Bug when function is passed an expression that contains an assignment

[sebffischer]

> f = fn(x) x
> z = f({y = 2})
[1] 2
> z # The result  of {y = 2} is not bound to z
Error: object 'z' not found
backtrace:
> y # but the binding for y is created
[1] 2

[sebffischer]

This is related to the curly braces, because the same code with ( instead of { runs

[dgkf]

Poking at this I found another odd one that may be related.

f <- function(a, b) (a, b)
f({ x <- 1 }, { y <- 2 })
#> [[1]]
#> a @ <environment 0x14d1a4>
#> 
#> [[2]]
#> a @ <environment 0x14d1a4>

I’m guessing that something broke when the branches were added to support tail calls, meaning that expression results only resolve when they absolutely have to. Probably an overlooked code path.