is_syntactic_literal() returns TRUE in the presence of attributes.

[moodymudskipper]

x <- 1
attr(x, "foo") <- 42
rlang::is_syntactic_literal(x)
#> [1] TRUE

^{Created on 2024-01-23 with reprex v2.0.2}

I believe this contradicts the given definition, though the definition is a bit ambiguous :

is_syntactic_literal() is a predicate that returns TRUE for the subset of literals that are created by R when parsing text (see parse_expr()): numbers, strings and NULL. Along with symbols, these literals are the terminating nodes in an AST.