cgen: fix codegen for `for k,v in map_of_pointers {`

vlib/v/ast/table.v

@@ -1221,6 +1221,9 @@ pub fn (mut t Table) complete_interface_check() {
 			if idecl.fields.len > info.fields.len {
 				continue
 			}
+			if idecl.typ == 0 {
+				continue
+			}
 			// empty interface only generate type cast functions of the current module
 			if idecl.methods.len == 0 && idecl.fields.len == 0
 				&& tsym.mod != t.get_type_symbol(idecl.typ).mod {

vlib/v/gen/c/cgen.v

@@ -2120,7 +2120,11 @@ fn (mut g Gen) for_in_stmt(node ast.ForInStmt) {
 			} else {
 				val_styp := g.typ(node.val_type)
 				if node.val_type.is_ptr() {
-					g.write('$val_styp ${c_name(node.val_var)} = &(*($val_styp)')
+					if node.val_is_mut {
+						g.write('$val_styp ${c_name(node.val_var)} = &(*($val_styp)')
+					} else {
+						g.write('$val_styp ${c_name(node.val_var)} = (*($val_styp*)')
+					}
 				} else {
 					g.write('$val_styp ${c_name(node.val_var)} = (*($val_styp*)')
 				}

vlib/v/tests/for_in_map_of_pointers_test.v

@@ -0,0 +1,14 @@
+fn test_for_in_map_of_pointers() {
+	i := 123456
+	pi := &i
+	println('pi: $pi')
+	mut my_map := map[int]&int{}
+	my_map[0] = pi
+	for k, wrong_value in my_map {
+		good_value := my_map[k]
+		println('k: $k \n wrong_value: $wrong_value \n good_value: $good_value')
+		up_good_value := voidptr(good_value).hex_full()
+		up_wrong_value := voidptr(wrong_value).hex_full()
+		assert up_good_value == up_wrong_value
+	}
+}