DGen

- Handle `ReturnInstruction` with no expression

Test cases

- Added `simple_return_expressionless.t`

source/tlang/compiler/codegen/emit/dgen.d

@@ -392,10 +392,18 @@ public final class DCodeEmitter : CodeEmitter
             Context context = returnInstruction.getContext();
             assert(context);
 
-            /* Get the return expression instruction */
-            Value returnExpressionInstr = returnInstruction.getReturnExpInstr();
-
-            emmmmit = "return "~transform(returnExpressionInstr)~";";
+            /* If there is an expression returned */
+            if(returnInstruction.hasReturnExpInstr())
+            {
+                /* Get the return expression instruction */
+                Value returnExpressionInstr = returnInstruction.getReturnExpInstr();
+                emmmmit = "return "~transform(returnExpressionInstr)~";";
+            }
+            /* Expression-less return */
+            else
+            {
+                emmmmit = "return;";
+            }
         }
         /**
         * If statements (IfStatementInstruction)

source/tlang/testing/simple_return_expressionless.t

@@ -0,0 +1,6 @@
+module simple_return_expressionless;
+
+void func()
+{
+	return;
+}