Reparse fuzz failure (CONST_DEF)

original:
SOURCE_FILE@0..39
  FN_DEF@0..39
    FN_KW@0..2 "fn"
    WHITESPACE@2..3 " "
    NAME@3..7
      IDENT@3..7 "main"
    PARAM_LIST@7..9
      L_PAREN@7..8 "("
      R_PAREN@8..9 ")"
    BLOCK_EXPR@9..39
      L_CURLY@9..10 "{"
      WHITESPACE@10..12 "\n\t"
      EXPR_STMT@12..15
        PATH_EXPR@12..15
          PATH@12..15
            PATH_SEGMENT@12..15
              NAME_REF@12..15
                IDENT@12..15 "csn"
      COMMENT@15..20 "/////"
      WHITESPACE@20..22 "\n\n"
      CONST_DEF@22..36
        CONST_KW@22..27 "const"
        COMMENT@27..31 "///o"
        WHITESPACE@31..33 "\n\u{b}"
        NAME@33..34
          IDENT@33..34 "Y"
        WHITESPACE@34..35 "\u{b}"
        NEVER_TYPE@35..36
          BANG@35..36 "!"
      LITERAL@36..37
        INT_NUMBER@36..37 "0"
      WHITESPACE@37..38 "\n"
      R_CURLY@38..39 "}"
reparsed:
SOURCE_FILE@0..37
  FN_DEF@0..37
    FN_KW@0..2 "fn"
    WHITESPACE@2..3 " "
    NAME@3..7
      IDENT@3..7 "main"
    PARAM_LIST@7..9
      L_PAREN@7..8 "("
      R_PAREN@8..9 ")"
    BLOCK_EXPR@9..37
      L_CURLY@9..10 "{"
      WHITESPACE@10..12 "\n\t"
      EXPR_STMT@12..15
        PATH_EXPR@12..15
          PATH@12..15
            PATH_SEGMENT@12..15
              NAME_REF@12..15
                IDENT@12..15 "csn"
      COMMENT@15..18 "///"
      WHITESPACE@18..20 "\n\n"
      CONST_DEF@20..34
        CONST_KW@20..25 "const"
        COMMENT@25..29 "///o"
        WHITESPACE@29..31 "\n\u{b}"
        NAME@31..32
          IDENT@31..32 "Y"
        WHITESPACE@32..33 "\u{b}"
        NEVER_TYPE@33..34
          BANG@33..34 "!"
      LITERAL@34..35
        INT_NUMBER@34..35 "0"
      WHITESPACE@35..36 "\n"
      R_CURLY@36..37 "}"
full reparse:
SOURCE_FILE@0..37
  FN_DEF@0..37
    FN_KW@0..2 "fn"
    WHITESPACE@2..3 " "
    NAME@3..7
      IDENT@3..7 "main"
    PARAM_LIST@7..9
      L_PAREN@7..8 "("
      R_PAREN@8..9 ")"
    BLOCK_EXPR@9..37
      L_CURLY@9..10 "{"
      WHITESPACE@10..12 "\n\t"
      EXPR_STMT@12..15
        PATH_EXPR@12..15
          PATH@12..15
            PATH_SEGMENT@12..15
              NAME_REF@12..15
                IDENT@12..15 "csn"
      CONST_DEF@15..34
        COMMENT@15..18 "///"
        WHITESPACE@18..20 "\n\n"
        CONST_KW@20..25 "const"
        COMMENT@25..29 "///o"
        WHITESPACE@29..31 "\n\u{b}"
        NAME@31..32
          IDENT@31..32 "Y"
        WHITESPACE@32..33 "\u{b}"
        NEVER_TYPE@33..34
          BANG@33..34 "!"
      LITERAL@34..35
        INT_NUMBER@34..35 "0"
      WHITESPACE@35..36 "\n"
      R_CURLY@36..37 "}"
thread '<unnamed>' panicked at 'assertion failed: `(left == right)`
  left: `"CONST_DEF@20..34"`,
 right: `"CONST_DEF@15..34"`: different syntax tree produced by the full reparse'

2.zip

Start by reproducing the reparse failure from the attached 2.zip and compare the original, reparsed, and full-reparse trees shown in the report. Trace the parser path handling the CONST_DEF and preceding comment; done means the reparse no longer panics and produces the same syntax tree as a full reparse.