Remove trailing empty lines when optimizing #96

examples/yolol/unoptimized.yolol

@@ -3,4 +3,7 @@ myFavouriteVariable="hello world" // variable names are shortened
 myFavouriteVariable+=:aglobal+anothervar // global variables are not renamed (for obvious reasons)
 :x=(100*2+10/5)*10 // equations only containing constant values are evaluated at compile time
 :answ=(not :a) and not :b and not :c and not :d
-:answ=not(not(not :answ)) // boolean expressions are converted to shorter and equivalent expressions if possible
+:answ=not(not(not :answ)) // boolean expressions are converted to shorter and equivalent expressions if possible
+// If removing comments results in trailing empty lines
+// these emty lines are removed (because removing them can not mess up line-numberings)
+// This enables long comment-blocks at the end of a file

pkg/optimizers/comments.go

@@ -10,7 +10,24 @@ type CommentOptimizer struct {
 
 // Optimize is needed to implement Optimizer
 func (o *CommentOptimizer) Optimize(prog ast.Node) error {
-	return prog.Accept(o)
+	err := prog.Accept(o)
+	if err != nil {
+		return err
+	}
+
+	// remove trailing empty lines
+	if prog, is := prog.(*ast.Program); is {
+		for i := len(prog.Lines) - 1; i >= 0; i-- {
+			hasStatements := len(prog.Lines[i].Statements) > 0
+			if !hasStatements {
+				prog.Lines = prog.Lines[:i]
+			} else {
+				break
+			}
+		}
+	}
+
+	return nil
 }
 
 // Visit is needed to implement Visitor