Rename validation methods for type expressions and added recursive call for type validation.

Co-authored-by: Asgerf <asgerf@github.com>

Author: Napalys

javascript/extractor/src/com/semmle/js/ast/MemberExpression.java

@@ -71,7 +71,7 @@ public void setSymbol(int symbol) {
   }
 
   @Override 
-  public boolean isValidExpression() {
-    return object instanceof ITypeExpression || object instanceof DynamicImport;
+  public boolean isValidTypeExpression() {
+    return object instanceof ITypeExpression && ((ITypeExpression)object).isValidTypeExpression() || object instanceof DynamicImport;
   }
 }

javascript/extractor/src/com/semmle/ts/ast/ITypeExpression.java

@@ -11,5 +11,5 @@
  * TypeScript AST does not distinguish <code>null</code> literals from the <code>null</code> type.
  */
 public interface ITypeExpression extends INode, ITypedAstNode {
-    public default boolean isValidExpression() { return true; }
+    public default boolean isValidTypeExpression() { return true; }
 }

javascript/extractor/src/com/semmle/ts/extractor/TypeScriptASTConverter.java

@@ -1907,7 +1907,7 @@ private Node convertOptionalType(JsonObject node, SourceLocation loc) throws Par
   }
 
   private ITypeExpression asType(Node node) {
-    return node instanceof ITypeExpression && ((ITypeExpression)node).isValidExpression() ? (ITypeExpression) node : null;
+    return node instanceof ITypeExpression && ((ITypeExpression)node).isValidTypeExpression() ? (ITypeExpression) node : null;
   }
 
   private List<ITypeExpression> convertChildrenAsTypes(JsonObject node, String child)