Invalid variable names are not marked as errors

[NotWearingPants]

The following piece of code is invalid but it is parsed correctly:

let let = 5;
let const = 5;
const const = 2;
const let = 4;

const class = 3;
const if = 3;
const true = 2;

var const = 3;
var class = 2;

var in = 1;
let in = 2;
const in = 3;

Here's a link to the TypeScript Playground showing that the snippet above is invalid JavaScript or TypeScript

The output of tree-sitter playground is the following:

program [1, 0] - [13, 0]
  lexical_declaration [1, 0] - [1, 12]
    variable_declarator [1, 4] - [1, 11]
      name: identifier [1, 4] - [1, 7]
      value: number [1, 10] - [1, 11]
  lexical_declaration [2, 0] - [2, 14]
    variable_declarator [2, 4] - [2, 13]
      name: identifier [2, 4] - [2, 9]
      value: number [2, 12] - [2, 13]
  lexical_declaration [3, 0] - [3, 16]
    variable_declarator [3, 6] - [3, 15]
      name: identifier [3, 6] - [3, 11]
      value: number [3, 14] - [3, 15]
  lexical_declaration [4, 0] - [4, 14]
    variable_declarator [4, 6] - [4, 13]
      name: identifier [4, 6] - [4, 9]
      value: number [4, 12] - [4, 13]
  lexical_declaration [6, 0] - [6, 16]
    variable_declarator [6, 6] - [6, 15]
      name: identifier [6, 6] - [6, 11]
      value: number [6, 14] - [6, 15]
  lexical_declaration [7, 0] - [7, 13]
    variable_declarator [7, 6] - [7, 12]
      name: identifier [7, 6] - [7, 8]
      value: number [7, 11] - [7, 12]
  lexical_declaration [8, 0] - [8, 15]
    variable_declarator [8, 6] - [8, 14]
      name: identifier [8, 6] - [8, 10]
      value: number [8, 13] - [8, 14]
  variable_declaration [10, 0] - [10, 14]
    variable_declarator [10, 4] - [10, 13]
      name: identifier [10, 4] - [10, 9]
      value: number [10, 12] - [10, 13]
  variable_declaration [11, 0] - [11, 14]
    variable_declarator [11, 4] - [11, 13]
      name: identifier [11, 4] - [11, 9]
      value: number [11, 12] - [11, 13]

Each of these lines should be a syntax error.

A more special case is let: var let = 2 is valid, but let let = 2 or const let = 2 is not.
Also let in is a syntax error because it's an incomplete binary_expression unlike const in or let in which are errors because in is an invalid identifier.
The other identifiers I've listed are invalid in var/let/const.

[guillaumebrunerie]

I believe it will be possible to fix this issue only once tree-sitter/tree-sitter#246 is merged. Right now there is no way to say "an identifier but not a keyword" in the grammar.