fix(frontends/lean/util): assertion violation

fixes #559

src/frontends/lean/util.cpp

@@ -126,8 +126,10 @@ void collect_locals(expr const & type, expr const & value, parser const & p, buf
     buffer<expr> include_vars;
     p.get_include_variables(include_vars);
     for (expr const & param : include_vars) {
-        collect_locals_ignoring_tactics(mlocal_type(param), ls);
+        if (is_local(param)) {
-        ls.insert(param);
+            collect_locals_ignoring_tactics(mlocal_type(param), ls);
+            ls.insert(param);
+        }
     }
     collect_locals_ignoring_tactics(type, ls);
     collect_locals_ignoring_tactics(value, ls);

tests/lean/559.lean

@@ -0,0 +1,12 @@
+import algebra.ordered_field
+open algebra
+section sequence_c
+
+  parameter Q : Type
+  parameter lof_Q : linear_ordered_field Q
+  definition to_lof [instance] : linear_ordered_field Q := lof_Q
+  include to_lof
+
+  theorem foo (a b : Q) : a + b = b + a := !add.comm
+
+end sequence_c

tests/lean/559.lean.expected.out

@@ -0,0 +1,4 @@
+559.lean:10:28: error: failed to synthesize placeholder
+Q : Type,
+a b : Q
+⊢ has_add Q