Ensure that generic parameters always have a valid access level.

...just in case they end up in a situation where we want to check their
access level. Like code completion.

rdar://problem/21197042

Swift SVN r29453

Author: jrose-apple

lib/Sema/TypeCheckDecl.cpp

@@ -995,10 +995,19 @@ static void finalizeGenericParamList(ArchetypeBuilder &builder,
                                      GenericParamList *genericParams,
                                      DeclContext *dc,
                                      TypeChecker &TC) {
+  Accessibility access;
+  if (auto *fd = dyn_cast<FuncDecl>(dc))
+    access = fd->getFormalAccess();
+  else if (auto *nominal = dyn_cast<NominalTypeDecl>(dc))
+    access = nominal->getFormalAccess();
+  else
+    access = Accessibility::Internal;
+
   // Wire up the archetypes.
   for (auto GP : *genericParams) {
     GP->setArchetype(builder.getArchetype(GP));
     TC.checkInheritanceClause(GP);
+    GP->setAccessibility(access);
   }
   genericParams->setAllArchetypes(
     TC.Context.AllocateCopy(builder.getAllArchetypes()));

test/IDE/complete_crashes.swift

@@ -55,3 +55,15 @@ while true {
   }
 }
 
+// rdar://problem/21197042
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=GENERIC_PARAM_AND_ASSOC_TYPE | FileCheck %s -check-prefix=GENERIC_PARAM_AND_ASSOC_TYPE
+struct CustomGenericCollection<Key> : DictionaryLiteralConvertible {
+  // GENERIC_PARAM_AND_ASSOC_TYPE: Begin completions
+  // GENERIC_PARAM_AND_ASSOC_TYPE-DAG: Decl[InstanceVar]/CurrNominal:      count[#Int#]; name=count
+  // GENERIC_PARAM_AND_ASSOC_TYPE-DAG: Decl[TypeAlias]/CurrNominal:        Key[#Key#]; name=Key
+  // GENERIC_PARAM_AND_ASSOC_TYPE-DAG: Decl[TypeAlias]/CurrNominal:        Value[#Value#]; name=Value
+  // GENERIC_PARAM_AND_ASSOC_TYPE: End completions
+  
+  var count: Int { #^GENERIC_PARAM_AND_ASSOC_TYPE^# }
+}
+