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Reduce Linq usage in SymbolDisplayVisitor.CreateAliasMap #73793

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merged 2 commits into from
Jun 4, 2024
Merged

Reduce Linq usage in SymbolDisplayVisitor.CreateAliasMap #73793

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b17ab52
Reduce Linq usage in SymbolDisplayVisitor.CreateAliasMap
ToddGrun May 30, 2024
9721d18
Update comment to be a bit more clear
ToddGrun Jun 1, 2024
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52 changes: 27 additions & 25 deletions src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor_Minimal.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -195,27 +195,41 @@ private IDictionary<INamespaceOrTypeSymbol, IAliasSymbol> CreateAliasMap()

// NOTE(cyrusn): If we're currently in a block of usings, then we want to collect the
// aliases that are higher up than this block. Using aliases declared in a block of
// usings are not usable from within that same block.
var usingDirective = GetAncestorOrThis<UsingDirectiveSyntax>(startNode);
if (usingDirective != null)
// usings are not usable from within that same block. This loop moves us outside of the
// immediately enclosing using directive, if any.
while (startNode != null)
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while (startNode != null)

It looks like, if we are not in in a using directive, we will traverse syntax all the way to the top in this loop, and then restart reversion from the beginning looking for a namespace declaration or a compilation unit node. Instead, we could also stop once we reached a BaseNamespaceDeclarationSyntax or CompilationUnitSyntax node. Then the next loop could continue from the current startNode instead of resetting it.

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I think I'd prefer to pass on this unless you feel strongly. It seems like the current code is authentic to the original implementation, and making the change that you suggested will complicate things slightly. If this method shows up in CPU profiles, then this suggestion sounds like a good idea to pursue.

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@AlekseyTs AlekseyTs May 31, 2024 •
edited
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while (startNode != null)

It would be good to add a comment explaining that with this loop we are trying to get out of immediately enclosing using directive, if any. #Closed

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Done in commit 2

{
startNode = usingDirective.Parent!.Parent!;
if (startNode is UsingDirectiveSyntax)
{
startNode = startNode.Parent!.Parent!;
break;
}

startNode = startNode.Parent;
}

var usingAliases = GetAncestorsOrThis<BaseNamespaceDeclarationSyntax>(startNode)
.SelectMany(n => n.Usings)
.Concat(GetAncestorsOrThis<CompilationUnitSyntax>(startNode).SelectMany(c => c.Usings))
.Where(u => u.Alias != null)
.Select(u => semanticModel.GetDeclaredSymbol(u) as IAliasSymbol)
.WhereNotNull();
startNode ??= token.Parent;

var builder = ImmutableDictionary.CreateBuilder<INamespaceOrTypeSymbol, IAliasSymbol>();
foreach (var alias in usingAliases)
while (startNode != null)
{
if (!builder.ContainsKey(alias.Target))
var usings = (startNode as BaseNamespaceDeclarationSyntax)?.Usings;
usings ??= (startNode as CompilationUnitSyntax)?.Usings;

if (usings != null)
{
builder.Add(alias.Target, alias);
foreach (var u in usings)
{
if (u.Alias != null
&& semanticModel.GetDeclaredSymbol(u) is IAliasSymbol aliasSymbol
&& !builder.ContainsKey(aliasSymbol.Target))
{
builder.Add(aliasSymbol.Target, aliasSymbol);
}
}
}

startNode = startNode.Parent;
}

return builder.ToImmutable();
Expand Down Expand Up @@ -287,18 +301,6 @@ private string RemoveAttributeSuffixIfNecessary(INamedTypeSymbol symbol, string
return symbolName;
}

private static T? GetAncestorOrThis<T>(SyntaxNode node) where T : SyntaxNode
{
return GetAncestorsOrThis<T>(node).FirstOrDefault();
}

private static IEnumerable<T> GetAncestorsOrThis<T>(SyntaxNode node) where T : SyntaxNode
{
return node == null
? SpecializedCollections.EmptyEnumerable<T>()
: node.AncestorsAndSelf().OfType<T>();
}

private IDictionary<INamespaceOrTypeSymbol, IAliasSymbol> AliasMap
{
get
Expand Down
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