JS: add Parameter.getJSDocTag

javascript/ql/src/semmle/javascript/Expr.qll

@@ -29,6 +29,8 @@ class ExprOrType extends @exprortype, Documentable {
       not exists(getOwnDocumentation()) and
       if getParent() instanceof Property
       then result = getParent().(Property).getDocumentation()
+      else if getParent() instanceof MethodDeclaration
+      then result = getParent().(MethodDeclaration).getDocumentation()
       else result = getEnclosingStmt().getDocumentation()
     )
   }

javascript/ql/src/semmle/javascript/Variables.qll

@@ -585,6 +585,13 @@ class Parameter extends BindingPattern {
   int getNumDecorator() { result = count(getADecorator()) }
 
   override predicate isLValue() { any() }
+
+  /**
+   * Gets the JSDoc tag describing this parameter, if any.
+   */
+  JSDocTag getJSDocTag() {
+    none() // overridden in SimpleParameter
+  }
 }
 
 /** A parameter declaration that is not an object or array pattern. */
@@ -601,6 +608,15 @@ class SimpleParameter extends Parameter, VarDecl {
       result = ssa.getVariable().getAUse()
     )
   }
+
+  override JSDocTag getJSDocTag() {
+    exists(Function fun |
+      this = fun.getAParameter() and
+      result = fun.getDocumentation().getATag() and
+      result.getTitle() = "param" and
+      result.getName() = getName()
+    )
+  }
 }
 
 /**