[NCGenerics] printing class-constrained generics

In cases where the generic parameter is class-constrained,
`GenericSignature::requiresProtocol` will not contain `Copyable` or
`Escapable` because GenericSignature minimization will recognize that
the class already requires them.

Thus, because classes always require those protocols, we can
simply ask if the generic parameter is required to be a class to
determine if it had any inverses.

Author: kavon

lib/AST/ASTPrinter.cpp

@@ -1470,6 +1470,10 @@ static void reconstituteInverses(GenericSignature genericSig,
   for (auto tp : typeParams) {
     assert(tp);
 
+    // Any generic parameter requiring a class could not have an inverse.
+    if (genericSig->requiresClass(tp))
+      continue;
+
     auto defaults = InverseRequirement::expandDefault(tp);
     for (auto ip : defaults) {
       auto *proto = ctx.getProtocol(getKnownProtocolKind(ip));

test/ModuleInterface/Inputs/NoncopyableGenerics_Misc.swift

@@ -68,3 +68,11 @@ public typealias SomeAlias<G> = Hello<G>
 public typealias AliasWithInverse<G> = Hello<G> where G: ~Copyable, G: ~Escapable
 
 public struct RudePointer<T: ~Copyable>: Copyable {}
+
+public class C {}
+
+public func noInversesSTART() {}
+public func checkAny<Result>(_ t: Result) where Result: Any {}
+public func usingClassConstraint<Result>(arg: Result) -> Result? where Result: C { return arg }
+public func checkAnyObject<Result>(_ t: Result) where Result: AnyObject {}
+public func noInversesEND() {}

test/ModuleInterface/noncopyable_generics.swift

@@ -96,6 +96,10 @@ import NoncopyableGenerics_Misc
 // CHECK-MISC: #if compiler(>=5.3) && $NoncopyableGenerics
 // CHECK-MISC-NEXT: public struct RudePointer<T> : Swift.Copyable where T : ~Copyable {
 
+// CHECK-MISC: noInversesSTART
+// CHECK-MISC-NOT: ~
+// CHECK-MISC: noInversesEND
+
 ///////////////////////////////////////////////////////////////////////
 // Synthesized conditional conformances are next