[ParseableInterface] Don't print conformances for non-public types (#20656)

I have nothing to say but "oops".

Author: jrose-apple

lib/Frontend/ParseableInterfaceSupport.cpp

@@ -629,6 +629,9 @@ class InheritedProtocolCollector {
       return;
     }
 
+    if (!isPublicOrUsableFromInline(nominal))
+      return;
+
     map[nominal].recordProtocols(directlyInherited);
 
     // Recurse to find any nested types.
@@ -647,6 +650,9 @@ class InheritedProtocolCollector {
       return;
 
     const NominalTypeDecl *nominal = extension->getExtendedNominal();
+    if (!isPublicOrUsableFromInline(nominal))
+      return;
+
     map[nominal].recordConditionalConformances(extension->getInherited());
     // No recursion here because extensions are never nested.
   }

test/ParseableInterface/conformances.swift

@@ -3,6 +3,8 @@
 // RUN: %FileCheck -check-prefix CHECK-END %s < %t.swiftinterface
 // RUN: %FileCheck -check-prefix NEGATIVE %s < %t.swiftinterface
 
+// NEGATIVE-NOT: BAD
+
 // CHECK-LABEL: public protocol SimpleProto {
 public protocol SimpleProto {
   // CHECK: associatedtype Element
@@ -165,6 +167,20 @@ extension MultiGeneric: PublicProto where U: PrivateProto {}
 // CHECK: public struct MultiGeneric<T, U, V> {
 // CHECK-END: extension conformances.MultiGeneric : PublicProto where T : _ConstraintThatIsNotPartOfTheAPIOfThisLibrary {}
 
+internal struct InternalImpl_BAD: PrivateSubProto {}
+internal struct InternalImplConstrained_BAD<T> {}
+extension InternalImplConstrained_BAD: PublicProto where T: PublicProto {}
+internal struct InternalImplConstrained2_BAD<T> {}
+extension InternalImplConstrained2_BAD: PublicProto where T: PrivateProto {}
+
+public struct WrapperForInternal {
+  internal struct InternalImpl_BAD: PrivateSubProto {}
+  internal struct InternalImplConstrained_BAD<T> {}
+  internal struct InternalImplConstrained2_BAD<T> {}
+}
+extension WrapperForInternal.InternalImplConstrained_BAD: PublicProto where T: PublicProto {}
+extension WrapperForInternal.InternalImplConstrained2_BAD: PublicProto where T: PrivateProto {}
+
 
 // CHECK-END: @usableFromInline
 // CHECK-END-NEXT: internal protocol _ConstraintThatIsNotPartOfTheAPIOfThisLibrary {}