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Reduce Linq usage in SymbolDisplayVisitor.CreateAliasMap #73793

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merged 2 commits into from
Jun 4, 2024

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ToddGrun
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This method showed up in a customer profile, and I was able to reproduce locally. Local repro was open Roslyn.sln, wait for CPU to settle, in SyntaxTokenParser.cs, set caret inside cref="" value and invoke completion 10 times.

*** old memory allocations ***
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*** new memory allocations ***
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This method showed up in a customer profile, and I was able to reproduce locally.
@ToddGrun ToddGrun requested a review from a team as a code owner May 30, 2024 23:34
@dotnet-issue-labeler dotnet-issue-labeler bot added Area-Compilers untriaged Issues and PRs which have not yet been triaged by a lead labels May 30, 2024
@@ -196,26 +196,39 @@ private void MinimallyQualify(INamedTypeSymbol symbol)
// 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)
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.

@@ -196,26 +196,39 @@ private void MinimallyQualify(INamedTypeSymbol symbol)
// 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)
while (startNode != null)
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@AlekseyTs AlekseyTs May 31, 2024

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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

@AlekseyTs
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Done with review pass (commit 1)

@ToddGrun
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ToddGrun commented Jun 3, 2024

@AlekseyTs -- any remaining concerns?

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LGTM (commit 2)

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4 participants