ICE with Drop in static block

[samueltardieu]

ICE in illegal code in static block, rustc stable/beta/nightly. Found and reduced by @regar42.

Code

static T: () = {
    let test_arr: [String; 1];
    test_arr[0] = String::new();
};

fn main() {
}

Meta

rustc --version --verbose:

rustc 1.51.0-nightly (04caa632d 2021-01-30)
binary: rustc
commit-hash: 04caa632dd10c2bf64b69524c7f9c4c30a436877
commit-date: 2021-01-30
host: x86_64-unknown-linux-gnu
release: 1.51.0-nightly
LLVM version: 11.0.1

Also happens with

rustc 1.49.0 (e1884a8e3 2020-12-29)
binary: rustc
commit-hash: e1884a8e3c3e813aada8254edfa120e85bf5ffca
commit-date: 2020-12-29
host: x86_64-unknown-linux-gnu
release: 1.49.0

Error output

error[E0493]: destructors cannot be evaluated at compile-time
 --> t.rs:3:5
  |
3 |     test_arr[0] = String::new();
  |     ^^^^^^^^^^^
  |     |
  |     statics cannot evaluate destructors
  |     value is dropped here

error[E0493]: destructors cannot be evaluated at compile-time
 --> t.rs:2:9
  |
2 |     let test_arr: [String; 1];
  |         ^^^^^^^^ statics cannot evaluate destructors
3 |     test_arr[0] = String::new();
4 | };
  | - value is dropped here

error[E0381]: use of possibly-uninitialized variable: `test_arr`
 --> t.rs:3:5
  |
3 |     test_arr[0] = String::new();
  |     ^^^^^^^^^^^ use of possibly-uninitialized `test_arr`

error: internal compiler error: compiler/rustc_mir/src/transform/elaborate_drops.rs:316:25: drop of untracked, uninitialized value bb2, place _1[_3] (Parent(Some(mp1)))
 --> t.rs:3:5
  |
3 |     test_arr[0] = String::new();
  |     ^^^^^^^^^^^

thread 'rustc' panicked at 'Box<Any>', /rustc/04caa632dd10c2bf64b69524c7f9c4c30a436877/compiler/rustc_errors/src/lib.rs:904:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.51.0-nightly (04caa632d 2021-01-30) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [mir_drops_elaborated_and_const_checked] elaborating drops for `T`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 4 previous errors

Some errors have detailed explanations: E0381, E0493.
For more information about an error, try `rustc --explain E0381`.

Backtrace

   0: std::panicking::begin_panic
   1: rustc_errors::HandlerInner::span_bug
   2: rustc_errors::Handler::span_bug
   3: rustc_middle::ty::context::tls::with_opt
   4: rustc_middle::util::bug::opt_span_bug_fmt
   5: rustc_middle::util::bug::span_bug_fmt
   6: <rustc_mir::transform::elaborate_drops::ElaborateDrops as rustc_mir::transform::MirPass>::run_pass
   7: rustc_mir::transform::run_passes
   8: rustc_mir::transform::run_post_borrowck_cleanup_passes
   9: rustc_mir::transform::mir_drops_elaborated_and_const_checked
  10: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_drops_elaborated_and_const_checked>::compute
  11: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  12: rustc_data_structures::stack::ensure_sufficient_stack
  13: rustc_query_system::query::plumbing::force_query_with_job
  14: rustc_query_system::query::plumbing::get_query_impl
  15: rustc_query_system::query::plumbing::ensure_query_impl
  16: rustc_interface::passes::analysis
  17: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  18: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  19: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  20: rustc_query_system::query::plumbing::force_query_with_job
  21: rustc_query_system::query::plumbing::get_query_impl
  22: rustc_interface::passes::QueryContext::enter
  23: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  24: rustc_span::with_source_map

[camelid]

Assigning P-medium and removing I-prioritize as discussed in the prioritization working group.