protected override Task FixAllAsync(
Document document,
ImmutableArray <Diagnostic> diagnostics,
SyntaxEditor editor,
CancellationToken cancellationToken)
{
var syntaxRoot = editor.OriginalRoot;
foreach (var diagnostic in diagnostics)
{
var firstUnreachableStatementLocation = diagnostic.AdditionalLocations.Single();
var firstUnreachableStatement = (StatementSyntax)firstUnreachableStatementLocation.FindNode(cancellationToken);
editor.RemoveNode(firstUnreachableStatement, SyntaxRemoveOptions.KeepUnbalancedDirectives);
var sections = RemoveUnreachableCodeHelpers.GetSubsequentUnreachableSections(firstUnreachableStatement);
foreach (var section in sections)
{
foreach (var statement in section)
{
editor.RemoveNode(statement, SyntaxRemoveOptions.KeepUnbalancedDirectives);
}
}
}
return(Task.CompletedTask);
}
private void ProcessUnreachableDiagnostic(
SemanticModelAnalysisContext context, SyntaxNode root, TextSpan sourceSpan, bool fadeOutCode)
{
var node = root.FindNode(sourceSpan);
// Note: this approach works as the language only supports the concept of
// unreachable statements. If we ever get unreachable subexpressions, then
// we'll need to revise this code accordingly.
var firstUnreachableStatement = node.FirstAncestorOrSelf <StatementSyntax>();
if (firstUnreachableStatement == null ||
firstUnreachableStatement.SpanStart != sourceSpan.Start)
{
return;
}
// At a high level, we can think about us wanting to fade out a "section" of unreachable
// statements. However, the compiler only reports the first statement in that "section".
// We want to figure out what other statements are in that section and fade them all out
// along with the first statement. This is made somewhat tricky due to the fact that
// subsequent sibling statements possibly being reachable due to explicit gotos+labels.
//
// On top of this, an unreachable section might not be contiguous. This is possible
// when there is unreachable code that contains a local function declaration in-situ.
// This is legal, and the local function declaration may be called from other reachable code.
//
// As such, it's not possible to just get first unreachable statement, and the last, and
// then report that whole region as unreachable. Instead, when we are told about an
// unreachable statement, we simply determine which other statements are also unreachable
// and bucket them into contiguous chunks.
//
// We then fade each of these contiguous chunks, while also having each diagnostic we
// report point back to the first unreachable statement so that we can easily determine
// what to remove if the user fixes the issue. (The fix itself has to go recompute this
// as the total set of statements to remove may be larger than the actual faded code
// that that diagnostic corresponds to).
// Get the location of this first unreachable statement. It will be given to all
// the diagnostics we create off of this single compiler diagnostic so that we always
// know how to find it regardless of which of our diagnostics the user invokes the
// fix off of.
var firstStatementLocation = root.SyntaxTree.GetLocation(firstUnreachableStatement.FullSpan);
if (!firstUnreachableStatement.IsParentKind(SyntaxKind.Block) &&
!firstUnreachableStatement.IsParentKind(SyntaxKind.SwitchSection))
{
// Can't actually remove this statement (it's an embedded statement in something
// like an 'if-statement'). Just fade the code out, but don't offer to remove it.
if (fadeOutCode)
{
context.ReportDiagnostic(
Diagnostic.Create(UnnecessaryWithoutSuggestionDescriptor, firstStatementLocation));
}
return;
}
// 'additionalLocations' is how we always pass along the locaiton of the first unreachable
// statement in this group.
var additionalLocations = SpecializedCollections.SingletonEnumerable(firstStatementLocation);
var descriptor = fadeOutCode ? UnnecessaryWithSuggestionDescriptor : Descriptor;
context.ReportDiagnostic(
Diagnostic.Create(descriptor, firstStatementLocation, additionalLocations));
var sections = RemoveUnreachableCodeHelpers.GetSubsequentUnreachableSections(firstUnreachableStatement);
foreach (var section in sections)
{
var span = TextSpan.FromBounds(section[0].FullSpan.Start, section.Last().FullSpan.End);
var location = root.SyntaxTree.GetLocation(span);
// Mark subsequent sections as being 'cascaded'. We don't need to actually process them
// when doing a fix-all as they'll be scooped up when we process the fix for the first
// section.
context.ReportDiagnostic(
Diagnostic.Create(descriptor, location, additionalLocations, s_subsequentSectionProperties));
}
}