public CodeRefactoring GetRefactoring(IDocument document, TextSpan textSpan, CancellationToken cancellationToken)
{
SyntaxNode root = (SyntaxNode)document.GetSyntaxRoot(cancellationToken);
// If nothing selected, only cursor placed, increase the ending position by one
if (textSpan.Length == 0)
{
textSpan = new TextSpan(textSpan.Start, 1);
}
// Get nodes for highlighted code
IEnumerable <VariableDeclaratorSyntax> selectedNodes = root.DescendantNodes(textSpan).OfType <VariableDeclaratorSyntax>();
// Select the node that spans the selected text most
// Note: Here I have reversed the ranges ! node.Span.Contains, not textSpan.Contains
VariableDeclaratorSyntax selectedNode = null;
int bestSpan = -1;
foreach (var node in selectedNodes)
{
if (node.Span.Contains(textSpan))
{
int spanWidth = node.Span.Intersection(textSpan).Value.Length;
if (spanWidth > bestSpan)
{
bestSpan = spanWidth;
selectedNode = node;
}
}
}
if (selectedNode == null)
{
return(null);
}
VariableDeclaratorSyntax declarator = selectedNode;
// Verify does the variable declarator has value assigned
if (declarator.Initializer == null || declarator.HasDiagnostics)
{
return(null);
}
ISemanticModel model = document.GetSemanticModel(cancellationToken);
ISymbol declaredSymbol = model.GetDeclaredSymbol(declarator);
LocalDeclarationStatementSyntax declarationStatement = declarator.FirstAncestorOrSelf <LocalDeclarationStatementSyntax>();
// Note: declarator might be within ForStatement, but cannot be inlined
if (declarationStatement == null)
{
return(null);
}
var analysis = model.AnalyzeStatementDataFlow(declarationStatement);
// Verify that the variable is never re-assigned
if (analysis.WrittenOutside.Contains(declaredSymbol))
{
return(null);
}
// Variable inlineing is not allowed if variable is never used (side effects never take place then!)
if (!analysis.ReadOutside.Contains(declaredSymbol))
{
return(null);
}
BlockSyntax block = declarationStatement.FirstAncestorOrSelf <BlockSyntax>();
if (block == null)
{
return(null);
}
// Verify that the variables used in declaration are not re-assigned within variable usage scope
// Consider:
// int a = 1;
// int b = a;
// int c = b;
// a = 2;
// int d = b;
// `b' cannot be inlined because `d' would get other value
// Note: ChildNodes instead of DescendantNodes, because it must not be any other (nested) block
var blockAnalysis = model.AnalyzeStatementsDataFlow(declarationStatement, block.ChildNodes().OfType <StatementSyntax>().Last());
foreach (var initializerSymbol in model.AnalyzeExpressionDataFlow(declarator.Initializer.Value).ReadInside)
{
if (blockAnalysis.WrittenInside.Contains(initializerSymbol))
{
return(null);
}
}
return(new CodeRefactoring(
new[] { new InlineLocalAction(document, declarator) }
, declarator.Span));
}