feat(kernel/expr): add has_expr_metavar_strict

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/kernel/expr.cpp

@@ -19,6 +19,7 @@ Author: Leonardo de Moura
 #include "kernel/expr.h"
 #include "kernel/expr_eq_fn.h"
 #include "kernel/free_vars.h"
+#include "kernel/for_each_fn.h"
 
 #ifndef LEAN_INITIAL_EXPR_CACHE_CAPACITY
 #define LEAN_INITIAL_EXPR_CACHE_CAPACITY 1024*16
@@ -594,6 +595,19 @@ bool is_arrow(expr const & t) {
     }
 }
 
+bool has_expr_metavar_strict(expr const & e) {
+    if (!has_expr_metavar(e))
+        return false;
+    bool found = false;
+    for_each(e, [&](expr const & e, unsigned) {
+            if (found || !has_expr_metavar(e)) return false;
+            if (is_metavar(e)) { found = true; return false; }
+            if (is_local(e)) return false; // do not visit type
+            return true;
+        });
+    return found;
+}
+
 static bool has_free_var_in_domain(expr const & b, unsigned vidx) {
     if (is_pi(b)) {
         return has_free_var(binding_domain(b), vidx) || has_free_var_in_domain(binding_body(b), vidx+1);

src/kernel/expr.h

@@ -585,6 +585,8 @@ inline bool is_constant(expr const & e, name const & n) { return is_constant(e)
 inline bool has_metavar(expr const & e) { return e.has_metavar(); }
 inline bool has_expr_metavar(expr const & e) { return e.has_expr_metavar(); }
 inline bool has_univ_metavar(expr const & e) { return e.has_univ_metavar(); }
+/** \brief Similar to \c has_expr_metavar, but ignores metavariables occurring in local constant types. */
+bool has_expr_metavar_strict(expr const & e);
 inline bool has_local(expr const & e) { return e.has_local(); }
 inline bool has_param_univ(expr const & e) { return e.has_param_univ(); }
 unsigned get_depth(expr const & e);