internal static async Task<DebugDataTipInfo> GetInfoAsync(Document document, int position, CancellationToken cancellationToken)
{
var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
var token = root.FindToken(position);
var expression = token.Parent as ExpressionSyntax;
if (expression == null)
{
return token.IsKind(SyntaxKind.IdentifierToken)
? new DebugDataTipInfo(token.Span, text: null)
: default(DebugDataTipInfo);
}
if (expression.IsAnyLiteralExpression())
{
// If the user hovers over a literal, give them a DataTip for the type of the
// literal they're hovering over.
// Partial semantics should always be sufficient because the (unconverted) type
// of a literal can always easily be determined.
var partialDocument = await document.WithFrozenPartialSemanticsAsync(cancellationToken).ConfigureAwait(false);
var semanticModel = await partialDocument.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var type = semanticModel.GetTypeInfo(expression, cancellationToken).Type;
return type == null
? default(DebugDataTipInfo)
: new DebugDataTipInfo(expression.Span, type.ToNameDisplayString());
}
if (expression.IsRightSideOfDotOrArrow())
{
var curr = expression;
while (true)
{
var conditionalAccess = curr.GetParentConditionalAccessExpression();
if (conditionalAccess == null)
{
break;
}
curr = conditionalAccess;
}
if (curr == expression)
{
// NB: Parent.Span, not Span as below.
return new DebugDataTipInfo(expression.Parent.Span, text: null);
}
// NOTE: There may not be an ExpressionSyntax corresponding to the range we want.
// For example, for input a?.$$B?.C, we want span [|a?.B|]?.C.
return new DebugDataTipInfo(TextSpan.FromBounds(curr.SpanStart, expression.Span.End), text: null);
}
// NOTE(cyrusn): This behavior is to mimic what we did in Dev10, i'm not sure if it's
// necessary or not.
if (expression.IsKind(SyntaxKind.InvocationExpression))
{
expression = ((InvocationExpressionSyntax)expression).Expression;
}
string textOpt = null;
var typeSyntax = expression as TypeSyntax;
if (typeSyntax != null && typeSyntax.IsVar)
{
// If the user is hovering over 'var', then pass back the full type name that 'var'
// binds to.
var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
var type = semanticModel.GetTypeInfo(typeSyntax, cancellationToken).Type;
if (type != null)
{
textOpt = type.ToNameDisplayString();
}
}
return new DebugDataTipInfo(expression.Span, textOpt);
}