unified: Support @_exported imports

Author: asgerf

unified/ql/lib/codeql/unified/internal/NameBindingPluginSwift.qll

@@ -18,8 +18,9 @@ class NameBindingPluginSwift extends NameBindingPlugin {
     member = any(TopLevel top).getBody().getAStmt() and
     member.hasModifier(["private", "fileprivate"])
     or
-    // Imports are always file-local
-    member instanceof ImportDeclaration
+    // Imports are always file-local, except `@_exported` import which re-export everything
+    member instanceof ImportDeclaration and
+    not member.hasModifier("@_exported")
     //
     // Note: Private class members can be seen within type-extensions in the same file,
     // so we can't declare those private to their local scope.

unified/ql/lib/codeql/unified/internal/StaticNameBinding.qll

@@ -212,7 +212,6 @@ predicate valueStep(NameBindingNode node1, NameBindingNode node2) {
   |
     node2 = getNodeFromUncertainScope(scope)
     or
-    // TODO: Add support for '@_exported' with tests, so this gets exercised
     // Bulk re-exporting declarations
     exists(TopLevel top |
       declaration = top.getBody().getAStmt() and

unified/ql/test/library-tests/static-name-binding/package1/Sources/Target4/UseReExport.swift

@@ -1,11 +1,11 @@
 import Target3 // re-exports Target2
 
 private protocol P {
-    let x1: A; // $ MISSING: access=Target2.A
-    let x2: B.C; // $ MISSING: access=Target2.B access=Target2.B.C
+    let x1: A; // $ access=Target2.A
+    let x2: B.C; // $ access=Target2.B access=Target2.B.C
     let x3: C; // $ access=Target3.C
 
-    let x4: Target3.A; // $ MISSING: access=Target2.A
-    let x5: Target3.B.C; // $ MISSING: access=Target2.B access=Target2.B.C
+    let x4: Target3.A; // $ access=Target2.A
+    let x5: Target3.B.C; // $ access=Target2.B access=Target2.B.C
     let x6: Target3.C; // $ access=Target3.C
 }