Sema: Allow availability macros in embedded code

Availability macros are rejected from library-evolution inlinable code
as the compiler didn't know how to print them in the swiftinterface.
This isn't a concern with the embedded style of fragile functions, we
can allow availability macros there.

Author: xymus

lib/Sema/MiscDiagnostics.cpp

@@ -5223,7 +5223,8 @@ static bool diagnoseAvailabilityCondition(PoundAvailableInfo *info,
   // restriction, macros would need to either be expanded when printed in
   // swiftinterfaces or be parsable as macros by module clients.
   auto fragileKind = DC->getFragileFunctionKind();
-  if (fragileKind.kind != FragileFunctionKind::None) {
+  if (fragileKind.kind != FragileFunctionKind::None &&
+      fragileKind.kind != FragileFunctionKind::EmbeddedAlwaysEmitIntoClient) {
     for (auto availSpec : info->getQueries()) {
       if (availSpec->getMacroLoc().isValid()) {
         diags.diagnose(availSpec->getMacroLoc(),

test/Sema/implementation-only-import-embedded.swift

@@ -12,6 +12,7 @@
 
 // RUN: %target-swift-frontend -typecheck -verify %s -I %t \
 // RUN:   -swift-version 5 -target arm64-apple-macosx15.0 \
+// RUN:   -define-availability "availMacro:macOS 26.0, iOS 26.0" \
 // RUN:   -enable-experimental-feature Embedded
 
 // REQUIRES: swift_feature_Embedded
@@ -73,6 +74,8 @@ public func implicitlyInlinablePublic(arg: StructFromDirect = StructFromDirect()
   implicitlyInlinablePublic()
   implicitlyInlinablePrivate()
   explicitNonInliable()
+
+  if #available(availMacro, *) { }
 }
 
 private func implicitlyInlinablePrivate(arg: StructFromDirect = StructFromDirect()) {