Always supersede conformances implied by pre-macro-expansion conformances

include/swift/AST/DeclContext.h

@@ -153,15 +153,15 @@ enum class ConformanceEntryKind : unsigned {
   /// Explicitly specified.
   Explicit,
 
+  /// The conformance is generated by a macro that has not been
+  /// expanded yet.
+  PreMacroExpansion,
+
   /// Implicitly synthesized.
   Synthesized,
 
   /// Implied by an explicitly-specified conformance.
   Implied,
-
-  /// The conformance is generated by a macro that has not been
-  /// expanded yet.
-  PreMacroExpansion,
 };
 
 /// Describes the kind of conformance lookup desired.

lib/AST/ConformanceLookupTable.h

@@ -147,7 +147,7 @@ class ConformanceLookupTable : public ASTAllocated<ConformanceLookupTable> {
     ///
     /// The only difference between the ranking kind and the kind is
     /// that implied conformances originating from a synthesized
-    /// conformance are considered to be synthesized (which has a
+    /// or pre-macro-expansion conformance are considered to be synthesized (which has a
     /// lower ranking).
     ConformanceEntryKind getRankingKind() const {
       switch (auto kind = getKind()) {
@@ -157,11 +157,22 @@ class ConformanceLookupTable : public ASTAllocated<ConformanceLookupTable> {
       case ConformanceEntryKind::PreMacroExpansion:
         return kind;
 
-      case ConformanceEntryKind::Implied:
-        return (getImpliedSource()->getDeclaredConformance()->getKind()
-                  == ConformanceEntryKind::Synthesized)
-                 ? ConformanceEntryKind::Synthesized
-                 : ConformanceEntryKind::Implied;
+      case ConformanceEntryKind::Implied: {
+        auto impliedSourceKind =
+        getImpliedSource()->getDeclaredConformance()->getKind();
+        switch (impliedSourceKind) {
+          case ConformanceEntryKind::Synthesized:
+          case ConformanceEntryKind::PreMacroExpansion:
+            return impliedSourceKind;
+
+          case ConformanceEntryKind::Explicit:
+          case ConformanceEntryKind::Inherited:
+            return ConformanceEntryKind::Implied;
+
+          case ConformanceEntryKind::Implied:
+            return getImpliedSource()->getRankingKind();
+        }
+      }
       }
 
       llvm_unreachable("Unhandled ConformanceEntryKind in switch.");

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -1360,6 +1360,19 @@ public struct HashableMacro: ExtensionMacro {
   }
 }
 
+public struct ImpliesHashableMacro: ExtensionMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    attachedTo: some DeclGroupSyntax,
+    providingExtensionsOf type: some TypeSyntaxProtocol,
+    conformingTo protocols: [TypeSyntax],
+    in context: some MacroExpansionContext
+  ) throws -> [ExtensionDeclSyntax] {
+    let ext: DeclSyntax = "extension \(type.trimmed): ImpliesHashable {}"
+    return [ext.cast(ExtensionDeclSyntax.self)]
+  }
+}
+
 public struct DelegatedConformanceMacro: ExtensionMacro, MemberMacro {
   public static func expansion(
     of node: AttributeSyntax,

test/Macros/macro_expand_extensions.swift

@@ -10,6 +10,9 @@
 // RUN: not %target-swift-frontend -enable-experimental-feature ExtensionMacros -swift-version 5 -typecheck -load-plugin-library %t/%target-library-name(MacroDefinition) -module-name MacroUser -DTEST_DIAGNOSTICS -serialize-diagnostics-path %t/macro_expand.dia %s -emit-macro-expansion-files no-diagnostics
 // RUN: c-index-test -read-diagnostics %t/macro_expand.dia 2>&1 | %FileCheck -check-prefix CHECK-DIAGS %s
 
+// Ensure that we can serialize this file as a module.
+// RUN: %target-swift-frontend -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -I %t -disable-availability-checking -emit-module -o %t/MyModule.swiftmodule -enable-testing
+
 // RUN: %target-build-swift -enable-experimental-feature ExtensionMacros -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -o %t/main -module-name MacroUser -swift-version 5 -emit-tbd -emit-tbd-path %t/MacroUser.tbd -I %t
 // RUN: %target-codesign %t/main
 // RUN: %target-run %t/main | %FileCheck %s
@@ -198,3 +201,18 @@ func requiresEquatable<T: Equatable>(_: T) { }
 func testHasPropertyWrappers(hpw: HasPropertyWrappers) {
   requiresEquatable(hpw)
 }
+
+// Check that conformances implied by a macro-defined conformance are serialized
+// without issue.
+public protocol ImpliesHashable: Hashable { }
+
+@attached(extension, conformances: ImpliesHashable)
+macro ImpliesHashable() = #externalMacro(module: "MacroDefinition", type: "ImpliesHashableMacro")
+
+func requiresHashable<T: Hashable>(_: T) { }
+func testMakeMeHashable(mmh: MakeMeHashable, dict: [MakeMeHashable: Int]) {
+  requiresHashable(mmh)
+}
+
+@ImpliesHashable
+public struct MakeMeHashable { }