SE-0193: @inlinable implies @usableFromInline

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -3741,6 +3741,9 @@ ERROR(usable_from_inline_attr_with_explicit_access,
       "declarations, but %0 is %select{private|fileprivate|%error|public|open}1",
       (DeclName, AccessLevel))
 
+WARNING(inlinable_implies_usable_from_inline,none,
+        "'@inlinable' declaration is already '@usableFromInline'",())
+
 ERROR(usable_from_inline_attr_in_protocol,none,
       "'@usableFromInline' attribute cannot be used in protocols", ())
 

lib/AST/Decl.cpp

@@ -2106,12 +2106,16 @@ SourceLoc ValueDecl::getAttributeInsertionLoc(bool forModifier) const {
 bool ValueDecl::isUsableFromInline() const {
   assert(getFormalAccess() == AccessLevel::Internal);
 
-  if (getAttrs().hasAttribute<UsableFromInlineAttr>())
+  if (getAttrs().hasAttribute<UsableFromInlineAttr>() ||
+      getAttrs().hasAttribute<InlinableAttr>())
     return true;
 
-  if (auto *accessor = dyn_cast<AccessorDecl>(this))
-    if (accessor->getStorage()->getAttrs().hasAttribute<UsableFromInlineAttr>())
+  if (auto *accessor = dyn_cast<AccessorDecl>(this)) {
+    auto *storage = accessor->getStorage();
+    if (storage->getAttrs().hasAttribute<UsableFromInlineAttr>() ||
+        storage->getAttrs().hasAttribute<InlinableAttr>())
       return true;
+  }
 
   if (auto *EED = dyn_cast<EnumElementDecl>(this))
     if (EED->getParentEnum()->getAttrs().hasAttribute<UsableFromInlineAttr>())
@@ -2261,7 +2265,9 @@ void ValueDecl::copyFormalAccessFrom(ValueDecl *source) {
   }
 
   // Inherit the @usableFromInline attribute.
-  if (source->getAttrs().hasAttribute<UsableFromInlineAttr>()) {
+  if (source->getAttrs().hasAttribute<UsableFromInlineAttr>() &&
+      !getAttrs().hasAttribute<UsableFromInlineAttr>() &&
+      !getAttrs().hasAttribute<InlinableAttr>()) {
     auto &ctx = getASTContext();
     auto *clonedAttr = new (ctx) UsableFromInlineAttr(/*implicit=*/true);
     getAttrs().add(clonedAttr);

lib/Sema/CodeSynthesis.cpp

@@ -2025,7 +2025,8 @@ static void configureDesignatedInitAttributes(TypeChecker &tc,
                                       /*treatUsableFromInlineAsPublic=*/true)
         >= AccessLevel::Public) {
     if (access == AccessLevel::Internal &&
-        !superclassCtor->isDynamic()) {
+        !superclassCtor->isDynamic() &&
+        !ctor->getAttrs().hasAttribute<InlinableAttr>()) {
       auto *clonedAttr = new (ctx) UsableFromInlineAttr(/*implicit=*/true);
       ctor->getAttrs().add(clonedAttr);
     }

lib/Sema/TypeCheckAttr.cpp

@@ -1978,6 +1978,12 @@ void AttributeChecker::visitUsableFromInlineAttr(UsableFromInlineAttr *attr) {
     diagnoseAndRemoveAttr(attr, diag::usable_from_inline_dynamic_not_supported);
     return;
   }
+
+  // On internal declarations, @inlinable implies @usableFromInline.
+  if (VD->getAttrs().hasAttribute<InlinableAttr>()) {
+    diagnoseAndRemoveAttr(attr, diag::inlinable_implies_usable_from_inline);
+    return;
+  }
 }
 
 void AttributeChecker::visitInlinableAttr(InlinableAttr *attr) {
@@ -2004,11 +2010,9 @@ void AttributeChecker::visitInlinableAttr(InlinableAttr *attr) {
     return;
   }
 
-  // @inlinable can only be applied to public or @usableFromInline
-  // declarations.
-  auto access = VD->getFormalAccess(/*useDC=*/nullptr,
-                                    /*treatUsableFromInlineAsPublic=*/true);
-  if (access < AccessLevel::Public) {
+  // @inlinable can only be applied to public or internal declarations.
+  auto access = VD->getFormalAccess();
+  if (access < AccessLevel::Internal) {
     diagnoseAndRemoveAttr(attr, diag::inlinable_decl_not_public,
                           VD->getBaseName(),
                           access);

test/attr/attr_inlinable.swift

@@ -5,6 +5,9 @@
 @inlinable struct TestInlinableStruct {}
 // expected-error@-1 {{'@inlinable' attribute cannot be applied to this declaration}}
 
+@inlinable @usableFromInline func redundantAttribute() {}
+// expected-warning@-1 {{'@inlinable' declaration is already '@usableFromInline'}}
+
 private func privateFunction() {}
 // expected-note@-1{{global function 'privateFunction()' is not '@usableFromInline' or public}}
 fileprivate func fileprivateFunction() {}
@@ -101,8 +104,7 @@ public struct Struct {
   }
 
   @inlinable
-  @usableFromInline
-  func versionedInlinableMethod() {
+  func internalInlinableMethod() {
     struct Nested {}
     // expected-error@-1 {{type 'Nested' cannot be nested inside an '@inlinable' function}}
   }
@@ -121,8 +123,8 @@ public struct Struct {
   }
 
   @inlinable
-  func internalInlinableMethod() {
-  // expected-error@-2 {{'@inlinable' attribute can only be applied to public declarations, but 'internalInlinableMethod' is internal}}
+  private func privateInlinableMethod() {
+  // expected-error@-2 {{'@inlinable' attribute can only be applied to public declarations, but 'privateInlinableMethod' is private}}
     struct Nested {}
     // OK
   }
@@ -148,7 +150,6 @@ extension VersionedProtocol {
   // expected-note@-1 {{instance method 'internalMethod()' is not '@usableFromInline' or public}}
 
   @inlinable
-  @usableFromInline
   func versionedMethod() -> T {
     internalMethod()
     // expected-error@-1 {{instance method 'internalMethod()' is internal and cannot be referenced from an '@inlinable' function}}
@@ -199,7 +200,6 @@ class Middle : Base {}
 @usableFromInline
 @_fixed_layout
 class Derived : Middle {
-  @usableFromInline
   @inlinable
   init(y: Int) {
     super.init(x: y)
@@ -220,7 +220,6 @@ class Middle2 : Base2 {}
 @_fixed_layout
 @usableFromInline
 class Derived2 : Middle2 {
-  @usableFromInline
   @inlinable
   init(y: Int) {
     super.init(x: y)