
/// </summary>
private bool IsCountableAndIndexable(SyntaxNode node, TypeSymbol inputType, out PropertySymbol? lengthProperty)
{
var success = BindLengthAndIndexerForListPattern(node, inputType, BindingDiagnosticBag.Discarded,
indexerAccess: out _, out var lengthAccess, receiverPlaceholder: out _, argumentPlaceholder: out _);
lengthProperty = success ? GetPropertySymbol(lengthAccess, out _, out _) : null;
return success;
}
private bool BindLengthAndIndexerForListPattern(SyntaxNode node, TypeSymbol inputType, BindingDiagnosticBag diagnostics,
out BoundExpression indexerAccess, out BoundExpression lengthAccess, out BoundListPatternReceiverPlaceholder? receiverPlaceholder, out BoundListPatternIndexPlaceholder argumentPlaceholder)
{
Debug.Assert(!inputType.IsDynamic());
bool hasErrors = false;
receiverPlaceholder = new BoundListPatternReceiverPlaceholder(node, inputType) { WasCompilerGenerated = true };
if (inputType.IsSZArray())
{
hasErrors |= !TryGetSpecialTypeMember(Compilation, SpecialMember.System_Array__Length, node, diagnostics, out PropertySymbol lengthProperty);
if (lengthProperty is not null)
{
lengthAccess = new BoundPropertyAccess(node, receiverPlaceholder, initialBindingReceiverIsSubjectToCloning: ThreeState.False, lengthProperty, LookupResultKind.Viable, lengthProperty.Type) { WasCompilerGenerated = true };
}
else
{
lengthAccess = new BoundBadExpression(node, LookupResultKind.Empty, ImmutableArray<Symbol?>.Empty, ImmutableArray<BoundExpression>.Empty, CreateErrorType(), hasErrors: true) { WasCompilerGenerated = true };
}
}
else
{
if (!TryBindLengthOrCount(node, receiverPlaceholder, out lengthAccess, diagnostics))
{
hasErrors = true;
Error(diagnostics, ErrorCode.ERR_ListPatternRequiresLength, node, inputType);
}
}
var analyzedArguments = AnalyzedArguments.GetInstance();
var systemIndexType = GetWellKnownType(WellKnownType.System_Index, diagnostics, node);
argumentPlaceholder = new BoundListPatternIndexPlaceholder(node, systemIndexType) { WasCompilerGenerated = true };
analyzedArguments.Arguments.Add(argumentPlaceholder);
indexerAccess = BindElementAccessCore(node, receiverPlaceholder, analyzedArguments, diagnostics).MakeCompilerGenerated();
indexerAccess = CheckValue(indexerAccess, BindValueKind.RValue, diagnostics);
Debug.Assert(indexerAccess is BoundIndexerAccess or BoundImplicitIndexerAccess or BoundArrayAccess or BoundBadExpression or BoundDynamicIndexerAccess);
analyzedArguments.Free();
if (!systemIndexType.HasUseSiteError)
{
// Check required well-known member.
_ = GetWellKnownTypeMember(WellKnownMember.System_Index__ctor, diagnostics, syntax: node);
}
return !hasErrors && !lengthAccess.HasErrors && !indexerAccess.HasErrors;
}
private static BoundPattern BindDiscardPattern(DiscardPatternSyntax node, TypeSymbol inputType, BindingDiagnosticBag diagnostics)
{
MessageID.IDS_FeatureRecursivePatterns.CheckFeatureAvailability(diagnostics, node);
return new BoundDiscardPattern(node, inputType: inputType, narrowedType: inputType);
}
private BoundPattern BindConstantPatternWithFallbackToTypePattern(
ConstantPatternSyntax node,
TypeSymbol inputType,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
return BindConstantPatternWithFallbackToTypePattern(node, node.Expression, inputType, hasErrors, diagnostics);
}
internal BoundPattern BindConstantPatternWithFallbackToTypePattern(
SyntaxNode node,
ExpressionSyntax expression,
TypeSymbol inputType,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
ExpressionSyntax innerExpression = SkipParensAndNullSuppressions(expression, diagnostics, ref hasErrors);
var convertedExpression = BindExpressionOrTypeForPattern(inputType, innerExpression, ref hasErrors, diagnostics, out var constantValueOpt, out bool wasExpression, out Conversion patternConversion);
if (wasExpression)
{
var convertedType = convertedExpression.Type ?? inputType;
if (convertedType.SpecialType == SpecialType.System_String && inputType.IsSpanOrReadOnlySpanChar())
{
convertedType = inputType;
}
if ((constantValueOpt?.IsNumeric == true) && ShouldBlockINumberBaseConversion(patternConversion, inputType))
{
// Cannot use a numeric constant or relational pattern on '{0}' because it inherits from or extends 'INumberBase<T>'. Consider using a type pattern to narrow to a specific numeric type.
diagnostics.Add(ErrorCode.ERR_CannotMatchOnINumberBase, node.Location, inputType);
}
return new BoundConstantPattern(
node, convertedExpression, constantValueOpt ?? ConstantValue.Bad, inputType, convertedType, hasErrors || constantValueOpt is null);
}
else
{
if (!hasErrors)
CheckFeatureAvailability(innerExpression, MessageID.IDS_FeatureTypePattern, diagnostics);
var boundType = (BoundTypeExpression)convertedExpression;
bool isExplicitNotNullTest = boundType.Type.SpecialType == SpecialType.System_Object;
return new BoundTypePattern(node, boundType, isExplicitNotNullTest, inputType, boundType.Type, hasErrors);
}
}
private bool ShouldBlockINumberBaseConversion(Conversion patternConversion, TypeSymbol inputType)
{
// We want to block constant and relation patterns that have an input type constrained to or inherited from INumberBase<T>, if we don't
// know how to represent the constant being matched against in the input type. For example, `1.0 is 1` will work when written inline, but
// will fail if the input type is `INumberBase<T>`. We block this now so that we can make make it work as expected in the future without
// being a breaking change.
if (patternConversion.IsIdentity || patternConversion.IsConstantExpression || patternConversion.IsNumeric)
{
return false;
}
var interfaces = inputType is TypeParameterSymbol typeParam ? typeParam.EffectiveInterfacesNoUseSiteDiagnostics : inputType.AllInterfacesNoUseSiteDiagnostics;
return interfaces.Any(static (i, _) => i.IsWellKnownINumberBaseType(), 0) || inputType.IsWellKnownINumberBaseType();
}
private static ExpressionSyntax SkipParensAndNullSuppressions(ExpressionSyntax e, BindingDiagnosticBag diagnostics, ref bool hasErrors)
{
while (true)
{
switch (e.Kind())
{
case SyntaxKind.DefaultLiteralExpression:
diagnostics.Add(ErrorCode.ERR_DefaultPattern, e.Location);
hasErrors = true;
return e;
case SyntaxKind.ParenthesizedExpression:
e = ((ParenthesizedExpressionSyntax)e).Expression;
continue;
case SyntaxKind.SuppressNullableWarningExpression:
diagnostics.Add(ErrorCode.ERR_IllegalSuppression, e.Location);
hasErrors = true;
e = ((PostfixUnaryExpressionSyntax)e).Operand;
continue;
default:
return e;
}
}
}
/// <summary>
/// Binds the expression for a pattern. Sets <paramref name="wasExpression"/> if it was a type rather than an expression,
/// and in that case it returns a <see cref="BoundTypeExpression"/>.
/// </summary>
private BoundExpression BindExpressionOrTypeForPattern(
TypeSymbol inputType,
ExpressionSyntax patternExpression,
ref bool hasErrors,
BindingDiagnosticBag diagnostics,
out ConstantValue? constantValueOpt,
out bool wasExpression,
out Conversion patternExpressionConversion)
{
constantValueOpt = null;
BoundExpression expression = BindTypeOrRValue(patternExpression, diagnostics);
wasExpression = expression.Kind != BoundKind.TypeExpression;
if (wasExpression)
{
return BindExpressionForPatternContinued(expression, inputType, patternExpression, ref hasErrors, diagnostics, out constantValueOpt, out patternExpressionConversion);
}
else
{
Debug.Assert(expression is { Kind: BoundKind.TypeExpression, Type: { } });
hasErrors |= CheckValidPatternType(patternExpression, inputType, expression.Type, diagnostics: diagnostics);
patternExpressionConversion = Conversion.NoConversion;
return expression;
}
}
/// <summary>
/// Binds the expression for an is-type right-hand-side, in case it does not bind as a type.
/// </summary>
private BoundExpression BindExpressionForPattern(
TypeSymbol inputType,
ExpressionSyntax patternExpression,
ref bool hasErrors,
BindingDiagnosticBag diagnostics,
out ConstantValue? constantValueOpt,
out bool wasExpression,
out Conversion patternExpressionConversion)
{
constantValueOpt = null;
var expression = BindExpression(patternExpression, diagnostics: diagnostics, invoked: false, indexed: false);
expression = CheckValue(expression, BindValueKind.RValue, diagnostics);
wasExpression = expression.Kind switch { BoundKind.BadExpression => false, BoundKind.TypeExpression => false, _ => true };
patternExpressionConversion = Conversion.NoConversion;
return wasExpression ? BindExpressionForPatternContinued(expression, inputType, patternExpression, ref hasErrors, diagnostics, out constantValueOpt, out patternExpressionConversion) : expression;
}
private BoundExpression BindExpressionForPatternContinued(
BoundExpression expression,
TypeSymbol inputType,
ExpressionSyntax patternExpression,
ref bool hasErrors,
BindingDiagnosticBag diagnostics,
out ConstantValue? constantValueOpt,
out Conversion patternExpressionConversion)
{
BoundExpression convertedExpression = ConvertPatternExpression(
inputType, patternExpression, expression, out constantValueOpt, hasErrors, diagnostics, out patternExpressionConversion);
ConstantValueUtils.CheckLangVersionForConstantValue(convertedExpression, diagnostics);
if (!convertedExpression.HasErrors && !hasErrors)
{
if (constantValueOpt == null)
{
var strippedInputType = inputType.StrippedType();
if (strippedInputType.Kind is not SymbolKind.ErrorType and not SymbolKind.DynamicType and not SymbolKind.TypeParameter &&
strippedInputType.SpecialType is not SpecialType.System_Object and not SpecialType.System_ValueType)
{
diagnostics.Add(ErrorCode.ERR_ConstantValueOfTypeExpected, patternExpression.Location, strippedInputType);
}
else
{
diagnostics.Add(ErrorCode.ERR_ConstantExpected, patternExpression.Location);
}
hasErrors = true;
}
else if (inputType.IsPointerType())
{
CheckFeatureAvailability(patternExpression, MessageID.IDS_FeatureNullPointerConstantPattern, diagnostics);
}
}
if (convertedExpression.Type is null && constantValueOpt != ConstantValue.Null)
{
Debug.Assert(hasErrors);
convertedExpression = BindToTypeForErrorRecovery(convertedExpression);
}
return convertedExpression;
}
internal BoundExpression ConvertPatternExpression(
TypeSymbol inputType,
CSharpSyntaxNode node,
BoundExpression expression,
out ConstantValue? constantValue,
bool hasErrors,
BindingDiagnosticBag diagnostics,
out Conversion patternExpressionConversion)
{
BoundExpression convertedExpression;
// If we are pattern-matching against an open type, we do not convert the constant to the type of the input.
// This permits us to match a value of type `IComparable<T>` with a pattern of type `int`.
if (inputType.ContainsTypeParameter())
{
convertedExpression = expression;
// If the expression does not have a constant value, an error will be reported in the caller
if (!hasErrors && expression.ConstantValueOpt is object)
{
CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = GetNewCompoundUseSiteInfo(diagnostics);
if (expression.ConstantValueOpt == ConstantValue.Null)
{
// Pointers are value types, but they can be assigned null, so they can be matched against null.
if (inputType.IsNonNullableValueType() && !inputType.IsPointerOrFunctionPointer())
{
// We do not permit matching null against a struct type.
diagnostics.Add(ErrorCode.ERR_ValueCantBeNull, expression.Syntax.Location, inputType);
hasErrors = true;
}
}
else
{
RoslynDebug.Assert(expression.Type is { });
ConstantValue match = ExpressionOfTypeMatchesPatternType(Conversions, inputType, expression.Type, ref useSiteInfo, out _, operandConstantValue: null);
if (match == ConstantValue.False || match == ConstantValue.Bad)
{
diagnostics.Add(ErrorCode.ERR_PatternWrongType, expression.Syntax.Location, inputType, expression.Display);
hasErrors = true;
}
}
if (!hasErrors)
{
var requiredVersion = MessageID.IDS_FeatureRecursivePatterns.RequiredVersion();
patternExpressionConversion = this.Conversions.ClassifyConversionFromExpression(expression, inputType, isChecked: CheckOverflowAtRuntime, ref useSiteInfo);
if (Compilation.LanguageVersion < requiredVersion && !patternExpressionConversion.IsImplicit)
{
diagnostics.Add(ErrorCode.ERR_ConstantPatternVsOpenType,
expression.Syntax.Location, inputType, expression.Display, new CSharpRequiredLanguageVersion(requiredVersion));
}
}
else
{
patternExpressionConversion = Conversion.NoConversion;
}
diagnostics.Add(node, useSiteInfo);
}
else
{
patternExpressionConversion = Conversion.NoConversion;
}
}
else
{
if (expression.Type?.SpecialType == SpecialType.System_String && inputType.IsSpanOrReadOnlySpanChar())
{
if (MessageID.IDS_FeatureSpanCharConstantPattern.CheckFeatureAvailability(diagnostics, Compilation, node.Location))
{
// report missing member and use site diagnostics
bool isReadOnlySpan = inputType.IsReadOnlySpanChar();
_ = GetWellKnownTypeMember(
isReadOnlySpan ? WellKnownMember.System_MemoryExtensions__SequenceEqual_ReadOnlySpan_T : WellKnownMember.System_MemoryExtensions__SequenceEqual_Span_T,
diagnostics,
syntax: node);
_ = GetWellKnownTypeMember(WellKnownMember.System_MemoryExtensions__AsSpan_String, diagnostics, syntax: node);
_ = GetWellKnownTypeMember(isReadOnlySpan ? WellKnownMember.System_ReadOnlySpan_T__get_Length : WellKnownMember.System_Span_T__get_Length,
diagnostics,
syntax: node);
}
convertedExpression = BindToNaturalType(expression, diagnostics);
constantValue = convertedExpression.ConstantValueOpt;
if (constantValue == ConstantValue.Null)
{
diagnostics.Add(ErrorCode.ERR_PatternSpanCharCannotBeStringNull, convertedExpression.Syntax.Location, inputType);
}
patternExpressionConversion = Conversion.NoConversion;
return convertedExpression;
}
// This will allow user-defined conversions, even though they're not permitted here. This is acceptable
// because the result of a user-defined conversion does not have a ConstantValue. A constant pattern
// requires a constant value so we'll report a diagnostic to that effect later.
convertedExpression = GenerateConversionForAssignment(inputType, expression, diagnostics, out patternExpressionConversion);
if (convertedExpression.Kind == BoundKind.Conversion)
{
var conversion = (BoundConversion)convertedExpression;
BoundExpression operand = conversion.Operand;
if (inputType.IsNullableType() && (convertedExpression.ConstantValueOpt == null || !convertedExpression.ConstantValueOpt.IsNull))
{
// Null is a special case here because we want to compare null to the Nullable<T> itself, not to the underlying type.
// We are not interested in the diagnostic that get created here
convertedExpression = CreateConversion(operand, inputType.GetNullableUnderlyingType(), BindingDiagnosticBag.Discarded);
}
else if ((conversion.ConversionKind == ConversionKind.Boxing || conversion.ConversionKind == ConversionKind.ImplicitReference)
&& operand.ConstantValueOpt != null && convertedExpression.ConstantValueOpt == null)
{
// A boxed constant (or string converted to object) is a special case because we prefer
// to compare to the pre-converted value by casting the input value to the type of the constant
// (that is, unboxing or downcasting it) and then testing the resulting value using primitives.
// That is much more efficient than calling object.Equals(x, y), and we can share the downcasted
// input value among many constant tests.
convertedExpression = operand;
}
else if (conversion.ConversionKind == ConversionKind.ImplicitNullToPointer ||
(conversion.ConversionKind == ConversionKind.NoConversion && convertedExpression.Type?.IsErrorType() == true))
{
convertedExpression = operand;
}
}
}
constantValue = convertedExpression.ConstantValueOpt;
return convertedExpression;
}
/// <summary>
/// Check that the pattern type is valid for the operand. Return true if an error was reported.
/// </summary>
private bool CheckValidPatternType(
SyntaxNode typeSyntax,
TypeSymbol inputType,
TypeSymbol patternType,
BindingDiagnosticBag diagnostics)
{
RoslynDebug.Assert((object)inputType != null);
RoslynDebug.Assert((object)patternType != null);
if (inputType.IsErrorType() || patternType.IsErrorType())
{
return false;
}
else if (inputType.IsPointerOrFunctionPointer() || patternType.IsPointerOrFunctionPointer())
{
// pattern-matching is not permitted for pointer types
diagnostics.Add(ErrorCode.ERR_PointerTypeInPatternMatching, typeSyntax.Location);
return true;
}
else if (patternType.IsNullableType())
{
// It is an error to use pattern-matching with a nullable type, because you'll never get null. Use the underlying type.
Error(diagnostics, ErrorCode.ERR_PatternNullableType, typeSyntax, patternType.GetNullableUnderlyingType());
return true;
}
else if (typeSyntax is NullableTypeSyntax)
{
Error(diagnostics, ErrorCode.ERR_PatternNullableType, typeSyntax, patternType);
return true;
}
else if (patternType.IsStatic)
{
Error(diagnostics, ErrorCode.ERR_VarDeclIsStaticClass, typeSyntax, patternType);
return true;
}
else
{
if (patternType.IsDynamic())
{
Error(diagnostics, ErrorCode.ERR_PatternDynamicType, typeSyntax);
return true;
}
CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = GetNewCompoundUseSiteInfo(diagnostics);
ConstantValue matchPossible = ExpressionOfTypeMatchesPatternType(
Conversions, inputType, patternType, ref useSiteInfo, out Conversion conversion, operandConstantValue: null, operandCouldBeNull: true);
diagnostics.Add(typeSyntax, useSiteInfo);
if (matchPossible != ConstantValue.False && matchPossible != ConstantValue.Bad)
{
if (!conversion.Exists && (inputType.ContainsTypeParameter() || patternType.ContainsTypeParameter()))
{
// permit pattern-matching when one of the types is an open type in C# 7.1.
LanguageVersion requiredVersion = MessageID.IDS_FeatureGenericPatternMatching.RequiredVersion();
if (requiredVersion > Compilation.LanguageVersion)
{
Error(diagnostics, ErrorCode.ERR_PatternWrongGenericTypeInVersion, typeSyntax,
inputType, patternType,
Compilation.LanguageVersion.ToDisplayString(),
new CSharpRequiredLanguageVersion(requiredVersion));
return true;
}
}
}
else
{
Error(diagnostics, ErrorCode.ERR_PatternWrongType, typeSyntax, inputType, patternType);
return true;
}
}
return false;
}
/// <summary>
/// Does an expression of type <paramref name="expressionType"/> "match" a pattern that looks for
/// type <paramref name="patternType"/>?
/// - <see cref="ConstantValue.True"/> if the matched type catches all of them
/// - <see cref="ConstantValue.False"/> if it catches none of them
/// - <see cref="ConstantValue.Bad"/> - compiler doesn't support the type check, i.e. cannot perform it, even at runtime
/// - 'null' if it might catch some of them.
/// </summary>
internal static ConstantValue ExpressionOfTypeMatchesPatternType(
Conversions conversions,
TypeSymbol expressionType,
TypeSymbol patternType,
ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo,
out Conversion conversion,
ConstantValue? operandConstantValue = null,
bool operandCouldBeNull = false)
{
RoslynDebug.Assert((object)expressionType != null);
// Short-circuit a common case. This also improves recovery for some error
// cases, e.g. when the type is void.
if (expressionType.Equals(patternType, TypeCompareKind.AllIgnoreOptions))
{
conversion = Conversion.Identity;
return ConstantValue.True;
}
if (expressionType.IsDynamic())
{
// if operand is the dynamic type, we do the same thing as though it were object
expressionType = conversions.CorLibrary.GetSpecialType(SpecialType.System_Object);
}
conversion = conversions.ClassifyBuiltInConversion(expressionType, patternType, isChecked: false, ref useSiteInfo);
ConstantValue result = Binder.GetIsOperatorConstantResult(expressionType, patternType, conversion.Kind, operandConstantValue, operandCouldBeNull);
// Don't need to worry about checked user-defined operators
Debug.Assert(!conversion.IsUserDefined || result == ConstantValue.False || result == ConstantValue.Bad);
return result;
}
private BoundPattern BindDeclarationPattern(
DeclarationPatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
TypeSyntax typeSyntax = node.Type;
BoundTypeExpression boundDeclType = BindTypeForPattern(typeSyntax, inputType, diagnostics, ref hasErrors);
BindPatternDesignation(
designation: node.Designation, declType: boundDeclType.TypeWithAnnotations, permitDesignations, typeSyntax, diagnostics,
hasErrors: ref hasErrors, variableSymbol: out Symbol? variableSymbol, variableAccess: out BoundExpression? variableAccess);
return new BoundDeclarationPattern(node, boundDeclType, isVar: false, variableSymbol, variableAccess, inputType: inputType, narrowedType: boundDeclType.Type, hasErrors);
}
private BoundTypeExpression BindTypeForPattern(
TypeSyntax typeSyntax,
TypeSymbol inputType,
BindingDiagnosticBag diagnostics,
ref bool hasErrors)
{
RoslynDebug.Assert(inputType is { });
TypeWithAnnotations declType = BindType(typeSyntax, diagnostics, out AliasSymbol aliasOpt);
Debug.Assert(declType.HasType);
BoundTypeExpression boundDeclType = new BoundTypeExpression(typeSyntax, aliasOpt, typeWithAnnotations: declType);
hasErrors |= CheckValidPatternType(typeSyntax, inputType, declType.Type, diagnostics: diagnostics);
return boundDeclType;
}
private void BindPatternDesignation(
VariableDesignationSyntax? designation,
TypeWithAnnotations declType,
bool permitDesignations,
TypeSyntax? typeSyntax,
BindingDiagnosticBag diagnostics,
ref bool hasErrors,
out Symbol? variableSymbol,
out BoundExpression? variableAccess)
{
switch (designation)
{
case SingleVariableDesignationSyntax singleVariableDesignation:
SyntaxToken identifier = singleVariableDesignation.Identifier;
SourceLocalSymbol localSymbol = this.LookupLocal(identifier);
if (!permitDesignations && !identifier.IsMissing)
diagnostics.Add(ErrorCode.ERR_DesignatorBeneathPatternCombinator, identifier.GetLocation());
if (localSymbol is { })
{
RoslynDebug.Assert(ContainingMemberOrLambda is { });
if ((InConstructorInitializer || InFieldInitializer) && ContainingMemberOrLambda.ContainingSymbol.Kind == SymbolKind.NamedType)
CheckFeatureAvailability(designation, MessageID.IDS_FeatureExpressionVariablesInQueriesAndInitializers, diagnostics);
localSymbol.SetTypeWithAnnotations(declType);
// Check for variable declaration errors.
hasErrors |= localSymbol.ScopeBinder.ValidateDeclarationNameConflictsInScope(localSymbol, diagnostics);
if (!hasErrors)
CheckRestrictedTypeInAsyncMethod(this.ContainingMemberOrLambda, declType.Type, diagnostics, typeSyntax ?? (SyntaxNode)designation);
variableSymbol = localSymbol;
variableAccess = new BoundLocal(
syntax: designation, localSymbol: localSymbol, localSymbol.IsVar ? BoundLocalDeclarationKind.WithInferredType : BoundLocalDeclarationKind.WithExplicitType, constantValueOpt: null, isNullableUnknown: false, type: declType.Type);
return;
}
else
{
// We should have the right binder in the chain for a script or interactive, so we use the field for the pattern.
Debug.Assert(designation.SyntaxTree.Options.Kind != SourceCodeKind.Regular);
GlobalExpressionVariable expressionVariableField = LookupDeclaredField(singleVariableDesignation);
expressionVariableField.SetTypeWithAnnotations(declType, BindingDiagnosticBag.Discarded);
BoundExpression receiver = SynthesizeReceiver(designation, expressionVariableField, diagnostics);
variableSymbol = expressionVariableField;
variableAccess = new BoundFieldAccess(
syntax: designation, receiver: receiver, fieldSymbol: expressionVariableField, constantValueOpt: null, hasErrors: hasErrors);
return;
}
case DiscardDesignationSyntax _:
case null:
variableSymbol = null;
variableAccess = null;
return;
default:
throw ExceptionUtilities.UnexpectedValue(designation.Kind());
}
}
private TypeWithAnnotations BindRecursivePatternType(
TypeSyntax? typeSyntax,
TypeSymbol inputType,
BindingDiagnosticBag diagnostics,
ref bool hasErrors,
out BoundTypeExpression? boundDeclType)
{
if (typeSyntax != null)
{
boundDeclType = BindTypeForPattern(typeSyntax, inputType, diagnostics, ref hasErrors);
return boundDeclType.TypeWithAnnotations;
}
else
{
boundDeclType = null;
// remove the nullable part of the input's type; e.g. a nullable int becomes an int in a recursive pattern
return TypeWithAnnotations.Create(inputType.StrippedType(), NullableAnnotation.NotAnnotated);
}
}
// Work around https://github.com/dotnet/roslyn/issues/20648: The compiler's internal APIs such as `declType.IsTupleType`
// do not correctly treat the non-generic struct `System.ValueTuple` as a tuple type. We explicitly perform the tests
// required to identify it. When that bug is fixed we should be able to remove this code and its callers.
internal static bool IsZeroElementTupleType(TypeSymbol type)
{
return type.IsStructType() && type.Name == "ValueTuple" && type.GetArity() == 0 &&
type.ContainingSymbol is var declContainer && declContainer.Kind == SymbolKind.Namespace && declContainer.Name == "System" &&
(declContainer.ContainingSymbol as NamespaceSymbol)?.IsGlobalNamespace == true;
}
private BoundPattern BindRecursivePattern(
RecursivePatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
MessageID.IDS_FeatureRecursivePatterns.CheckFeatureAvailability(diagnostics, node);
if (inputType.IsPointerOrFunctionPointer())
{
diagnostics.Add(ErrorCode.ERR_PointerTypeInPatternMatching, node.Location);
hasErrors = true;
inputType = CreateErrorType();
}
TypeSyntax? typeSyntax = node.Type;
TypeWithAnnotations declTypeWithAnnotations = BindRecursivePatternType(typeSyntax, inputType, diagnostics, ref hasErrors, out BoundTypeExpression? boundDeclType);
TypeSymbol declType = declTypeWithAnnotations.Type;
MethodSymbol? deconstructMethod = null;
ImmutableArray<BoundPositionalSubpattern> deconstructionSubpatterns = default;
if (node.PositionalPatternClause != null)
{
PositionalPatternClauseSyntax positionalClause = node.PositionalPatternClause;
var patternsBuilder = ArrayBuilder<BoundPositionalSubpattern>.GetInstance(positionalClause.Subpatterns.Count);
if (IsZeroElementTupleType(declType))
{
// Work around https://github.com/dotnet/roslyn/issues/20648: The compiler's internal APIs such as `declType.IsTupleType`
// do not correctly treat the non-generic struct `System.ValueTuple` as a tuple type. We explicitly perform the tests
// required to identify it. When that bug is fixed we should be able to remove this if statement.
BindValueTupleSubpatterns(
positionalClause, declType, ImmutableArray<TypeWithAnnotations>.Empty, permitDesignations, ref hasErrors, patternsBuilder, diagnostics);
}
else if (declType.IsTupleType)
{
// It is a tuple type. Work according to its elements
BindValueTupleSubpatterns(positionalClause, declType, declType.TupleElementTypesWithAnnotations, permitDesignations, ref hasErrors, patternsBuilder, diagnostics);
}
else
{
// It is not a tuple type. Seek an appropriate Deconstruct method.
var inputPlaceholder = new BoundImplicitReceiver(positionalClause, declType); // A fake receiver expression to permit us to reuse binding logic
var deconstructDiagnostics = BindingDiagnosticBag.GetInstance(diagnostics);
BoundExpression deconstruct = MakeDeconstructInvocationExpression(
positionalClause.Subpatterns.Count, inputPlaceholder, positionalClause,
deconstructDiagnostics, outPlaceholders: out ImmutableArray<BoundDeconstructValuePlaceholder> outPlaceholders,
out bool anyDeconstructCandidates);
if (!anyDeconstructCandidates &&
ShouldUseITupleForRecursivePattern(node, declType, diagnostics, out var iTupleType, out var iTupleGetLength, out var iTupleGetItem))
{
// There was no Deconstruct, but the constraints for the use of ITuple are satisfied.
// Use that and forget any errors from trying to bind Deconstruct.
deconstructDiagnostics.Free();
BindITupleSubpatterns(positionalClause, patternsBuilder, permitDesignations, diagnostics);
deconstructionSubpatterns = patternsBuilder.ToImmutableAndFree();
return new BoundITuplePattern(node, iTupleGetLength, iTupleGetItem, deconstructionSubpatterns, inputType, iTupleType, hasErrors);
}
else
{
diagnostics.AddRangeAndFree(deconstructDiagnostics);
}
deconstructMethod = BindDeconstructSubpatterns(
positionalClause, permitDesignations, deconstruct, outPlaceholders, patternsBuilder, ref hasErrors, diagnostics);
}
deconstructionSubpatterns = patternsBuilder.ToImmutableAndFree();
}
ImmutableArray<BoundPropertySubpattern> properties = default;
if (node.PropertyPatternClause != null)
{
properties = BindPropertyPatternClause(node.PropertyPatternClause, declType, permitDesignations, diagnostics, ref hasErrors);
}
BindPatternDesignation(
node.Designation, declTypeWithAnnotations, permitDesignations, typeSyntax, diagnostics,
ref hasErrors, out Symbol? variableSymbol, out BoundExpression? variableAccess);
bool isExplicitNotNullTest =
node.Designation is null &&
boundDeclType is null &&
properties.IsDefaultOrEmpty &&
deconstructMethod is null &&
deconstructionSubpatterns.IsDefault;
return new BoundRecursivePattern(
syntax: node, declaredType: boundDeclType, deconstructMethod: deconstructMethod,
deconstruction: deconstructionSubpatterns, properties: properties, isExplicitNotNullTest: isExplicitNotNullTest,
variable: variableSymbol, variableAccess: variableAccess, inputType: inputType,
narrowedType: boundDeclType?.Type ?? inputType.StrippedType(), hasErrors);
}
private MethodSymbol? BindDeconstructSubpatterns(
PositionalPatternClauseSyntax node,
bool permitDesignations,
BoundExpression deconstruct,
ImmutableArray<BoundDeconstructValuePlaceholder> outPlaceholders,
ArrayBuilder<BoundPositionalSubpattern> patterns,
ref bool hasErrors,
BindingDiagnosticBag diagnostics)
{
var deconstructMethod = deconstruct.ExpressionSymbol as MethodSymbol;
if (deconstructMethod is null)
hasErrors = true;
int skippedExtensionParameters = deconstructMethod?.IsExtensionMethod == true ? 1 : 0;
for (int i = 0; i < node.Subpatterns.Count; i++)
{
var subPattern = node.Subpatterns[i];
bool isError = hasErrors || outPlaceholders.IsDefaultOrEmpty || i >= outPlaceholders.Length;
TypeSymbol elementType = isError ? CreateErrorType() : outPlaceholders[i].Type;
ParameterSymbol? parameter = null;
if (!isError)
{
int parameterIndex = i + skippedExtensionParameters;
if (parameterIndex < deconstructMethod!.ParameterCount)
{
parameter = deconstructMethod.Parameters[parameterIndex];
}
if (subPattern.NameColon != null)
{
// Check that the given name is the same as the corresponding parameter of the method.
if (parameter is { })
{
string name = subPattern.NameColon.Name.Identifier.ValueText;
string parameterName = parameter.Name;
if (name != parameterName)
{
diagnostics.Add(ErrorCode.ERR_DeconstructParameterNameMismatch, subPattern.NameColon.Name.Location, name, parameterName);
}
}
}
else if (subPattern.ExpressionColon != null)
{
MessageID.IDS_FeatureExtendedPropertyPatterns.CheckFeatureAvailability(diagnostics, subPattern.ExpressionColon.ColonToken);
diagnostics.Add(ErrorCode.ERR_IdentifierExpected, subPattern.ExpressionColon.Expression.Location);
}
}
var boundSubpattern = new BoundPositionalSubpattern(
subPattern,
parameter,
BindPattern(subPattern.Pattern, elementType, permitDesignations, isError, diagnostics)
);
patterns.Add(boundSubpattern);
}
return deconstructMethod;
}
private void BindITupleSubpatterns(
PositionalPatternClauseSyntax node,
ArrayBuilder<BoundPositionalSubpattern> patterns,
bool permitDesignations,
BindingDiagnosticBag diagnostics)
{
var objectType = Compilation.GetSpecialType(SpecialType.System_Object);
foreach (var subpatternSyntax in node.Subpatterns)
{
if (subpatternSyntax.NameColon != null)
{
// error: name not permitted in ITuple deconstruction
diagnostics.Add(ErrorCode.ERR_ArgumentNameInITuplePattern, subpatternSyntax.NameColon.Location);
}
else if (subpatternSyntax.ExpressionColon != null)
{
diagnostics.Add(ErrorCode.ERR_IdentifierExpected, subpatternSyntax.ExpressionColon.Expression.Location);
}
var boundSubpattern = new BoundPositionalSubpattern(
subpatternSyntax,
null,
BindPattern(subpatternSyntax.Pattern, objectType, permitDesignations, hasErrors: false, diagnostics));
patterns.Add(boundSubpattern);
}
}
private void BindITupleSubpatterns(
ParenthesizedVariableDesignationSyntax node,
ArrayBuilder<BoundPositionalSubpattern> patterns,
bool permitDesignations,
BindingDiagnosticBag diagnostics)
{
var objectType = Compilation.GetSpecialType(SpecialType.System_Object);
foreach (var variable in node.Variables)
{
BoundPattern pattern = BindVarDesignation(variable, objectType, permitDesignations, hasErrors: false, diagnostics);
var boundSubpattern = new BoundPositionalSubpattern(
variable,
null,
pattern);
patterns.Add(boundSubpattern);
}
}
private void BindValueTupleSubpatterns(
PositionalPatternClauseSyntax node,
TypeSymbol declType,
ImmutableArray<TypeWithAnnotations> elementTypesWithAnnotations,
bool permitDesignations,
ref bool hasErrors,
ArrayBuilder<BoundPositionalSubpattern> patterns,
BindingDiagnosticBag diagnostics)
{
if (elementTypesWithAnnotations.Length != node.Subpatterns.Count && !hasErrors)
{
diagnostics.Add(ErrorCode.ERR_WrongNumberOfSubpatterns, node.Location, declType, elementTypesWithAnnotations.Length, node.Subpatterns.Count);
hasErrors = true;
}
for (int i = 0; i < node.Subpatterns.Count; i++)
{
var subpatternSyntax = node.Subpatterns[i];
bool isError = i >= elementTypesWithAnnotations.Length;
TypeSymbol elementType = isError ? CreateErrorType() : elementTypesWithAnnotations[i].Type;
FieldSymbol? foundField = null;
if (!isError)
{
if (subpatternSyntax.NameColon != null)
{
string name = subpatternSyntax.NameColon.Name.Identifier.ValueText;
foundField = CheckIsTupleElement(subpatternSyntax.NameColon.Name, (NamedTypeSymbol)declType, name, i, diagnostics);
}
else if (subpatternSyntax.ExpressionColon != null)
{
diagnostics.Add(ErrorCode.ERR_IdentifierExpected, subpatternSyntax.ExpressionColon.Expression.Location);
}
}
BoundPositionalSubpattern boundSubpattern = new BoundPositionalSubpattern(
subpatternSyntax,
foundField,
BindPattern(subpatternSyntax.Pattern, elementType, permitDesignations, isError, diagnostics));
patterns.Add(boundSubpattern);
}
}
private bool ShouldUseITupleForRecursivePattern(
RecursivePatternSyntax node,
TypeSymbol declType,
BindingDiagnosticBag diagnostics,
[NotNullWhen(true)] out NamedTypeSymbol? iTupleType,
[NotNullWhen(true)] out MethodSymbol? iTupleGetLength,
[NotNullWhen(true)] out MethodSymbol? iTupleGetItem)
{
iTupleType = null;
iTupleGetLength = iTupleGetItem = null;
if (node.Type != null)
{
// ITuple matching only applies if no type is given explicitly.
return false;
}
if (node.PropertyPatternClause != null)
{
// ITuple matching only applies if there is no property pattern part.
return false;
}
if (node.PositionalPatternClause == null)
{
// ITuple matching only applies if there is a positional pattern part.
// This can only occur as a result of syntax error recovery, if at all.
return false;
}
if (node.Designation?.Kind() == SyntaxKind.SingleVariableDesignation)
{
// ITuple matching only applies if there is no variable declared (what type would the variable be?)
return false;
}
return ShouldUseITuple(node, declType, diagnostics, out iTupleType, out iTupleGetLength, out iTupleGetItem);
}
private bool ShouldUseITuple(
SyntaxNode node,
TypeSymbol declType,
BindingDiagnosticBag diagnostics,
[NotNullWhen(true)] out NamedTypeSymbol? iTupleType,
[NotNullWhen(true)] out MethodSymbol? iTupleGetLength,
[NotNullWhen(true)] out MethodSymbol? iTupleGetItem)
{
iTupleType = null;
iTupleGetLength = iTupleGetItem = null;
Debug.Assert(!declType.IsTupleType);
Debug.Assert(!IsZeroElementTupleType(declType));
if (Compilation.LanguageVersion < MessageID.IDS_FeatureRecursivePatterns.RequiredVersion())
{
return false;
}
iTupleType = Compilation.GetWellKnownType(WellKnownType.System_Runtime_CompilerServices_ITuple);
if (iTupleType.TypeKind != TypeKind.Interface)
{
// When compiling to a platform that lacks the interface ITuple (i.e. it is an error type), we simply do not match using it.
return false;
}
// Resolution 2017-11-20 LDM: permit matching via ITuple only for `object`, `ITuple`, and types that are
// declared to implement `ITuple`.
if (declType != (object)Compilation.GetSpecialType(SpecialType.System_Object) &&
declType != (object)Compilation.DynamicType &&
declType != (object)iTupleType &&
!hasBaseInterface(declType, iTupleType))
{
return false;
}
// Ensure ITuple has a Length and indexer
iTupleGetLength = (MethodSymbol?)Compilation.GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_ITuple__get_Length);
iTupleGetItem = (MethodSymbol?)Compilation.GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_ITuple__get_Item);
if (iTupleGetLength is null || iTupleGetItem is null)
{
// This might not result in an ideal diagnostic
return false;
}
// passed all the filters; permit using ITuple
_ = diagnostics.ReportUseSite(iTupleType, node) ||
diagnostics.ReportUseSite(iTupleGetLength, node) ||
diagnostics.ReportUseSite(iTupleGetItem, node);
return true;
bool hasBaseInterface(TypeSymbol type, NamedTypeSymbol possibleBaseInterface)
{
CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = GetNewCompoundUseSiteInfo(diagnostics);
var result = Compilation.Conversions.ClassifyBuiltInConversion(type, possibleBaseInterface, isChecked: CheckOverflowAtRuntime, ref useSiteInfo).IsImplicit;
diagnostics.Add(node, useSiteInfo);
return result;
}
}
/// <summary>
/// Check that the given name designates a tuple element at the given index, and return that element.
/// </summary>
private static FieldSymbol? CheckIsTupleElement(SyntaxNode node, NamedTypeSymbol tupleType, string name, int tupleIndex, BindingDiagnosticBag diagnostics)
{
FieldSymbol? foundElement = null;
foreach (var symbol in tupleType.GetMembers(name))
{
if (symbol is FieldSymbol field && field.IsTupleElement())
{
foundElement = field;
break;
}
}
if (foundElement is null || foundElement.TupleElementIndex != tupleIndex)
{
diagnostics.Add(ErrorCode.ERR_TupleElementNameMismatch, node.Location, name, $"Item{tupleIndex + 1}");
}
return foundElement;
}
private BoundPattern BindVarPattern(
VarPatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
if ((inputType.IsPointerOrFunctionPointer() && node.Designation.Kind() == SyntaxKind.ParenthesizedVariableDesignation)
|| (inputType.IsPointerType() && Compilation.LanguageVersion < MessageID.IDS_FeatureRecursivePatterns.RequiredVersion()))
{
diagnostics.Add(ErrorCode.ERR_PointerTypeInPatternMatching, node.Location);
hasErrors = true;
inputType = CreateErrorType();
}
Symbol foundSymbol = BindTypeOrAliasOrKeyword(node.VarKeyword, node, diagnostics, out bool isVar).Symbol;
if (!isVar)
{
// Give an error if there is a bindable type "var" in scope
diagnostics.Add(ErrorCode.ERR_VarMayNotBindToType, node.VarKeyword.GetLocation(), foundSymbol.ToDisplayString());
hasErrors = true;
}
return BindVarDesignation(node.Designation, inputType, permitDesignations, hasErrors, diagnostics);
}
private BoundPattern BindVarDesignation(
VariableDesignationSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
switch (node.Kind())
{
case SyntaxKind.DiscardDesignation:
{
return new BoundDiscardPattern(node, inputType: inputType, narrowedType: inputType);
}
case SyntaxKind.SingleVariableDesignation:
{
var declType = TypeWithState.ForType(inputType).ToTypeWithAnnotations(Compilation);
BindPatternDesignation(
designation: node, declType: declType, permitDesignations: permitDesignations,
typeSyntax: null, diagnostics: diagnostics, hasErrors: ref hasErrors,
variableSymbol: out Symbol? variableSymbol, variableAccess: out BoundExpression? variableAccess);
var boundOperandType = new BoundTypeExpression(syntax: node, aliasOpt: null, typeWithAnnotations: declType); // fake a type expression for the variable's type
// We continue to use a BoundDeclarationPattern for the var pattern, as they have more in common.
Debug.Assert(node.Parent is { });
return new BoundDeclarationPattern(
node.Parent.Kind() == SyntaxKind.VarPattern ? node.Parent : node, // for `var x` use whole pattern, otherwise use designation for the syntax
boundOperandType, isVar: true, variableSymbol, variableAccess,
inputType: inputType, narrowedType: inputType, hasErrors);
}
case SyntaxKind.ParenthesizedVariableDesignation:
{
MessageID.IDS_FeatureRecursivePatterns.CheckFeatureAvailability(diagnostics, node);
var tupleDesignation = (ParenthesizedVariableDesignationSyntax)node;
var subPatterns = ArrayBuilder<BoundPositionalSubpattern>.GetInstance(tupleDesignation.Variables.Count);
MethodSymbol? deconstructMethod = null;
var strippedInputType = inputType.StrippedType();
if (IsZeroElementTupleType(strippedInputType))
{
// Work around https://github.com/dotnet/roslyn/issues/20648: The compiler's internal APIs such as `declType.IsTupleType`
// do not correctly treat the non-generic struct `System.ValueTuple` as a tuple type. We explicitly perform the tests
// required to identify it. When that bug is fixed we should be able to remove this if statement.
addSubpatternsForTuple(ImmutableArray<TypeWithAnnotations>.Empty);
}
else if (strippedInputType.IsTupleType)
{
// It is a tuple type. Work according to its elements
addSubpatternsForTuple(strippedInputType.TupleElementTypesWithAnnotations);
}
else
{
// It is not a tuple type. Seek an appropriate Deconstruct method.
var inputPlaceholder = new BoundImplicitReceiver(node, strippedInputType); // A fake receiver expression to permit us to reuse binding logic
var deconstructDiagnostics = BindingDiagnosticBag.GetInstance(diagnostics);
BoundExpression deconstruct = MakeDeconstructInvocationExpression(
tupleDesignation.Variables.Count, inputPlaceholder, node, deconstructDiagnostics,
outPlaceholders: out ImmutableArray<BoundDeconstructValuePlaceholder> outPlaceholders,
out bool anyDeconstructCandidates);
if (!anyDeconstructCandidates &&
ShouldUseITuple(node, strippedInputType, diagnostics, out var iTupleType, out var iTupleGetLength, out var iTupleGetItem))
{
// There was no applicable candidate Deconstruct, and the constraints for the use of ITuple are satisfied.
// Use that and forget any errors from trying to bind Deconstruct.
deconstructDiagnostics.Free();
BindITupleSubpatterns(tupleDesignation, subPatterns, permitDesignations, diagnostics);
return new BoundITuplePattern(node, iTupleGetLength, iTupleGetItem, subPatterns.ToImmutableAndFree(), strippedInputType, iTupleType, hasErrors);
}
else
{
diagnostics.AddRangeAndFree(deconstructDiagnostics);
}
deconstructMethod = deconstruct.ExpressionSymbol as MethodSymbol;
if (!hasErrors)
hasErrors = outPlaceholders.IsDefault || tupleDesignation.Variables.Count != outPlaceholders.Length;
for (int i = 0; i < tupleDesignation.Variables.Count; i++)
{
var variable = tupleDesignation.Variables[i];
bool isError = outPlaceholders.IsDefaultOrEmpty || i >= outPlaceholders.Length;
TypeSymbol elementType = isError ? CreateErrorType() : outPlaceholders[i].Type;
BoundPattern pattern = BindVarDesignation(variable, elementType, permitDesignations, isError, diagnostics);
subPatterns.Add(new BoundPositionalSubpattern(variable, symbol: null, pattern));
}
}
return new BoundRecursivePattern(
syntax: node, declaredType: null, deconstructMethod: deconstructMethod,
deconstruction: subPatterns.ToImmutableAndFree(), properties: default, variable: null, variableAccess: null,
isExplicitNotNullTest: false, inputType: inputType, narrowedType: inputType.StrippedType(), hasErrors: hasErrors);
void addSubpatternsForTuple(ImmutableArray<TypeWithAnnotations> elementTypes)
{
if (elementTypes.Length != tupleDesignation.Variables.Count && !hasErrors)
{
diagnostics.Add(ErrorCode.ERR_WrongNumberOfSubpatterns, tupleDesignation.Location,
strippedInputType, elementTypes.Length, tupleDesignation.Variables.Count);
hasErrors = true;
}
for (int i = 0; i < tupleDesignation.Variables.Count; i++)
{
var variable = tupleDesignation.Variables[i];
bool isError = i >= elementTypes.Length;
TypeSymbol elementType = isError ? CreateErrorType() : elementTypes[i].Type;
BoundPattern pattern = BindVarDesignation(variable, elementType, permitDesignations, isError, diagnostics);
subPatterns.Add(new BoundPositionalSubpattern(variable, symbol: null, pattern));
}
}
}
default:
{
throw ExceptionUtilities.UnexpectedValue(node.Kind());
}
}
}
private ImmutableArray<BoundPropertySubpattern> BindPropertyPatternClause(
PropertyPatternClauseSyntax node,
TypeSymbol inputType,
bool permitDesignations,
BindingDiagnosticBag diagnostics,
ref bool hasErrors)
{
var builder = ArrayBuilder<BoundPropertySubpattern>.GetInstance(node.Subpatterns.Count);
foreach (SubpatternSyntax p in node.Subpatterns)
{
if (p.ExpressionColon is ExpressionColonSyntax)
MessageID.IDS_FeatureExtendedPropertyPatterns.CheckFeatureAvailability(diagnostics, p.ExpressionColon.ColonToken);
ExpressionSyntax? expr = p.ExpressionColon?.Expression;
PatternSyntax pattern = p.Pattern;
BoundPropertySubpatternMember? member;
TypeSymbol memberType;
bool isLengthOrCount = false;
if (expr == null)
{
if (!hasErrors)
diagnostics.Add(ErrorCode.ERR_PropertyPatternNameMissing, pattern.Location, pattern);
memberType = CreateErrorType();
member = null;
hasErrors = true;
}
else
{
member = LookupMembersForPropertyPattern(inputType, expr, diagnostics, ref hasErrors);
memberType = member.Type;
// If we're dealing with the member that makes the type countable, and the type is also indexable, then it will be assumed to always return a non-negative value
if (memberType.SpecialType == SpecialType.System_Int32 &&
member.Symbol is { Name: WellKnownMemberNames.LengthPropertyName or WellKnownMemberNames.CountPropertyName, Kind: SymbolKind.Property } memberSymbol)
{
TypeSymbol receiverType = member.Receiver?.Type ?? inputType;
if (!receiverType.IsErrorType())
{
isLengthOrCount = IsCountableAndIndexable(node, receiverType, out PropertySymbol? lengthProperty) &&
memberSymbol.Equals(lengthProperty, TypeCompareKind.ConsiderEverything); // If Length and Count are both present, only the former is assumed to be non-negative.
}
}
}
BoundPattern boundPattern = BindPattern(pattern, memberType, permitDesignations, hasErrors, diagnostics);
builder.Add(new BoundPropertySubpattern(p, member, isLengthOrCount, boundPattern));
}
return builder.ToImmutableAndFree();
}
private BoundPropertySubpatternMember LookupMembersForPropertyPattern(
TypeSymbol inputType, ExpressionSyntax expr, BindingDiagnosticBag diagnostics, ref bool hasErrors)
{
BoundPropertySubpatternMember? receiver = null;
Symbol? symbol = null;
switch (expr)
{
case IdentifierNameSyntax name:
symbol = BindPropertyPatternMember(inputType, name, ref hasErrors, diagnostics);
break;
case MemberAccessExpressionSyntax { Name: IdentifierNameSyntax name } memberAccess when memberAccess.IsKind(SyntaxKind.SimpleMemberAccessExpression):
receiver = LookupMembersForPropertyPattern(inputType, memberAccess.Expression, diagnostics, ref hasErrors);
symbol = BindPropertyPatternMember(receiver.Type.StrippedType(), name, ref hasErrors, diagnostics);
break;
default:
Error(diagnostics, ErrorCode.ERR_InvalidNameInSubpattern, expr);
hasErrors = true;
break;
}
TypeSymbol memberType = symbol switch
{
FieldSymbol field => field.Type,
PropertySymbol property => property.Type,
_ => CreateErrorType()
};
return new BoundPropertySubpatternMember(expr, receiver, symbol, type: memberType, hasErrors);
}
private Symbol? BindPropertyPatternMember(
TypeSymbol inputType,
IdentifierNameSyntax memberName,
ref bool hasErrors,
BindingDiagnosticBag diagnostics)
{
// TODO: consider refactoring out common code with BindObjectInitializerMember
BoundImplicitReceiver implicitReceiver = new BoundImplicitReceiver(memberName, inputType);
string name = memberName.Identifier.ValueText;
BoundExpression boundMember = BindInstanceMemberAccess(
node: memberName,
right: memberName,
boundLeft: implicitReceiver,
rightName: name,
rightArity: 0,
typeArgumentsSyntax: default(SeparatedSyntaxList<TypeSyntax>),
typeArgumentsWithAnnotations: default(ImmutableArray<TypeWithAnnotations>),
invoked: false,
indexed: false,
diagnostics: diagnostics);
if (boundMember.Kind == BoundKind.PropertyGroup)
{
boundMember = BindIndexedPropertyAccess(
(BoundPropertyGroup)boundMember, mustHaveAllOptionalParameters: true, diagnostics: diagnostics);
}
hasErrors |= boundMember.HasAnyErrors || implicitReceiver.HasAnyErrors;
switch (boundMember.Kind)
{
case BoundKind.FieldAccess:
case BoundKind.PropertyAccess:
break;
case BoundKind.IndexerAccess:
case BoundKind.DynamicIndexerAccess:
case BoundKind.EventAccess:
default:
if (!hasErrors)
{
switch (boundMember.ResultKind)
{
case LookupResultKind.Empty:
Error(diagnostics, ErrorCode.ERR_NoSuchMember, memberName, implicitReceiver.Type, name);
break;
case LookupResultKind.Inaccessible:
boundMember = CheckValue(boundMember, BindValueKind.RValue, diagnostics);
Debug.Assert(boundMember.HasAnyErrors);
break;
default:
Error(diagnostics, ErrorCode.ERR_PropertyLacksGet, memberName, name);
break;
}
hasErrors = true;
}
break;
}
if (!hasErrors && !CheckValueKind(node: memberName.Parent, expr: boundMember, valueKind: BindValueKind.RValue,
checkingReceiver: false, diagnostics: diagnostics))
{
hasErrors = true;
}
return boundMember.ExpressionSymbol;
}
private BoundPattern BindTypePattern(
TypePatternSyntax node,
TypeSymbol inputType,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
MessageID.IDS_FeatureTypePattern.CheckFeatureAvailability(diagnostics, node);
var patternType = BindTypeForPattern(node.Type, inputType, diagnostics, ref hasErrors);
bool isExplicitNotNullTest = patternType.Type.SpecialType == SpecialType.System_Object;
return new BoundTypePattern(node, patternType, isExplicitNotNullTest, inputType, patternType.Type, hasErrors);
}
private BoundPattern BindRelationalPattern(
RelationalPatternSyntax node,
TypeSymbol inputType,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
MessageID.IDS_FeatureRelationalPattern.CheckFeatureAvailability(diagnostics, node.OperatorToken);
BoundExpression value = BindExpressionForPattern(inputType, node.Expression, ref hasErrors, diagnostics, out var constantValueOpt, out _, out Conversion patternConversion);
ExpressionSyntax innerExpression = SkipParensAndNullSuppressions(node.Expression, diagnostics, ref hasErrors);
var type = value.Type ?? inputType;
Debug.Assert(type is { });
BinaryOperatorKind operation = tokenKindToBinaryOperatorKind(node.OperatorToken.Kind());
if (operation == BinaryOperatorKind.Equal)
{
diagnostics.Add(ErrorCode.ERR_InvalidExprTerm, node.OperatorToken.GetLocation(), node.OperatorToken.Text);
hasErrors = true;
}
BinaryOperatorKind opType = RelationalOperatorType(type.EnumUnderlyingTypeOrSelf());
switch (opType)
{
case BinaryOperatorKind.Float:
case BinaryOperatorKind.Double:
if (!hasErrors && constantValueOpt != null && !constantValueOpt.IsBad && double.IsNaN(constantValueOpt.DoubleValue))
{
diagnostics.Add(ErrorCode.ERR_RelationalPatternWithNaN, node.Expression.Location);
hasErrors = true;
}
break;
case BinaryOperatorKind.String:
case BinaryOperatorKind.Bool:
case BinaryOperatorKind.Error:
if (!hasErrors)
{
diagnostics.Add(ErrorCode.ERR_UnsupportedTypeForRelationalPattern, node.Location, type.ToDisplayString());
hasErrors = true;
}
break;
}
if (constantValueOpt is null)
{
hasErrors = true;
constantValueOpt = ConstantValue.Bad;
}
if (!hasErrors && ShouldBlockINumberBaseConversion(patternConversion, inputType))
{
// Cannot use a numeric constant or relational pattern on '{0}' because it inherits from or extends 'INumberBase<T>'. Consider using a type pattern to narrow to a specific numeric type.
diagnostics.Add(ErrorCode.ERR_CannotMatchOnINumberBase, node.Location, inputType);
hasErrors = true;
}
return new BoundRelationalPattern(node, operation | opType, value, constantValueOpt, inputType, type, hasErrors);
static BinaryOperatorKind tokenKindToBinaryOperatorKind(SyntaxKind kind) => kind switch
{
SyntaxKind.LessThanEqualsToken => BinaryOperatorKind.LessThanOrEqual,
SyntaxKind.LessThanToken => BinaryOperatorKind.LessThan,
SyntaxKind.GreaterThanToken => BinaryOperatorKind.GreaterThan,
SyntaxKind.GreaterThanEqualsToken => BinaryOperatorKind.GreaterThanOrEqual,
// The following occurs in error recovery scenarios
_ => BinaryOperatorKind.Equal,
};
}
/// <summary>
/// Compute the type code for the comparison operator to be used. When comparing `byte`s for example,
/// the compiler actually uses the operator on the type `int` as there is no corresponding operator for
/// the type `byte`.
/// </summary>
internal static BinaryOperatorKind RelationalOperatorType(TypeSymbol type) => type.SpecialType switch
{
SpecialType.System_Single => BinaryOperatorKind.Float,
SpecialType.System_Double => BinaryOperatorKind.Double,
SpecialType.System_Char => BinaryOperatorKind.Char,
SpecialType.System_SByte => BinaryOperatorKind.Int, // operands are converted to int
SpecialType.System_Byte => BinaryOperatorKind.Int, // operands are converted to int
SpecialType.System_UInt16 => BinaryOperatorKind.Int, // operands are converted to int
SpecialType.System_Int16 => BinaryOperatorKind.Int, // operands are converted to int
SpecialType.System_Int32 => BinaryOperatorKind.Int,
SpecialType.System_UInt32 => BinaryOperatorKind.UInt,
SpecialType.System_Int64 => BinaryOperatorKind.Long,
SpecialType.System_UInt64 => BinaryOperatorKind.ULong,
SpecialType.System_Decimal => BinaryOperatorKind.Decimal,
SpecialType.System_String => BinaryOperatorKind.String,
SpecialType.System_Boolean => BinaryOperatorKind.Bool,
SpecialType.System_IntPtr when type.IsNativeIntegerType => BinaryOperatorKind.NInt,
SpecialType.System_UIntPtr when type.IsNativeIntegerType => BinaryOperatorKind.NUInt,
_ => BinaryOperatorKind.Error,
};
private BoundPattern BindUnaryPattern(
UnaryPatternSyntax node,
TypeSymbol inputType,
bool hasErrors,
BindingDiagnosticBag diagnostics,
bool underIsPattern)
{
MessageID.IDS_FeatureNotPattern.CheckFeatureAvailability(diagnostics, node.OperatorToken);
bool permitDesignations = underIsPattern; // prevent designators under 'not' except under an is-pattern
var subPattern = BindPattern(node.Pattern, inputType, permitDesignations, hasErrors, diagnostics, underIsPattern);
return new BoundNegatedPattern(node, subPattern, inputType: inputType, narrowedType: inputType, hasErrors);
}
private BoundPattern BindBinaryPattern(
BinaryPatternSyntax node,
TypeSymbol inputType,
bool permitDesignations,
bool hasErrors,
BindingDiagnosticBag diagnostics)
{
bool isDisjunction = node.Kind() == SyntaxKind.OrPattern;
if (isDisjunction)
{
MessageID.IDS_FeatureOrPattern.CheckFeatureAvailability(diagnostics, node.OperatorToken);
permitDesignations = false; // prevent designators under 'or'
var left = BindPattern(node.Left, inputType, permitDesignations, hasErrors, diagnostics);
var right = BindPattern(node.Right, inputType, permitDesignations, hasErrors, diagnostics);
// Compute the common type. This algorithm is quadratic, but disjunctive patterns are unlikely to be huge
var narrowedTypeCandidates = ArrayBuilder<TypeSymbol>.GetInstance(2);
collectCandidates(left, narrowedTypeCandidates);
collectCandidates(right, narrowedTypeCandidates);
var narrowedType = leastSpecificType(node, narrowedTypeCandidates, diagnostics) ?? inputType;
narrowedTypeCandidates.Free();
return new BoundBinaryPattern(node, disjunction: isDisjunction, left, right, inputType: inputType, narrowedType: narrowedType, hasErrors);
static void collectCandidates(BoundPattern pat, ArrayBuilder<TypeSymbol> candidates)
{
if (pat is BoundBinaryPattern { Disjunction: true } p)
{
collectCandidates(p.Left, candidates);
collectCandidates(p.Right, candidates);
}
else
{
candidates.Add(pat.NarrowedType);
}
}
TypeSymbol? leastSpecificType(SyntaxNode node, ArrayBuilder<TypeSymbol> candidates, BindingDiagnosticBag diagnostics)
{
Debug.Assert(candidates.Count >= 2);
CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = GetNewCompoundUseSiteInfo(diagnostics);
TypeSymbol? bestSoFar = candidates[0];
// first pass: select a candidate for which no other has been shown to be an improvement.
for (int i = 1, n = candidates.Count; i < n; i++)
{
TypeSymbol candidate = candidates[i];
bestSoFar = lessSpecificCandidate(bestSoFar, candidate, ref useSiteInfo) ?? bestSoFar;
}
// second pass: check that it is no more specific than any candidate.
for (int i = 0, n = candidates.Count; i < n; i++)
{
TypeSymbol candidate = candidates[i];
TypeSymbol? spoiler = lessSpecificCandidate(candidate, bestSoFar, ref useSiteInfo);
if (spoiler is null)
{
bestSoFar = null;
break;
}
// Our specificity criteria are transitive
Debug.Assert(spoiler.Equals(bestSoFar, TypeCompareKind.ConsiderEverything));
}
diagnostics.Add(node, useSiteInfo);
return bestSoFar;
}
// Given a candidate least specific type so far, attempt to refine it with a possibly less specific candidate.
TypeSymbol? lessSpecificCandidate(TypeSymbol bestSoFar, TypeSymbol possiblyLessSpecificCandidate, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
if (bestSoFar.Equals(possiblyLessSpecificCandidate, TypeCompareKind.AllIgnoreOptions))
{
// When the types are equivalent, merge them.
return bestSoFar.MergeEquivalentTypes(possiblyLessSpecificCandidate, VarianceKind.Out);
}
else if (Conversions.HasImplicitReferenceConversion(bestSoFar, possiblyLessSpecificCandidate, ref useSiteInfo))
{
// When there is an implicit reference conversion from T to U, U is less specific
return possiblyLessSpecificCandidate;
}
else if (Conversions.HasBoxingConversion(bestSoFar, possiblyLessSpecificCandidate, ref useSiteInfo))
{
// when there is a boxing conversion from T to U, U is less specific.
return possiblyLessSpecificCandidate;
}
else
{
// We have no improved candidate to offer.
return null;
}
}
}
else
{
MessageID.IDS_FeatureAndPattern.CheckFeatureAvailability(diagnostics, node.OperatorToken);
var left = BindPattern(node.Left, inputType, permitDesignations, hasErrors, diagnostics);
var right = BindPattern(node.Right, left.NarrowedType, permitDesignations, hasErrors, diagnostics);
return new BoundBinaryPattern(node, disjunction: isDisjunction, left, right, inputType: inputType, narrowedType: right.NarrowedType, hasErrors);
}
}
}
}
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