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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#nullable disable
using System;
using System.Collections;
using System.Collections.Generic;
using System.Composition;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeRefactorings;
using Microsoft.CodeAnalysis.ConvertLinq;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Operations;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Simplification;
namespace Microsoft.CodeAnalysis.CSharp.ConvertLinq;
using static CSharpSyntaxTokens;
using static SyntaxFactory;
[ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.ConvertLinqQueryToForEach), Shared]
internal sealed class CSharpConvertLinqQueryToForEachProvider : AbstractConvertLinqQueryToForEachProvider<QueryExpressionSyntax, StatementSyntax>
{
private static readonly TypeSyntax VarNameIdentifier = IdentifierName("var");
[ImportingConstructor]
[SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
public CSharpConvertLinqQueryToForEachProvider()
{
}
protected override string Title => CSharpFeaturesResources.Convert_to_foreach;
protected override bool TryConvert(
QueryExpressionSyntax queryExpression,
SemanticModel semanticModel,
ISemanticFactsService semanticFacts,
CancellationToken cancellationToken,
out DocumentUpdateInfo documentUpdateInfo)
=> new Converter(semanticModel, semanticFacts, queryExpression, cancellationToken).TryConvert(out documentUpdateInfo);
/// <summary>
/// Finds a QueryExpressionSyntax node for the span.
/// </summary>
protected override Task<QueryExpressionSyntax> FindNodeToRefactorAsync(CodeRefactoringContext context)
=> context.TryGetRelevantNodeAsync<QueryExpressionSyntax>();
private sealed class Converter(SemanticModel semanticModel, ISemanticFactsService semanticFacts, QueryExpressionSyntax source, CancellationToken cancellationToken)
{
private readonly SemanticModel _semanticModel = semanticModel;
private readonly ISemanticFactsService _semanticFacts = semanticFacts;
private readonly CancellationToken _cancellationToken = cancellationToken;
private readonly QueryExpressionSyntax _source = source;
private readonly List<string> _introducedLocalNames = [];
public bool TryConvert(out DocumentUpdateInfo documentUpdateInfo)
{
// Do not try refactoring queries with comments or conditional compilation in them.
// We can consider supporting queries with comments in the future.
if (_source.DescendantTrivia().Any(trivia => trivia is (kind:
SyntaxKind.SingleLineCommentTrivia or
SyntaxKind.MultiLineCommentTrivia or
SyntaxKind.MultiLineDocumentationCommentTrivia) ||
_source.ContainsDirectives))
{
documentUpdateInfo = null;
return false;
}
// Bail out if there is no chance to convert it even with a local function.
if (!CanTryConvertToLocalFunction() ||
!TryCreateStackFromQueryExpression(out var queryExpressionProcessingInfo))
{
documentUpdateInfo = null;
return false;
}
// GetDiagnostics is expensive. Move it to the end if there were no bail outs from the algorithm.
// TODO likely adding more semantic checks will perform checks we expect from GetDiagnostics
// We may consider removing GetDiagnostics.
// https://github.com/dotnet/roslyn/issues/25639
if ((TryConvertInternal(queryExpressionProcessingInfo, out documentUpdateInfo) ||
TryReplaceWithLocalFunction(queryExpressionProcessingInfo, out documentUpdateInfo)) && // second attempt: at least to a local function
!_semanticModel.GetDiagnostics(_source.Span, _cancellationToken).Any(static diagnostic => diagnostic.DefaultSeverity == DiagnosticSeverity.Error))
{
if (!documentUpdateInfo.Source.IsParentKind(SyntaxKind.Block) &&
documentUpdateInfo.Destinations.Length > 1)
{
documentUpdateInfo = new DocumentUpdateInfo(documentUpdateInfo.Source, Block(documentUpdateInfo.Destinations));
}
return true;
}
documentUpdateInfo = null;
return false;
}
private StatementSyntax ProcessClause(
CSharpSyntaxNode node,
StatementSyntax statement,
bool isLastClause,
bool hasExtraDeclarations,
out StatementSyntax extraStatementToAddAbove)
{
extraStatementToAddAbove = null;
switch (node.Kind())
{
case SyntaxKind.WhereClause:
return Block(IfStatement(((WhereClauseSyntax)node).Condition.WithAdditionalAnnotations(Simplifier.Annotation).WithoutTrivia(), statement));
case SyntaxKind.FromClause:
var fromClause = (FromClauseSyntax)node;
// If we are processing the first from and
// there were joins and some evaluations were moved into declarations above the foreach
// Check if the declaration on the first fromclause should be moved for the evaluation above declarations already moved upfront.
ExpressionSyntax expression1;
if (isLastClause && hasExtraDeclarations && !IsLocalOrParameterSymbol(_source.FromClause.Expression))
{
var expressionName = _semanticFacts.GenerateNameForExpression(
_semanticModel,
fromClause.Expression,
capitalize: false,
_cancellationToken);
var variable = GetFreeSymbolNameAndMarkUsed(expressionName);
extraStatementToAddAbove = CreateLocalDeclarationStatement(variable, fromClause.Expression, generateTypeFromExpression: false);
expression1 = IdentifierName(variable);
}
else
{
expression1 = fromClause.Expression.WithoutTrivia();
}
return ForEachStatement(
fromClause.Type ?? VarNameIdentifier,
fromClause.Identifier,
expression1,
WrapWithBlock(statement));
case SyntaxKind.LetClause:
var letClause = (LetClauseSyntax)node;
return AddToBlockTop(CreateLocalDeclarationStatement(letClause.Identifier, letClause.Expression, generateTypeFromExpression: false), statement);
case SyntaxKind.JoinClause:
var joinClause = (JoinClauseSyntax)node;
if (joinClause.Into != null)
{
// This must be caught on the validation step. Therefore, here is an exception.
throw new ArgumentException("GroupJoin is not supported");
}
else
{
ExpressionSyntax expression2;
if (IsLocalOrParameterSymbol(joinClause.InExpression))
{
expression2 = joinClause.InExpression;
}
else
{
// Input: var q = from x in XX() from z in ZZ() join y in YY() on x equals y select x + y;
// Add
// var xx = XX();
// var yy = YY();
// Do not add for ZZ()
var expressionName = _semanticFacts.GenerateNameForExpression(
_semanticModel,
joinClause.InExpression,
capitalize: false,
_cancellationToken);
var variable = GetFreeSymbolNameAndMarkUsed(expressionName);
extraStatementToAddAbove = CreateLocalDeclarationStatement(variable, joinClause.InExpression, generateTypeFromExpression: false);
// Replace YY() with yy declared above.
expression2 = IdentifierName(variable);
}
// Output for the join
// var yy == YY(); this goes to extraStatementToAddAbove
// ...
// foreach (var y in yy)
// {
// if (object.Equals(x, y))
// {
// ...
return Block(
ForEachStatement(
joinClause.Type ?? VarNameIdentifier,
joinClause.Identifier,
expression2,
Block(
IfStatement(
InvocationExpression(
MemberAccessExpression(
SyntaxKind.SimpleMemberAccessExpression,
PredefinedType(ObjectKeyword),
IdentifierName(nameof(object.Equals))),
ArgumentList([
Argument(joinClause.LeftExpression),
Argument(joinClause.RightExpression.WithoutTrailingTrivia())])),
statement)))).WithAdditionalAnnotations(Simplifier.Annotation);
}
case SyntaxKind.SelectClause:
// This is not the latest Select in the Query Expression
// There is a QueryBody with the Continuation as a parent.
var selectClause = (SelectClauseSyntax)node;
var identifier = ((QueryBodySyntax)selectClause.Parent).Continuation.Identifier;
return AddToBlockTop(CreateLocalDeclarationStatement(identifier, selectClause.Expression, generateTypeFromExpression: true), statement);
default:
throw new ArgumentException($"Unexpected node kind {node.Kind()}");
}
}
private bool TryConvertInternal(QueryExpressionProcessingInfo queryExpressionProcessingInfo, out DocumentUpdateInfo documentUpdateInfo)
{
// (from a in b select a);
var parent = _source.WalkUpParentheses().Parent;
switch (parent.Kind())
{
// return from a in b select a;
case SyntaxKind.ReturnStatement:
return TryConvertIfInReturnStatement((ReturnStatementSyntax)parent, queryExpressionProcessingInfo, out documentUpdateInfo);
// foreach(var x in from a in b select a)
case SyntaxKind.ForEachStatement:
return TryConvertIfInForEach((ForEachStatementSyntax)parent, queryExpressionProcessingInfo, out documentUpdateInfo);
// (from a in b select a).ToList(), (from a in b select a).Count(), etc.
case SyntaxKind.SimpleMemberAccessExpression:
return TryConvertIfInMemberAccessExpression((MemberAccessExpressionSyntax)parent, queryExpressionProcessingInfo, out documentUpdateInfo);
}
documentUpdateInfo = null;
return false;
}
/// <summary>
/// Checks if the location of the query expression allows to convert it at least to a local function.
/// It still does not guarantees that the conversion can be performed. There can be bail outs of later stages.
/// </summary>
/// <returns></returns>
private bool CanTryConvertToLocalFunction()
{
SyntaxNode currentNode = _source;
while (currentNode != null)
{
if (currentNode is StatementSyntax)
{
return true;
}
if (currentNode is ExpressionSyntax or
ArgumentSyntax or
ArgumentListSyntax or
EqualsValueClauseSyntax or
VariableDeclaratorSyntax or
VariableDeclarationSyntax)
{
currentNode = currentNode.Parent;
}
else
{
return false;
}
}
return false;
}
private bool TryConvertIfInMemberAccessExpression(
MemberAccessExpressionSyntax memberAccessExpression,
QueryExpressionProcessingInfo queryExpressionProcessingInfo,
out DocumentUpdateInfo documentUpdateInfo)
{
if (memberAccessExpression.Parent is InvocationExpressionSyntax invocationExpression)
{
// This also covers generic names (i.e. with type arguments) like 'ToList<int>'.
// The ValueText is still just 'ToList'.
switch (memberAccessExpression.Name.Identifier.ValueText)
{
case nameof(Enumerable.ToList):
return TryConvertIfInToListInvocation(invocationExpression, queryExpressionProcessingInfo, out documentUpdateInfo);
case nameof(Enumerable.Count):
return TryConvertIfInCountInvocation(invocationExpression, queryExpressionProcessingInfo, out documentUpdateInfo);
}
}
documentUpdateInfo = null;
return false;
}
private bool TryConvertIfInCountInvocation(
InvocationExpressionSyntax invocationExpression,
QueryExpressionProcessingInfo queryExpressionProcessingInfo,
out DocumentUpdateInfo documentUpdateInfo)
{
if (_semanticModel.GetSymbolInfo(invocationExpression, _cancellationToken).Symbol is IMethodSymbol methodSymbol &&
methodSymbol.Parameters.Length == 0 &&
methodSymbol.ReturnType?.SpecialType == SpecialType.System_Int32 &&
methodSymbol.RefKind == RefKind.None)
{
// before var count = (from a in b select a).Count();
// after
// var count = 0;
// foreach (var a in b)
// {
// count++;
// }
return TryConvertIfInInvocation(
invocationExpression,
queryExpressionProcessingInfo,
IsInt,
(variableIdentifier, expression) => ExpressionStatement(
PostfixUnaryExpression(SyntaxKind.PostIncrementExpression, variableIdentifier)), // Generating 'count++'
LiteralExpression(SyntaxKind.NumericLiteralExpression, Literal(0)), // count = 0
variableName: "count",
out documentUpdateInfo);
}
documentUpdateInfo = null;
return false;
}
private bool TryConvertIfInToListInvocation(
InvocationExpressionSyntax invocationExpression,
QueryExpressionProcessingInfo queryExpressionProcessingInfo,
out DocumentUpdateInfo documentUpdateInfo)
{
// before var list = (from a in b select a).ToList();
// after
// var list = new List<T>();
// foreach (var a in b)
// {
// list.Add(a)
// }
if (_semanticModel.GetSymbolInfo(invocationExpression, _cancellationToken).Symbol is IMethodSymbol methodSymbol &&
methodSymbol.RefKind == RefKind.None &&
IsList(methodSymbol.ReturnType) &&
methodSymbol.Parameters.Length == 0)
{
return TryConvertIfInInvocation(
invocationExpression,
queryExpressionProcessingInfo,
IsList,
(listIdentifier, expression) => ExpressionStatement(InvocationExpression(
MemberAccessExpression(
SyntaxKind.SimpleMemberAccessExpression,
listIdentifier,
IdentifierName(nameof(IList.Add))),
ArgumentList([Argument(expression)]))),
ObjectCreationExpression(
methodSymbol.GenerateReturnTypeSyntax().WithAdditionalAnnotations(Simplifier.Annotation),
ArgumentList(),
initializer: null),
variableName: "list",
out documentUpdateInfo);
}
documentUpdateInfo = null;
return false;
}
private bool IsInt(ITypeSymbol typeSymbol)
=> typeSymbol.SpecialType == SpecialType.System_Int32;
private bool IsList(ITypeSymbol typeSymbol)
=> Equals(typeSymbol.OriginalDefinition, _semanticModel.Compilation.GetTypeByMetadataName(typeof(List<>).FullName));
private bool TryConvertIfInInvocation(
InvocationExpressionSyntax invocationExpression,
QueryExpressionProcessingInfo queryExpressionProcessingInfo,
Func<ITypeSymbol, bool> typeCheckMethod,
Func<ExpressionSyntax, ExpressionSyntax, StatementSyntax> leafExpressionCreationMethod,
ExpressionSyntax initializer,
string variableName,
out DocumentUpdateInfo documentUpdateInfo)
{
var parentStatement = invocationExpression.GetAncestorOrThis<StatementSyntax>();
if (parentStatement != null)
{
if (TryConvertIfInInvocationInternal(
invocationExpression,
typeCheckMethod,
parentStatement,
initializer,
variableName,
out var variable,
out var nodesBefore,
out var nodesAfter))
{
var statements = GenerateStatements(expression => leafExpressionCreationMethod(variable, expression), queryExpressionProcessingInfo);
var list = new List<StatementSyntax>();
list.AddRange(nodesBefore);
list.AddRange(statements);
list.AddRange(nodesAfter);
documentUpdateInfo = new DocumentUpdateInfo(parentStatement, list);
return true;
}
}
documentUpdateInfo = null;
return false;
}
private bool TryConvertIfInInvocationInternal(
InvocationExpressionSyntax invocationExpression,
Func<ITypeSymbol, bool> typeCheckMethod,
StatementSyntax parentStatement,
ExpressionSyntax initializer,
string variableName,
out ExpressionSyntax variable,
out StatementSyntax[] nodesBefore,
out StatementSyntax[] nodesAfter)
{
var invocationParent = invocationExpression.WalkUpParentheses().Parent;
var symbolName = GetFreeSymbolNameAndMarkUsed(variableName);
void Convert(
ExpressionSyntax variableExpression,
ExpressionSyntax expressionToVerifyType,
bool checkForLocalOrParameter,
out ExpressionSyntax variableLocal,
out StatementSyntax[] nodesBeforeLocal,
out StatementSyntax[] nodesAfterLocal)
{
// Check that we can re-use the local variable or parameter
if (typeCheckMethod(_semanticModel.GetTypeInfo(expressionToVerifyType, _cancellationToken).Type) &&
(!checkForLocalOrParameter || IsLocalOrParameterSymbol(variableExpression)))
{
// before
// a = (from a in b select a).ToList(); or var a = (from a in b select a).ToList()
// after
// a = new List<T>(); or var a = new List<T>();
// foreach(...)
variableLocal = variableExpression;
nodesBeforeLocal = [parentStatement.ReplaceNode(invocationExpression, initializer.WithAdditionalAnnotations(Simplifier.Annotation))];
nodesAfterLocal = [];
}
else
{
// before
// IReadOnlyList<int> a = (from a in b select a).ToList(); or an assignment
// after
// var list = new List<T>(); or assignment
// foreach(...)
// IReadOnlyList<int> a = list;
variableLocal = IdentifierName(symbolName);
nodesBeforeLocal = new[] { CreateLocalDeclarationStatement(symbolName, initializer, generateTypeFromExpression: false) };
nodesAfterLocal = [parentStatement.ReplaceNode(invocationExpression, variableLocal.WithAdditionalAnnotations(Simplifier.Annotation))];
}
}
switch (invocationParent.Kind())
{
case SyntaxKind.EqualsValueClause:
// Avoid for(int i = (from x in a select x).Count(); i < 10; i++)
if (invocationParent?.Parent.Kind() is
SyntaxKind.VariableDeclarator or
SyntaxKind.VariableDeclaration or
SyntaxKind.LocalDeclarationStatement &&
// Avoid int i = (from x in a select x).Count(), j = i;
((VariableDeclarationSyntax)invocationParent.Parent.Parent).Variables.Count == 1)
{
var variableDeclarator = ((VariableDeclaratorSyntax)invocationParent.Parent);
Convert(
IdentifierName(variableDeclarator.Identifier),
((VariableDeclarationSyntax)variableDeclarator.Parent).Type,
checkForLocalOrParameter: false,
out variable,
out nodesBefore,
out nodesAfter);
return true;
}
break;
case SyntaxKind.SimpleAssignmentExpression:
var assignmentExpression = (AssignmentExpressionSyntax)invocationParent;
if (assignmentExpression.Right.WalkDownParentheses() == invocationExpression)
{
Convert(
assignmentExpression.Left,
assignmentExpression.Left,
checkForLocalOrParameter: true,
out variable,
out nodesBefore,
out nodesAfter);
return true;
}
break;
case SyntaxKind.ReturnStatement:
// before return (from a in b select a).ToList();
// after var list = new List<T>();
// foreach(...)
// return list;
variable = IdentifierName(symbolName);
nodesBefore = new[] { CreateLocalDeclarationStatement(symbolName, initializer, generateTypeFromExpression: false) };
nodesAfter = new[] { ReturnStatement(variable).WithAdditionalAnnotations(Simplifier.Annotation) };
return true;
// SyntaxKind.Argument:
// SyntaxKind.ArrowExpressionClause is not supported
}
// Will still try to replace with a local function above.
nodesBefore = null;
nodesAfter = null;
variable = null;
return false;
}
private LocalDeclarationStatementSyntax CreateLocalDeclarationStatement(
SyntaxToken identifier,
ExpressionSyntax expression,
bool generateTypeFromExpression)
{
var typeSyntax = generateTypeFromExpression
? _semanticModel.GetTypeInfo(expression, _cancellationToken).ConvertedType.GenerateTypeSyntax()
: VarNameIdentifier;
return LocalDeclarationStatement(
VariableDeclaration(
typeSyntax,
[VariableDeclarator(
identifier,
argumentList: null,
EqualsValueClause(expression))])).WithAdditionalAnnotations(Simplifier.Annotation);
}
private bool TryReplaceWithLocalFunction(QueryExpressionProcessingInfo queryExpressionProcessingInfo, out DocumentUpdateInfo documentUpdateInfo)
{
var parentStatement = _source.GetAncestorOrThis<StatementSyntax>();
if (parentStatement == null)
{
documentUpdateInfo = null;
return false;
}
// before statement ... from a in select b ...
// after
// IEnumerable<T> localFunction()
// {
// foreach(var a in b)
// {
// yield return a;
// }
// }
// statement ... localFunction();
var returnTypeInfo = _semanticModel.GetTypeInfo(_source, _cancellationToken);
ITypeSymbol returnedType;
if (returnTypeInfo.Type.OriginalDefinition?.SpecialType == SpecialType.System_Collections_Generic_IEnumerable_T)
{
returnedType = returnTypeInfo.Type;
}
else
{
if (returnTypeInfo.ConvertedType.OriginalDefinition?.SpecialType == SpecialType.System_Collections_Generic_IEnumerable_T)
{
returnedType = returnTypeInfo.ConvertedType;
}
else
{
documentUpdateInfo = null;
return false;
}
}
static StatementSyntax internalNodeMethod(ExpressionSyntax expression)
=> YieldStatement(SyntaxKind.YieldReturnStatement, expression);
var statements = GenerateStatements(internalNodeMethod, queryExpressionProcessingInfo);
var localFunctionNamePrefix = _semanticFacts.GenerateNameForExpression(
_semanticModel,
_source,
capitalize: false,
_cancellationToken);
var localFunctionToken = GetFreeSymbolNameAndMarkUsed(localFunctionNamePrefix);
var localFunctionDeclaration = LocalFunctionStatement(
modifiers: default,
returnType: returnedType.GenerateTypeSyntax().WithAdditionalAnnotations(Simplifier.Annotation),
identifier: localFunctionToken,
typeParameterList: null,
parameterList: ParameterList(),
constraintClauses: default,
body: Block(
Token(
[],
SyntaxKind.OpenBraceToken,
[EndOfLine(Environment.NewLine)]),
[.. statements],
CloseBraceToken),
expressionBody: null);
var localFunctionInvocation = InvocationExpression(IdentifierName(localFunctionToken)).WithAdditionalAnnotations(Simplifier.Annotation);
var newParentExpressionStatement = parentStatement.ReplaceNode(_source.WalkUpParentheses(), localFunctionInvocation.WithAdditionalAnnotations(Simplifier.Annotation));
documentUpdateInfo = new DocumentUpdateInfo(parentStatement, [localFunctionDeclaration, newParentExpressionStatement]);
return true;
}
private SyntaxToken GetFreeSymbolNameAndMarkUsed(string prefix)
{
var freeToken = _semanticFacts.GenerateUniqueName(_semanticModel, _source, container: null, baseName: prefix, _introducedLocalNames, _cancellationToken);
_introducedLocalNames.Add(freeToken.ValueText);
return freeToken;
}
private bool TryConvertIfInForEach(
ForEachStatementSyntax forEachStatement,
QueryExpressionProcessingInfo queryExpressionProcessingInfo,
out DocumentUpdateInfo documentUpdateInfo)
{
// before foreach(var x in from a in b select a)
if (forEachStatement.Expression.WalkDownParentheses() != _source)
{
documentUpdateInfo = null;
return false;
}
// check that the body of the forEach does not contain any identifiers from the query
foreach (var identifierName in queryExpressionProcessingInfo.IdentifierNames)
{
// Identifier from the foreach can already be in scope of the foreach statement.
if (forEachStatement.Identifier.ValueText != identifierName)
{
if (_semanticFacts.GenerateUniqueName(
_semanticModel,
location: forEachStatement.Statement,
container: forEachStatement.Statement,
baseName: identifierName,
usedNames: [],
_cancellationToken).ValueText != identifierName)
{
documentUpdateInfo = null;
return false;
}
}
}
// If query does not contains identifier with the same name as declared in the foreach,
// declare this identifier in the body.
if (!queryExpressionProcessingInfo.ContainsIdentifier(forEachStatement.Identifier))
{
documentUpdateInfo = ConvertIfInToForeachWithExtraVariableDeclaration(forEachStatement, queryExpressionProcessingInfo);
return true;
}
else
{
// The last select expression in the query returns this identifier:
// foreach(var thisIdentifier in from ....... select thisIdentifier)
// if thisIdentifier in foreach is var, it is OK
// if a type is specified for thisIdentifier in forEach, check that the type is the same as in the select expression
// foreach(MyType thisIdentifier in from ....... from MyType thisIdentifier ... select thisIdentifier)
// The last clause in query stack must be SelectClauseSyntax.
var lastSelectExpression = ((SelectClauseSyntax)queryExpressionProcessingInfo.Stack.Peek()).Expression;
if (lastSelectExpression is IdentifierNameSyntax identifierName &&
forEachStatement.Identifier.ValueText == identifierName.Identifier.ValueText &&
queryExpressionProcessingInfo.IdentifierNames.Contains(identifierName.Identifier.ValueText))
{
var forEachStatementTypeSymbolType = _semanticModel.GetTypeInfo(forEachStatement.Type, _cancellationToken).Type;
var lastSelectExpressionTypeInfo = _semanticModel.GetTypeInfo(lastSelectExpression, _cancellationToken);
if (Equals(lastSelectExpressionTypeInfo.ConvertedType, lastSelectExpressionTypeInfo.Type) &&
Equals(lastSelectExpressionTypeInfo.ConvertedType, forEachStatementTypeSymbolType))
{
documentUpdateInfo = ConvertIfInToForeachWithoutExtraVariableDeclaration(forEachStatement, queryExpressionProcessingInfo);
return true;
}
}
}
// in all other cases try to replace with a local function - this is called above.
documentUpdateInfo = null;
return false;
}
private DocumentUpdateInfo ConvertIfInToForeachWithExtraVariableDeclaration(
ForEachStatementSyntax forEachStatement,
QueryExpressionProcessingInfo queryExpressionProcessingInfo)
{
// before foreach(var x in from ... a) { dosomething(x); }
// after
// foreach (var a in ...)
// ...
// {
// var x = a;
// dosomething(x);
// }
var statements = GenerateStatements(
expression => AddToBlockTop(LocalDeclarationStatement(
VariableDeclaration(
forEachStatement.Type,
[VariableDeclarator(
forEachStatement.Identifier,
argumentList: null,
EqualsValueClause(expression))])),
forEachStatement.Statement).WithAdditionalAnnotations(Formatter.Annotation), queryExpressionProcessingInfo);
return new DocumentUpdateInfo(forEachStatement, statements);
}
private DocumentUpdateInfo ConvertIfInToForeachWithoutExtraVariableDeclaration(
ForEachStatementSyntax forEachStatement,
QueryExpressionProcessingInfo queryExpressionProcessingInfo)
{
// before
// foreach (var a in from a in b where a > 5 select a)
// {
// dosomething(a);
// }
// after
// foreach (var a in b)
// {
// if (a > 5)
// {
// dosomething(a);
// }
// }
var statements = GenerateStatements(
expression => forEachStatement.Statement.WithAdditionalAnnotations(Formatter.Annotation),
queryExpressionProcessingInfo);
return new DocumentUpdateInfo(forEachStatement, statements);
}
private bool TryConvertIfInReturnStatement(
ReturnStatementSyntax returnStatement,
QueryExpressionProcessingInfo queryExpressionProcessingInfo,
out DocumentUpdateInfo documentUpdateInfo)
{
// The conversion requires yield return which cannot be added to lambdas and anonymous method declarations.
if (IsWithinImmediateLambdaOrAnonymousMethod(returnStatement))
{
documentUpdateInfo = null;
return false;
}
var memberDeclarationNode = FindParentMemberDeclarationNode(returnStatement, out var declaredSymbol);
if (declaredSymbol is not IMethodSymbol methodSymbol)
{
documentUpdateInfo = null;
return false;
}
if (methodSymbol.ReturnType.OriginalDefinition?.SpecialType != SpecialType.System_Collections_Generic_IEnumerable_T)
{
documentUpdateInfo = null;
return false;
}
// if there are more than one return in the method, convert to local function.
if (memberDeclarationNode.DescendantNodes().OfType<ReturnStatementSyntax>().Count() == 1)
{
// before: return from a in b select a;
// after:
// foreach(var a in b)
// {
// yield return a;
// }
//
// yield break;
var statements = GenerateStatements((ExpressionSyntax expression)
=> YieldStatement(SyntaxKind.YieldReturnStatement, expression), queryExpressionProcessingInfo);
// add an yield break to avoid throws after the return.
var yieldBreakStatement = YieldStatement(SyntaxKind.YieldBreakStatement);
documentUpdateInfo = new DocumentUpdateInfo(returnStatement, statements.Concat([yieldBreakStatement]));
return true;
}
documentUpdateInfo = null;
return false;
}
// We may assume that the query is defined within a method, field, property and so on and it is declare just once.
private SyntaxNode FindParentMemberDeclarationNode(SyntaxNode node, out ISymbol declaredSymbol)
{
declaredSymbol = _semanticModel.GetEnclosingSymbol(node.SpanStart, _cancellationToken);
return declaredSymbol.DeclaringSyntaxReferences.Single().GetSyntax();
}
private bool TryCreateStackFromQueryExpression(out QueryExpressionProcessingInfo queryExpressionProcessingInfo)
{
queryExpressionProcessingInfo = new QueryExpressionProcessingInfo(_source.FromClause);
return TryProcessQueryBody(_source.Body, queryExpressionProcessingInfo);
}
private StatementSyntax[] GenerateStatements(
Func<ExpressionSyntax, StatementSyntax> leafExpressionCreationMethod,
QueryExpressionProcessingInfo queryExpressionProcessingInfo)
{
StatementSyntax statement = null;
var stack = queryExpressionProcessingInfo.Stack;
// Executes syntax building methods from bottom to the top of the tree.
// Process last clause
if (stack.Any())
{
var node = stack.Pop();
if (node is SelectClauseSyntax selectClause)
{
statement = WrapWithBlock(leafExpressionCreationMethod(selectClause.Expression));
}
else
{
throw new ArgumentException("Last node must me the select clause");
}
}
// Process all other clauses
var statements = new List<StatementSyntax>();
while (stack.Any())
{
statement = ProcessClause(
stack.Pop(),
statement,
isLastClause: !stack.Any(),
hasExtraDeclarations: statements.Any(),
out var extraStatement);
if (extraStatement != null)
{
statements.Add(extraStatement);
}
}
// The stack was processed in the reverse order, but the extra statements should be provided in the direct order.
statements.Reverse();
statements.Add(statement.WithAdditionalAnnotations(Simplifier.Annotation));
return [.. statements];
}
private bool TryProcessQueryBody(QueryBodySyntax queryBody, QueryExpressionProcessingInfo queryExpressionProcessingInfo)
{
do
{
foreach (var queryClause in queryBody.Clauses)
{
switch (queryClause.Kind())
{
case SyntaxKind.WhereClause:
queryExpressionProcessingInfo.Add(queryClause);
break;
case SyntaxKind.LetClause:
if (!queryExpressionProcessingInfo.TryAdd(queryClause, ((LetClauseSyntax)queryClause).Identifier))
{
return false;
}
break;
case SyntaxKind.FromClause:
var fromClause = (FromClauseSyntax)queryClause;
if (!queryExpressionProcessingInfo.TryAdd(queryClause, fromClause.Identifier))
{
return false;
}
break;
case SyntaxKind.JoinClause:
var joinClause = (JoinClauseSyntax)queryClause;
if (joinClause.Into == null) // GroupJoin is not supported
{
if (queryExpressionProcessingInfo.TryAdd(joinClause, joinClause.Identifier))
{
break;
}
}
return false;
// OrderBy is not supported by foreach.
default:
return false;
}
}
// GroupClause is not supported by the conversion
if (queryBody.SelectOrGroup is not SelectClauseSyntax selectClause)
{
return false;
}
if (_semanticModel.GetTypeInfo(selectClause.Expression, _cancellationToken).Type.ContainsAnonymousType())
{
return false;
}
queryExpressionProcessingInfo.Add(selectClause);
queryBody = queryBody.Continuation?.Body;
} while (queryBody != null);
return true;
}
private static BlockSyntax AddToBlockTop(StatementSyntax newStatement, StatementSyntax statement)
{
if (statement is BlockSyntax block)
{
return block.WithStatements(block.Statements.Insert(0, newStatement));
}
else
{
return Block(newStatement, statement);
}
}
private bool IsLocalOrParameterSymbol(ExpressionSyntax expression)
=> IsLocalOrParameterSymbol(_semanticModel.GetOperation(expression, _cancellationToken));
private static bool IsLocalOrParameterSymbol(IOperation operation)
{
if (operation is IConversionOperation conversion && conversion.IsImplicit)
{
return IsLocalOrParameterSymbol(conversion.Operand);
}
return operation.Kind is OperationKind.LocalReference or OperationKind.ParameterReference;
}
private static BlockSyntax WrapWithBlock(StatementSyntax statement)
=> statement is BlockSyntax block ? block : Block(statement);
// Checks if the node is within an immediate lambda or within an immediate anonymous method.
// 'lambda => node' returns true
// 'lambda => localfunction => node' returns false
// 'member => node' returns false
private static bool IsWithinImmediateLambdaOrAnonymousMethod(SyntaxNode node)
{
while (node != null)
{
switch (node.Kind())
{
case SyntaxKind.AnonymousMethodExpression:
case SyntaxKind.ParenthesizedLambdaExpression:
case SyntaxKind.SimpleLambdaExpression:
return true;
case SyntaxKind.LocalFunctionStatement:
return false;
default:
if (node is MemberDeclarationSyntax)
{
return false;
}
break;
}
node = node.Parent;
}
return false;
}
private class QueryExpressionProcessingInfo
{
public Stack<CSharpSyntaxNode> Stack { get; private set; }
public HashSet<string> IdentifierNames { get; private set; }
public QueryExpressionProcessingInfo(FromClauseSyntax fromClause)
{
Stack = new Stack<CSharpSyntaxNode>();
Stack.Push(fromClause);
IdentifierNames = [fromClause.Identifier.ValueText];
}
public bool TryAdd(CSharpSyntaxNode node, SyntaxToken identifier)
{
// Duplicate identifiers are not allowed.
// var q = from x in new[] { 1 } select x + 2 into x where x > 0 select 7 into y let x = ""aaa"" select x;
if (!IdentifierNames.Add(identifier.ValueText))
{
return false;
}
Stack.Push(node);
return true;
}
public void Add(CSharpSyntaxNode node) => Stack.Push(node);
public bool ContainsIdentifier(SyntaxToken identifier)
=> IdentifierNames.Contains(identifier.ValueText);
}
}
}
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