AST: Inherit access level of opaque type decls from naming decl.

When an `OpaqueTypeDecl` is constructed, the access level attributes of the
decl that names the opaque type were copied on to it. However, the
`@usableFromInline` attribute is not permitted on every decl, so it does not
get copied. This in turn causes access level computations for opaque types to
fail to take `@usableFromInline` into account and that results in the emitted
symbol getting the wrong linkage during IRGen. The fix is to make access level
computations take this quirk of opaque types into account directly (like they
already to for several other kinds of decls), instead of relying on copying of
attributes.

Resolves rdar://110544170

Author: tshortli

lib/AST/AccessRequests.cpp

@@ -67,6 +67,13 @@ AccessLevelRequest::evaluate(Evaluator &evaluator, ValueDecl *D) const {
     }
   }
 
+  // Special case for opaque type decls, which inherit the access of their
+  // naming decls.
+  if (auto *opaqueType = dyn_cast<OpaqueTypeDecl>(D)) {
+    if (auto *namingDecl = opaqueType->getNamingDecl())
+      return namingDecl->getFormalAccess();
+  }
+
   DeclContext *DC = D->getDeclContext();
 
   // Special case for generic parameters; we just give them a dummy

lib/AST/Decl.cpp

@@ -3749,6 +3749,15 @@ bool ValueDecl::isUsableFromInline() const {
       return true;
   }
 
+  if (auto *opaqueType = dyn_cast<OpaqueTypeDecl>(this)) {
+    if (auto *namingDecl = opaqueType->getNamingDecl()) {
+      if (namingDecl->getAttrs().hasAttribute<UsableFromInlineAttr>() ||
+          namingDecl->getAttrs().hasAttribute<AlwaysEmitIntoClientAttr>() ||
+          namingDecl->getAttrs().hasAttribute<InlinableAttr>())
+        return true;
+    }
+  }
+
   if (auto *EED = dyn_cast<EnumElementDecl>(this))
     if (EED->getParentEnum()->getAttrs().hasAttribute<UsableFromInlineAttr>())
       return true;

lib/Sema/TypeCheckGeneric.cpp

@@ -213,7 +213,6 @@ OpaqueResultTypeRequest::evaluate(Evaluator &evaluator,
   auto opaqueDecl = OpaqueTypeDecl::get(
       originatingDecl, genericParams, parentDC, interfaceSignature,
       opaqueReprs);
-  opaqueDecl->copyFormalAccessFrom(originatingDecl);
   if (auto originatingSig = originatingDC->getGenericSignatureOfContext()) {
     opaqueDecl->setGenericSignature(originatingSig);
   } else {

test/IRGen/Inputs/AlwaysInlineIntoWithOpaque.swift

@@ -14,3 +14,16 @@ public func testInlineWithOpaque() -> some P {
   }
   return 2.0
 }
+
+@_alwaysEmitIntoClient
+public func testInlineWithOpaqueUsableFromInline() -> some P {
+  if #available(macOS 9.0, *) {
+    return usableFromInline()
+  }
+  return 4.0
+}
+
+@usableFromInline
+func usableFromInline() -> some P {
+  return 3
+}

test/IRGen/Inputs/AlwaysInlineIntoWithOpaqueReplacement.swift

@@ -6,3 +6,8 @@ extension Int : P {
 
 extension Double : P {
 }
+
+@usableFromInline
+func usableFromInline() -> some P {
+  return 3
+}

test/IRGen/opaque_result_alwaysInlineIntoClient.swift

@@ -1,11 +1,11 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-build-swift -target %target-cpu-apple-macosx10.15 -parse-as-library -emit-library -emit-module-path %t/AlwaysInlineIntoWithOpaque.swiftmodule -module-name AlwaysInlineIntoWithOpaque %S/Inputs/AlwaysInlineIntoWithOpaque.swift -o %t/%target-library-name(AlwaysInlineIntoWithOpaque)
+// RUN: %target-build-swift -target %target-cpu-apple-macosx10.15 -parse-as-library -emit-library -emit-module-path %t/AlwaysInlineIntoWithOpaque.swiftmodule -module-name AlwaysInlineIntoWithOpaque -enable-library-evolution %S/Inputs/AlwaysInlineIntoWithOpaque.swift -o %t/%target-library-name(AlwaysInlineIntoWithOpaque)
 // RUN: %target-codesign %t/%target-library-name(AlwaysInlineIntoWithOpaque)
 // RUN: %target-build-swift -target %target-cpu-apple-macosx10.15 -lAlwaysInlineIntoWithOpaque -module-name main -I %t -L %t %s -o %t/a.out
 // RUN: %target-codesign %t/a.out
 // RUN: %target-run %t/a.out | %FileCheck %s
 
-// RUN: %target-build-swift -target %target-cpu-apple-macosx10.15 -parse-as-library -emit-library -emit-module-path %t/AlwaysInlineIntoWithOpaque.swiftmodule -module-name AlwaysInlineIntoWithOpaque %S/Inputs/AlwaysInlineIntoWithOpaqueReplacement.swift -o %t/%target-library-name(AlwaysInlineIntoWithOpaque)
+// RUN: %target-build-swift -target %target-cpu-apple-macosx10.15 -parse-as-library -emit-library -emit-module-path %t/AlwaysInlineIntoWithOpaque.swiftmodule -module-name AlwaysInlineIntoWithOpaque -enable-library-evolution %S/Inputs/AlwaysInlineIntoWithOpaqueReplacement.swift -o %t/%target-library-name(AlwaysInlineIntoWithOpaque)
 // RUN: %target-codesign %t/a.out
 // RUN: %target-run %t/a.out | %FileCheck %s
 
@@ -27,3 +27,11 @@ public func test() {
 
 test()
 // CHECK: 1
+
+public func testUsableFromInline() {
+  let p = testInlineWithOpaqueUsableFromInline()
+  print(p)
+}
+
+testUsableFromInline()
+// CHECK: 3

test/TBD/opaque_result_type.swift

@@ -77,6 +77,11 @@ public func dynReplacement(x: String) -> some P {
   return "replaced"
 }
 
+@usableFromInline
+func ufi() -> some O {
+  return 1
+}
+
 extension String: P {
   public func poo() -> some O {
     return 0