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List patterns: binding and lowering #53299

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Jun 3, 2021
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List patterns: binding and lowering #53299

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190 changes: 108 additions & 82 deletions src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Reflection;
using System.Runtime.CompilerServices;
Expand Down Expand Up @@ -7843,12 +7844,13 @@ private BoundExpression BindIndexerOrIndexedPropertyAccess(
return propertyAccess;
}

#nullable enable
private bool TryBindIndexOrRangeIndexer(
SyntaxNode syntax,
BoundExpression receiverOpt,
BoundExpression? receiverOpt,
AnalyzedArguments arguments,
BindingDiagnosticBag diagnostics,
out BoundIndexOrRangePatternIndexerAccess patternIndexerAccess)
[NotNullWhen(true)] out BoundIndexOrRangePatternIndexerAccess? patternIndexerAccess)
{
patternIndexerAccess = null;

Expand All @@ -7864,19 +7866,55 @@ private bool TryBindIndexOrRangeIndexer(
var argument = arguments.Arguments[0];

var argType = argument.Type;
bool argIsIndex = TypeSymbol.Equals(argType,
Compilation.GetWellKnownType(WellKnownType.System_Index),
TypeCompareKind.ConsiderEverything);
bool argIsRange = !argIsIndex && TypeSymbol.Equals(argType,
Compilation.GetWellKnownType(WellKnownType.System_Range),
TypeCompareKind.ConsiderEverything);

if ((!argIsIndex && !argIsRange) ||
ThreeState argIsIndexNotRange =
TypeSymbol.Equals(argType, Compilation.GetWellKnownType(WellKnownType.System_Index), TypeCompareKind.ConsiderEverything) ? ThreeState.True :
TypeSymbol.Equals(argType, Compilation.GetWellKnownType(WellKnownType.System_Range), TypeCompareKind.ConsiderEverything) ? ThreeState.False :
ThreeState.Unknown;

if (!argIsIndexNotRange.HasValue() ||
!(receiverOpt?.Type is TypeSymbol receiverType))
{
return false;
}

bool argIsIndex = argIsIndexNotRange.Value();
var useSiteInfo = CompoundUseSiteInfo<AssemblySymbol>.Discarded;
if (!TryFindIndexOrRangeIndexerPattern(syntax, receiverOpt, receiverType, argIsIndex: argIsIndex,
out PropertySymbol? lengthOrCountProperty, out Symbol? patternSymbol, diagnostics, ref useSiteInfo))
{
return false;
}

patternIndexerAccess = new BoundIndexOrRangePatternIndexerAccess(
syntax,
receiverOpt,
lengthOrCountProperty,
patternSymbol,
BindToNaturalType(argument, diagnostics),
patternSymbol.GetTypeOrReturnType().Type);

_ = MessageID.IDS_FeatureIndexOperator.CheckFeatureAvailability(diagnostics, syntax);
if (arguments.Names.Count > 0)
{
diagnostics.Add(
argIsIndex
? ErrorCode.ERR_ImplicitIndexIndexerWithName
: ErrorCode.ERR_ImplicitRangeIndexerWithName,
arguments.Names[0].GetLocation());
}
return true;
}

private bool TryFindIndexOrRangeIndexerPattern(
SyntaxNode syntax,
BoundExpression? receiverOpt,
TypeSymbol receiverType,
bool argIsIndex,
[NotNullWhen(true)] out PropertySymbol? lengthOrCountProperty,
[NotNullWhen(true)] out Symbol? patternSymbol,
BindingDiagnosticBag diagnostics,
ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
// SPEC:

// An indexer invocation with a single argument of System.Index or System.Range will
Expand All @@ -7887,21 +7925,32 @@ private bool TryBindIndexOrRangeIndexer(
// 2. For Index: Has an accessible indexer with a single int parameter
// For Range: Has an accessible Slice method that takes two int parameters

PropertySymbol lengthOrCountProperty;

var lookupResult = LookupResult.GetInstance();
var discardedUseSiteInfo = CompoundUseSiteInfo<AssemblySymbol>.Discarded;

// Look for Length first

if (!tryLookupLengthOrCount(WellKnownMemberNames.LengthPropertyName, out lengthOrCountProperty) &&
!tryLookupLengthOrCount(WellKnownMemberNames.CountPropertyName, out lengthOrCountProperty))
if (TryLookupLengthOrCount(receiverType, lookupResult, out lengthOrCountProperty, ref useSiteInfo) &&
TryFindIndexOrRangeIndexerPattern(syntax, lookupResult, receiverOpt, receiverType, argIsIndex, out patternSymbol, diagnostics, ref useSiteInfo))
{
return false;
CheckImplicitThisCopyInReadOnlyMember(receiverOpt, lengthOrCountProperty.GetMethod, diagnostics);
lookupResult.Free();
return true;
}

Debug.Assert(lengthOrCountProperty is { });
patternSymbol = null;
lookupResult.Free();
return false;
}

private bool TryFindIndexOrRangeIndexerPattern(
SyntaxNode syntax,
LookupResult lookupResult,
BoundExpression? receiverOpt,
TypeSymbol receiverType,
bool argIsIndex,
[NotNullWhen(true)] out Symbol? patternSymbol,
BindingDiagnosticBag diagnostics,
ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo,
bool forPattern = false)
{
if (argIsIndex)
{
// Look for `T this[int i]` indexer
Expand All @@ -7915,53 +7964,44 @@ private bool TryBindIndexOrRangeIndexer(
LookupOptions.Default,
originalBinder: this,
diagnose: false,
ref discardedUseSiteInfo);
ref useSiteInfo);

if (lookupResult.IsMultiViable)
{
foreach (var candidate in lookupResult.Symbols)
{
if (!candidate.IsStatic &&
candidate is PropertySymbol property &&
IsAccessible(property, ref discardedUseSiteInfo) &&
IsAccessible(property, ref useSiteInfo) &&
property.OriginalDefinition is { ParameterCount: 1 } original &&
isIntNotByRef(original.Parameters[0]))
original.Parameters[0] is { Type: { SpecialType: SpecialType.System_Int32 }, RefKind: RefKind.None })
{
CheckImplicitThisCopyInReadOnlyMember(receiverOpt, lengthOrCountProperty.GetMethod, diagnostics);
// note: implicit copy check on the indexer accessor happens in CheckPropertyValueKind
patternIndexerAccess = new BoundIndexOrRangePatternIndexerAccess(
syntax,
receiverOpt,
lengthOrCountProperty,
property,
BindToNaturalType(argument, diagnostics),
property.Type);
break;
patternSymbol = property;
checkWellKnown(WellKnownMember.System_Index__GetOffset);
return true;
}
}
}
}
else if (receiverType.SpecialType == SpecialType.System_String)
{
Debug.Assert(argIsRange);
Debug.Assert(!argIsIndex);
// Look for Substring
var substring = (MethodSymbol)Compilation.GetSpecialTypeMember(SpecialMember.System_String__Substring);
// PROTOTYPE(list-patterns) Consider reporting a missing member for string.Substring
if (substring is object)
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{
patternIndexerAccess = new BoundIndexOrRangePatternIndexerAccess(
syntax,
receiverOpt,
lengthOrCountProperty,
substring,
BindToNaturalType(argument, diagnostics),
substring.ReturnType);
patternSymbol = substring;
checkWellKnown(WellKnownMember.System_Range__get_Start);
checkWellKnown(WellKnownMember.System_Range__get_End);
checkWellKnown(WellKnownMember.System_Index__GetOffset);
return true;
}
}
else
{
Debug.Assert(argIsRange);
Debug.Assert(!argIsIndex);
// Look for `T Slice(int, int)` indexer

LookupMembersInType(
Expand All @@ -7973,73 +8013,58 @@ candidate is PropertySymbol property &&
LookupOptions.Default,
originalBinder: this,
diagnose: false,
ref discardedUseSiteInfo);
ref useSiteInfo);

if (lookupResult.IsMultiViable)
{
foreach (var candidate in lookupResult.Symbols)
{
if (!candidate.IsStatic &&
IsAccessible(candidate, ref discardedUseSiteInfo) &&
IsAccessible(candidate, ref useSiteInfo) &&
candidate is MethodSymbol method &&
method.OriginalDefinition is var original &&
!original.ReturnsVoid &&
original.ParameterCount == 2 &&
isIntNotByRef(original.Parameters[0]) &&
isIntNotByRef(original.Parameters[1]))
original.Parameters[0] is { Type: { SpecialType: SpecialType.System_Int32 }, RefKind: RefKind.None } &&
original.Parameters[1] is { Type: { SpecialType: SpecialType.System_Int32 }, RefKind: RefKind.None })
{
CheckImplicitThisCopyInReadOnlyMember(receiverOpt, lengthOrCountProperty.GetMethod, diagnostics);
patternSymbol = method;
CheckImplicitThisCopyInReadOnlyMember(receiverOpt, method, diagnostics);
patternIndexerAccess = new BoundIndexOrRangePatternIndexerAccess(
syntax,
receiverOpt,
lengthOrCountProperty,
method,
BindToNaturalType(argument, diagnostics),
method.ReturnType);
checkWellKnown(WellKnownMember.System_Range__get_Start);
checkWellKnown(WellKnownMember.System_Range__get_End);
break;
checkWellKnown(WellKnownMember.System_Index__GetOffset);
return true;
}
}
}
}

cleanup(lookupResult);
if (patternIndexerAccess is null)
{
return false;
}

_ = MessageID.IDS_FeatureIndexOperator.CheckFeatureAvailability(diagnostics, syntax);
checkWellKnown(WellKnownMember.System_Index__GetOffset);
if (arguments.Names.Count > 0)
{
diagnostics.Add(
argIsRange
? ErrorCode.ERR_ImplicitRangeIndexerWithName
: ErrorCode.ERR_ImplicitIndexIndexerWithName,
arguments.Names[0].GetLocation());
}
return true;

static void cleanup(LookupResult lookupResult)
{
lookupResult.Free();
}

static bool isIntNotByRef(ParameterSymbol param)
=> param.Type.SpecialType == SpecialType.System_Int32 &&
param.RefKind == RefKind.None;
patternSymbol = null;
return false;

void checkWellKnown(WellKnownMember member)
{
// For list or slice patterns, there's no index or range expression in the source so we won't report missing members here.
if (forPattern)
return;
// Check required well-known member. They may not be needed
// during lowering, but it's simpler to always require them to prevent
// the user from getting surprising errors when optimizations fail
_ = GetWellKnownTypeMember(member, diagnostics, syntax: syntax);
}
}

private bool TryLookupLengthOrCount(
TypeSymbol receiverType,
LookupResult lookupResult,
[NotNullWhen(true)] out PropertySymbol? lengthOrCountProperty,
ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
// PROTOTYPE(list-patterns) Assert about whether diagnostics and dependencies are being accumulated.
return tryLookupLengthOrCount(WellKnownMemberNames.LengthPropertyName, out lengthOrCountProperty, ref useSiteInfo) ||
tryLookupLengthOrCount(WellKnownMemberNames.CountPropertyName, out lengthOrCountProperty, ref useSiteInfo);

bool tryLookupLengthOrCount(string propertyName, out PropertySymbol valid)
bool tryLookupLengthOrCount(string propertyName, out PropertySymbol? valid, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
LookupMembersInType(
lookupResult,
Expand All @@ -8050,15 +8075,15 @@ bool tryLookupLengthOrCount(string propertyName, out PropertySymbol valid)
LookupOptions.Default,
originalBinder: this,
diagnose: false,
useSiteInfo: ref discardedUseSiteInfo);
useSiteInfo: ref useSiteInfo);
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useSiteInfo

Consider adding an assert about whether diagnostics and dependencies are being accumulated, or we'll eventually have an issue when a refactor is performed.

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We've been passing Discard here for ranges too, I followed suit. I can add a prototype comment to revise.


if (lookupResult.IsSingleViable &&
lookupResult.Symbols[0] is PropertySymbol property &&
property.GetOwnOrInheritedGetMethod()?.OriginalDefinition is MethodSymbol getMethod &&
getMethod.ReturnType.SpecialType == SpecialType.System_Int32 &&
getMethod.RefKind == RefKind.None &&
!getMethod.IsStatic &&
IsAccessible(getMethod, ref discardedUseSiteInfo))
IsAccessible(getMethod, ref useSiteInfo))
{
lookupResult.Clear();
valid = property;
Expand All @@ -8069,6 +8094,7 @@ lookupResult.Symbols[0] is PropertySymbol property &&
return false;
}
}
#nullable disable

private ErrorPropertySymbol CreateErrorPropertySymbol(ImmutableArray<PropertySymbol> propertyGroup)
{
Expand Down
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