rlang::new_function() and rlang::as_function() with nested quosures

rlang_function.R

library(rlang)
library(pryr)

# ===========================
# Normal quosures
# ===========================
# as_function() with a quosure: OK
a <- 1
x <- quo(a + 10)
a <- 2
f <- as_function(x)
parenvs(f)
#>   label                         name
#> 1 <environment: 0x7f9f34b01e48> ""  
#> 2 <environment: R_GlobalEnv>    ""
stopifnot(identical(f(), 12))

# new_function() with expr and env extracted from quosure: OK
a <- 1
x <- quo(a + 10)
a <- 2
f <- new_function(NULL, get_expr(x), get_env(x))
parenvs(f)
#>   label                      name
#> 1 <environment: R_GlobalEnv> ""
stopifnot(identical(f(), 12))


# ===========================
# Nested quosures
# ===========================
# as_function() with nested quosures: OK
a <- 1
y <- quo(a)
x <- quo(!!y + 10)
a <- 2
f <- as_function(x)
parenvs(f)
#>   label                         name
#> 1 <environment: 0x7f9f643eaa10> ""  
#> 2 <environment: R_GlobalEnv>    ""
stopifnot(identical(f(), 12))

# new_function() with expr and env extracted from nested quosure: Error
a <- 1
y <- quo(a)
x <- quo(!!y + 10)
a <- 2
f <- new_function(NULL, get_expr(x), get_env(x))
parenvs(f)
#>   label                      name
#> 1 <environment: R_GlobalEnv> ""
stopifnot(identical(f(), 12))
#> Error: Base operators are not defined for quosures.
#> Do you need to unquote the quosure?
#> 
#>   # Bad:
#>   myquosure + rhs
#> 
#>   # Good:
#>   !!myquosure + rhs

# Look at the contents of x
z <- get_expr(x)
z
#> (~a) + 10
z[[2]]  # A quosure is part of the AST
#> <quosure>
#> expr: ^a
#> env:  global