commit 2bf81922f7d0b9042e64d298b2d6c5e6f3be3a61
author Aleksey Kladov <aleksey.kladov@gmail.com> Sun Sep 26 12:12:57 2021 +0300
committer Aleksey Kladov <aleksey.kladov@gmail.com> Sun Sep 26 19:16:09 2021 +0300
tree 55866a76e191f647a145f7a1ecbd4183fe1bcd55
parent c51a3c78cfda0d0a83da8510d603c1bf136357b0

internal: more reasonable grammar for blocks

Consider these expples

        { 92 }
  async { 92 }
    'a: { 92 }
   #[a] { 92 }

Previously the tree for them were

  BLOCK_EXPR
    { ... }

  EFFECT_EXPR
    async
    BLOCK_EXPR
      { ... }

  EFFECT_EXPR
    'a:
    BLOCK_EXPR
      { ... }

  BLOCK_EXPR
    #[a]
    { ... }

As you see, it gets progressively worse :) The last two items are
especially odd. The last one even violates the balanced curleys
invariant we have (#10357) The new approach is to say that the stuff in
`{}` is stmt_list, and the block is stmt_list + optional modifiers

  BLOCK_EXPR
    STMT_LIST
      { ... }

  BLOCK_EXPR
    async
    STMT_LIST
      { ... }

  BLOCK_EXPR
    'a:
    STMT_LIST
      { ... }

  BLOCK_EXPR
    #[a]
    STMT_LIST
      { ... }