chore: simplify serialization codegen and fix RS2007 release tracking

[thygrrr]

Code-quality cleanup from a /simplify pass over the recently-merged work (serialization + constraints). No behavior change.

Serialization converter codegen (AliasCodeGenerator)

• Dedup the string case. For [newtype<string>], typeof(T) is typeof(string), so the generated TypeConverter previously contained duplicate conditions (typeof(string) || typeof(string)) and unreachable is string / destinationType == typeof(string) branches. Now gated on AliasedTypeSpecialType == System_String to emit a single string arm.
• Cache the inner converter. ConvertFrom/ConvertTo re-ran TypeDescriptor.GetConverter(typeof(T)) on every call. Now resolved once into a static readonly _inner field (emitted only for the non-string path that uses it).

AliasModelExtractor

• ToLocationStruct called GetLineSpan() twice; now once via .Span.
• Removed a no-op .Where(x => x is not null) over GetAttributes() (Roslyn never returns null elements).

Release tracking (AnalyzerReleases.Unshipped.md)

• The rules table was written as a GitHub-Flavored-Markdown table (surrounding pipes + backtick-quoted category), which the RS2xxx release-tracking parser rejects → RS2007 warning, and the NEWTYPE001/NEWTYPE002 entries were silently discarded (not actually tracked).
• Rewritten into the strict format (no surrounding pipes, bare Category). Category/Severity match the DiagnosticDescriptors, so the entries validate and RS2007 is gone.

Validation

• Generated output confirmed: string newtype has no _inner field and a single typeof(string) term; int newtype has one cached _inner.
• Full solution builds with 0 warnings, 0 errors.
• 395/395 tests pass in Debug (net8.0/9.0/10.0).

Note: the *_Throws constraint tests fail under -c Release because the constraints feature wraps its validation throw in #if DEBUG (unless IncludeInRelease=true). That's pre-existing and unrelated to this PR — worth confirming CI runs them in Debug.

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Summary by CodeRabbit

• Bug Fixes

  • Improved type conversion behavior for aliased string types in generated TypeConverter classes, with better handling of conversion scenarios.
  • Enhanced performance of type conversion operations through optimized converter caching in generated code.

• Refactor

  • Refined validation method extraction and location span computation logic.

• Documentation

  • Updated release notes formatting.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 434e10a6-1930-4e54-8bf5-9cf004dacae7

📥 Commits

Reviewing files that changed from the base of the PR and between 03da871 and 9d9ab14.

📒 Files selected for processing (3)

• NewType.Generator/AliasCodeGenerator.cs
• NewType.Generator/AliasModelExtractor.cs
• NewType.Generator/AnalyzerReleases.Unshipped.md

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Walkthrough

The source generator's AppendSerializationConverters is updated to detect when the aliased type is string and branch ConvertFrom/ConvertTo accordingly, caching _inner only for non-string aliases. The model extractor drops a redundant null filter on attributes and compacts ToLocationStruct into a ternary. The unshipped release notes table is reformatted from Markdown pipe syntax to plain-text pipe-delimited layout.

Changes

TypeConverter string specialization and generator cleanup

Layer / File(s)	Summary
Generated TypeConverter string specialization NewType.Generator/AliasCodeGenerator.cs	Adds aliasedIsString flag; ConvertFrom constructs alias directly from string when aliased type is string, otherwise uses cached _inner; ConvertTo returns wrapped._value for string destination when aliased type is string, or delegates to _inner.ConvertToString for other types.
Model extractor cleanup NewType.Generator/AliasModelExtractor.cs	Removes .Where(x => x is not null) guard from ExtractValidationMethod attribute iteration; ToLocationStruct rewritten as a compact ternary using GetLineSpan().Span.
Release notes reformatting NewType.Generator/AnalyzerReleases.Unshipped.md	Replaces Markdown pipe-table with backticks with a plain-text pipe-delimited layout for NEWTYPE001 and NEWTYPE002 entries.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• outfox/newtype#6: Introduced the AppendSerializationConverters method in AliasCodeGenerator.cs that this PR extends with string-alias specialization.

Poem

🐇 Hop hop, the converter's bright,
When T is string, no inner in sight!
A ternary here, a null check gone,
The generator hops swiftly along.
Cleaner code under the warren's moon —
This rabbit ships a tidy tune! 🌙

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/simplify-serialization-and-release-tracking

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