[NFC] Add test for ~Escapable features without NonEscapable feature flag

Author: meg-gupta

lib/Parse/ParseDecl.cpp

@@ -2807,7 +2807,7 @@ ParserResult<LifetimeAttr> Parser::parseLifetimeAttribute(SourceLoc atLoc,
   SmallVector<LifetimeEntry> lifetimeEntries;
 
   if (!Context.LangOpts.hasFeature(Feature::NonescapableTypes)) {
-    diagnose(loc, diag::requires_experimental_feature, "lifetime attribute",
+    diagnose(loc, diag::requires_experimental_feature, "@lifetime",
              false, getFeatureName(Feature::NonescapableTypes));
     status.setIsParseError();
     return status;

test/Sema/lifetime_attr_nofeature.swift

@@ -0,0 +1,11 @@
+// RUN: %target-typecheck-verify-swift -disable-availability-checking
+// REQUIRES: asserts
+
+struct NE : ~Escapable { // expected-error{{type 'Escapable' requires -enable-experimental-feature NonescapableTypes}}
+
+}
+
+@lifetime(ne) // expected-error{{'@lifetime' attribute is only valid when experimental feature NonescapableTypes is enabled}} expected-error{{expected declaration}}
+func derive(_ ne: NE) -> NE {
+  ne
+}