From b80401e1eee08b5bbef39eaa89cfee951cb85949 Mon Sep 17 00:00:00 2001
From: Martin Whitaker <icarus@martin-whitaker.me.uk>
Date: Mon, 11 Mar 2013 19:46:00 +0000
Subject: [PATCH] Improved error reporting for constant user functions.

---
 elab_expr.cc     | 13 +++++++++++--
 net_func_eval.cc |  7 +------
 netlist.h        |  3 +++
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/elab_expr.cc b/elab_expr.cc
index 5f3183ae0..9a0345054 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -1280,6 +1280,16 @@ NetExpr* PECallFunction::elaborate_sfunc_(Design*des, NetScope*scope,
       NetESFunc*fun = new NetESFunc(name, expr_type_, expr_width_, nparms);
       fun->set_line(*this);
 
+      if (!fun->is_built_in()) {
+	    if (scope->need_const_func()) {
+		  cerr << get_fileline() << ": error: " << name
+		       << " is not a built-in function, so cannot"
+		       << " be used in a constant function." << endl;
+		  des->errors += 1;
+	    }
+	    scope->is_const_func(false);
+      }
+
 	/* Now run through the expected parameters. If we find that
 	   there are missing parameters, print an error message.
 
@@ -1785,7 +1795,7 @@ NetExpr* PECallFunction::elaborate_expr(Design*des, NetScope*scope,
         // fully elaborated. If this is the case, elaborate it now. This
         // ensures we know whether or not it is a constant function.
       if (dscope->elab_stage() < 3) {
-            dscope->need_const_func(need_const);
+            dscope->need_const_func(need_const || scope->need_const_func());
             const PFunction*pfunc = dscope->func_pform();
             ivl_assert(*this, pfunc);
             pfunc->elaborate(des, dscope);
@@ -1797,7 +1807,6 @@ NetExpr* PECallFunction::elaborate_expr(Design*des, NetScope*scope,
                           "a constant function must be a constant function "
                           "local to the current module." << endl;
                   des->errors += 1;
-                  return 0;
             }
             scope->is_const_func(false);
       }
diff --git a/net_func_eval.cc b/net_func_eval.cc
index a9d281754..472de4aa5 100644
--- a/net_func_eval.cc
+++ b/net_func_eval.cc
@@ -487,12 +487,7 @@ NetExpr* NetESFunc::evaluate_function(const LineInfo&loc,
 				      map<perm_string,NetExpr*>&context_map) const
 {
       ID id = built_in_id_();
-      if (id == NOT_BUILT_IN) {
-	    cerr << get_fileline() << ": error: " << name_
-		 << " is not a built-in function, so cannot"
-		 << " be used in a constant function." << endl;
-	    return 0;
-      }
+      ivl_assert(*this, id != NOT_BUILT_IN);
 
       NetExpr*val0 = 0;
       NetExpr*val1 = 0;
diff --git a/netlist.h b/netlist.h
index b0628cc6e..2ec36da49 100644
--- a/netlist.h
+++ b/netlist.h
@@ -4066,6 +4066,9 @@ class NetESFunc  : public NetExpr {
       NetExpr* evaluate_min_max_(ID id, const NetExpr*arg0,
 					const NetExpr*arg1) const;
 
+    public:
+      bool is_built_in() const { return built_in_id_() != NOT_BUILT_IN; };
+
     private: // not implemented
       NetESFunc(const NetESFunc&);
       NetESFunc& operator= (const NetESFunc&);