FP `Syntax Error: A block in this position cannot accept inner attributes`

[matthiaskrgr]

The following code

fn bla() -> ((),) {
    (
        {
            #![allow(unreachable_code, irrefutable_let_patterns)]
        },
    )
}

fn main() {}

comiled with rustc (cargo check):

    Checking _main v0.1.0 (/tmp/icemaker_global_tempdir.SjUS4CVu3Z7a/rustc_testrunner_tmpdir.OawYhBfM7wxi/_main)
warning: function `bla` is never used
 --> src/main.rs:1:4
  |
1 | fn bla() -> ((),) {
  |    ^^^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default

warning: `_main` (bin "_main") generated 1 warning
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.06s

but errors were issued by rust-analyzer diagnostics

at crate _main, file /tmp/icemaker_global_tempdir.SjUS4CVu3Z7a/rustc_testrunner_tmpdir.OawYhBfM7wxi/_main/src/main.rs: Error SyntaxError from LineCol { line: 3, col: 12 } to LineCol { line: 3, col: 65 }: Syntax Error: A block in this position cannot accept inner attributes

diagnostic scan complete


Error: diagnostic error detected

Stack backtrace:
   0: <anyhow::Error>::msg::<&str>
             at /home/matthias/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.102/src/backtrace.rs:10:14
   1: anyhow::__private::format_err
             at /home/matthias/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/anyhow-1.0.102/src/lib.rs:687:13
   2: <rust_analyzer::cli::flags::Diagnostics>::run_
             at /home/matthias/vcs/github/rust-analyzer/crates/rust-analyzer/src/cli/diagnostics.rs:123:13
   3: <rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}
             at /home/matthias/vcs/github/rust-analyzer/crates/rust-analyzer/src/cli/diagnostics.rs:20:29
   4: <stdx::thread::Builder>::spawn::<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}
             at /home/matthias/vcs/github/rust-analyzer/crates/stdx/src/thread.rs:74:13
   5: std::sys::backtrace::__rust_begin_short_backtrace::<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:166:18
   6: std::thread::lifecycle::spawn_unchecked::<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#1}::{closure#0}
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/lifecycle.rs:70:13
   7: <core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#1}::{closure#0}> as core::ops::function::FnOnce<()>>::call_once
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:275:9
   8: std::panicking::catch_unwind::do_call::<core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#1}::{closure#0}>, core::result::Result<(), anyhow::Error>>
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:576:43
   9: std::panicking::catch_unwind::<core::result::Result<(), anyhow::Error>, core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#1}::{closure#0}>>
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:544:19
  10: std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#1}::{closure#0}>, core::result::Result<(), anyhow::Error>>
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:359:14
  11: std::thread::lifecycle::spawn_unchecked::<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#1}
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/lifecycle.rs:68:26
  12: <std::thread::lifecycle::spawn_unchecked<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
             at /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  13: <alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output = ()> + core::marker::Send> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/8fa1c96cfd489e4c27654c144ae871ce2c4db6c6/library/alloc/src/boxed.rs:2320:9
  14: <std::sys::thread::unix::Thread>::new::thread_start
             at /rustc/8fa1c96cfd489e4c27654c144ae871ce2c4db6c6/library/std/src/sys/thread/unix.rs:123:17
  15: <unknown>
  16: <unknown>

version information

rust-analyzer 0.0.0 (0356f5bf5a 2026-08-18)

[dfireBird]

This can be fixed by adding TUPLE_EXPR here and corresponding tests needs to be added as well, for reference, see PR #23020:

rust-analyzer/crates/syntax/src/validation/block.rs

Lines 9 to 17 in 69d0e26

	pub(crate) fn validate_block_expr(block: ast::BlockExpr, errors: &mut Vec<SyntaxError>) {
	if let Some(parent) = block.syntax().parent() {
	match parent.kind() {
	FN | EXPR_STMT | STMT_LIST | MACRO_STMTS | LOOP_EXPR | WHILE_EXPR | FOR_EXPR => {
	return;
	}
	_ => {}
	}
	}

[sandaruwijewardhana]

Thanks for the pointer @dfireBird
I'd like to take this.

Plan is to add TUPLE_EXPR to the parent-kind match in validate_block_expr (crates/syntax/src/validation/block.rs), extend
crates/syntax/test_data/parser/validation/0031_block_inner_attrs.rs with the tuple case from the report, and regenerate the .rast, following #23020.

[Aditya-PS-05]

@rustbot claim