Per other error message discussions, please follow the "Error. Explanation. Suggestion" format.

(e.g. Try reading your error message interpreting the first sentence as a description of an error - i.e. a negative - rather than the positive explanation you intend).

Oh, also be careful of using the word return. That will be misinterpreted to mean a C-like return, e.g. return 3.

Together those two observations would give something like:

The block following this '%s' is unfinished. Every code block is an expression and must have a result. '%s' cannot be the final code element in a block. Consider giving this block an explicit result.

Error message is changed to @dsyme's proposal. Appveyor is green. Jenkins is red because of unrelated issue (see #1169).

ready for review

@forki When you update the error message could you update the screen shot too? Or just remove it. Thanks

The code and new message look good to me, it's ready to go (as far as I can see :) )

something is strange with appveyor - @KevinRansom @otawfik-ms

it's green and ready