unified: Support scoped imports

Scoped imports like 'import class B.C' are mapped to an AST of form

ImportDeclartion
  pattern: NamePattern "C"
  importedExpr:  MemberAccessExpr
    base: "B"
    member: "C"

The NamePattern introduces a local alias for 'C', but unlike type aliases we also resolve to the ultimate target, when it's coming through an import.

Author: asgerf

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

@@ -181,6 +181,11 @@ predicate valueStep(NameBindingNode node1, NameBindingNode node2) {
     node1 = getModuleNodeFromFile(top.getFile()) and
     node2.isLocalNamespace(top.getBody()) // implicitly import own module
   )
+  or
+  exists(ImportDeclaration imprt |
+    node1 = getNodeFromRef(imprt.getImportedExpr()) and
+    node2 = getNodeFromRef(imprt.getPattern())
+  )
 }
 
 predicate inheritanceStep(NameBindingNode supertype, NameBindingNode subtype) {

unified/ql/test/library-tests/static-name-binding/package1/Sources/Target1/File2.swift

@@ -1 +1,6 @@
 class A {} // name=Target1.A
+
+private import class Target2.B // $ access=Target2.B // name=LocalB
+
+// Note: currently the local name 'B' introduced by the scoped import is also resolved as a target
+private let x: B.C; // $ access=Target2.B access=Target2.B.C access=LocalB

unified/ql/test/library-tests/static-name-binding/package1/Sources/Target2/File3.swift

@@ -1 +1,5 @@
 class A {} // name=Target2.A
+
+class B { // name=Target2.B
+    class C {} // name=Target2.B.C
+}