[Parser] Intro parser support and flag for access level on imports

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -2044,6 +2044,16 @@ ERROR(spi_only_imports_not_enabled, none,
       "'@_spiOnly' requires setting the frontend flag '-experimental-spi-only-imports'",
       ())
 
+// Access level on imports
+ERROR(access_level_on_import_not_enabled, none,
+      "Access level on imports require '-enable-experimental-feature AccessLevelOnImport'",
+      ())
+ERROR(access_level_on_import_unsupported, none,
+      "The access level %0 is unsupported on imports: "
+      "only 'public', 'package', 'internal', 'fileprivate' and 'private' "
+      "are unsupported",
+      (DeclAttribute))
+
 // Opaque return types
 ERROR(opaque_type_invalid_constraint,none,
       "an 'opaque' type must specify only 'Any', 'AnyObject', protocols, "

include/swift/Basic/Features.def

@@ -115,7 +115,9 @@ EXPERIMENTAL_FEATURE(MoveOnlyClasses, true)
 EXPERIMENTAL_FEATURE(OneWayClosureParameters, false)
 EXPERIMENTAL_FEATURE(TypeWitnessSystemInference, false)
 EXPERIMENTAL_FEATURE(LayoutPrespecialization, true)
+
 EXPERIMENTAL_FEATURE(ModuleInterfaceExportAs, true)
+EXPERIMENTAL_FEATURE(AccessLevelOnImport, false)
 
 /// Whether to enable experimental differentiable programming features:
 /// `@differentiable` declaration attribute, etc.

lib/AST/ASTPrinter.cpp

@@ -3119,6 +3119,10 @@ static bool usesFeatureModuleInterfaceExportAs(Decl *decl) {
   return false;
 }
 
+static bool usesFeatureAccessLevelOnImport(Decl *decl) {
+  return false;
+}
+
 static bool usesFeatureNamedOpaqueTypes(Decl *decl) {
   return false;
 }

lib/Sema/TypeCheckAttr.cpp

@@ -934,7 +934,7 @@ void AttributeChecker::visitLazyAttr(LazyAttr *attr) {
 bool AttributeChecker::visitAbstractAccessControlAttr(
     AbstractAccessControlAttr *attr) {
   // Access control attr may only be used on value decls and extensions.
-  if (!isa<ValueDecl>(D) && !isa<ExtensionDecl>(D)) {
+  if (!isa<ValueDecl>(D) && !isa<ExtensionDecl>(D) && !isa<ImportDecl>(D)) {
     diagnoseAndRemoveAttr(attr, diag::invalid_decl_modifier, attr);
     return true;
   }
@@ -960,6 +960,19 @@ bool AttributeChecker::visitAbstractAccessControlAttr(
     return true;
   }
 
+  if (auto importDecl = dyn_cast<ImportDecl>(D)) {
+    if (!D->getASTContext().LangOpts.hasFeature(Feature::AccessLevelOnImport)) {
+      diagnoseAndRemoveAttr(attr, diag::access_level_on_import_not_enabled);
+      return true;
+    }
+
+    if (attr->getAccess() == AccessLevel::Open) {
+      diagnoseAndRemoveAttr(attr, diag::access_level_on_import_unsupported,
+                            attr);
+      return true;
+    }
+  }
+
   return false;
 }
 

test/Sema/access-level-import-flag-check.swift

@@ -0,0 +1,27 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+/// Build the libraries.
+// RUN: %target-swift-frontend -emit-module %t/PublicLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/PackageLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/InternalLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/FileprivateLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/PrivateLib.swift -o %t
+
+/// Check flag requirement, without and with the flag.
+// RUN: %target-swift-frontend -typecheck %t/ClientWithoutTheFlag.swift -I %t -verify
+// RUN: %target-swift-frontend -typecheck %t/ClientWithoutTheFlag.swift -I %t \
+// RUN:   -enable-experimental-feature AccessLevelOnImport
+
+//--- PublicLib.swift
+//--- PackageLib.swift
+//--- InternalLib.swift
+//--- FileprivateLib.swift
+//--- PrivateLib.swift
+
+//--- ClientWithoutTheFlag.swift
+public import PublicLib // expected-error@:1 {{Access level on imports require '-enable-experimental-feature AccessLevelOnImport'}}
+package import PackageLib // expected-error@:1 {{Access level on imports require '-enable-experimental-feature AccessLevelOnImport'}}
+internal import InternalLib // expected-error@:1 {{Access level on imports require '-enable-experimental-feature AccessLevelOnImport'}}
+fileprivate import FileprivateLib // expected-error@:1 {{Access level on imports require '-enable-experimental-feature AccessLevelOnImport'}}
+private import PrivateLib // expected-error@:1 {{Access level on imports require '-enable-experimental-feature AccessLevelOnImport'}}

test/Sema/access-level-import-parsing.swift

@@ -0,0 +1,29 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+/// Build the libraries.
+// RUN: %target-swift-frontend -emit-module %t/PublicLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/PackageLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/InternalLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/FileprivateLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/PrivateLib.swift -o %t
+// RUN: %target-swift-frontend -emit-module %t/OpenLib.swift -o %t
+
+/// Check that all access levels are accepted, except for 'open'.
+// RUN: %target-swift-frontend -typecheck %t/Client.swift -I %t \
+// RUN:   -enable-experimental-feature AccessLevelOnImport -verify
+
+//--- PublicLib.swift
+//--- PackageLib.swift
+//--- InternalLib.swift
+//--- FileprivateLib.swift
+//--- PrivateLib.swift
+//--- OpenLib.swift
+
+//--- Client.swift
+public import PublicLib
+package import PackageLib
+internal import InternalLib
+fileprivate import FileprivateLib
+private import PrivateLib
+open import OpenLib // expected-error {{The access level 'open' is unsupported on imports: only 'public', 'package', 'internal', 'fileprivate' and 'private' are unsupported}}

test/attr/accessibility.swift

@@ -63,7 +63,7 @@ var unterminatedEmptySubject = 0
 duplicateAttr(1) // expected-error{{argument passed to call that takes no arguments}}
 
 // CHECK ALLOWED DECLS
-private import Swift // expected-error {{'private' modifier cannot be applied to this declaration}} {{1-9=}}
+private import Swift // expected-error {{Access level on imports require '-enable-experimental-feature AccessLevelOnImport}}
 private(set) infix operator ~~~ // expected-error {{'private' modifier cannot be applied to this declaration}} {{1-14=}}
 
 private typealias MyInt = Int

utils/gyb_syntax_support/AttributeKinds.py

@@ -825,7 +825,7 @@ def __init__(self, name, swift_name=None):
                                   code=44),
     DeclAttribute('private', 'AccessControl',
                   OnFunc, OnAccessor, OnExtension, OnGenericType, OnVar, OnSubscript,
-                  OnConstructor, OnMacro,
+                  OnConstructor, OnMacro, OnImport,
                   DeclModifier,
                   NotSerialized,
                   ABIStableToAdd, ABIStableToRemove, APIStableToAdd, APIStableToRemove,