Change the return type of StandardVisitor.VisitForAllExpr() from

ForAllExpr to Expr. Enforcing the return type be ForAllExpr 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

2 files changed, 3 insertions, 3 deletions

diff --git a/Source/Core/Duplicator.cs b/Source/Core/Duplicator.cs
index da2b5b95..6164c23b 100644
--- a/Source/Core/Duplicator.cs
+++ b/Source/Core/Duplicator.cs
@@ -219,7 +219,7 @@ namespace Microsoft.Boogie {
       Contract.Ensures(Contract.Result<List<Expr>>() != null);

       return base.VisitExprSeq(new List<Expr>(list));

     }

-    public override ForallExpr VisitForallExpr(ForallExpr node) {

+    public override Expr VisitForallExpr(ForallExpr node) {

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

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

       return base.VisitForallExpr((ForallExpr)node.Clone());

diff --git a/Source/Core/StandardVisitor.cs b/Source/Core/StandardVisitor.cs
index a50acdba..a19bf78b 100644
--- a/Source/Core/StandardVisitor.cs
+++ b/Source/Core/StandardVisitor.cs
@@ -290,7 +290,7 @@ namespace Microsoft.Boogie {
         ensuresSeq[i] = this.VisitEnsures(ensuresSeq[i]);

       return ensuresSeq;

     }

-    public virtual ForallExpr VisitForallExpr(ForallExpr node) {

+    public virtual Expr VisitForallExpr(ForallExpr node) {

       Contract.Requires(node != null);

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

       node = (ForallExpr)this.VisitQuantifierExpr(node);

@@ -854,7 +854,7 @@ namespace Microsoft.Boogie {
               this.VisitEnsures(ensuresSeq[i]);

           return ensuresSeq;

       }

-      public override ForallExpr VisitForallExpr(ForallExpr node)

+      public override Expr VisitForallExpr(ForallExpr node)

       {

           Contract.Ensures(Contract.Result<ForallExpr>() == node);

           return (ForallExpr)this.VisitQuantifierExpr(node);