---input---
let
  bar = "bar";
in {
  foo.${bar} = 3;
  foo.${bar + "bar"} = 3;
}

---tokens---
'let'         Keyword
'\n  '        Text
'bar'         Literal.String.Symbol
' '           Text
'='           Operator
' '           Text
'"'           Literal.String.Double
'bar'         Literal.String.Double
'"'           Literal.String.Double
';'           Punctuation
'\n'          Text

'in'          Keyword
' '           Text
'{'           Punctuation
'\n  '        Text
'foo'         Text
'.'           Operator
'${'          Literal.String.Interpol
'bar'         Text
'}'           Literal.String.Interpol
' '           Text
'='           Operator
' '           Text
'3'           Literal.Number.Integer
';'           Punctuation
'\n  '        Text
'foo'         Text
'.'           Operator
'${'          Literal.String.Interpol
'bar'         Text
' '           Text
'+'           Operator
' '           Text
'"'           Literal.String.Double
'bar'         Literal.String.Double
'"'           Literal.String.Double
'}'           Literal.String.Interpol
' '           Text
'='           Operator
' '           Text
'3'           Literal.Number.Integer
';'           Punctuation
'\n'          Text

'}'           Punctuation
'\n'          Text