[Sema] Report public imports of private modules with access levels

Take into account access-level on imports to raise an error only on
public imports, non-public imports of a private module are safe.

Author: xymus

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1959,6 +1959,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
       if (target &&
           !ID->getAttrs().hasAttribute<ImplementationOnlyAttr>() &&
           !ID->getAttrs().hasAttribute<SPIOnlyAttr>() &&
+          ID->getAccessLevel() == AccessLevel::Public &&
           target->getLibraryLevel() == LibraryLevel::SPI) {
 
         auto &diags = ID->getASTContext().Diags;

test/Sema/implementation-only-import-suggestion.swift

@@ -92,3 +92,60 @@ import PublicClang_Private
 import FullyPrivateClang
 import LocalClang
 @_exported import MainLib
+
+// RUN: %target-swift-frontend -typecheck -sdk %t/sdk %t/InternalImports.swift \
+// RUN:   -enable-experimental-feature AccessLevelOnImport \
+// RUN:   -module-name MainLib -module-cache-path %t \
+// RUN:   -F %t/sdk/System/Library/PrivateFrameworks/ \
+// RUN:   -library-level api -verify
+//--- InternalImports.swift
+internal import PublicSwift
+internal import PrivateSwift
+
+internal import PublicClang
+internal import PublicClang_Private
+internal import FullyPrivateClang
+internal import LocalClang
+
+// RUN: %target-swift-frontend -typecheck -sdk %t/sdk %t/FileprivateImports.swift \
+// RUN:   -enable-experimental-feature AccessLevelOnImport \
+// RUN:   -module-name MainLib -module-cache-path %t \
+// RUN:   -F %t/sdk/System/Library/PrivateFrameworks/ \
+// RUN:   -library-level api -verify
+//--- FileprivateImports.swift
+fileprivate import PublicSwift
+fileprivate import PrivateSwift
+
+fileprivate import PublicClang
+fileprivate import PublicClang_Private
+fileprivate import FullyPrivateClang
+fileprivate import LocalClang
+
+// RUN: %target-swift-frontend -typecheck -sdk %t/sdk %t/PrivateImports.swift \
+// RUN:   -enable-experimental-feature AccessLevelOnImport \
+// RUN:   -module-name MainLib -module-cache-path %t \
+// RUN:   -F %t/sdk/System/Library/PrivateFrameworks/ \
+// RUN:   -library-level api -verify
+//--- PrivateImports.swift
+private import PublicSwift
+private import PrivateSwift
+
+private import PublicClang
+private import PublicClang_Private
+private import FullyPrivateClang
+private import LocalClang
+
+// RUN: %target-swift-frontend -typecheck -sdk %t/sdk %t/ExplicitlyPublicImports.swift \
+// RUN:   -enable-experimental-feature AccessLevelOnImport \
+// RUN:   -module-name MainLib -module-cache-path %t \
+// RUN:   -F %t/sdk/System/Library/PrivateFrameworks/ \
+// RUN:   -library-level api -verify
+//--- ExplicitlyPublicImports.swift
+public import PublicSwift
+public import PrivateSwift // expected-error{{private module 'PrivateSwift' is imported publicly from the public module 'MainLib'}}
+
+public import PublicClang
+public import PublicClang_Private // expected-error{{private module 'PublicClang_Private' is imported publicly from the public module 'MainLib'}}
+public import FullyPrivateClang // expected-error{{private module 'FullyPrivateClang' is imported publicly from the public module 'MainLib'}}
+public import LocalClang // expected-error{{private module 'LocalClang' is imported publicly from the public module 'MainLib'}}
+@_exported public import MainLib // expected-warning{{private module 'MainLib' is imported publicly from the public module 'MainLib'}}