vlib/v/checker/tests/var_duplicate_const.vv:4:5: warning: duplicate of a const name `size` 2 | 3 | fn main() { 4 | size := 11 | ~~~~ 5 | println(main.size) 6 | } vlib/v/checker/tests/var_duplicate_const.vv:4:5: warning: unused variable: `size` 2 | 3 | fn main() { 4 | size := 11 | ~~~~ 5 | println(main.size) 6 | } vlib/v/checker/tests/var_duplicate_const.vv:1:7: notice: unused constant: `size` 1 | const size = 22 | ~~~~~~~~~ 2 | 3 | fn main() { ================== C compilation error (from cc): ============== cc: /tmp/v_502/var_duplicate_const.01KNN5X7W4MVH2B58E9FG5GJKE.tmp.c:2139:36: error: use of undeclared identifier 'size' cc: 2139 | builtin__println(builtin__int_str(size)); cc: | ^ cc: 1 error generated. ================================================================ Try passing `-g` when compiling, to see a .v file:line information, that correlates more with the C error. (Alternatively, pass `-show-c-output`, to print the full C error message). builder error: ================== C error found while compiling generated C code. This can be caused by invalid C interop code, C compiler flags, or a V compiler bug. If your code is pure V and this still happens, please report it using `v bug file.v`, or goto https://github.com/vlang/v/issues/new/choose . You can also use #help on Discord: https://discord.gg/vlang .