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Track override chain assemblies in symbol-based mode #143

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Merged
dfederm merged 1 commit into from
Apr 30, 2026
Merged

Track override chain assemblies in symbol-based mode #143

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36 changes: 36 additions & 0 deletions src/Analyzer/ReferenceTrimmerAnalyzer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -307,6 +307,40 @@ void TrackPatternTypes(IPatternOperation pattern)
}
}

// When a member is referenced via an `override`, the C# compiler validates the entire
// override chain at compile time, so any assembly along the chain must remain a reference.
// The IOperation only points at the override (the "near" symbol); without walking
// OverriddenMethod/Property/Event we miss assemblies that declare the original or any
// intermediate base member, producing false-positive RT0002 diagnostics whose removal
// results in CS0012 errors.
void TrackOverriddenChain(ISymbol? member)
{
switch (member)
{
case IMethodSymbol method:
for (IMethodSymbol? overridden = method.OverriddenMethod; overridden != null; overridden = overridden.OverriddenMethod)
{
TrackAssembly(overridden.ContainingAssembly);
}

break;
case IPropertySymbol property:
for (IPropertySymbol? overridden = property.OverriddenProperty; overridden != null; overridden = overridden.OverriddenProperty)
{
TrackAssembly(overridden.ContainingAssembly);
}

break;
case IEventSymbol evt:
for (IEventSymbol? overridden = evt.OverriddenEvent; overridden != null; overridden = overridden.OverriddenEvent)
{
TrackAssembly(overridden.ContainingAssembly);
}

break;
}
}

// Track declaration-level type references: base types, interfaces, member signatures, attributes.
context.RegisterSymbolAction(
ctx =>
Expand Down Expand Up @@ -426,6 +460,7 @@ void TrackPatternTypes(IPatternOperation pattern)
{
case IInvocationOperation invocation:
TrackAssembly(invocation.TargetMethod.ContainingAssembly);
TrackOverriddenChain(invocation.TargetMethod);
foreach (ITypeSymbol typeArg in invocation.TargetMethod.TypeArguments)
{
TrackType(typeArg);
Expand All @@ -439,6 +474,7 @@ void TrackPatternTypes(IPatternOperation pattern)

case IMemberReferenceOperation memberRef:
TrackAssembly(memberRef.Member.ContainingAssembly);
TrackOverriddenChain(memberRef.Member);
break;

case ITypeOfOperation typeOfOp:
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111 changes: 111 additions & 0 deletions src/Tests/AnalyzerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -587,6 +587,117 @@ public async Task UsedViaInheritedStaticField()
AssertNoDiagnostics(diagnostics);
}

[TestMethod]
public async Task UsedViaOverridePropertyAccess()
{
// Property is *defined* abstract on the base in another assembly, overridden on the
// derived in a second assembly, and accessed via the derived type. Without walking
// OverriddenProperty, only the derived assembly is credited and the base assembly
// would be wrongly flagged removable — yet removing it produces CS0012 because the
// C# compiler validates the override chain.
var baseAsm = EmitDependency(
"namespace Dep { public abstract class Base { public abstract string SomeProperty { get; } } }",
assemblyName: "BaseAsm");
var derivedAsm = EmitDependency(
"namespace Dep { public class Derived : Base { public override string SomeProperty => \"value\"; } }",
assemblyName: "DerivedAsm",
additionalReferences: [baseAsm.Reference]);
var diagnostics = await RunAnalyzerAsync(
"class C { string M(Dep.Derived d) => d.SomeProperty; }",
[(baseAsm.Reference, baseAsm.Path, "ProjectReference", "../Base/Base.csproj"),
(derivedAsm.Reference, derivedAsm.Path, "ProjectReference", "../Derived/Derived.csproj")]);
AssertNoDiagnostics(diagnostics);
}

[TestMethod]
public async Task UsedViaOverrideMethodCall()
{
// Method is *defined* abstract on the base in another assembly, overridden on the
// derived in a second assembly, and invoked via the derived type.
var baseAsm = EmitDependency(
"namespace Dep { public abstract class Base { public abstract void Run(); } }",
assemblyName: "BaseAsm");
var derivedAsm = EmitDependency(
"namespace Dep { public class Derived : Base { public override void Run() {} } }",
assemblyName: "DerivedAsm",
additionalReferences: [baseAsm.Reference]);
var diagnostics = await RunAnalyzerAsync(
"class C { void M(Dep.Derived d) => d.Run(); }",
[(baseAsm.Reference, baseAsm.Path, "ProjectReference", "../Base/Base.csproj"),
(derivedAsm.Reference, derivedAsm.Path, "ProjectReference", "../Derived/Derived.csproj")]);
AssertNoDiagnostics(diagnostics);
}

[TestMethod]
public async Task UsedViaOverrideEventAccess()
{
// Event is *defined* abstract on the base in another assembly, overridden on the
// derived in a second assembly, and subscribed to via the derived type.
var baseAsm = EmitDependency(
"namespace Dep { public abstract class Base { public abstract event System.EventHandler Changed; } }",
assemblyName: "BaseAsm");
var derivedAsm = EmitDependency(
"namespace Dep { public class Derived : Base { public override event System.EventHandler Changed; } }",
assemblyName: "DerivedAsm",
additionalReferences: [baseAsm.Reference]);
var diagnostics = await RunAnalyzerAsync(
"class C { void M(Dep.Derived d, System.EventHandler h) => d.Changed += h; }",
[(baseAsm.Reference, baseAsm.Path, "ProjectReference", "../Base/Base.csproj"),
(derivedAsm.Reference, derivedAsm.Path, "ProjectReference", "../Derived/Derived.csproj")]);
AssertNoDiagnostics(diagnostics);
}

[TestMethod]
public async Task UsedViaOverrideMultiLevelChain()
{
// Three-level override chain: A defines abstract, B overrides, C overrides again.
// Consumer accesses via C — every assembly in the chain must be credited because
// the C# compiler validates the full chain.
var aAsm = EmitDependency(
"namespace Dep { public abstract class A { public abstract string SomeProperty { get; } } }",
assemblyName: "AAsm");
var bAsm = EmitDependency(
"namespace Dep { public abstract class B : A { public override string SomeProperty => \"b\"; } }",
assemblyName: "BAsm",
additionalReferences: [aAsm.Reference]);
var cAsm = EmitDependency(
"namespace Dep { public class C : B { public override string SomeProperty => \"c\"; } }",
assemblyName: "CAsm",
additionalReferences: [aAsm.Reference, bAsm.Reference]);
var diagnostics = await RunAnalyzerAsync(
"class Consumer { string M(Dep.C c) => c.SomeProperty; }",
[(aAsm.Reference, aAsm.Path, "ProjectReference", "../A/A.csproj"),
(bAsm.Reference, bAsm.Path, "ProjectReference", "../B/B.csproj"),
(cAsm.Reference, cAsm.Path, "ProjectReference", "../C/C.csproj")]);
AssertNoDiagnostics(diagnostics);
}

[TestMethod]
public async Task UnrelatedReferenceNotMarkedByOverride()
{
// Negative test: accessing an overridden member on a derived type from one assembly
// should not credit an entirely unrelated external assembly. Only the assemblies on
// the override chain (and the qualifier's assembly) are required.
var baseAsm = EmitDependency(
"namespace Dep { public abstract class Base { public abstract string SomeProperty { get; } } }",
assemblyName: "BaseAsm");
var derivedAsm = EmitDependency(
"namespace Dep { public class Derived : Base { public override string SomeProperty => \"value\"; } }",
assemblyName: "DerivedAsm",
additionalReferences: [baseAsm.Reference]);
var unrelated = EmitDependency(
"namespace Other { public class Unused {} }",
assemblyName: "UnrelatedAsm");
var diagnostics = await RunAnalyzerAsync(
"class C { string M(Dep.Derived d) => d.SomeProperty; }",
[(baseAsm.Reference, baseAsm.Path, "ProjectReference", "../Base/Base.csproj"),
(derivedAsm.Reference, derivedAsm.Path, "ProjectReference", "../Derived/Derived.csproj"),
(unrelated.Reference, unrelated.Path, "ProjectReference", "../Unrelated/Unrelated.csproj")]);
Assert.AreEqual(1, diagnostics.Length);
Assert.AreEqual("RT0002", diagnostics[0].Id);
StringAssert.Contains(diagnostics[0].GetMessage(CultureInfo.InvariantCulture), "Unrelated");
}

// ──────────────────────────────────────────────────────────────────────
// Test infrastructure
// ──────────────────────────────────────────────────────────────────────
Expand Down
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