private static IfRefactoring CreateIfToAssignmentWithWithCoalesceExpression(
IfStatementSyntax ifStatement,
ExpressionSyntax left,
ExpressionSyntax expression1,
ExpressionSyntax expression2,
NullCheckExpression nullCheck,
SemanticModel semanticModel,
CancellationToken cancellationToken)
{
if (nullCheck.Kind == NullCheckKind.EqualsToNull ||
nullCheck.Kind == NullCheckKind.NotEqualsToNull)
{
if (IsEquivalent(nullCheck.Expression, expression1))
{
return(new IfElseToAssignmentWithCoalesceExpression(ifStatement, left, expression1, expression2));
}
}
if (expression1.IsKind(SyntaxKind.SimpleMemberAccessExpression) &&
SemanticUtilities.IsPropertyOfNullableOfT(expression1, "Value", semanticModel, cancellationToken))
{
expression1 = ((MemberAccessExpressionSyntax)expression1).Expression;
if (IsEquivalent(nullCheck.Expression, expression1))
{
return(new IfElseToAssignmentWithCoalesceExpression(ifStatement, left, expression1, expression2));
}
}
return(null);
}
private static IfRefactoring CreateIfToReturnWithCoalesceExpression(
IfStatementSyntax ifStatement,
ExpressionSyntax expression1,
ExpressionSyntax expression2,
NullCheckExpression nullCheck,
bool isYield,
SemanticModel semanticModel,
CancellationToken cancellationToken)
{
if (nullCheck.Kind == NullCheckKind.EqualsToNull ||
nullCheck.Kind == NullCheckKind.NotEqualsToNull)
{
if (SyntaxComparer.AreEquivalent(nullCheck.Expression, expression1, requireNotNull: true))
{
return(IfToReturnWithCoalesceExpression.Create(ifStatement, expression1, expression2, isYield));
}
}
if (expression1.IsKind(SyntaxKind.SimpleMemberAccessExpression) &&
SemanticUtilities.IsPropertyOfNullableOfT(expression1, "Value", semanticModel, cancellationToken))
{
expression1 = ((MemberAccessExpressionSyntax)expression1).Expression;
if (SyntaxComparer.AreEquivalent(nullCheck.Expression, expression1, requireNotNull: true))
{
return(IfToReturnWithCoalesceExpression.Create(ifStatement, expression1, expression2, isYield));
}
}
return(null);
}
public static async Task <Document> RefactorAsync(
Document document,
ConditionalExpressionSyntax conditionalExpressionSyntax,
CancellationToken cancellationToken)
{
ConditionalExpressionInfo conditionalExpression;
if (ConditionalExpressionInfo.TryCreate(conditionalExpressionSyntax, out conditionalExpression))
{
SemanticModel semanticModel = await document.GetSemanticModelAsync().ConfigureAwait(false);
NullCheckExpression nullCheck;
if (NullCheckExpression.TryCreate(conditionalExpression.Condition, semanticModel, out nullCheck, cancellationToken))
{
ExpressionSyntax whenNotNull = (nullCheck.IsCheckingNotNull)
? conditionalExpression.WhenTrue
: conditionalExpression.WhenFalse;
ExpressionSyntax whenNull = (nullCheck.IsCheckingNull)
? conditionalExpression.WhenTrue
: conditionalExpression.WhenFalse;
ExpressionSyntax expression = FindExpressionThatCanBeConditionallyAccessed(nullCheck.Expression, whenNotNull);
ExpressionSyntax newNode;
if (expression.Parent == whenNotNull &&
whenNotNull.IsKind(SyntaxKind.SimpleMemberAccessExpression) &&
SemanticUtilities.IsPropertyOfNullableOfT(whenNotNull, "Value", semanticModel, cancellationToken))
{
newNode = expression;
}
else
{
newNode = SyntaxFactory.ParseExpression(whenNotNull.ToString().Insert(expression.Span.End - whenNotNull.SpanStart, "?"));
}
if (!semanticModel.GetTypeSymbol(whenNotNull, cancellationToken).IsReferenceType)
{
newNode = CSharpFactory.CoalesceExpression(newNode.Parenthesize(), whenNull.Parenthesize());
}
newNode = newNode
.WithTriviaFrom(conditionalExpressionSyntax)
.Parenthesize();
return(await document.ReplaceNodeAsync(conditionalExpressionSyntax, newNode, cancellationToken).ConfigureAwait(false));
}
}
Debug.Fail(conditionalExpressionSyntax.ToString());
return(document);
}
private static bool IsPropertyOfNullableOfT(ExpressionSyntax expression, string name, SemanticModel semanticModel, CancellationToken cancellationToken)
{
if (expression?.IsKind(SyntaxKind.SimpleMemberAccessExpression) == true)
{
var memberAccessExpression = (MemberAccessExpressionSyntax)expression;
SimpleNameSyntax simpleName = memberAccessExpression.Name;
if (simpleName?.IsKind(SyntaxKind.IdentifierName) == true)
{
var identifierName = (IdentifierNameSyntax)simpleName;
return(string.Equals(identifierName.Identifier.ValueText, name, StringComparison.Ordinal) &&
SemanticUtilities.IsPropertyOfNullableOfT(expression, name, semanticModel, cancellationToken));
}
}
return(false);
}
public static bool TryCreate(
SyntaxNode node,
SemanticModel semanticModel,
out NullCheckExpression result,
CancellationToken cancellationToken = default(CancellationToken))
{
if (node != null)
{
var expression = node as ExpressionSyntax;
if (expression != null)
{
expression = expression.WalkDownParentheses();
SyntaxKind kind = expression.Kind();
switch (kind)
{
case SyntaxKind.EqualsExpression:
case SyntaxKind.NotEqualsExpression:
{
var binaryExpression = (BinaryExpressionSyntax)expression;
ExpressionSyntax left = binaryExpression.Left?.WalkDownParentheses();
ExpressionSyntax right = binaryExpression.Right?.WalkDownParentheses();
return(TryCreate(binaryExpression, kind, left, right, semanticModel, cancellationToken, out result) ||
TryCreate(binaryExpression, kind, right, left, semanticModel, cancellationToken, out result));
}
case SyntaxKind.SimpleMemberAccessExpression:
{
if (SemanticUtilities.IsPropertyOfNullableOfT(expression, "HasValue", semanticModel, cancellationToken))
{
var memberAccessExpression = (MemberAccessExpressionSyntax)expression;
result = new NullCheckExpression(expression, memberAccessExpression.Expression, NullCheckKind.HasValue);
return(true);
}
break;
}
case SyntaxKind.LogicalNotExpression:
{
var logicalNotExpression = (PrefixUnaryExpressionSyntax)expression;
ExpressionSyntax operand = logicalNotExpression.Operand?.WalkDownParentheses();
if (operand?.IsKind(SyntaxKind.SimpleMemberAccessExpression) == true &&
SemanticUtilities.IsPropertyOfNullableOfT(operand, "HasValue", semanticModel, cancellationToken))
{
var memberAccessExpression = (MemberAccessExpressionSyntax)operand;
result = new NullCheckExpression(expression, memberAccessExpression.Expression, NullCheckKind.NotHasValue);
return(true);
}
break;
}
}
}
}
result = default(NullCheckExpression);
return(false);
}
private static bool TryCreate(
BinaryExpressionSyntax binaryExpression,
SyntaxKind kind,
ExpressionSyntax expression1,
ExpressionSyntax expression2,
SemanticModel semanticModel,
CancellationToken cancellationToken,
out NullCheckExpression result)
{
if (expression1 != null &&
expression2 != null)
{
switch (expression1.Kind())
{
case SyntaxKind.NullLiteralExpression:
{
result = new NullCheckExpression(
binaryExpression,
expression2,
(kind == SyntaxKind.EqualsExpression) ? NullCheckKind.EqualsToNull : NullCheckKind.NotEqualsToNull);
return(true);
}
case SyntaxKind.TrueLiteralExpression:
{
if (expression2?.IsKind(SyntaxKind.SimpleMemberAccessExpression) == true &&
SemanticUtilities.IsPropertyOfNullableOfT(expression2, "HasValue", semanticModel, cancellationToken))
{
result = new NullCheckExpression(
binaryExpression,
((MemberAccessExpressionSyntax)expression2).Expression,
(kind == SyntaxKind.EqualsExpression) ? NullCheckKind.HasValue : NullCheckKind.NotHasValue);
return(true);
}
break;
}
case SyntaxKind.FalseLiteralExpression:
{
if (expression2?.IsKind(SyntaxKind.SimpleMemberAccessExpression) == true &&
SemanticUtilities.IsPropertyOfNullableOfT(expression2, "HasValue", semanticModel, cancellationToken))
{
result = new NullCheckExpression(
binaryExpression,
((MemberAccessExpressionSyntax)expression2).Expression,
(kind == SyntaxKind.EqualsExpression) ? NullCheckKind.NotHasValue : NullCheckKind.HasValue);
return(true);
}
break;
}
}
}
result = default(NullCheckExpression);
return(false);
}