Check that signatures of @usableFromInline declarations only reference @usableFromInline or public types

include/swift/AST/Decl.h

@@ -2162,9 +2162,6 @@ class ValueDecl : public Decl {
   llvm::PointerIntPair<Type, 3, OptionalEnum<AccessLevel>> TypeAndAccess;
   unsigned LocalDiscriminator = 0;
 
-private:
-    bool isUsableFromInline() const;
-
 protected:
   ValueDecl(DeclKind K,
             llvm::PointerUnion<DeclContext *, ASTContext *> context,
@@ -2238,6 +2235,8 @@ class ValueDecl : public Decl {
   SourceLoc getNameLoc() const { return NameLoc; }
   SourceLoc getLoc() const { return NameLoc; }
 
+  bool isUsableFromInline() const;
+
   bool hasAccess() const {
     return TypeAndAccess.getInt().hasValue();
   }
@@ -2266,7 +2265,6 @@ class ValueDecl : public Decl {
     if (treatUsableFromInlineAsPublic &&
         result == AccessLevel::Internal &&
         isUsableFromInline()) {
-      assert(!useDC);
       return AccessLevel::Public;
     }
     if (useDC && (result == AccessLevel::Internal ||

include/swift/AST/DiagnosticsSema.def

@@ -1292,6 +1292,28 @@ WARNING(pattern_type_access_inferred_warn,none,
         "because its type %6 uses "
         "%select{a private|a fileprivate|an internal|%error|%error}5 type",
         (bool, bool, bool, AccessLevel, bool, AccessLevel, Type))
+ERROR(pattern_type_not_usable_from_inline,none,
+      "type referenced from a '@usableFromInline' "
+      "%select{%select{variable|constant}0|property}1 "
+      "must be '@usableFromInline' or public",
+      (bool, bool))
+WARNING(pattern_type_not_usable_from_inline_warn,none,
+        "type referenced from a '@usableFromInline' "
+        "%select{%select{variable|constant}0|property}1 "
+        "should be '@usableFromInline' or public",
+        (bool, bool))
+ERROR(pattern_type_not_usable_from_inline_inferred,none,
+      "type referenced from a '@usableFromInline' "
+      "%select{%select{variable|constant}0|property}1 "
+      "with inferred type %2 "
+      "must be '@usableFromInline' or public",
+      (bool, bool, Type))
+WARNING(pattern_type_not_usable_from_inline_inferred_warn,none,
+        "type referenced from a '@usableFromInline' "
+        "%select{%select{variable|constant}0|property}1 "
+        "with inferred type %2 "
+        "should be '@usableFromInline' or public",
+        (bool, bool, Type))
 ERROR(pattern_binds_no_variables,none,
       "%select{property|global variable}0 declaration does not bind any "
       "variables",
@@ -1346,6 +1368,16 @@ WARNING(type_alias_underlying_type_access_warn,none,
         "because its underlying type uses "
         "%select{a private|a fileprivate|an internal|%error|%error}2 type",
         (bool, AccessLevel, AccessLevel, bool))
+ERROR(type_alias_underlying_type_not_usable_from_inline,none,
+      "type referenced from the underlying type of a "
+      "'@usableFromInline' type alias "
+      "must be '@usableFromInline' or public",
+      ())
+WARNING(type_alias_underlying_type_not_usable_from_inline_warn,none,
+        "type referenced from the underlying type of a "
+        "'@usableFromInline' type alias "
+        "should be '@usableFromInline' or public",
+        ())
 
 // Subscripts
 ERROR(subscript_type_access,none,
@@ -1363,6 +1395,14 @@ WARNING(subscript_type_access_warn,none,
         "because its %select{index|element type}3 uses "
         "%select{a private|a fileprivate|an internal|%error|%error}2 type",
         (bool, AccessLevel, AccessLevel, bool))
+ERROR(subscript_type_usable_from_inline,none,
+      "%select{index type|element type}0 of a '@usableFromInline' subscript "
+      "must be '@usableFromInline' or public",
+      (bool))
+WARNING(subscript_type_usable_from_inline_warn,none,
+        "%select{index type|element type}0 of a '@usableFromInline' subscript "
+        "should be '@usableFromInline' or public",
+        (bool))
 
 // Functions
 ERROR(function_type_access,none,
@@ -1381,6 +1421,16 @@ WARNING(function_type_access_warn,none,
         "because its %select{parameter|result}5 uses "
         "%select{a private|a fileprivate|an internal|%error|%error}3 type",
         (bool, AccessLevel, bool, AccessLevel, unsigned, bool))
+ERROR(function_type_usable_from_inline,none,
+      "the %select{parameter|result}1 of a "
+      "'@usableFromInline' %select{function|method|initializer}0 "
+      "must be '@usableFromInline' or public",
+      (unsigned, bool))
+WARNING(function_type_usable_from_inline_warn,none,
+        "the %select{parameter|result}1 of a "
+        "'@usableFromInline' %select{function|method|initializer}0 "
+        "should be '@usableFromInline' or public",
+        (unsigned, bool))
 ERROR(noreturn_not_supported,none,
       "'@noreturn' has been removed; functions that never return should have a "
       "return type of 'Never' instead", ())
@@ -1585,6 +1635,12 @@ WARNING(protocol_access_warn,none,
         "%select{protocol should not refine|protocol's 'where' clause should not use}2}0 "
         "%select{a private|a fileprivate|an internal|%error|%error}3 protocol",
         (bool, AccessLevel, bool, AccessLevel, bool))
+ERROR(protocol_usable_from_inline,none,
+      "protocol %select{refined|used}0 by '@usableFromInline' protocol "
+      "must be '@usableForInline' or public", (bool))
+WARNING(protocol_usable_from_inline_warn,none,
+        "protocol %select{refined|used}0 by '@usableFromInline' protocol "
+        "should be '@usableForInline' or public", (bool))
 ERROR(protocol_property_must_be_computed_var,none,
       "immutable property requirement must be declared as 'var' with a "
       "'{ get }' specifier", ())
@@ -1627,6 +1683,16 @@ WARNING(associated_type_access_warn,none,
         "%select{a private|a fileprivate|an internal|%error|%error}1 type in its "
         "%select{default definition|requirement}2 ",
         (AccessLevel, AccessLevel, unsigned))
+ERROR(associated_type_not_usable_from_inline,none,
+      "type referenced from a "
+      "%select{default definition|requirement}0 of an associated type in a "
+      "'@usableFromInline' protocol must be '@usableFromInline' or public",
+      (unsigned))
+WARNING(associated_type_not_usable_from_inline_warn,none,
+        "type referenced from a "
+        "%select{default definition|requirement}0 of an associated type in a "
+        "'@usableFromInline' protocol should be '@usableFromInline' or public",
+        (unsigned))
 
 NOTE(bad_associated_type_deduction,none,
      "unable to infer associated type %0 for protocol %1",
@@ -1879,6 +1945,16 @@ WARNING(generic_param_access_warn,none,
         "because its generic %select{parameter|requirement}5 uses "
         "%select{a private|a fileprivate|an internal|%error|%error}3 type",
         (DescriptiveDeclKind, bool, AccessLevel, AccessLevel, bool, bool))
+ERROR(generic_param_usable_from_inline,none,
+      "type referenced from a "
+      "generic %select{parameter|requirement}1 of a '@usableFromInline' %0 "
+      "must be '@usableFromInline' or public",
+      (DescriptiveDeclKind, bool))
+WARNING(generic_param_usable_from_inline_warn,none,
+        "type referenced from a "
+        "generic %select{parameter|requirement}1 of a '@usableFromInline' %0 "
+        "should be '@usableFromInline' or public",
+        (DescriptiveDeclKind, bool))
 
 ERROR(override_multiple_decls_base,none,
       "declaration %0 cannot override more than one superclass declaration",
@@ -2108,6 +2184,12 @@ WARNING(enum_case_access_warn,none,
         "enum case in %select{a private|a fileprivate|an internal|a public|%error}0 enum "
         "uses %select{a private|a fileprivate|an internal|%error|%error}1 type",
         (AccessLevel, AccessLevel))
+ERROR(enum_case_usable_from_inline,none,
+      "type of enum case in '@usableFromInline' enum "
+      "must be '@usableFromInline' or public", ())
+WARNING(enum_case_usable_from_inline_warn,none,
+        "type of enum case in '@usableFromInline' enum "
+        "should be '@usableFromInline' or public", ())
 ERROR(enum_stored_property,none,
       "enums must not contain stored properties", ())
 
@@ -2145,6 +2227,17 @@ WARNING(enum_raw_type_access_warn,none,
         "%select{a private|a fileprivate|an internal|%error|%error}2 type",
         (bool, AccessLevel, AccessLevel, bool))
 
+ERROR(enum_raw_type_not_usable_from_inline,none,
+      "type referenced from the raw type of a "
+      "'@usableFromInline' enum "
+      "must be '@usableFromInline' or public",
+      ())
+WARNING(enum_raw_type_not_usable_from_inline_warn,none,
+        "type referenced from the raw type of a "
+        "'@usableFromInline' enum "
+        "should be '@usableFromInline' or public",
+        ())
+
 ERROR(empty_enum_raw_type,none,
       "an enum with no cases cannot declare a raw type", ())
 ERROR(enum_raw_value_without_raw_type,none,
@@ -3263,6 +3356,17 @@ WARNING(class_super_access_warn,none,
       "|uses %select{a private|a fileprivate|an internal|%error|%error}2 "
       "type as a generic parameter}4",
       (bool, AccessLevel, AccessLevel, bool, bool))
+ERROR(class_super_not_usable_from_inline,none,
+      "%select{type referenced from |}0the superclass of "
+      "a '@usableFromInline' class "
+      "must be '@usableFromInline' or public",
+      (bool))
+WARNING(class_super_not_usable_from_inline_warn,none,
+        "%select{type referenced from |}0the superclass of "
+        "a '@usableFromInline' class "
+        "should be '@usableFromInline' or public",
+        (bool))
+
 ERROR(dot_protocol_on_non_existential,none,
       "cannot use 'Protocol' with non-protocol type %0", (Type))
 ERROR(tuple_single_element,none,

lib/AST/Decl.cpp

@@ -2148,6 +2148,10 @@ bool ValueDecl::isUsableFromInline() const {
     if (EED->getParentEnum()->getAttrs().hasAttribute<UsableFromInlineAttr>())
       return true;
 
+  if (auto *ATD = dyn_cast<AssociatedTypeDecl>(this))
+    if (ATD->getProtocol()->getAttrs().hasAttribute<UsableFromInlineAttr>())
+      return true;
+
   return false;
 }
 

lib/Sema/CMakeLists.txt

@@ -32,6 +32,7 @@ add_swift_library(swiftSema STATIC
   PlaygroundTransform.cpp
   ResilienceDiagnostics.cpp
   SourceLoader.cpp
+  TypeCheckAccess.cpp
   TypeCheckAttr.cpp
   TypeCheckAvailability.cpp
   TypeCheckCaptures.cpp