Change the return type of StandardVisitor.VisitBvConcatExpr() from

BvConcatExpr to Expr. Enforcing the return type be BvConcatExpr is
too restrictive. For example it prevents anyone from implementing
a visitor that does constant folding of an Expr tree.

There is precedence for this. For example VisitNAryExpr() returns
an Expr not an NAryExpr.

Unfortunately this a breaking API change so anyone who subclasses
the StandardVisitor (or one of its sub classes) and overrides this
method will get compilation errors until they change the return type.

1 files changed, 1 insertions, 1 deletions

diff --git a/Source/AbsInt/IntervalDomain.cs b/Source/AbsInt/IntervalDomain.cs
index 6cce0aac..c0303cb3 100644
--- a/Source/AbsInt/IntervalDomain.cs
+++ b/Source/AbsInt/IntervalDomain.cs
@@ -944,7 +944,7 @@ namespace Microsoft.Boogie.AbstractInterpretation
         // don't recurse on subexpression

         return node;

       }

-      public override BvConcatExpr VisitBvConcatExpr(BvConcatExpr node) {

+      public override Expr VisitBvConcatExpr(BvConcatExpr node) {

         // don't recurse on subexpression

         return node;

       }