extended polymorphism, il weavers off-the-shelf support

[lofcz]

No description provided.

[Copilot]

Pull request overview

This PR extends FastCloner’s reflection cloner and source generator to better handle (1) polymorphic cloning through non-abstract base references, (2) assembly-level “external ignore” attributes, and (3) IL-weaver injected runtime state (e.g., PostSharp/Metalama patterns) so cloning remains safe and consistent across both cloning modes.

Changes:

• Add [FastClonerPolymorphic] support (including generic roots) with subtype dispatch and validation diagnostics.
• Add [assembly: FastClonerExternalIgnore(...)] support so framework ignore attributes can be honored without per-member FastCloner attributes.
• Detect and special-case weaver-injected state fields and prefer weaver-declared MemberwiseClone() when present; add regression tests and documentation.

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/FastCloner/Code/FastClonerWeaverState.cs	Detect weaver state fields and discover weaver-declared MemberwiseClone().
src/FastCloner/Code/FastClonerExternalIgnoreRegistry.cs	Reflection-side cache/lookup for assembly-registered external ignore attributes.
src/FastCloner/Code/FastClonerExternalIgnoreAttribute.cs	Assembly-level attribute to register external ignore marker types.
src/FastCloner/Code/FastClonerExprGenerator.cs	Apply external ignore + weaver-state handling in reflection expression generation.
src/FastCloner/Code/FastClonerCache.cs	Extend TypeShape with HasWeaverStateFields.
src/FastCloner/Code/ClonerToExprGenerator.cs	Skip copying weaver state fields during DeepCloneTo deep member population.
src/FastCloner.Tests/PostSharpAspectTests.cs	Regression tests simulating PostSharp IL shapes (issue #48).
src/FastCloner.Tests/PolymorphicCloneTests.cs	End-to-end tests for polymorphic dispatch, including generic roots and fallback.
src/FastCloner.Tests/ExternalIgnoreAttributeTests.cs	Tests for [assembly: FastClonerExternalIgnore] behavior and precedence.
src/FastCloner.Tests/DiagnosticTests.cs	Generator diagnostics + generated-source structural assertions for polymorphic behavior.
src/FastCloner.Tests/AbstractClassTests.cs	Verify abstract root dispatch to derived clonable generators.
src/FastCloner.SourceGenerator/TypeModelFactory.cs	Thread external ignore registry; add polymorphic root modeling and derived collection.
src/FastCloner.SourceGenerator/TypeModel.cs	Add IsPolymorphicRoot flag to the model.
src/FastCloner.SourceGenerator/SubtypeUsageCollector.cs	Collect closed generic subtype constructions from usages for dispatch lists.
src/FastCloner.SourceGenerator/PolymorphicValidationInfo.cs	Add validation diagnostics for [FastClonerPolymorphic] misuse.
src/FastCloner.SourceGenerator/MemberModel.cs	Track weaver-state members and backing-field storage for safe population.
src/FastCloner.SourceGenerator/MemberCollector.cs	Apply external-ignore matching (by declaring assembly) during member collection.
src/FastCloner.SourceGenerator/MemberCloneGenerator.cs	Adapt member population for uninitialized instances + weaver state handling.
src/FastCloner.SourceGenerator/IncludeAttributeCollector.cs	Avoid treating included subtypes as generic-arg usages; thread external ignores.
src/FastCloner.SourceGenerator/ImplicitTypeAnalyzer.cs	Thread external ignore registry through implicit analysis.
src/FastCloner.SourceGenerator/GenericUsageCollector.cs	Thread external ignore registry through usage analysis.
src/FastCloner.SourceGenerator/GenericTypeAnalyzer.cs	Skip unbound type arguments; thread external ignores into implicit analysis.
src/FastCloner.SourceGenerator/FastClonerIncrementalGenerator.cs	Integrate external ignore registry + subtype usage pipeline + polymorphic validation.
src/FastCloner.SourceGenerator/ExternalIgnoreCollector.cs	Collect per-assembly external ignore registrations into an equatable registry.
src/FastCloner.SourceGenerator/DerivedTypeCollector.cs	Support generic roots + external ignore threading for derived type models.
src/FastCloner.SourceGenerator/ContextCollector.cs	Thread external ignore registry through context collection.
src/FastCloner.SourceGenerator/CloneGeneratorContext.cs	Ensure derived-type helper method names are unique (generic constructions).
src/FastCloner.SourceGenerator/CloneCodeGenerator.cs	Implement polymorphic root dispatch + subtype-usage-derived dispatch branches.
src/FastCloner.SourceGenerator/ClassCloneBodyGenerator.cs	Pass “created without ctor” flag to avoid invoking setters and handle weaver state.
src/FastCloner.SourceGenerator.Shared/FastClonerPolymorphicAttribute.cs	New attribute enabling polymorphic dispatch on concrete roots.
src/FastCloner.Benchmark/BenchPolymorphic.cs	Benchmark for polymorphic root overhead and dispatch cost.
README.md	Document external ignore registration and [FastClonerPolymorphic] usage and precedence.

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[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated no new comments.

Suppressed comments (2)

src/FastCloner.SourceGenerator/MemberCollector.cs:57

• ResolveExternalIgnores only takes the first matching ExternalIgnoreAssemblyRegistration and breaks. Since FastClonerExternalIgnoreAttribute is AllowMultiple=true, multiple registrations on the same assembly will be ignored here, diverging from the reflection cloner (and from the attribute contract). Merge all matching registrations for the assembly instead of stopping at the first one.

                foreach (ExternalIgnoreAssemblyRegistration registration in externalIgnores.Registrations)
                {
                    if (registration.AssemblyName == displayName)
                    {
                        resolved = [.. registration.AttributeTypeFqns];

src/FastCloner.SourceGenerator/SubtypeUsageCollector.cs:58

• SubtypeUsageCollector.Collect computes FindAllDispatchRoots(symbol) twice; the second call can reuse the already-computed 'roots' list to avoid repeating the base-chain walk.

        foreach (INamedTypeSymbol chainRoot in FindAllDispatchRoots(symbol))
        {
            usages.Add(new ClosedSubtypeUsage(
                chainRoot.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat),
                model));

[github-actions]

Deep Clone Benchmarks

• OS: ubuntu-latest
• Generated (UTC): 2026-08-18 10:35:34

Current FastCloner vs DeepCloner

Benchmark	DeepCloner	FastCloner	Delta Time	DC Alloc	FC Alloc	Delta Alloc
SmallObject	65.53 ns	53.66 ns	-18% faster	184 B	48 B	-74% less
FileSpec	378.41 ns	216.61 ns	-43% faster	920 B	416 B	-55% less
StringArray_1000	411.31 ns	404.82 ns	~same	8,160 B	8,024 B	~same
SmallObjectWithCollections	477.31 ns	268.67 ns	-44% faster	1,096 B	576 B	-47% less
DynamicWithDictionary	987.70 ns	790.32 ns	-20% faster	2,712 B	1,600 B	-41% less
MediumNestedObject	1,221.93 ns	821.00 ns	-33% faster	3,416 B	1,616 B	-53% less
DynamicWithNestedObject	1,446.37 ns	969.01 ns	-33% faster	3,560 B	1,776 B	-50% less
DynamicWithArray	4,120.24 ns	3,762.84 ns	-9% faster	8,800 B	2,744 B	-69% less
LargeEventDocument_10MB	52,053.58 ns	28,536.02 ns	-45% faster	129,792 B	49,824 B	-62% less
ObjectList_100	125,999.26 ns	79,230.51 ns	-37% faster	318,888 B	149,816 B	-53% less
ObjectDictionary_50	660,219.70 ns	137,245.00 ns	-79% faster	549,654 B	218,768 B	-60% less
LargeLogBatch_10MB	4,875,880.56 ns	2,860,742.50 ns	-41% faster	3,564,656 B	2,649,102 B	-26% less

FastCloner vs latest next baseline

• Baseline generated (UTC): 2026-08-18 10:35:31
• Regression thresholds: time > 5%, alloc > 5%

Status	Benchmark	Delta Time	Delta Alloc
🔴	DynamicWithArray	+13% slower	~same
🔴	DynamicWithDictionary	+5% slower	~same
⚪	DynamicWithNestedObject	~same	~same
⚪	FileSpec	-4% faster	~same
🟢	LargeEventDocument_10MB	-5% faster	~same
⚪	LargeLogBatch_10MB	-3% faster	~same
🔴	MediumNestedObject	+6% slower	~same
⚪	ObjectDictionary_50	~same	~same
⚪	ObjectList_100	~same	~same
⚪	SmallObject	~same	~same
⚪	SmallObjectWithCollections	+3% slower	~same
⚪	StringArray_1000	-3% faster	~same

Regressions

• DynamicWithArray: time +13% slower, alloc ~same
• DynamicWithDictionary: time +5% slower, alloc ~same
• MediumNestedObject: time +6% slower, alloc ~same

Improvements

• LargeEventDocument_10MB: time -5% faster, alloc ~same

Mixed changes

• none