Retain static @_dynamicReplacement members (#924)

Author: ileitch

CHANGELOG.md

@@ -24,6 +24,7 @@
 - Fix slow baseline filtering for large projects with many results.
 - Fix inconsistent unused parameter results when the function is declared in a file that is a member of multiple targets.
 - Fix inconsistent results caused by identical extensions declared in different modules.
+- Static `@_dynamicReplacement` members are now retained.
 
 ## 3.1.0 (2025-04-05)
 

Sources/SourceGraph/Elements/Declaration.swift

@@ -49,6 +49,10 @@ public final class Declaration {
             Set(Kind.allCases.filter(\.isFunctionKind))
         }
 
+        static var variableKinds: Set<Kind> {
+            Set(Kind.allCases.filter(\.isVariableKind))
+        }
+
         static var protocolMemberKinds: [Kind] {
             let functionKinds: [Kind] = [.functionMethodInstance, .functionMethodStatic, .functionSubscript, .functionOperator, .functionOperatorInfix, .functionOperatorPostfix, .functionOperatorPrefix, .functionConstructor]
             let variableKinds: [Kind] = [.varInstance, .varStatic]
@@ -73,10 +77,6 @@ public final class Declaration {
             rawValue.hasPrefix("function")
         }
 
-        static var variableKinds: Set<Kind> {
-            Set(Kind.allCases.filter(\.isVariableKind))
-        }
-
         public var isVariableKind: Bool {
             rawValue.hasPrefix("var")
         }

Sources/SourceGraph/Mutators/DynamicMemberRetainer.swift

@@ -16,7 +16,7 @@ final class DynamicMemberRetainer: SourceGraphMutator {
             }
         }
 
-        for decl in graph.declarations(ofKinds: [.functionSubscript, .varInstance, .functionMethodInstance]) {
+        for decl in graph.declarations(ofKinds: Declaration.Kind.functionKinds.union(Declaration.Kind.variableKinds)) {
             if decl.attributes.contains("_dynamicReplacement") {
                 graph.markRetained(decl)
             }

Tests/Fixtures/Sources/RetentionFixtures/testRetainsDynamicReplacement.swift

@@ -6,6 +6,9 @@ struct FixtureStruct8 {
 }
 
 extension FixtureStruct8 {
+    @_dynamicReplacement(for: originalStaticMethod)
+    static func replacementStaticMethod() {}
+
     @_dynamicReplacement(for: originalMethod)
     func replacementMethod() {}
 
@@ -18,6 +21,7 @@ extension FixtureStruct8 {
 
 public struct FixtureStruct8Retainer {
     public func retain() {
+        _ = FixtureStruct8.originalStaticMethod()
         let strct = FixtureStruct8()
         strct.originalMethod()
         _ = strct.originalProperty

Tests/PeripheryTests/RetentionTest.swift

@@ -1035,6 +1035,9 @@ final class RetentionTest: FixtureSourceGraphTestCase {
     func testRetainsDynamicReplacement() {
         analyze(retainPublic: true) {
             assertReferenced(.struct("FixtureStruct8")) {
+                self.assertReferenced(.functionMethodStatic("originalStaticMethod()"))
+                self.assertReferenced(.functionMethodStatic("replacementStaticMethod()"))
+
                 self.assertReferenced(.functionMethodInstance("originalMethod()"))
                 self.assertReferenced(.functionMethodInstance("replacementMethod()"))