Add source generator

[buvinghausen]

Replace hand-written boilerplate with a Roslyn source generator

The 2,710-line TaskTupleExtensions.cs was entirely hand-written boilerplate — the same awaiter
pattern copy-pasted and incremented 16 times. Every feature addition (e.g. the ConfigureAwaitOptions
overloads) had to be replicated manually across every arity. This PR eliminates that maintenance burden
by replacing the file with a Roslyn incremental source generator.

Changes

src/TaskTupleAwaiter.Generator/ (new project)

A new netstandard2.0 project containing the generator. Key properties:

• IsRoslynComponent=true + EnforceExtendedAnalyzerRules=true — correct configuration for a Roslyn component
• IsPackable=false — the generator DLL is a build-time tool only and is never surfaced to consumers of the library

The generator implements IIncrementalGenerator and uses RegisterSourceOutput keyed to
ParseOptionsProvider rather than RegisterPostInitializationOutput. This lets Roslyn query
PreprocessorSymbolNames.Contains("NET8_0_OR_GREATER") once per TFM and cache the result — the
generator only reruns when preprocessor symbols actually change. The output is clean, #if-free code
tailored to each TFM variant.

TFM	_options field type	ConfigureAwait(ConfigureAwaitOptions) overloads
netstandard2.0, net462	bool	✗
net8.0	ConfigureAwaitOptions	✓

The 2,710 lines of boilerplate are replaced by ~230 lines of generator logic.

src/TaskTupleAwaiter/TaskTupleAwaiter.csproj (modified)

The generator is wired in as an internal build-time analyzer:

<ProjectReference Include="..\TaskTupleAwaiter.Generator\TaskTupleAwaiter.Generator.csproj"
                  OutputItemType="Analyzer"
                  ReferenceOutputAssembly="false" />

OutputItemType="Analyzer" loads the generator into the compiler. ReferenceOutputAssembly="false"
ensures the generator DLL is never emitted as a transitive dependency for consumers of the library.

src/TaskTupleAwaiter/TaskTupleExtensions.cs (deleted)

Replaced entirely by the generator output. Any future changes to the awaiter pattern — adding
ValueTask<T> support, changing the ConfigureAwait mapping, new TFM-specific overloads — now
happen in one place.

TaskTupleAwaiter.slnx (modified)

Generator project registered alongside the library project.

Verification

All existing tests pass unchanged across every TFM:

TFM	Tests
net10.0	483 ✓
net9.0	483 ✓
net8.0	483 ✓
net472	499 ✓ (includes the 16 FirstExceptionIsThrown pre-NET8 cases)

[Copilot]

Pull request overview

This PR replaces the hand-written TaskTupleExtensions boilerplate with a Roslyn incremental source generator, reducing maintenance overhead while preserving the tuple-awaiting API surface across TFMs (with ConfigureAwaitOptions only emitted for NET8+).

Changes:

• Deleted the large hand-written TaskTupleExtensions.cs implementation.
• Added a new TaskTupleAwaiter.Generator project implementing an IIncrementalGenerator that emits TaskTupleExtensions per-TFM.
• Wired the generator into the main library project as a build-time analyzer and registered the new project in the solution.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/TaskTupleAwaiter/TaskTupleExtensions.cs	Removes the previously hand-authored tuple awaiter/ConfigureAwait implementations (now generated).
src/TaskTupleAwaiter/TaskTupleAwaiter.csproj	Adds the generator as an analyzer-only project reference so it runs at build time without flowing to consumers.
src/TaskTupleAwaiter.Generator/TaskTupleExtensionsGenerator.cs	Implements the incremental generator that emits TaskTupleExtensions.g.cs tailored to NET8_0_OR_GREATER.
src/TaskTupleAwaiter.Generator/TaskTupleAwaiter.Generator.csproj	Introduces the generator project with Roslyn-component settings and required package reference.
TaskTupleAwaiter.slnx	Registers the generator project in the solution.

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[buvinghausen]

@jnm2 thoughts on the revised structure?

[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

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