Crashes when formatting tuple heavy code example

[drbartling]

Describe the bug

Rustfmt crashes on the following code example. I had it saved to edge.rs This code compiles fine. No promises on the accuracy of edge the logic, though ;)

To Reproduce

Run rustfmt on this code sample:

e1: ((f64, f64), (f64, f64)),
e2: ((f64, f64), (f64, f64)),
) -> bool {
let slope_1 = (e1.1.1 - e1.0.1) / (e1.1.0 - e1.0.0);
let slope_2 = (e2.1.1 - e2.0.1) / (e2.1.0 - e2.0.0);
slope_1 != slope_2
}

Expected behavior

thread 'main' panicked at 'bad span: `.`: ``', src/tools/rustfmt/src/source_map.rs:52:13
stack backtrace:
   0: rust_begin_unwind
             at /rustc/18bf6b4f01a6feaf7259ba7cdae58031af1b7b39/library/std/src/panicking.rs:475
   1: std::panicking::begin_panic_fmt
             at /rustc/18bf6b4f01a6feaf7259ba7cdae58031af1b7b39/library/std/src/panicking.rs:429
   2: <rustfmt_nightly::visitor::SnippetProvider as rustfmt_nightly::source_map::SpanUtils>::span_before::{{closure}}
   3: <rustfmt_nightly::visitor::SnippetProvider as rustfmt_nightly::source_map::SpanUtils>::span_before
   4: rustfmt_nightly::chains::rewrite_chain
   5: rustfmt_nightly::expr::format_expr
   6: <rustc_ap_rustc_ast::ast::Expr as rustfmt_nightly::pairs::FlattenPair>::flatten
   7: rustfmt_nightly::pairs::rewrite_all_pairs
   8: rustfmt_nightly::expr::format_expr
   9: rustfmt_nightly::expr::format_expr
  10: <rustc_ap_rustc_ast::ast::Expr as rustfmt_nightly::pairs::FlattenPair>::flatten
  11: rustfmt_nightly::pairs::rewrite_all_pairs
  12: rustfmt_nightly::expr::format_expr
  13: rustfmt_nightly::expr::rewrite_assign_rhs_with
  14: rustfmt_nightly::items::<impl rustfmt_nightly::rewrite::Rewrite for rustc_ap_rustc_ast::ast::Local>::rewrite
  15: rustfmt_nightly::stmt::format_stmt
  16: rustfmt_nightly::visitor::FmtVisitor::walk_stmts
  17: rustfmt_nightly::visitor::FmtVisitor::visit_block
  18: rustfmt_nightly::visitor::FmtVisitor::visit_fn
  19: rustfmt_nightly::visitor::FmtVisitor::visit_item
  20: rustfmt_nightly::reorder::<impl rustfmt_nightly::visitor::FmtVisitor>::visit_items_with_reordering
  21: rustfmt_nightly::visitor::FmtVisitor::format_separate_mod
  22: rustfmt_nightly::formatting::format_project
  23: scoped_tls::ScopedKey<T>::set
  24: rustc_ap_rustc_ast::attr::with_session_globals
  25: rustfmt_nightly::Session<T>::format
  26: rustfmt::format_and_emit_report
  27: rustfmt_nightly::Session<T>::override_config
  28: rustfmt::execute
  29: rustfmt::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Meta

• rustfmt version: rustfmt 1.4.20-stable (48f6c32 2020-08-09)
• From where did you install rustfmt?: rustup component add rustfmt
• How do you run rustfmt: cargo fmt

[swooster]

I've encountered the same issue. An even smaller reproducible test-case is:

fn foo(x: ((u32,),)) {
    x.0.0;
}

Changing x.0.0 to (x.0).0 avoids the crash.

[calebcartwright]

Duplicate of #4355, resolved in the upcoming 1.4.23 release

[drbartling]

I've encountered the same issue. An even smaller reproducible test-case is:

fn foo(x: ((u32,),)) {
    x.0.0;
}

Changing x.0.0 to (x.0).0 avoids the crash.

Thanks for the work-around :)