parse: split up literal logic
parse: split up literal logic

name                 old time/op    new time/op    delta
Parse/Whitespace-4     1.58µs ± 1%    1.58µs ± 1%    ~             (p=0.405 n=6+6)
Parse/Comment-4         629ns ± 2%     626ns ± 3%    ~             (p=0.463 n=6+6)
Parse/LongLit-4        3.46µs ± 2%    3.38µs ± 1%  -2.34%          (p=0.009 n=6+5)
Parse/Cmds-4           17.8µs ± 1%    17.9µs ± 2%    ~             (p=0.699 n=6+6)
Parse/Quoted-4         2.45µs ± 3%    2.47µs ± 2%    ~             (p=0.411 n=6+6)
Parse/NestedStmts-4    9.77µs ± 1%    9.85µs ± 1%    ~             (p=0.132 n=6+6)
Parse/Clauses-4        6.77µs ± 2%    6.70µs ± 1%  -1.05%          (p=0.009 n=6+5)
Parse/Binary-4         6.47µs ± 3%    6.45µs ± 1%    ~             (p=1.000 n=6+6)
Parse/Redirect-4       8.46µs ± 1%    8.49µs ± 2%    ~             (p=0.589 n=6+6)
Parse/Arithm-4         5.87µs ± 1%    5.81µs ± 0%    ~             (p=0.134 n=6+5)

mvdan/sh,mvdan/sh,mvdan/sh,mvdan/sh