checker: allow voidptr arithmetic in translated code

vlib/v/ast/ast.v

@@ -1087,7 +1087,7 @@ pub mut:
 	expr_type Type // from type
 }
 
-// an enum value, like OS.macos or .macos
+// An enum value, like OS.macos or .macos
 pub struct EnumVal {
 pub:
 	enum_name string

vlib/v/checker/checker.v

@@ -589,7 +589,7 @@ pub fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 			if !c.inside_unsafe && !node.left.is_auto_deref_var() && !node.right.is_auto_deref_var() {
 				c.warn('pointer arithmetic is only allowed in `unsafe` blocks', left_right_pos)
 			}
-			if left_type == ast.voidptr_type {
+			if left_type == ast.voidptr_type && !c.pref.translated {
 				c.error('`$node.op` cannot be used with `voidptr`', left_pos)
 			}
 		}
@@ -3962,6 +3962,8 @@ pub fn (mut c Checker) index_expr(mut node ast.IndexExpr) ast.Type {
 // with this value.
 pub fn (mut c Checker) enum_val(mut node ast.EnumVal) ast.Type {
 	mut typ_idx := if node.enum_name == '' {
+		// Get the type of the enum without enum name by looking at the expected type.
+		// e.g. `set_color(.green)`, V knows that `Green` is the expected type.
 		if c.expected_type == ast.void_type && c.expected_expr_type != ast.void_type {
 			c.expected_expr_type.idx()
 		} else {

vlib/v/gen/c/cgen.v

@@ -5353,7 +5353,8 @@ fn (mut g Gen) enum_val(node ast.EnumVal) {
 	// && g.inside_switch
 	if g.pref.translated && node.typ.is_number() {
 		// Mostly in translated code, when C enums are used as ints in switches
-		g.write('/*enum val is_number $node.mod styp=$styp*/_const_main__$node.val')
+		sym := g.table.sym(node.typ)
+		g.write('/* $node enum val is_number $node.mod styp=$styp sym=$sym*/_const_main__$node.val')
 	} else {
 		g.write('${styp}__$node.val')
 	}