[Sema] Fix some walking logic

`walkToTypeReprPost` should return `true` to keep
walking, so we really want to check if the
`offendingType` hasn't been found yet. Otherwise
we'll bail as soon as we visit the first type.

Author: hamishknight

lib/Sema/TypeCheckAccess.cpp

@@ -142,7 +142,7 @@ class TypeAccessScopeDiagnoser : private ASTWalker {
 
   bool walkToTypeReprPost(TypeRepr *T) override {
     // Exit early if we've already found a problem type.
-    return offendingType != nullptr;
+    return offendingType == nullptr;
   }
 
   explicit TypeAccessScopeDiagnoser(AccessScope accessScope,

test/Sema/accessibility_typealias.swift

@@ -27,7 +27,7 @@ public final class ReplayableGenerator<S: Sequence> : IteratorProtocol {
 }
 
 struct Generic<T> {
-  fileprivate typealias Dependent = T
+  fileprivate typealias Dependent = T // expected-note 2{{type declared here}}
 }
 
 var x: Generic<Int>.Dependent = 3 // expected-error {{variable must be declared private or fileprivate because its type uses a fileprivate type}}

test/Sema/availability_compound.swift

@@ -6,6 +6,7 @@ public struct PublicStruct {
   public struct Inner {}
   @available(*, unavailable)
   internal struct Obsolete {} // expected-note * {{marked unavailable here}}
+  // expected-note@-1 3{{type declared here}}
 }
 
 @available(*, unavailable, renamed: "PublicStruct")