Resolve a concurrency issue (reported by Alex Summers).

1 files changed, 14 insertions, 6 deletions

diff --git a/Source/Core/AbsyType.cs b/Source/Core/AbsyType.cs
index 5274a20b..4efe1aea 100644
--- a/Source/Core/AbsyType.cs
+++ b/Source/Core/AbsyType.cs
@@ -2950,9 +2950,13 @@ Contract.Requires(that != null);
       if (subst.Count == 0)

         return this;

       List<Type> newArgs = new List<Type>();

-      foreach (Type/*!*/ t in Arguments) {

-        Contract.Assert(t != null);

-        newArgs.Add(t.Substitute(subst));

+      lock (Arguments)

+      {

+        foreach (Type/*!*/ t in Arguments)

+        {

+          Contract.Assert(t != null);

+          newArgs.Add(t.Substitute(subst));

+        }

       }

       return new CtorType(tok, Decl, newArgs);

     }

@@ -3336,9 +3340,13 @@ Contract.Assert(var != null);
       }

 

       List<Type> newArgs = new List<Type>();

-      foreach (Type/*!*/ t in Arguments) {

-        Contract.Assert(t != null);

-        newArgs.Add(t.Substitute(subst));

+      lock (Arguments)

+      {

+        foreach (Type/*!*/ t in Arguments)

+        {

+          Contract.Assert(t != null);

+          newArgs.Add(t.Substitute(subst));

+        }

       }

       Type/*!*/ newResult = Result.Substitute(subst);

       Contract.Assert(newResult != null);