if let compound statement

[dfarnham]

Code

fn main() {
    let jobj = json::parse(r#"{ "config": [ { "label": { "active": true } } ] }"#).unwrap();

    for obj in jobj["config"].members() {
        for (k, v) in obj.entries().take(1) {
            if let json::JsonValue::Boolean(state) = v["active"] && true {
                if state {
                    println!("{}", k)
                }
            }
        }
    }
}

Meta

rustc --version --verbose:

rustc 1.51.0 (2fd73fabe 2021-03-23)
binary: rustc
commit-hash: 2fd73fabe469357a12c2c974c140f67e7cdd76d0
commit-date: 2021-03-23
host: x86_64-apple-darwin
release: 1.51.0
LLVM version: 11.0.1

Error output

<output>

Backtrace

$ RUST_BACKTRACE=1 cargo build
   Compiling bug v0.1.0 (/private/tmp/bug)
error[E0658]: `let` expressions in this position are experimental
 --> src/main.rs:6:16
  |
6 |             if let json::JsonValue::Boolean(state) = v["active"] && true {
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information

thread 'rustc' panicked at 'expected `NodeId` to be lowered already for res Local(
    NodeId(44),
)', compiler/rustc_ast_lowering/src/lib.rs:714:17
stack backtrace:
   0: _rust_begin_unwind
   1: std::panicking::begin_panic_fmt
   2: rustc_ast_lowering::LoweringContext::lower_res::{{closure}}::{{closure}}
   3: rustc_ast_lowering::LoweringContext::lower_node_id_generic
   4: rustc_ast_lowering::path::<impl rustc_ast_lowering::LoweringContext>::lower_qpath
   5: rustc_data_structures::stack::ensure_sufficient_stack
   6: rustc_ast_lowering::expr::<impl rustc_ast_lowering::LoweringContext>::lower_expr_if
   7: rustc_data_structures::stack::ensure_sufficient_stack
   8: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
   9: <core::iter::adapters::flatten::Flatten<I> as core::iter::traits::iterator::Iterator>::next
  10: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
  11: rustc_arena::cold_path
  12: rustc_ast_lowering::expr::<impl rustc_ast_lowering::LoweringContext>::lower_expr_if
  13: rustc_data_structures::stack::ensure_sufficient_stack
  14: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  15: <core::iter::adapters::flatten::Flatten<I> as core::iter::traits::iterator::Iterator>::next
  16: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
  17: rustc_arena::cold_path
  18: rustc_ast_lowering::expr::<impl rustc_ast_lowering::LoweringContext>::lower_expr_for
  19: rustc_data_structures::stack::ensure_sufficient_stack
  20: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  21: <core::iter::adapters::flatten::Flatten<I> as core::iter::traits::iterator::Iterator>::next
  22: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
  23: rustc_arena::cold_path
  24: rustc_ast_lowering::expr::<impl rustc_ast_lowering::LoweringContext>::lower_expr_for
  25: rustc_data_structures::stack::ensure_sufficient_stack
  26: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  27: <core::iter::adapters::flatten::Flatten<I> as core::iter::traits::iterator::Iterator>::next
  28: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
  29: rustc_arena::cold_path
  30: rustc_ast_lowering::item::<impl rustc_ast_lowering::LoweringContext>::lower_block_expr_opt
  31: rustc_ast_lowering::item::<impl rustc_ast_lowering::LoweringContext>::lower_fn_body_block
  32: rustc_ast_lowering::item::<impl rustc_ast_lowering::LoweringContext>::lower_item
  33: rustc_ast_lowering::LoweringContext::with_hir_id_owner
  34: <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_mod
  35: rustc_ast_lowering::lower_crate
  36: rustc_interface::passes::BoxedResolver::access::{{closure}}
  37: rustc_interface::passes::configure_and_expand::{{closure}}
  38: rustc_interface::passes::BoxedResolver::access
  39: rustc_interface::queries::Queries::lower_to_hir
  40: rustc_interface::queries::Queries::global_ctxt
  41: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  42: rustc_span::with_source_map
  43: rustc_interface::interface::create_compiler_and_run
  44: rustc_span::with_session_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

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 (2fd73fabe 2021-03-23) running on x86_64-apple-darwin

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.
error: could not compile `bug`

To learn more, run the command again with --verbose.

[osa1]

I can't reproduce this with current master (7637fd5).

$ cargo +stage1 build
   Compiling issue83504 v0.1.0 (/home/omer/rust/issue83504)
error[E0658]: `let` expressions in this position are experimental
 --> src/main.rs:6:16
  |
6 |             if let json::JsonValue::Boolean(state) = v["active"] && true {
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
  = help: add `#![feature(let_chains)]` to the crate attributes to enable
  = help: you can write `matches!(<expr>, <pattern>)` instead of `let <pattern> = <expr>`

error: `let` expressions are not supported here
 --> src/main.rs:6:16
  |
6 |             if let json::JsonValue::Boolean(state) = v["active"] && true {
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: only supported directly without parentheses in conditions of `if`- and `while`-expressions, as well as in `let` chains within parentheses

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.
error: could not compile `issue83504`

To learn more, run the command again with --verbose.

My Cargo.toml:

[package]
name = "issue83504"
version = "0.1.0"
edition = "2018"

[dependencies]
json = "0.12.4"

@dfarnham could you share the Cargo.toml you used? I'm able to reproduce using 1.51 so the Cargo.toml should be right.

[osa1]

Smaller repro, without deps:

struct MyBool(bool);

fn f() -> MyBool {
    MyBool(true)
}

fn main() {
    if let MyBool(b) = f() && true {
        if b {}
    }
}

Panics with 1.51 as in the original report. Does not panic with nightly.

@rustbot label -E-needs-mcve

[SNCPlay42]

Duplicate of #82290, which is fixed on nightly.

[JohnTitor]

Triage: Indeed this should be a duplicate of #82290, and #82308 has a regression test that should cover the issue, closing as fixed/duplicate.