cgen: fix printing reference enum (#15606)

vlib/v/gen/c/auto_str_methods.v

@@ -921,7 +921,7 @@ fn (mut g Gen) gen_str_for_struct(info ast.Struct, styp string, str_fn_name stri
 			funcprefix += 'isnil(it.${c_name(field.name)})'
 			funcprefix += ' ? _SLIT("nil") : '
 			// struct, floats and ints have a special case through the _str function
-			if sym.kind !in [.struct_, .alias] && !field.typ.is_int_valptr()
+			if sym.kind !in [.struct_, .alias, .enum_] && !field.typ.is_int_valptr()
 				&& !field.typ.is_float_valptr() {
 				funcprefix += '*'
 			}
@@ -963,7 +963,7 @@ fn struct_auto_str_func(sym &ast.TypeSymbol, _field_type ast.Type, fn_name strin
 	sufix := if field_type.has_flag(.shared_f) { '->val' } else { '' }
 	deref, _ := deref_kind(expects_ptr, field_type.is_ptr(), field_type)
 	if sym.kind == .enum_ {
-		return '${fn_name}(${deref}it.${c_name(field_name)})', true
+		return '${fn_name}(${deref}(it.${c_name(field_name)}))', true
 	} else if should_use_indent_func(sym.kind) {
 		obj := '${deref}it.${c_name(field_name)}$sufix'
 		if has_custom_str {

vlib/v/gen/c/str.v

@@ -86,6 +86,9 @@ fn (mut g Gen) gen_expr_to_string(expr ast.Expr, etype ast.Type) {
 		if expr !is ast.EnumVal {
 			str_fn_name := g.get_str_fn(typ)
 			g.write('${str_fn_name}(')
+			if typ.is_ptr() {
+				g.write('*')
+			}
 			g.enum_expr(expr)
 			g.write(')')
 		} else {

vlib/v/tests/inout/printing_reference_enum.out

@@ -0,0 +1,4 @@
+on
+Foo{
+    i: &on
+}

vlib/v/tests/inout/printing_reference_enum.vv

@@ -0,0 +1,23 @@
+module main
+
+enum State {
+	undef
+	off
+	on
+}
+
+struct Foo {
+	i &State
+}
+
+fn main() {
+	mut i := State.on
+
+	mut r := &i
+	println(r)
+
+	mut f := Foo{
+		i: &i
+	}
+	println(f)
+}