From 82c8a4957317ffd9343ba28fc7ed7688455bfe07 Mon Sep 17 00:00:00 2001
From: Martin Whitaker <icarus@martin-whitaker.me.uk>
Date: Sat, 9 Nov 2019 13:11:16 +0000
Subject: [PATCH] Fix for issue #281 - the condition operator may return a
 valid enum type.

If the condition expression is 2-state, the result won't be blended, so
the result will be a valid enum value if both true and false expressions
return the same enum type.
---
 netlist.cc | 14 ++++++++++++++
 netlist.h  |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/netlist.cc b/netlist.cc
index c0650959e..328e1a42b 100644
--- a/netlist.cc
+++ b/netlist.cc
@@ -2524,6 +2524,20 @@ NetETernary::~NetETernary()
       delete false_val_;
 }
 
+const netenum_t* NetETernary::enumeration() const
+{
+	// If the condition can evaluate to an ambiguous value,
+	// the result may be blended, and so is not guaranteed
+	// to be a valid enumeration value.
+      if (cond_->expr_type() != IVL_VT_BOOL)
+	    return 0;
+
+      if (true_val_->enumeration() != false_val_->enumeration())
+	    return 0;
+
+      return true_val_->enumeration();
+}
+
 const NetExpr* NetETernary::cond_expr() const
 {
       return cond_;
diff --git a/netlist.h b/netlist.h
index ae546bc94..66eb0890e 100644
--- a/netlist.h
+++ b/netlist.h
@@ -4757,6 +4757,8 @@ class NetETernary  : public NetExpr {
       NetETernary(NetExpr*c, NetExpr*t, NetExpr*f, unsigned wid, bool signed_flag);
       ~NetETernary();
 
+      const netenum_t* enumeration() const;
+
       const NetExpr*cond_expr() const;
       const NetExpr*true_expr() const;
       const NetExpr*false_expr() const;