fix(extractor): resolve member-group symbols in IsStaticHandler (mined ImageSharp FP #4/4)

.github/workflows/ci.yml

@@ -141,6 +141,7 @@ jobs:
             frontend/roslyn/samples/InjectedDcViewSample.xaml.cs \
             frontend/roslyn/samples/ResolvedDisposableSample.cs \
             frontend/roslyn/samples/FieldReleaseSample.cs \
+            frontend/roslyn/samples/StaticClassEscapeSample.cs \
             -o "$RUNNER_TEMP/facts.json"
           cat "$RUNNER_TEMP/facts.json"
       - name: Check facts through the core
@@ -321,6 +322,14 @@ jobs:
           if echo "$out" | grep -q "CleanStaticEventViewModel"; then
             echo "FAIL: an unsubscribed (released) static-event subscription was wrongly reported"; exit 1
           fi
+          # P-004 robust static-handler exemption (mined: ImageSharp MemoryAllocatorValidator): a
+          # static-METHOD handler on a static event stores a null-target delegate -> no instance is
+          # retained -> OWN014 must NOT fire, even when the method-group symbol surfaces as a member
+          # group (now resolved via CandidateSymbols). (StaticEventEscapeViewModel above proves an
+          # INSTANCE handler on the same static event still escapes, so this stays scoped.)
+          if echo "$out" | grep -q "StaticAllocationCounter"; then
+            echo "FAIL: a static-method handler on a static event was wrongly reported as a region escape"; exit 1
+          fi
           # P-004 process-lived-subscriber exemption (mined: ScreenToGif App +
           # Translator): the WPF `App` singleton hooking the process-lived
           # AppDomain.UnhandledException promotes nothing, so the static-source region

frontend/roslyn/OwnSharp.Extractor/Program.cs

@@ -185,10 +185,23 @@
 // Target is null, so no instance is retained — the subscription cannot leak a
 // subscriber, however long-lived the source. Only method-group handlers
 // (identifier / member access) are judged; lambdas and delegate-typed values may
-// capture state and are left as leak candidates.
-static bool IsStaticHandler(ExpressionSyntax right, SemanticModel model) =>
-    IsHandler(right)
-        && model.GetSymbolInfo(right).Symbol is IMethodSymbol { IsStatic: true };
+// capture state and are left as leak candidates. A method group's symbol can surface
+// as a MEMBER GROUP (Symbol == null, CandidateSymbols populated) instead of the bound
+// method, so fall back to the candidates — else a genuinely static-method handler is
+// missed and a static-source subscription that retains NO instance is mis-reported as
+// a region escape (mined: ImageSharp MemoryAllocatorValidator's static MemoryDiagnostics
+// handlers). When falling back, require ALL candidates static so an overload set that
+// mixes a static and an instance method is not wrongly exempted.
+static bool IsStaticHandler(ExpressionSyntax right, SemanticModel model)
+{
+    if (!IsHandler(right))
+        return false;
+    var info = model.GetSymbolInfo(right);
+    if (info.Symbol is { } s)
+        return s is IMethodSymbol { IsStatic: true };
+    var cands = info.CandidateSymbols;
+    return cands.Length > 0 && cands.All(c => c is IMethodSymbol { IsStatic: true });
+}
 
 // P-004 process-lived-subscriber exemption: the WPF application object (`App`) is a
 // process-lived singleton — exactly one instance, created at startup, alive until
@@ -1931,7 +1944,7 @@
     .Split(Path.PathSeparator, StringSplitOptions.RemoveEmptyEntries)
     .Where(p => p.EndsWith(".dll", StringComparison.OrdinalIgnoreCase))
     .ToList();
 var refNames = new HashSet<string>(tpa.Select(Path.GetFileName), StringComparer.OrdinalIgnoreCase);
 var references = tpa.Select(p => (MetadataReference)MetadataReference.CreateFromFile(p)).ToList();
 // P-004 WPF profile: widen the reference set with assemblies named by the
 // OWN_EXTRA_REF_DIRS env var (colon-separated dirs) — e.g. the WindowsDesktop ref

frontend/roslyn/samples/StaticClassEscapeSample.cs

@@ -0,0 +1,29 @@
+using System;
+
+namespace Own.Samples;
+
+// P-004 static-handler exemption, robustly (mined: ImageSharp MemoryAllocatorValidator).
+//
+// A static class whose static ctor hooks a process-lived STATIC event with a STATIC METHOD
+// handler stores a delegate whose Target is null — no instance is retained, so OWN014 must NOT
+// fire. The mined case slipped through because the method-group symbol can surface as a member
+// group (Symbol == null), which IsStaticHandler now resolves via CandidateSymbols. Contrast:
+// StaticEventEscapeViewModel — an INSTANCE handler on a static event — must still raise OWN014
+// (capturing lambdas in a static class likewise still escape: the closure is retained).
+
+public static class StaticDiagnosticsBus
+{
+    public static event EventHandler? Allocated;
+
+    public static void Raise() => Allocated?.Invoke(null, EventArgs.Empty);
+}
+
+public static class StaticAllocationCounter
+{
+    static StaticAllocationCounter()
+    {
+        StaticDiagnosticsBus.Allocated += OnAllocated;   // static-method handler -> null target -> SILENT
+    }
+
+    private static void OnAllocated(object? sender, EventArgs e) { }
+}