[NFC] Basic: Do not return true in LangOptions::hasFeature if adoption mode

This check is used to enact features, whereas adoption mode should not
change behavior.

Author: AnthonyLatsis

lib/Basic/LangOptions.cpp

@@ -295,7 +295,7 @@ bool LangOptions::isCustomConditionalCompilationFlagSet(StringRef Name) const {
 }
 
 bool LangOptions::FeatureState::isEnabled() const {
-  return this->state != FeatureState::Kind::Off;
+  return this->state == FeatureState::Kind::Enabled;
 }
 
 bool LangOptions::FeatureState::isEnabledForAdoption() const {

lib/Sema/TypeCheckType.cpp

@@ -6411,8 +6411,10 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
       return false;
     }
 
-    // A missing `any` or `some` is always diagnosed if this feature is enabled.
-    if (ctx.LangOpts.hasFeature(Feature::ExistentialAny)) {
+    // A missing `any` or `some` is always diagnosed if this feature not
+    // disabled.
+    auto featureState = ctx.LangOpts.getFeatureState(Feature::ExistentialAny);
+    if (featureState.isEnabled() || featureState.isEnabledForAdoption()) {
       return true;
     }