[ast] Always emit compiler(>= 5.3) when emitting guards for suppressable features to guard against parser errors.

The code here was assuming that if we already emitted a compiler guard for
non-Suppressable features, we could avoid doing it for suppressable
features. The problem with this is that compiler() does more than just check for
compiler versions... it also tells the compiler that parser errors in the if
block should be ignored when if evaluates to false.

rdar://129045783
(cherry picked from commit 521a70f)

Author: gottesmm

lib/AST/ASTPrinter.cpp

@@ -3295,10 +3295,13 @@ void swift::printWithCompatibilityFeatureChecks(ASTPrinter &printer,
   // features, or else just print the body.
   if (features.hasAnySuppressible()) {
     auto generator = features.generateSuppressibleFeatures();
+
+    // NOTE: We emit the compiler check here as well since that also implicitly
+    // ensures that we ignore parsing errors in the if block. It is harmless
+    // otherwise.
     printWithSuppressibleFeatureChecks(printer, options,
-                             /*first*/ true,
-                    /*compiler check*/ !hasRequiredFeatures,
-                                       generator,
+                                       /*first*/ true,
+                                       /*compiler check*/ true, generator,
                                        printBody);
   } else {
     printBody();

test/Concurrency/sending_conditional_suppression.swift

@@ -91,3 +91,23 @@ public struct TestInStruct {
   // CHECK-NEXT: #endif
   public func testKlassArgAndResult(_ x: NonSendableKlass, _ y: sending NonSendableKlass, z: NonSendableKlass) -> sending NonSendableKlass { fatalError() }
 }
+
+// Make sure that we emit compiler(>= 5.3) when emitting the suppressing check
+// to make sure we do not fail if we fail to parse sending in the if block.
+
+// CHECK: #if compiler(>=5.3) && $OptionalIsolatedParameters && $ExpressionMacroDefaultArguments
+// CHECK-NEXT: #if compiler(>=5.3) && $SendingArgsAndResults
+// CHECK-NEXT: @available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
+// CHECK-NEXT: @backDeployed(before: macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, visionOS 9999)
+// CHECK-NEXT: @inlinable public func withCheckedContinuation<T>(isolation:
+@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
+@backDeployed(before: macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, visionOS 9999)
+@inlinable public func withCheckedContinuation<T>(
+  isolation: isolated (any _Concurrency.Actor)? = #isolation,
+  function: String = #function,
+  _ body: (_Concurrency.CheckedContinuation<T, Swift.Never>) -> Swift.Void
+) async -> sending T {
+  return await withUnsafeContinuation {
+    body(CheckedContinuation(continuation: $0, function: function))
+  }
+}