Change the return type of StandardVisitor.VisitBvExtractExpr() from

BvExtractExpr to Expr. Enforcing the return type be BvExtractExpr 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.
a visitor that does constant folding of an Expr tree

1 files changed, 1 insertions, 1 deletions

diff --git a/Source/VCExpr/Boogie2VCExpr.cs b/Source/VCExpr/Boogie2VCExpr.cs
index 3e78bb4b..d53a75a4 100644
--- a/Source/VCExpr/Boogie2VCExpr.cs
+++ b/Source/VCExpr/Boogie2VCExpr.cs
@@ -557,7 +557,7 @@ namespace Microsoft.Boogie.VCExprAST {
 

     ///////////////////////////////////////////////////////////////////////////////////

 

-    public override BvExtractExpr VisitBvExtractExpr(BvExtractExpr node) {

+    public override Expr VisitBvExtractExpr(BvExtractExpr node) {

       //Contract.Requires(node != null);

       Contract.Ensures(Contract.Result<BvExtractExpr>() != null);

       Push(TranslateBvExtractExpr(node));