Improvements to PathConcatenation, but restricted by PathExpr legacy

Author: asgerf

javascript/ql/lib/semmle/javascript/internal/paths/PathConcatenation.qll

@@ -1,7 +1,7 @@
 private import javascript
 
 /**
- * A path expression that can be constant-folded by concatenating other paths.
+ * A path expression that can be constant-folded by concatenating subexpressions.
  */
 abstract class PathConcatenation extends Expr {
   /** Gets the separator to insert between paths */
@@ -19,10 +19,14 @@ private class AddExprConcatenation extends PathConcatenation, AddExpr {
   }
 }
 
+private class TemplateConcatenation extends PathConcatenation, TemplateLiteral {
+  override Expr getOperand(int n) { result = this.getElement(n) }
+}
+
 private class JoinCallConcatenation extends PathConcatenation, CallExpr {
   JoinCallConcatenation() {
     this.getReceiver().(VarAccess).getName() = "path" and
-    this.getCalleeName() = "join"
+    this.getCalleeName() = ["join", "resolve"]
   }
 
   override Expr getOperand(int n) { result = this.getArgument(n) }