Extend transitive availability checking to initial value expressions

lib/Sema/TypeCheckAvailability.cpp

@@ -18,6 +18,7 @@
 #include "TypeChecker.h"
 #include "MiscDiagnostics.h"
 #include "swift/AST/ASTWalker.h"
+#include "swift/AST/Initializer.h"
 #include "swift/AST/NameLookup.h"
 #include "swift/AST/Pattern.h"
 #include "swift/AST/TypeRefinementContext.h"
@@ -1408,6 +1409,30 @@ someEnclosingDeclMatches(SourceRange ReferenceRange,
   // Climb the DeclContext hierarchy to see if any of the containing
   // declarations matches the predicate.
   const DeclContext *DC = ReferenceDC;
+
+  if (auto *InitializerDC = dyn_cast<PatternBindingInitializer>(DC)) {
+    const PatternBindingDecl *BindingDecl = InitializerDC->getBinding();
+    assert(BindingDecl);
+
+    const Pattern *RelevantPattern =
+        BindingDecl->getPattern(InitializerDC->getBindingIndex());
+
+    // FIXME: Every variable in the same pattern will have the same attributes,
+    // so for all the predicates we care about it's a waste to test more than
+    // one.
+    // FIXME: If there are /no/ variables in the pattern, we won't be able to
+    // check anything, even though there may have been attributes syntactically
+    // written on the PatternBindingDecl (`var` or `let`).
+    bool SatisfiesPredicate = false;
+    RelevantPattern->forEachVariable([&](const VarDecl *Var) {
+      SatisfiesPredicate |= Pred(Var);
+    });
+    if (SatisfiesPredicate)
+      return true;
+
+    DC = InitializerDC->getParent();
+  }
+
   do {
     auto *D = DC->getInnermostDeclarationDeclContext();
     if (!D)

test/attr/attr_availability_transitive_osx.swift

@@ -1,14 +1,18 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -parse-as-library
 // REQUIRES: OS=macosx
 
 // Allow referencing unavailable API in situations where the caller is marked unavailable in the same circumstances.
 
 @available(OSX, unavailable)
-func osx() {} // expected-note 2{{'osx()' has been explicitly marked unavailable here}}
+@discardableResult
+func osx() -> Int { return 0 } // expected-note 7 {{'osx()' has been explicitly marked unavailable here}}
 
 @available(OSXApplicationExtension, unavailable)
 func osx_extension() {}
 
+@available(OSX, unavailable)
+func osx_pair() -> (Int, Int) { return (0, 0) } // expected-note {{'osx_pair()' has been explicitly marked unavailable here}}
+
 func call_osx_extension() {
     osx_extension() // OK; osx_extension is only unavailable if -application-extension is passed.
 }
@@ -35,3 +39,43 @@ func osx_extension_call_osx_extension() {
 func osx_extension_call_osx() {
     osx() // expected-error {{'osx()' is unavailable}}
 }
+
+@available(OSX, unavailable)
+var osx_init_osx = osx() // OK
+
+@available(OSXApplicationExtension, unavailable)
+var osx_extension_init_osx = osx() // expected-error {{'osx()' is unavailable}}
+
+struct Outer {
+  @available(OSX, unavailable)
+  var osx_init_osx = osx() // OK
+
+  @available(OSX, unavailable)
+  lazy var osx_lazy_osx = osx() // OK
+
+  @available(OSXApplicationExtension, unavailable)
+  var osx_extension_init_osx = osx() // expected-error {{'osx()' is unavailable}}
+
+  @available(OSXApplicationExtension, unavailable)
+  var osx_extension_lazy_osx = osx() // expected-error {{'osx()' is unavailable}}
+
+  @available(OSX, unavailable)
+  var osx_init_multi1_osx = osx(), osx_init_multi2_osx = osx() // OK
+
+  @available(OSXApplicationExtension, unavailable)
+  var osx_extension_init_multi1_osx = osx(), osx_extension_init_multi2_osx = osx() // expected-error 2 {{'osx()' is unavailable}}
+
+  @available(OSX, unavailable)
+  var (osx_init_deconstruct1_osx, osx_init_deconstruct2_osx) = osx_pair() // OK
+
+  @available(OSXApplicationExtension, unavailable)
+  var (osx_extension_init_deconstruct1_osx, osx_extension_init_deconstruct2_osx) = osx_pair() // expected-error {{'osx_pair()' is unavailable}}
+}
+
+@available(OSX, unavailable)
+struct NotOnOSX {
+  var osx_init_osx = osx() // OK
+  lazy var osx_lazy_osx = osx() // OK
+  var osx_init_multi1_osx = osx(), osx_init_multi2_osx = osx() // OK
+  var (osx_init_deconstruct1_osx, osx_init_deconstruct2_osx) = osx_pair() // OK
+}