IRGen: Fix linkage of opaque type descriptor with @_alwaysEmitIntoClient owner decl

Author: slavapestov

lib/IRGen/Linking.cpp

@@ -748,16 +748,17 @@ SILLinkage LinkEntity::getLinkage(ForDefinition_t forDefinition) const {
   case Kind::OpaqueTypeDescriptor: {
     auto *opaqueType = cast<OpaqueTypeDecl>(getDecl());
 
-    // The opaque result type descriptor with availability conditions
-    // has to be emitted into a client module when associated with
+    // With conditionally available substitutions, the opaque result type
+    // descriptor has to be emitted into a client module when associated with
     // `@_alwaysEmitIntoClient` declaration which means it's linkage
     // has to be "shared".
-    if (opaqueType->hasConditionallyAvailableSubstitutions()) {
-      if (auto *srcDecl = opaqueType->getNamingDecl()) {
-        if (srcDecl->getAttrs().hasAttribute<AlwaysEmitIntoClientAttr>())
-          return SILLinkage::Shared;
-      }
-    }
+    //
+    // If we don't have conditionally available substitutions, we won't emit
+    // the descriptor at all, but still make sure we report "shared" linkage
+    // so that TBD files don't include a bogus symbol.
+    auto *srcDecl = opaqueType->getNamingDecl();
+    if (srcDecl->getAttrs().hasAttribute<AlwaysEmitIntoClientAttr>())
+      return SILLinkage::Shared;
 
     return getSILLinkage(getDeclLinkage(opaqueType), forDefinition);
   }

test/TBD/resolve_imports.swift

@@ -0,0 +1,17 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -resolve-imports -emit-tbd -emit-tbd-path %t/resolve_imports.tbd %s
+// RUN: %FileCheck %s < %t/resolve_imports.tbd
+
+// REQUIRES: OS=macosx 
+
+@_alwaysEmitIntoClient public var x: some Any {
+  get {
+  if #available(macOS 20, *) {
+    return 3
+  } else {
+    return "hi"
+  }
+  }
+}
+
+// CHECK: symbols: [ _main ]