[AST] Decl::is*AccessibleFrom methods should respect access control flag

Otherwise integrated REPL and other tools like LLDB would produce
incorrect results or crash.

Resolves: rdar://problem/30933988

Author: xedin

lib/AST/Decl.cpp

@@ -2750,6 +2750,12 @@ ValueDecl::getFormalAccessScope(const DeclContext *useDC,
                                        treatUsableFromInlineAsPublic);
 }
 
+/// Check whether it's important to respect access control restrictions
+/// in current context.
+static bool isAccessControlDisabled(const ASTContext &ctx) {
+  return !ctx.LangOpts.EnableAccessControl;
+}
+
 /// Checks if \p VD may be used from \p useDC, taking \@testable imports into
 /// account.
 ///
@@ -2760,6 +2766,9 @@ ValueDecl::getFormalAccessScope(const DeclContext *useDC,
 static bool checkAccessUsingAccessScopes(const DeclContext *useDC,
                                          const ValueDecl *VD,
                                          AccessLevel access) {
+  if (isAccessControlDisabled(VD->getASTContext()))
+    return true;
+
   AccessScope accessScope =
       getAccessScopeForFormalAccess(VD, access, useDC,
                                     /*treatUsableFromInlineAsPublic*/false);
@@ -2779,6 +2788,9 @@ static bool checkAccessUsingAccessScopes(const DeclContext *useDC,
 /// See ValueDecl::isAccessibleFrom for a description of \p forConformance.
 static bool checkAccess(const DeclContext *useDC, const ValueDecl *VD,
                         AccessLevel access, bool forConformance) {
+  if (isAccessControlDisabled(VD->getASTContext()))
+    return true;
+
   auto *sourceDC = VD->getDeclContext();
 
   if (!forConformance) {

lib/Sema/CSApply.cpp

@@ -6791,9 +6791,8 @@ static Type adjustSelfTypeForMember(Type baseTy, ValueDecl *member,
   // If the base of the access is mutable, then we may be invoking a getter or
   // setter that requires the base to be mutable.
   auto *SD = cast<AbstractStorageDecl>(member);
-  bool isSettableFromHere = SD->isSettable(UseDC)
-    && (!UseDC->getASTContext().LangOpts.EnableAccessControl
-        || SD->isSetterAccessibleFrom(UseDC));
+  bool isSettableFromHere =
+      SD->isSettable(UseDC) && SD->isSetterAccessibleFrom(UseDC);
 
   // If neither the property's getter nor its setter are mutating, the base
   // can be an rvalue.

lib/Sema/ConstraintSystem.cpp

@@ -732,8 +732,7 @@ static bool doesStorageProduceLValue(TypeChecker &TC,
   if (!storage->isSettable(useDC, base))
     return false;
 
-  if (TC.Context.LangOpts.EnableAccessControl &&
-      !storage->isSetterAccessibleFrom(useDC))
+  if (!storage->isSetterAccessibleFrom(useDC))
     return false;
 
   // If there is no base, or if the base isn't being used, it is settable.

lib/Sema/LookupVisibleDecls.cpp

@@ -129,8 +129,7 @@ static bool isDeclVisibleInLookupMode(ValueDecl *Member, LookupState LS,
 
   // Check access when relevant.
   if (!Member->getDeclContext()->isLocalContext() &&
-      !isa<GenericTypeParamDecl>(Member) && !isa<ParamDecl>(Member) &&
-      FromContext->getASTContext().LangOpts.EnableAccessControl) {
+      !isa<GenericTypeParamDecl>(Member) && !isa<ParamDecl>(Member)) {
     if (!Member->isAccessibleFrom(FromContext))
       return false;
   }

validation-test/Sema/Inputs/rdar30933988_enum.swift

@@ -0,0 +1,4 @@
+enum E<T> {
+  case foo
+  case bar(T)
+}

validation-test/Sema/rdar30933988.swift

@@ -0,0 +1,13 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -o %t/rdar30933988_enum.swiftmodule %S/Inputs/rdar30933988_enum.swift
+// RUN:  %target-typecheck-verify-swift -I %t  -disable-access-control
+
+import rdar30933988_enum
+
+let _: E = .foo
+// expected-error@-1 {{generic parameter 'T' could not be inferred}}
+let _: E<Int> = .foo // Ok
+let _: E = .bar(42)  // Ok
+let _: E<String> = .bar(42)
+// expected-error@-1 {{member 'bar' in 'E<String>' produces result of type 'E<T>', but context expects 'E<String>'}}
+let _: E<Int> = .bar(42) // Ok