Implement boolean not processing in expression language.

Also adds some more error catching to be more robust in the face
of malformed customer rules.

Fixes https://gitlab.com/kicad/code/kicad/issues/5694

common/libeval_compiler/grammar.lemon

@@ -128,6 +128,12 @@ nt(A) ::= nt(B) G_BOOL_OR nt(C).
     A->leaf[1] = C;
 }
 
+nt(A) ::= G_BOOL_NOT nt(B).
+{
+    A = newNode( pEval, TR_OP_BOOL_NOT );
+    A->leaf[0] = B;
+}
+
 nt(A) ::= nt(B) G_PLUS nt(C).
 {
     A = newNode( pEval, TR_OP_ADD );

common/libeval_compiler/libeval_compiler.cpp

@@ -1031,7 +1031,24 @@ void UOP::Exec( CONTEXT* ctx )
     }
     else if( m_op & TR_OP_UNARY_MASK )
     {
-        // fixme : not operator
+        LIBEVAL::VALUE* arg1 = ctx->Pop();
+        double          arg1Value = arg1 ? arg1->AsDouble() : 0.0;
+        double          result;
+
+        switch( m_op )
+        {
+        case TR_OP_BOOL_NOT:
+            result = arg1Value != 0.0 ? 0 : 1;
+            break;
+        default:
+            result = 0.0;
+            break;
+        }
+
+        auto rp = ctx->AllocValue();
+        rp->Set( result );
+        ctx->Push( rp );
+        return;
     }
 }
 
@@ -1040,8 +1057,16 @@ VALUE* UCODE::Run( CONTEXT* ctx )
 {
     static VALUE g_false( 0 );
 
-    for( UOP* op : m_ucode )
-        op->Exec( ctx );
+    try
+    {
+        for( UOP* op : m_ucode )
+            op->Exec( ctx );
+    }
+    catch(...)
+    {
+        // rules which fail outright should not be fired
+        return &g_false;
+    }
 
     // non-well-formed rules should not be fired
     if( ctx->SP() != 1 )

include/libeval_compiler/libeval_compiler.h

@@ -276,6 +276,12 @@ public:
 
     VALUE* Pop()
     {
+        if( m_stack.size() == 0 )
+        {
+            ReportError( _( "Malformed expression" ) );
+            return AllocValue();
+        }
+
         VALUE* value = m_stack.top();
         m_stack.pop();
         return value;

pcbnew/dialogs/panel_setup_rules_help.txt

@@ -44,7 +44,7 @@ pad          hole        graphic         text             zone
 
 (rule HV_unshielded
    (constraint clearance (min 2mm))
-   (condition "A.NetClass == 'HV' && not A.insideArea('Shield*')))
+   (condition "A.NetClass == 'HV' && !A.insideArea('Shield*')))
 
 
 # ---- Notes