From 1b2168af1e5c29ac1c79d501a21eab90c5837d6d Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Fri, 16 Oct 2020 12:41:19 +0100
Subject: [PATCH] Don't throw implicit rules out after failing to compile user
 rules.

---
 pcbnew/drc/drc_engine.cpp | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/pcbnew/drc/drc_engine.cpp b/pcbnew/drc/drc_engine.cpp
index 5201aef37c..33a17e2de2 100644
--- a/pcbnew/drc/drc_engine.cpp
+++ b/pcbnew/drc/drc_engine.cpp
@@ -497,10 +497,26 @@ void DRC_ENGINE::InitEngine( const wxFileName& aRulePath )
     m_rules.clear();
     m_rulesValid = false;
 
-    loadImplicitRules();
-    loadRules( aRulePath );
+    try         // attempt to load full set of rules (implicit + user rules)
+    {
+        loadImplicitRules();
+        loadRules( aRulePath );
+        compileRules();
+    }
+    catch( PARSE_ERROR& original_parse_error )
+    {
+        try     // try again with just our implicit rules
+        {
+            loadImplicitRules();
+            compileRules();
+        }
+        catch( PARSE_ERROR& ignore )
+        {
+            wxFAIL_MSG( "Compiling implict rules failed." );
+        }
 
-    compileRules();
+        throw original_parse_error;
+    }
 
     for( int ii = DRCE_FIRST; ii < DRCE_LAST; ++ii )
         m_errorLimits[ ii ] = INT_MAX;