[Macros] Add tests for conditional conformance expansion.

Author: hborla

test/Demangle/Inputs/manglings.txt

@@ -456,3 +456,4 @@ $s9MacroUser016testFreestandingA9ExpansionyyF4Foo3L_V23bitwidthNumberedStructsfM
 @__swiftmacro_1a13testStringifyAA1bySi_SitF9stringifyfMf_  ---> freestanding macro expansion #1 of stringify in a.testStringify(a: Swift.Int, b: Swift.Int) -> ()
 @__swiftmacro_15accessor_macros8MyStructV4nameSSvp17myPropertyWrapperfMa_ ---> accessor macro expansion #1 of myPropertyWrapper in accessor_macros.MyStruct.name : Swift.String
 @__swiftmacro_18macro_expand_peers1SV1f1a3for_SSSi_SSSdtYaF20addCompletionHandlerfMp_ ---> peer macro expansion #1 of addCompletionHandler in macro_expand_peers.S.f(a: Swift.Int, for: Swift.String, _: Swift.Double) async -> Swift.String
+@__swiftmacro_25macro_expand_conformances7GenericV20DelegatedConformancefMc_ ---> conformance macro expansion #1 of DelegatedConformance in macro_expand_conformances.Generic

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -1023,3 +1023,38 @@ public struct EquatableMacro: ConformanceMacro {
     return [(protocolName, nil)]
   }
 }
+
+public struct DelegatedConformanceMacro: ConformanceMacro, MemberMacro {
+  public static func expansion(
+    of node: AttributeSyntax,
+    providingConformancesOf decl: some DeclGroupSyntax,
+    in context: some MacroExpansionContext
+  ) throws -> [(TypeSyntax, GenericWhereClauseSyntax?)] {
+    let protocolName: TypeSyntax = "P"
+    let conformance: DeclSyntax =
+      """
+      extension Placeholder where Element: P {}
+      """
+
+    guard let extensionDecl = conformance.as(ExtensionDeclSyntax.self) else {
+      return []
+    }
+
+    return [(protocolName, extensionDecl.genericWhereClause)]
+  }
+
+  public static func expansion(
+    of node: AttributeSyntax,
+    providingMembersOf decl: some DeclGroupSyntax,
+    in context: some MacroExpansionContext
+  ) throws -> [DeclSyntax] {
+    let requirement: DeclSyntax =
+      """
+      static func requirement() where Element : P {
+        Element.requirement()
+      }
+      """
+
+    return [requirement]
+  }
+}

test/Macros/macro_expand_conformances.swift

@@ -1,6 +1,7 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-build-swift -swift-version 5 -I %swift-host-lib-dir -L %swift-host-lib-dir -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
-// RUNx: %target-swift-frontend -dump-macro-expansions -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir %s -module-name MacroUser 2>&1 | %FileCheck --check-prefix CHECK-DUMP %s
+// RUN: %target-swift-frontend -swift-version 5 -typecheck -enable-experimental-feature Macros -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir %s -disable-availability-checking -dump-macro-expansions > %t/expansions-dump.txt 2>&1
+// RUN: %FileCheck -check-prefix=CHECK-DUMP %s < %t/expansions-dump.txt
 // RUN: %target-typecheck-verify-swift -swift-version 5 -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -module-name MacroUser -DTEST_DIAGNOSTICS -swift-version 5
 // RUN: %target-build-swift -swift-version 5 -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -L %swift-host-lib-dir %s -o %t/main -module-name MacroUser -swift-version 5
 // RUN: %target-run %t/main | %FileCheck %s
@@ -19,7 +20,35 @@ func requireEquatable(_ value: some Equatable) {
 @Equatable
 struct S {}
 
+// CHECK-DUMP: @__swiftmacro_25macro_expand_conformances1SV9EquatablefMc_.swift
 // CHECK-DUMP: extension S : Equatable  {}
 
 // CHECK: true
 requireEquatable(S())
+
+@attached(conformance)
+@attached(member)
+macro DelegatedConformance() = #externalMacro(module: "MacroDefinition", type: "DelegatedConformanceMacro")
+
+protocol P {
+  static func requirement()
+}
+
+struct Wrapped: P {
+  static func requirement() {
+    print("Wrapped.requirement")
+  }
+}
+
+@DelegatedConformance
+struct Generic<Element> {}
+
+// CHECK-DUMP: @__swiftmacro_25macro_expand_conformances7GenericV20DelegatedConformancefMc_.swift
+// CHECK-DUMP: extension Generic : P where Element: P {}
+
+func requiresP(_ value: (some P).Type) {
+  value.requirement()
+}
+
+// CHECK: Wrapped.requirement
+requiresP(Generic<Wrapped>.self)