private bool TryDecomposeIfCondition(
IConditionalOperation ifStatement,
out ISymbol localOrParameter)
{
localOrParameter = null;
var condition = ifStatement.Condition;
if (!(condition is IBinaryOperation binaryOperator))
{
return(false);
}
if (binaryOperator.OperatorKind != BinaryOperatorKind.Equals)
{
return(false);
}
if (IsNull(binaryOperator.LeftOperand))
{
return(TryGetLocalOrParameterSymbol(
binaryOperator.RightOperand, out localOrParameter));
}
if (IsNull(binaryOperator.RightOperand))
{
return(TryGetLocalOrParameterSymbol(
binaryOperator.LeftOperand, out localOrParameter));
}
return(false);
}
private EvaluationResult AnalyzeConditional([NotNull] IConditionalOperation conditional)
{
EvaluationResult trueResult = AnalyzeExpression(conditional.WhenTrue);
EvaluationResult falseResult = AnalyzeExpression(conditional.WhenFalse);
return(EvaluationResult.Unify(trueResult, falseResult));
}
private void Remove([NotNull] IConditionalOperation ifStatementToRemove,
[NotNull] IDictionary <Location, IConditionalOperation> ifStatements)
{
Location location = ifStatementToRemove.TryGetLocationForKeyword();
ifStatements.Remove(location);
}
public static bool CanConvert(
ISyntaxFacts syntaxFacts, IConditionalOperation ifOperation,
IOperation whenTrue, IOperation whenFalse)
{
// Will likely screw things up if the if directive spans any preprocessor directives. So
// do not offer for now. Note: we pass in both the node for the ifOperation and the
// whenFalse portion. The whenFalse portion isn't necessary under the ifOperation. For
// example in:
//
// ```c#
// #if DEBUG
// if (check)
// return 3;
// #endif
// return 2;
// ```
//
// In this case, we want to see that this cross the `#endif`
if (syntaxFacts.SpansPreprocessorDirective(ifOperation.Syntax, whenFalse.Syntax))
{
return(false);
}
// User may have comments on the when-true/when-false statements. These statements can
// be very important. Often they indicate why the true/false branches are important in
// the first place. We don't have any place to put these, so we don't offer here.
if (HasRegularComments(syntaxFacts, whenTrue.Syntax) ||
HasRegularComments(syntaxFacts, whenFalse.Syntax))
{
return(false);
}
return(true);
}
private bool TryConvertWhenAssignmentToLocalDeclaredImmediateAbove(
ISyntaxFactsService syntaxFacts, SyntaxEditor editor, IConditionalOperation ifOperation,
ISimpleAssignmentOperation?trueAssignment,
ISimpleAssignmentOperation?falseAssignment,
TExpressionSyntax conditionalExpression)
{
if (!TryFindMatchingLocalDeclarationImmediatelyAbove(
ifOperation, trueAssignment, falseAssignment,
out var localDeclarationOperation, out var declarator))
{
return(false);
}
// We found a valid local declaration right above the if-statement.
var localDeclaration = localDeclarationOperation.Syntax;
var variable = GetDeclaratorSyntax(declarator);
// Initialize that variable with the conditional expression.
var updatedVariable = WithInitializer(variable, conditionalExpression);
// Because we merged the initialization and the variable, the variable may now be able
// to use 'var' (c#), or elide its type (vb). Add the simplification annotation
// appropriately so that can happen later down the line.
var updatedLocalDeclaration = localDeclaration.ReplaceNode(variable, updatedVariable);
updatedLocalDeclaration = AddSimplificationToType(
(TLocalDeclarationStatementSyntax)updatedLocalDeclaration);
editor.ReplaceNode(localDeclaration, updatedLocalDeclaration);
editor.RemoveNode(ifOperation.Syntax, GetRemoveOptions(syntaxFacts, ifOperation.Syntax));
return(true);
}
/// <summary>
/// Helper to create a conditional expression out of two original IOperation values
/// corresponding to the whenTrue and whenFalse parts. The helper will add the appropriate
/// annotations and casts to ensure that the conditional expression preserves semantics, but
/// is also properly simplified and formatted.
/// </summary>
protected async Task <TExpressionSyntax> CreateConditionalExpressionAsync(
Document document, IConditionalOperation ifOperation,
IOperation trueStatement, IOperation falseStatement,
IOperation trueValue, IOperation falseValue,
bool isRef, CancellationToken cancellationToken)
{
var generator = SyntaxGenerator.GetGenerator(document);
var syntaxFacts = document.GetLanguageService <ISyntaxFactsService>();
var condition = ifOperation.Condition.Syntax;
var conditionalExpression = (TConditionalExpressionSyntax)generator.ConditionalExpression(
condition.WithoutTrivia(),
MakeRef(generator, isRef, CastValueIfNecessary(generator, trueValue)),
MakeRef(generator, isRef, CastValueIfNecessary(generator, falseValue)));
conditionalExpression = conditionalExpression.WithAdditionalAnnotations(Simplifier.Annotation);
var makeMultiLine = await MakeMultiLineAsync(
document, condition,
trueValue.Syntax, falseValue.Syntax, cancellationToken).ConfigureAwait(false);
if (makeMultiLine)
{
conditionalExpression = conditionalExpression.WithAdditionalAnnotations(
SpecializedFormattingAnnotation);
}
return(MakeRef(generator, isRef, conditionalExpression));
}
private static bool ValueIsAccessed(SemanticModel semanticModel, IConditionalOperation ifOperation, IBlockOperation containingBlock, ISymbol localOrParameter, IExpressionStatementOperation expressionStatement, IAssignmentOperation assignmentExpression)
{
var statements = containingBlock.Operations;
var ifOperationIndex = statements.IndexOf(ifOperation);
var expressionStatementIndex = statements.IndexOf(expressionStatement);
if (expressionStatementIndex > ifOperationIndex + 1)
{
// There are intermediary statements between the check and the assignment.
// Make sure they don't try to access the local.
var dataFlow = semanticModel.AnalyzeDataFlow(
statements[ifOperationIndex + 1].Syntax,
statements[expressionStatementIndex - 1].Syntax);
if (dataFlow.ReadInside.Contains(localOrParameter) ||
dataFlow.WrittenInside.Contains(localOrParameter))
{
return(true);
}
}
// Also, have to make sure there is no read/write of the local/parameter on the left
// of the assignment. For example: map[val.Id] = val;
var exprDataFlow = semanticModel.AnalyzeDataFlow(assignmentExpression.Target.Syntax);
return(exprDataFlow.ReadInside.Contains(localOrParameter) ||
exprDataFlow.WrittenInside.Contains(localOrParameter));
}
public static bool TryMatchPattern(
ISyntaxFacts syntaxFacts,
IConditionalOperation ifOperation,
out ISimpleAssignmentOperation trueAssignment,
out ISimpleAssignmentOperation falseAssignment)
{
trueAssignment = null;
falseAssignment = null;
var trueStatement = ifOperation.WhenTrue;
var falseStatement = ifOperation.WhenFalse;
trueStatement = UseConditionalExpressionHelpers.UnwrapSingleStatementBlock(trueStatement);
falseStatement = UseConditionalExpressionHelpers.UnwrapSingleStatementBlock(falseStatement);
if (!TryGetAssignment(trueStatement, out trueAssignment) ||
!TryGetAssignment(falseStatement, out falseAssignment))
{
return(false);
}
// The left side of both assignment statements has to be syntactically identical (modulo
// trivia differences).
if (!syntaxFacts.AreEquivalent(trueAssignment.Target.Syntax, falseAssignment.Target.Syntax))
{
return(false);
}
return(UseConditionalExpressionHelpers.CanConvert(
syntaxFacts, ifOperation, trueAssignment, falseAssignment));
}
public IfElseIfConstructAnalyzer([NotNull] IfStatementAnalyzer owner,
[NotNull] IConditionalOperation topIfStatement)
{
this.owner = owner;
topIfKeywordLocation = topIfStatement.TryGetLocationForKeyword();
ifStatement = topIfStatement;
}
private static AbstractExpression ReadConditional(IConditionalOperation op)
{
return(new ConditionalExpression {
Condition = ReadExpression(op.Condition),
WhenTrue = ReadExpression(op.WhenTrue),
WhenFalse = ReadExpression(op.WhenFalse)
});
}
public override Location VisitConditional([NotNull] IConditionalOperation operation, [CanBeNull] object argument)
{
if (operation.IsStatement())
{
var syntax = (IfStatementSyntax)operation.Syntax;
return(syntax.IfKeyword.GetLocation());
}
return(base.VisitConditional(operation, argument));
}
public override void VisitConditional([NotNull] IConditionalOperation operation)
{
if (operation.IsStatement())
{
Location location = operation.GetLocationForKeyword();
CollectedIfStatements.Add(location, operation);
}
base.VisitConditional(operation);
}
private void AnalyzeTopIfStatement()
{
IConditionalOperation ifStatement = ConsumeNextIfStatement();
if (IsIfElseIfConstruct(ifStatement))
{
var analyzer = new IfElseIfConstructAnalyzer(this, ifStatement);
analyzer.Analyze();
}
}
public override void VisitConditional([NotNull] IConditionalOperation operation)
{
if (operation.IsStatement())
{
Visit(operation.Condition);
}
else
{
base.VisitConditional(operation);
}
}
protected override bool TryMatchPattern(
IConditionalOperation ifOperation,
ISymbol containingSymbol
) =>
UseConditionalExpressionForAssignmentHelpers.TryMatchPattern(
GetSyntaxFacts(),
ifOperation,
out _,
out _,
out _,
out _
);
public override TAbstractAnalysisValue VisitConditional(IConditionalOperation operation, object argument)
{
var _ = Visit(operation.Condition, argument);
var whenTrue = Visit(operation.WhenTrue, argument);
var whenFalse = Visit(operation.WhenFalse, argument);
if (operation.Condition.ConstantValue.HasValue &&
operation.Condition.ConstantValue.Value is bool condition)
{
return(condition ? whenTrue : whenFalse);
}
return(ValueDomain.Merge(whenTrue, whenFalse));
}
public override void VisitConditional(IConditionalOperation operation)
{
Assert.Equal(OperationKind.Conditional, operation.Kind);
bool isRef = operation.IsRef;
if (operation.WhenFalse != null)
{
AssertEx.Equal(new[] { operation.Condition, operation.WhenTrue, operation.WhenFalse }, operation.Children);
}
else
{
AssertEx.Equal(new[] { operation.Condition, operation.WhenTrue }, operation.Children);
}
}
private bool TryFindAssignmentExpression(
IBlockOperation containingBlock,
IConditionalOperation ifOperation,
ISymbol localOrParameter,
out IExpressionStatementOperation expressionStatement,
out IAssignmentOperation assignmentExpression
)
{
var ifOperationIndex = containingBlock.Operations.IndexOf(ifOperation);
// walk forward until we find an assignment of this local/parameter into
// something else.
for (var i = ifOperationIndex + 1; i < containingBlock.Operations.Length; i++)
{
expressionStatement =
containingBlock.Operations[i] as IExpressionStatementOperation;
if (expressionStatement == null)
{
continue;
}
assignmentExpression = expressionStatement.Operation as IAssignmentOperation;
if (assignmentExpression == null)
{
continue;
}
if (
!TryGetLocalOrParameterSymbol(
assignmentExpression.Value,
out var assignmentValue
)
)
{
continue;
}
if (!Equals(localOrParameter, assignmentValue))
{
continue;
}
return(true);
}
expressionStatement = null;
assignmentExpression = null;
return(false);
}
public override void VisitConditional([NotNull] IConditionalOperation operation)
{
EvaluationResult trueResult = owner.AnalyzeExpression(operation.WhenTrue);
if (operation.WhenFalse == null || trueResult.IsDeferred)
{
Result.CopyFrom(trueResult);
}
else
{
EvaluationResult falseResult = owner.AnalyzeExpression(operation.WhenFalse);
Result.CopyFrom(EvaluationResult.Unify(trueResult, falseResult));
}
}
/// <summary>
/// Helper to create a conditional expression out of two original IOperation values
/// corresponding to the whenTrue and whenFalse parts. The helper will add the appropriate
/// annotations and casts to ensure that the conditional expression preserves semantics, but
/// is also properly simplified and formatted.
/// </summary>
protected async Task <TExpressionSyntax> CreateConditionalExpressionAsync(
Document document, IConditionalOperation ifOperation,
IOperation trueStatement, IOperation falseStatement,
IOperation trueValue, IOperation falseValue,
bool isRef, CancellationToken cancellationToken)
{
var generator = SyntaxGenerator.GetGenerator(document);
var generatorInternal = document.GetRequiredLanguageService <SyntaxGeneratorInternal>();
var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var condition = ifOperation.Condition.Syntax;
if (!isRef)
{
// If we are going to generate "expr ? true : false" then just generate "expr"
// instead.
if (IsBooleanLiteral(trueValue, true) && IsBooleanLiteral(falseValue, false))
{
return((TExpressionSyntax)condition.WithoutTrivia());
}
// If we are going to generate "expr ? false : true" then just generate "!expr"
// instead.
if (IsBooleanLiteral(trueValue, false) && IsBooleanLiteral(falseValue, true))
{
return((TExpressionSyntax)generator.Negate(generatorInternal,
condition, semanticModel, cancellationToken).WithoutTrivia());
}
}
var conditionalExpression = (TConditionalExpressionSyntax)generator.ConditionalExpression(
condition.WithoutTrivia(),
MakeRef(generatorInternal, isRef, CastValueIfNecessary(generator, trueStatement, trueValue)),
MakeRef(generatorInternal, isRef, CastValueIfNecessary(generator, falseStatement, falseValue)));
conditionalExpression = conditionalExpression.WithAdditionalAnnotations(Simplifier.Annotation);
var makeMultiLine = await MakeMultiLineAsync(
document, condition,
trueValue.Syntax, falseValue.Syntax, cancellationToken).ConfigureAwait(false);
if (makeMultiLine)
{
conditionalExpression = conditionalExpression.WithAdditionalAnnotations(
SpecializedFormattingAnnotation);
}
return(MakeRef(generatorInternal, isRef, conditionalExpression));
}
private void ConvertOnlyIfToConditionalExpression(
SyntaxEditor editor, IConditionalOperation ifOperation,
ISimpleAssignmentOperation trueAssignment, ISimpleAssignmentOperation falseAssignment,
TExpressionSyntax conditionalExpression)
{
var generator = editor.Generator;
var ifStatement = (TIfStatementSyntax)ifOperation.Syntax;
var expressionStatement = (TStatementSyntax)generator.ExpressionStatement(
generator.AssignmentStatement(
trueAssignment.Target.Syntax,
conditionalExpression)).WithTriviaFrom(ifStatement);
editor.ReplaceNode(
ifOperation.Syntax,
this.WrapWithBlockIfAppropriate(ifStatement, expressionStatement));
}
private static SyntaxNode CreateThrowIfCancellationRequestedExpressionStatement(
DocumentEditor editor,
IConditionalOperation conditional,
IPropertyReferenceOperation isCancellationRequestedPropertyReference)
{
SyntaxNode memberAccess = editor.Generator.MemberAccessExpression(
isCancellationRequestedPropertyReference.Instance.Syntax,
nameof(CancellationToken.ThrowIfCancellationRequested));
SyntaxNode invocation = editor.Generator.InvocationExpression(memberAccess, Array.Empty <SyntaxNode>());
var firstWhenTrueStatement = conditional.WhenTrue is IBlockOperation block?block.Operations.FirstOrDefault() : conditional.WhenTrue;
var result = editor.Generator.ExpressionStatement(invocation);
result = firstWhenTrueStatement is not null?result.WithTriviaFrom(firstWhenTrueStatement.Syntax) : result;
return(result.WithAdditionalAnnotations(Formatter.Annotation));
}
public static bool TryMatchPattern(
ISyntaxFacts syntaxFacts,
IConditionalOperation ifOperation,
[NotNullWhen(true)] out IOperation trueStatement,
[NotNullWhen(true)] out IOperation falseStatement,
out ISimpleAssignmentOperation?trueAssignment,
out ISimpleAssignmentOperation?falseAssignment)
{
trueAssignment = null;
falseAssignment = null;
trueStatement = ifOperation.WhenTrue;
falseStatement = ifOperation.WhenFalse;
trueStatement = UseConditionalExpressionHelpers.UnwrapSingleStatementBlock(trueStatement);
falseStatement = UseConditionalExpressionHelpers.UnwrapSingleStatementBlock(falseStatement);
if (!TryGetAssignmentOrThrow(trueStatement, out trueAssignment, out var trueThrow) ||
!TryGetAssignmentOrThrow(falseStatement, out falseAssignment, out var falseThrow))
{
return(false);
}
var anyAssignment = trueAssignment ?? falseAssignment;
if (UseConditionalExpressionHelpers.HasInconvertibleThrowStatement(
syntaxFacts, anyAssignment?.IsRef == true, trueThrow, falseThrow))
{
return(false);
}
// The left side of both assignment statements has to be syntactically identical (modulo
// trivia differences).
if (trueAssignment != null && falseAssignment != null &&
!syntaxFacts.AreEquivalent(trueAssignment.Target.Syntax, falseAssignment.Target.Syntax))
{
return(false);
}
return(UseConditionalExpressionHelpers.CanConvert(
syntaxFacts, ifOperation, trueStatement, falseStatement));
}
public static bool CanConvert(
ISyntaxFactsService syntaxFacts, IConditionalOperation ifOperation,
IOperation whenTrue, IOperation whenFalse)
{
// Will likely screw things up if the if directive spans any preprocessor directives.
// So do not offer for now.
if (syntaxFacts.SpansPreprocessorDirective(ifOperation.Syntax))
{
return(false);
}
// User may have comments on the when-true/when-false statements. These statements can
// be very important. Often they indicate why the true/false branches are important in
// the first place. We don't have any place to put these, so we don't offer here.
if (HasRegularComments(syntaxFacts, whenTrue.Syntax) ||
HasRegularComments(syntaxFacts, whenFalse.Syntax))
{
return(false);
}
return(true);
}
protected abstract bool TryMatchPattern(IConditionalOperation ifOperation);
private bool HandleElseIf([NotNull] IConditionalOperation ifElseStatement)
{
Remove(ifElseStatement, owner.ifStatementsLeftToAnalyze);
ifStatement = ifElseStatement;
return(true);
}
private bool IsIfElseIfConstruct([NotNull] IConditionalOperation ifStatement)
{
return(ifStatement.WhenFalse is IConditionalOperation);
}
private bool TryFindMatchingLocalDeclarationImmediatelyAbove(
IConditionalOperation ifOperation,
ISimpleAssignmentOperation?trueAssignment,
ISimpleAssignmentOperation?falseAssignment,
[NotNullWhen(true)] out IVariableDeclarationGroupOperation?localDeclaration,
[NotNullWhen(true)] out IVariableDeclaratorOperation?declarator)
{
localDeclaration = null;
declarator = null;
ILocalSymbol?local = null;
if (trueAssignment != null)
{
if (!(trueAssignment.Target is ILocalReferenceOperation trueLocal))
{
return(false);
}
local = trueLocal.Local;
}
if (falseAssignment != null)
{
if (!(falseAssignment.Target is ILocalReferenceOperation falseLocal))
{
return(false);
}
// See if both assignments are to the same local.
if (local != null && !Equals(local, falseLocal.Local))
{
return(false);
}
local = falseLocal.Local;
}
// We weren't assigning to a local.
if (local == null)
{
return(false);
}
// If so, see if that local was declared immediately above the if-statement.
if (!(ifOperation.Parent is IBlockOperation parentBlock))
{
return(false);
}
var ifIndex = parentBlock.Operations.IndexOf(ifOperation);
if (ifIndex <= 0)
{
return(false);
}
localDeclaration = parentBlock.Operations[ifIndex - 1] as IVariableDeclarationGroupOperation;
if (localDeclaration == null)
{
return(false);
}
if (localDeclaration.IsImplicit)
{
return(false);
}
if (localDeclaration.Declarations.Length != 1)
{
return(false);
}
var declaration = localDeclaration.Declarations[0];
var declarators = declaration.Declarators;
if (declarators.Length != 1)
{
return(false);
}
declarator = declarators[0];
var variable = declarator.Symbol;
if (!Equals(variable, local))
{
// wasn't a declaration of the local we're assigning to.
return(false);
}
var variableInitializer = declarator.Initializer ?? declaration.Initializer;
if (variableInitializer?.Value != null)
{
var unwrapped = UnwrapImplicitConversion(variableInitializer.Value);
// the variable has to either not have an initializer, or it needs to be basic
// literal/default expression.
if (!(unwrapped is ILiteralOperation) &&
!(unwrapped is IDefaultValueOperation))
{
return(false);
}
}
// If the variable is referenced in the condition of the 'if' block, we can't merge the
// declaration and assignments.
return(!ReferencesLocalVariable(ifOperation.Condition, variable));
}
protected abstract bool TryMatchPattern(IConditionalOperation ifOperation, ISymbol containingSymbol);
public static bool TryMatchPattern(
ISyntaxFactsService syntaxFacts,
IConditionalOperation ifOperation,
out IReturnOperation trueReturn,
out IReturnOperation falseReturn)
{
trueReturn = null;
falseReturn = null;
var trueStatement = ifOperation.WhenTrue;
var falseStatement = ifOperation.WhenFalse;
// we support:
//
// if (expr)
// return a;
// else
// return b;
//
// and
//
// if (expr)
// return a;
//
// return b;
if (falseStatement == null)
{
var parentBlock = ifOperation.Parent as IBlockOperation;
if (parentBlock == null)
{
return(false);
}
var ifIndex = parentBlock.Operations.IndexOf(ifOperation);
if (ifIndex < 0)
{
return(false);
}
if (ifIndex + 1 < parentBlock.Operations.Length)
{
falseStatement = parentBlock.Operations[ifIndex + 1];
if (falseStatement.IsImplicit)
{
return(false);
}
}
}
trueStatement = UseConditionalExpressionHelpers.UnwrapSingleStatementBlock(trueStatement);
falseStatement = UseConditionalExpressionHelpers.UnwrapSingleStatementBlock(falseStatement);
// Both return-statements must be of the form "return value"
if (!(trueStatement is IReturnOperation trueReturnOp) ||
!(falseStatement is IReturnOperation falseReturnOp) ||
trueReturnOp.ReturnedValue == null ||
falseReturnOp.ReturnedValue == null)
{
return(false);
}
if (trueReturnOp.Kind != falseReturnOp.Kind)
{
// Not allowed if these are different types of returns. i.e.
// "yield return ..." and "return ...".
return(false);
}
if (trueReturnOp.Kind == OperationKind.YieldBreak)
{
// This check is just paranoia. We likely shouldn't get here since we already
// checked if .ReturnedValue was null above.
return(false);
}
if (trueReturnOp.Kind == OperationKind.YieldReturn &&
ifOperation.WhenFalse == null)
{
// we have the following:
//
// if (...) {
// yield return ...
// }
//
// yield return ...
//
// It is *not* correct to replace this with:
//
// yield return ... ? ... ? ...
//
// as both yields need to be hit.
return(false);
}
trueReturn = trueReturnOp;
falseReturn = falseReturnOp;
return(UseConditionalExpressionHelpers.CanConvert(
syntaxFacts, ifOperation, trueReturn, falseReturn));
}