Eliminate closure allocation by referencing UriString property instead of captured uriString parameter

[nareshjo]

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• Issue: The DocumentUri(string uriString) constructor allocates a closure/display class (<>c__DisplayClass1_0) on every invocation because the lambda () => ParseUri(uriString) captures the uriString parameter instead of using already-assigned instance property, causing unnecessary display class allocations.
  Evidence:

1. Stack trace shows allocation type TypeAllocated!<>c__DisplayClass1_0 (compiler-generated closure)
2. Source code at line 28 shows: _parsedUriLazy = new(() => ParseUri(uriString)); which captures the uriString parameter
3. The UriString property is assigned before the Lazy<> creation, so we can use this.UriString instead to avoid parameter capture

TypeAllocated!<>c__DisplayClass1_0
clr.dll!JIT_New
microsoft.codeanalysis.languageserver.protocol.dll!Roslyn.LanguageServer.Protocol.DocumentUri..ctor
microsoft.codeanalysis.languageserver.protocol.dll!Roslyn.LanguageServer.Protocol.DocumentUriConverter.Read
system.text.json.dll!System.Text.Json.Serialization.JsonConverter`[System.__Canon].TryRead

• Issue type: AVOID creating lambdas that capture variables on hot path

• Proposed fix: Change the lambda in DocumentUri(string uriString) constructor to reference the instance property UriString instead of the captured parameter uriString. UriString is a get-only auto-property set in the constructor and never mutated afterward. So this is a minimal and safe fix that eliminates the display class allocation while maintaining identical behavior.

Best practices wiki
See related failure in PRISM
ADO work item

[CyrusNajmabadi]

Won't the new code allocate a delegate too so as to capture this?

[CyrusNajmabadi]

I don't really see why we need a lazy at all. We already store the string. Just have another Nullable string that is lazily computed if null when accessed.

[jasonmalinowski]

@CyrusNajmabadi We'll allocate the delegate regardless, but we won't need a separate closure to capture the local.

[CyrusNajmabadi]

I'd rather us move to no-alloc.

[jasonmalinowski]

@CyrusNajmabadi Go right ahead! I'll sign off on that.