fixing python build errors

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/ast/rewriter/expr_safe_replace.cpp

@@ -19,7 +19,6 @@ Revision History:
 --*/
 
 #include "ast/rewriter/expr_safe_replace.h"
-#include "ast/rewriter/rewriter.h"
 #include "ast/ast_pp.h"
 
 

src/ast/rewriter/expr_safe_replace.h

@@ -23,6 +23,7 @@ Revision History:
 #define EXPR_SAFE_REPLACE_H_
 
 #include "ast/ast.h"
+#include "ast/rewriter/var_subst.h"
 
 class expr_safe_replace {
     ast_manager& m;

src/ast/rewriter/recfun_replace.h

@@ -0,0 +1,41 @@
+/*++
+Copyright (c) 2018 Microsoft Corporation
+
+Module Name:
+
+    recfun_replace.h
+
+Abstract:
+
+    replace function for recfun.
+    recfun_decl_plugin relies on being able to do expression replacement.
+    It uses expr_safe_replace from ast/rewriter, which depends on ast.
+    To break the dependency cycle we hoist the relevant functionality into 
+    an argument to functionality exposed by recfun::set_definition
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2018-11-01
+
+Revision History:
+
+
+--*/
+
+#ifndef RECFUN_REPLACE_H_
+#define RECFUN_REPLACE_H_
+
+#include "ast/recfun_decl_plugin.h"
+#include "ast/rewriter/expr_safe_replace.h"
+
+class recfun_replace : public recfun::replace {
+    ast_manager& m;
+    expr_safe_replace m_replace;
+public:
+    recfun_replace(ast_manager& m): m(m), m_replace(m) {}
+    void reset() override { m_replace.reset(); }
+    void insert(expr* s, expr* t) { m_replace.insert(s, t); }
+    expr_ref operator()(expr* e) { expr_ref r(m); m_replace(e, r); return r; }
+};
+
+#endif /* RECFUN_REPLACE_H_ */