Deinit-Devirtualization: fix a crash when trying to de-virtualize a non-copyable generic

rdar://129980818

Author: eeckstein

Diff for: SwiftCompilerSources/Sources/Optimizer/Utilities/Devirtualization.swift

@@ -33,7 +33,11 @@ private func devirtualize(destroy: some DevirtualizableDestroy, _ context: some
   if !type.isMoveOnly {
     return true
   }
-  precondition(type.isNominal, "non-copyable non-nominal types not supported, yet")
+
+  if !type.isNominal {
+    // E.g. a non-copyable generic function parameter
+    return true
+  }
 
   let result: Bool
   if type.nominal.hasValueDeinit && !destroy.shouldDropDeinit {

Diff for: test/SILOptimizer/devirt_deinits.sil

@@ -273,6 +273,16 @@ bb0(%0 : $*S4):
   return %r : $()
 }
 
+// CHECK-LABEL: sil [ossa] @nonCopyable_generic :
+// CHECK:         destroy_addr %0
+// CHECK:       } // end sil function 'nonCopyable_generic'
+sil [ossa] @nonCopyable_generic : $@convention(thin) <T where T : ~Copyable> (@in T) -> () {
+bb0(%0 : $*T):
+  destroy_addr %0 : $*T
+  %r = tuple ()
+  return %r : $()
+}
+
 sil @s1_deinit : $@convention(method) (@owned S1) -> ()
 sil @s2_deinit : $@convention(method) (@owned S2) -> ()
 sil @s3_deinit : $@convention(method) <T> (@in S3<T>) -> ()