SSAValue exposed in error message

This error message shows an SSAValue instead of `x`. It also points to `f.(x)` when the `.-=` is also problematic (e.g. if it were `.-` there would be no error).
```julia-repl
julia> a = f.(x) .-= 1
ERROR: syntax: invalid syntax "f.(SSAValue(4718))" around REPL[3]:1
Stacktrace:
 [1] top-level scope
   @ REPL[3]:1
```