implementation of useful error messages

test-inputs/efficient-fibonacci.flup

@@ -3,7 +3,7 @@ fib: int n -> int
 		| iterations 0 == -> a b +
 		| 1               -> a b + println	b a b + iterations 1 - fib
 		;
-	1 1 n fib
+	0 1 n fib
     ;
 
 50 fib println

test-inputs/test_error_messages.flup

@@ -0,0 +1,13 @@
+# test stack pop while stack empty in builtin-function equal
+# 0 ==
+
+# test incompatible types
+# 1 1.1 +
+
+# test expected identifier for type in function param list
+# a: 1 b -> int
+# 	|1 -> 0
+
+# test expected identifier for name in function param list
+a: int 1 -> int
+    |1 -> 0