PackageCMO: fix serializability check for keypath

When keypath was checked for serializability, its referenced method was
sometimes incorrectly deemed serializable even if its referenced function was not.
This inconsistency could result in serializing a function that contained such keypath.
This PR fixes the issue by ensuring the serializability of the referenced function is
properly tracked.

Resolves rdar://142950306

Author: elsh

lib/SILOptimizer/IPO/CrossModuleOptimization.cpp

@@ -625,7 +625,8 @@ bool CrossModuleOptimization::canSerializeFieldsByInstructionKind(
         [&](SILDeclRef method) {
           if (method.isForeign)
             canUse = false;
-          else if (isPackageCMOEnabled(method.getModuleContext())) {
+          else if (canUse &&
+                   isPackageCMOEnabled(method.getModuleContext())) {
             // If the referenced keypath is internal, do not
             // serialize.
             auto methodScope = method.getDecl()->getFormalAccessScope(

test/SILOptimizer/package-cmo-cast-internal-dst

@@ -0,0 +1,124 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+/// Verify a function with a cast instruction with an internal decl as dst
+/// does not get serialized with PackageCMO in both scenarios below.
+
+/// Scenario 1.
+// RUN: %target-swift-frontend -emit-sil %t/Lib.swift -package-name pkg \
+// RUN:   -wmo -allow-non-resilient-access -package-cmo \
+// RUN:   -enable-library-evolution -swift-version 5 \
+// RUN:   -Xllvm -sil-print-function=topFunc -o %t/Lib.sil
+// RUN: %FileCheck %s < %t/Lib.sil
+
+/// Scenario 2.
+// RUN: %target-build-swift %t/Mod.swift \
+// RUN: -module-name=Mod -package-name pkg \
+// RUN: -parse-as-library -emit-module -emit-module-path %t/Mod.swiftmodule -I%t \
+// RUN: -Xfrontend -experimental-package-cmo -Xfrontend -experimental-allow-non-resilient-access \
+// RUN: -O -wmo -enable-library-evolution
+// RUN: %target-sil-opt -enable-sil-verify-all %t/Mod.swiftmodule -o %t/Mod.sil
+// RUN: %FileCheck %s --check-prefix=CHECK-MOD < %t/Mod.sil
+
+
+//--- Lib.swift
+public class Pub {
+  public var pubVar: Int
+  public init(_ arg: Int) {
+    pubVar = arg
+  }
+}
+
+class InternalKlass: Pub {}
+
+/// Verify that `InternalKlass` is visited and the instruction containing it is not serialized.
+// CHECK: sil @$s3Lib7topFuncySiAA3PubCF : $@convention(thin) (@guaranteed Pub) -> Int {
+// CHECK:   checked_cast_br Pub in %0 to InternalKlass
+public func topFunc(_ arg: Pub) -> Int {
+  let x = arg as? InternalKlass
+  return x != nil ? 1 : 0
+}
+
+
+//--- Mod.swift
+struct SymmetricTextChildQuery<Provider: PubProto> {
+  var source: Text
+  init(_ arg: Text) {
+    source = arg
+  }
+  /// This function references isCollapsible(), which contains an internal decl.
+  /// If isCollapsible() were serialized, building a client of this module would fail
+  /// due to a linker error: undefined symbol `CollapsibleTextModifier`.
+  mutating func updateValue() {
+    let resolvedSource = ResolvedStyledText.styledText(canCollapse: source.isCollapsible())
+  }
+}
+
+@frozen
+public struct Text: Equatable, Sendable {
+  public init() {}
+  @frozen
+  @usableFromInline
+  package enum Modifier: Equatable {
+    case font
+    case anyTextModifier(AnyTextModifier)
+    
+    @usableFromInline
+    package static func ==(lhs: Modifier, rhs: Modifier) -> Bool {
+      return true
+    }
+  }
+  
+  @usableFromInline
+  package var modifiers = [Modifier]()
+  
+}
+
+extension Text {
+  /// Verify that function containing an internal decl CollapsibleTextModifier is
+  /// not serialized with Package CMO.
+  // CHECK-MOD-NOT: sil package [serialized_for_package] [canonical] @$s3Mod4TextV13isCollapsibleSbyF : $@convention(method) (@guaranteed Text) -> Bool {
+  // CHECK-MOD-NOT: checked_cast_br AnyTextModifier in {{.*}} : $AnyTextModifier to CollapsibleTextModifier
+  package func isCollapsible() -> Bool {
+    modifiers.contains { modifier in
+      guard case .anyTextModifier(let anyModifier) = modifier
+      else { return false }
+      return anyModifier is CollapsibleTextModifier
+    }
+  }
+}
+
+final class CollapsibleTextModifier: AnyTextModifier {
+  override func isEqual(to other: AnyTextModifier) -> Bool {
+    other is CollapsibleTextModifier
+  }
+}
+
+public protocol PubProto {
+  var pubVar: String { get set }
+}
+
+public struct PubStruct {
+  public static func makeView<P: PubProto>(_ type: P.Type, _ arg: Text) {
+    var child = SymmetricTextChildQuery<P>(arg)
+    child.updateValue()
+  }
+}
+
+public class ResolvedStyledText {
+  package var canCollapse: Bool
+  package init(_ arg: Bool) {
+    canCollapse = arg
+  }
+}
+
+extension ResolvedStyledText {
+  package static func styledText(canCollapse: Bool) -> ResolvedStyledText {
+    return ResolvedStyledText(canCollapse)
+  }
+}
+
+@usableFromInline
+package class AnyTextModifier {
+  func isEqual(to other: AnyTextModifier) -> Bool { fatalError() }
+}

test/SILOptimizer/package-cmo-check-cast-dst.swift

@@ -0,0 +1,41 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-build-swift %t/Lib.swift \
+// RUN: -module-name=Lib -package-name Pkg \
+// RUN: -parse-as-library -emit-module -emit-module-path %t/Lib.swiftmodule -I%t \
+// RUN: -Xfrontend -experimental-package-cmo -Xfrontend -experimental-allow-non-resilient-access \
+// RUN: -O -wmo -enable-library-evolution
+// RUN: %target-sil-opt -enable-sil-verify-all %t/Lib.swiftmodule -o %t/Lib.sil
+
+// RUN: %FileCheck %s < %t/Lib.sil
+
+// REQUIRES: swift_in_compiler
+
+//--- Lib.swift
+package protocol PkgProto {
+    var pkgVar: String { get }
+}
+
+package struct Foo: PkgProto {
+    package var pkgVar: String {
+      return "Foo pkgVar"
+    }
+}
+
+// testKeyPath<A>(_:)
+// CHECK-NOT: sil package [serialized_for_package] [canonical] @$s3Lib11testKeyPathys0cD0CyxSSGSayxGAA8PkgProtoRzlF : $@convention(thin) <T where T : PkgProto> (@guaranteed Array<T>) -> @owned KeyPath<T, String> {
+// CHECK-NOT: keypath $KeyPath<T, String>, <τ_0_0 where τ_0_0 : PkgProto> (root $τ_0_0; gettable_property $String,  id #PkgProto.pkgVar!getter : <Self where Self : PkgProto> (Self) -> () -> String, getter @$s3Lib8PkgProtoP6pkgVarSSvpAaBRzlxTK : $@convention(keypath_accessor_getter) <τ_0_0 where τ_0_0 : PkgProto> (@in_guaranteed τ_0_0) -> @out String) <T>
+// CHECK-NOT: } // end sil function '$s3Lib11testKeyPathys0cD0CyxSSGSayxGAA8PkgProtoRzlF'
+package func testKeyPath<T: PkgProto>(_ array: [T]) -> KeyPath<T, String> {
+  return \T.pkgVar
+}
+
+// key path getter for PkgProto.pkgVar : <A>A
+// CHECK-NOT: sil [serialized_for_package] [thunk] [canonical] @$s3Lib8PkgProtoP6pkgVarSSvpAaBRzlxTK : $@convention(keypath_accessor_getter) <T where T : PkgProto> (@in_guaranteed T) -> @out String {
+// CHECK-NOT: witness_method $T, #PkgProto.pkgVar!getter : <Self where Self : PkgProto> (Self) -> () -> String : $@convention(witness_method: PkgProto) <τ_0_0 where τ_0_0 : PkgProto> (@in_guaranteed τ_0_0) -> @owned String // user: %3
+// CHECK-NOT: // end sil function '$s3Lib8PkgProtoP6pkgVarSSvpAaBRzlxTK'
+
+// CHECK: sil_witness_table package [serialized_for_package] Foo: PkgProto module Lib {
+// CHECK:  method #PkgProto.pkgVar!getter: <Self where Self : PkgProto> (Self) -> () -> String : @$s3Lib3FooVAA8PkgProtoA2aDP6pkgVarSSvgTW
+