return_call with call.without.effects optimizes incorrectly

[stevenfontanella]

In the following module, $f always returns 1.

(module
  (import "binaryen-intrinsics" "call.without.effects" (func $call-without-effects (param funcref) (result i32)))
  (func $g (result i32)
    (i32.const 1)
  )
  (func $f (result i32)
    (return_call $call-without-effects (ref.func $g))
    (unreachable)
  )
)

But when optimized with bin/wasm-opt -all --vacuum a.wat -S -o - (from the current main), we end up with the following module which returns 0:

(module
 (type $0 (func (result i32)))
 (type $1 (func (param funcref) (result i32)))
 (import "binaryen-intrinsics" "call.without.effects" (func $call-without-effects (type $1) (param funcref) (result i32)))
 (func $g (type $0) (result i32)
  (i32.const 1)
 )
 (func $f (type $0) (result i32)
  (i32.const 0)
 )
)

The problem is that call.without.effects doesn't set a branchesOut effect. Although call.without.effects assumes that the call body has no effects, the return_call does have the effect of branching out which isn't reflected correctly here.