Panic when duplicating field in record destructuring

[matthew-healy]

Describe the bug

The following program:

let f : { x : Number, y : Number } -> Number = fun { x, x, .. } => x in f { x = 1, y = 2 }

panics with the following error message:

thread 'main' panicked at 'Scopes of identifiers in destruct patterns should be checked already', src/typecheck/destructuring.rs:247:14

Expected behavior

Ideally a parser error noting that record destructurings cannot contain duplicate fields, but just not panicking is a good first step.

Additional context

Full backtrace

thread 'main' panicked at 'Scopes of identifiers in destruct patterns should be checked already', src/typecheck/destructuring.rs:247:14
stack backtrace:
   0:     0x5568a92baf4a - std::backtrace_rs::backtrace::libunwind::trace::h595f06c70adcc478
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x5568a92baf4a - std::backtrace_rs::backtrace::trace_unsynchronized::h177a0149c76cdde9
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x5568a92baf4a - std::sys_common::backtrace::_print_fmt::hc0701fd2c3530c58
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x5568a92baf4a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hd4cd115d8750fd6c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x5568a92e06de - core::fmt::write::h93e2f5923c7eca08
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/fmt/mod.rs:1213:17
   5:     0x5568a92b7ce5 - std::io::Write::write_fmt::h8162dbb45f0b9e62
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/io/mod.rs:1682:15
   6:     0x5568a92bad15 - std::sys_common::backtrace::_print::h1835ef8a8f9066da
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x5568a92bad15 - std::sys_common::backtrace::print::hcb5e6388b9235f41
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x5568a92bc39f - std::panicking::default_hook::{{closure}}::h9c084969ccf9a722
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:267:22
   9:     0x5568a92bc0db - std::panicking::default_hook::h68fa2ba3c3c6c12f
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:286:9
  10:     0x5568a92bcaa9 - std::panicking::rust_panic_with_hook::h8d5c434518ef298c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:688:13
  11:     0x5568a92bc849 - std::panicking::begin_panic_handler::{{closure}}::hf33414f5dabf6faf
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:579:13
  12:     0x5568a92bb3fc - std::sys_common::backtrace::__rust_end_short_backtrace::hc50389427413bb75
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:137:18
  13:     0x5568a92bc552 - rust_begin_unwind
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:575:5
  14:     0x5568a84b1d73 - core::panicking::panic_fmt::h2de7a7938f816de8
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/panicking.rs:64:14
  15:     0x5568a92de721 - core::panicking::panic_display::h20dbb78c57df5693
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/panicking.rs:147:5
  16:     0x5568a92de6cb - core::panicking::panic_str::hb46d5710e4ab412a
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/panicking.rs:131:5
  17:     0x5568a84b1d36 - core::option::expect_failed::h0b5d04c30548770b
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/option.rs:1924:5
  18:     0x5568a8a3bc99 - core::option::Option<T>::expect::h6d8c9ee88dc7065d
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/option.rs:786:21
  19:     0x5568a88a1654 - nickel_lang::typecheck::destructuring::RecordTypes::get_type::h93ee428ae91dbc08
                               at /home/matthew/projects/tweag/nickel/src/typecheck/destructuring.rs:245:9
  20:     0x5568a8552003 - nickel_lang::typecheck::destructuring::inject_pattern_variables::{{closure}}::hdcbcb524b0fe83f2
                               at /home/matthew/projects/tweag/nickel/src/typecheck/destructuring.rs:150:22
  21:     0x5568a850da44 - <core::slice::iter::Iter<T> as core::iter::traits::iterator::Iterator>::for_each::h09b6b4f4c7e2be3a
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/slice/iter/macros.rs:201:21
  22:     0x5568a88a10fb - nickel_lang::typecheck::destructuring::inject_pattern_variables::hb489469de17ee90b
                               at /home/matthew/projects/tweag/nickel/src/typecheck/destructuring.rs:148:5
  23:     0x5568a8718c12 - nickel_lang::typecheck::check::h38230333c6737771
                               at /home/matthew/projects/tweag/nickel/src/typecheck/mod.rs:1231:13
  24:     0x5568a8711d0c - nickel_lang::typecheck::walk_with_annot::hfccd3a73a9a3ad20
                               at /home/matthew/projects/tweag/nickel/src/typecheck/mod.rs:1103:13
  25:     0x5568a8711817 - nickel_lang::typecheck::walk_annotated::hbd6d76235fca61f7
                               at /home/matthew/projects/tweag/nickel/src/typecheck/mod.rs:1076:5
  26:     0x5568a870eaf1 - nickel_lang::typecheck::walk::hb432fd114ee9f501
                               at /home/matthew/projects/tweag/nickel/src/typecheck/mod.rs:989:13
  27:     0x5568a870ff6a - nickel_lang::typecheck::walk::hb432fd114ee9f501
                               at /home/matthew/projects/tweag/nickel/src/typecheck/mod.rs:904:13
  28:     0x5568a870dea7 - nickel_lang::typecheck::type_check_linearize::h3257ed68140ce287
                               at /home/matthew/projects/tweag/nickel/src/typecheck/mod.rs:797:9
  29:     0x5568a870dab2 - nickel_lang::typecheck::type_check::h32824a8e4d2c9d65
                               at /home/matthew/projects/tweag/nickel/src/typecheck/mod.rs:760:5
  30:     0x5568a8733c61 - nickel_lang::repl::ReplImpl<EC>::prepare::hf894c25bed851a71
                               at /home/matthew/projects/tweag/nickel/src/repl/mod.rs:120:13
  31:     0x5568a8734b3d - nickel_lang::repl::ReplImpl<EC>::eval_::hc7728a17ab7aa4e4
                               at /home/matthew/projects/tweag/nickel/src/repl/mod.rs:181:25
  32:     0x5568a8735317 - <nickel_lang::repl::ReplImpl<EC> as nickel_lang::repl::Repl>::eval_full::h1114207f84015fb5
                               at /home/matthew/projects/tweag/nickel/src/repl/mod.rs:200:9
  33:     0x5568a88bfd88 - nickel_lang::repl::rustyline_frontend::repl::hc8040fe009c478b2
                               at /home/matthew/projects/tweag/nickel/src/repl/rustyline_frontend.rs:122:23
  34:     0x5568a84d6f29 - nickel::main::haa397c64b8c52d44
                               at /home/matthew/projects/tweag/nickel/src/bin/nickel.rs:147:12
  35:     0x5568a84eb83b - core::ops::function::FnOnce::call_once::h8e2db0c97b9470e0
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/ops/function.rs:250:5
  36:     0x5568a84f8dee - std::sys_common::backtrace::__rust_begin_short_backtrace::h99e3a67a48b8bf1b
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:121:18
  37:     0x5568a84ca771 - std::rt::lang_start::{{closure}}::h40c3e8d2cd41369c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/rt.rs:166:18
  38:     0x5568a92b155c - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h699977d052768608
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/ops/function.rs:287:13
  39:     0x5568a92b155c - std::panicking::try::do_call::h4e121e623c70f903
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:483:40
  40:     0x5568a92b155c - std::panicking::try::hf9d919e062bc178a
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:447:19
  41:     0x5568a92b155c - std::panic::catch_unwind::h7a7b12272684cb97
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panic.rs:140:14
  42:     0x5568a92b155c - std::rt::lang_start_internal::{{closure}}::hd96b0eb4844b8762
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/rt.rs:148:48
  43:     0x5568a92b155c - std::panicking::try::do_call::h1af1f88f4f92a22c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:483:40
  44:     0x5568a92b155c - std::panicking::try::hf20d7abea7f0f097
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:447:19
  45:     0x5568a92b155c - std::panic::catch_unwind::hb0e084c3a9c042e4
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panic.rs:140:14
  46:     0x5568a92b155c - std::rt::lang_start_internal::hca9d5c7277f5b67c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/rt.rs:148:20
  47:     0x5568a84ca74a - std::rt::lang_start::h5c2fdacb750165c9
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/rt.rs:165:17
  48:     0x5568a84de4ce - main
  49:     0x7f36afa2924e - __libc_start_call_main
  50:     0x7f36afa29309 - __libc_start_main_alias_1
  51:     0x5568a84b2405 - _start
  52:                0x0 - <unknown>