Revert "JavaScript: Patch CFG to improve support for non-top level import declarations."

This reverts commit f05e777e64.

javascript/ql/src/semmle/javascript/CFG.qll

@@ -281,7 +281,7 @@ import javascript
  */
 class ControlFlowNode extends @cfg_node, Locatable {
   /** Gets a node succeeding this node in the CFG. */
-  cached ControlFlowNode getASuccessor() {
+  ControlFlowNode getASuccessor() {
     successor(this, result)
   }
 
@@ -457,47 +457,3 @@ class ConcreteControlFlowNode extends ControlFlowNode {
     not this instanceof SyntheticControlFlowNode
   }
 }
-
-/**
- * A CFG node corresponding to a nested (that is, non-toplevel) import declaration.
- *
- * This is a non-standard language feature that is not currently supported very well
- * by the extractor, in particular such imports do not appear in the control flow graph
- * generated by the extractor. We patch them in by overriding `getASuccessor`; once an
- * extractor fix becomes available, this class can be removed.
- */
-private class NestedImportDeclaration extends ImportDeclaration {
-  NestedImportDeclaration() {
-    exists (ASTNode p | p = getParent() |
-      not p instanceof TopLevel
-    ) and
-    // if there are no specifiers, the default control flow graph is fine
-    exists(getASpecifier())
-  }
-
-  override ControlFlowNode getASuccessor() {
-    result = getSpecifier(0).getFirstControlFlowNode()
-  }
-}
-
-/**
- * A CFG node corresponding to an import specifier in a nested import declaration.
- *
- * As for `NestedImportDeclaration` above, this is a temporary workaround that will be
- * removed once extractor support for this non-standard language feature becomes available.
- */
-private class NestedImportSpecifier extends ImportSpecifier {
-  NestedImportDeclaration decl;
-  int i;
-
-  NestedImportSpecifier() {
-    this = decl.getSpecifier(i)
-  }
-
-  override ControlFlowNode getASuccessor() {
-    result = decl.getSpecifier(i+1).getFirstControlFlowNode()
-    or
-    not exists(decl.getSpecifier(i+1)) and
-    successor(decl, result)
-  }
-}