original file
-----------------------------------
export let a: string
    | boolean | number;
-----------------------------------

Grammar: TypeScript.tmLanguage
-----------------------------------
>export let a: string
 ^^^^^^
 source.ts meta.var.expr.ts keyword.control.export.ts
       ^
       source.ts meta.var.expr.ts
        ^^^
        source.ts meta.var.expr.ts storage.type.ts
           ^
           source.ts meta.var.expr.ts
            ^
            source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.definition.variable.ts variable.other.readwrite.ts
             ^
             source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts keyword.operator.type.annotation.ts
              ^
              source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts
               ^^^^^^
               source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts support.type.primitive.ts
>    | boolean | number;
 ^^^^
 source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts
     ^
     source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts keyword.operator.type.ts
      ^
      source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts
       ^^^^^^^
       source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts support.type.primitive.ts
              ^
              source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts
               ^
               source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts keyword.operator.type.ts
                ^
                source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts
                 ^^^^^^
                 source.ts meta.var.expr.ts meta.var-single-variable.expr.ts meta.type.annotation.ts support.type.primitive.ts
                       ^
                       source.ts punctuation.terminator.statement.ts