minimal addition to rewrite bit-vector to character conversion using constant folding.

src/ast/rewriter/char_rewriter.h

@@ -0,0 +1,54 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    char_rewriter.h
+
+Abstract:
+
+    Basic rewriting rules for characters constraints.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2022-03-10
+
+Notes:
+
+--*/
+#pragma once
+
+#include "ast/char_decl_plugin.h"
+#include "ast/rewriter/rewriter_types.h"
+#include "util/params.h"
+#include "util/lbool.h"
+
+
+/**
+   \brief Cheap rewrite rules for character constraints
+*/
+class char_rewriter {
+    ast_manager& m;
+    char_decl_plugin* m_char;
+
+    br_status mk_char_from_bv(expr* e, expr_ref& result);
+public:
+
+    char_rewriter(ast_manager& m);
+
+    family_id get_fid();
+
+    br_status mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result);
+
+    expr_ref mk_app(func_decl* f, expr_ref_vector const& args) { return mk_app(f, args.size(), args.data()); }
+
+    expr_ref mk_app(func_decl* f, unsigned n, expr* const* args) { 
+        expr_ref result(m);
+        if (f->get_family_id() != get_fid() ||
+            BR_FAILED == mk_app_core(f, n, args, result))
+            result = m.mk_app(f, n, args);
+        return result;
+    }
+
+};
+