From a1229692b06bd659a2485ff1ff4ea73654dab1f7 Mon Sep 17 00:00:00 2001
From: Soonho Kong <soonhok@cs.cmu.edu>
Date: Thu, 8 Aug 2013 16:12:27 -0700
Subject: [PATCH] Add static_asserts for higher-order functions in
 kernel/for_each.h and kernel/pp.cpp

---
 src/kernel/for_each.h | 4 +++-
 src/kernel/pp.cpp     | 2 ++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/kernel/for_each.h b/src/kernel/for_each.h
index f828fd96c..cc24b88c5 100644
--- a/src/kernel/for_each.h
+++ b/src/kernel/for_each.h
@@ -13,6 +13,8 @@ template<typename F>
 class for_each_fn {
     expr_cell_offset_set m_visited;
     F                    m_f;
+    static_assert(std::is_same<typename std::result_of<F(expr const &, unsigned)>::type, void>::value,
+                  "for_each_fn: return type of m_f is not void");
 
     void apply(expr const & e, unsigned offset) {
         if (is_shared(e)) {
@@ -22,7 +24,7 @@ class for_each_fn {
             m_visited.insert(p);
         }
 
-       m_f(e, offset);
+        m_f(e, offset);
 
         switch (e.kind()) {
         case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value: case expr_kind::Var:
diff --git a/src/kernel/pp.cpp b/src/kernel/pp.cpp
index 3aa234c8b..bd5f47a04 100644
--- a/src/kernel/pp.cpp
+++ b/src/kernel/pp.cpp
@@ -117,6 +117,8 @@ struct pp_fn {
 
     template<typename It>
     format pp_bnames(It const & begin, It const & end, bool use_line) {
+        static_assert(std::is_same<typename std::iterator_traits<It>::value_type, expr>::value,
+                      "pp_bnames takes an argument which is not an iterator containing expr.");
         auto it = begin;
         format r = pp_bname(*it);
         ++it;