Wrong number of arguments to `String.concat` results in confusing error on the result.

[fridis]

Try this

 > FUZION_DISABLE_ANSI_ESCAPES=true ./build/bin/fz -e 'a := String.concat 1 2 3 4 5 6; x := a.utf8'

command line:1:40: error 1: Could not find called feature
a := String.concat 1 2 3 4 5 6; x := a.utf8
---------------------------------------^^^^
Feature not found: 'utf8' (no arguments)
Target feature: 'String.type.concat'
In call: 'a.utf8'

one error.

the error should be that String.concat can not be called with 6 arguments (but with 0 or 2), but we only get an error when using the result!