Panic with nested tuple access syntax

[virtualritz]

Running rustfmt on a source that uses a double dot syntax to access a nested tuple causes a panic:

thread 'main' panicked at 'bad span: `.`: ``', src/tools/rustfmt/src/source_map.rs:52:13
stack backtrace:
   0: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
   1: core::fmt::write
   2: std::io::Write::write_fmt
   3: std::panicking::default_hook::{{closure}}
   4: std::panicking::default_hook
   5: std::panicking::rust_panic_with_hook
   6: rust_begin_unwind
   7: std::panicking::begin_panic_fmt
   8: <rustfmt_nightly::visitor::SnippetProvider as rustfmt_nightly::source_map::SpanUtils>::span_before::{{closure}}
   9: <rustfmt_nightly::visitor::SnippetProvider as rustfmt_nightly::source_map::SpanUtils>::span_before
  10: rustfmt_nightly::chains::rewrite_chain
  11: rustfmt_nightly::expr::format_expr
  12: <rustfmt_nightly::overflow::OverflowableItem as rustfmt_nightly::rewrite::Rewrite>::rewrite
  13: <rustfmt_nightly::lists::ListItems<I,F1,F2,F3> as core::iter::traits::iterator::Iterator>::next
  14: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  15: rustfmt_nightly::overflow::Context::rewrite_items
  16: rustfmt_nightly::overflow::Context::rewrite
  17: rustfmt_nightly::expr::format_expr
  18: rustfmt_nightly::closures::rewrite_closure_expr
  19: rustfmt_nightly::closures::rewrite_closure
  20: rustfmt_nightly::expr::format_expr
  21: rustfmt_nightly::closures::rewrite_last_closure
  22: rustfmt_nightly::overflow::Context::rewrite_items
  23: rustfmt_nightly::overflow::Context::rewrite
  24: rustfmt_nightly::expr::rewrite_call
  25: <rustfmt_nightly::chains::ChainItem as rustfmt_nightly::rewrite::Rewrite>::rewrite
  26: <rustfmt_nightly::chains::ChainFormatterBlock as rustfmt_nightly::chains::ChainFormatter>::format_children
  27: <rustfmt_nightly::chains::Chain as rustfmt_nightly::rewrite::Rewrite>::rewrite
  28: rustfmt_nightly::chains::rewrite_chain
  29: rustfmt_nightly::expr::format_expr
  30: rustfmt_nightly::stmt::format_stmt
  31: rustfmt_nightly::visitor::FmtVisitor::walk_stmts
  32: rustfmt_nightly::visitor::FmtVisitor::visit_block
  33: rustfmt_nightly::visitor::FmtVisitor::visit_fn
  34: rustfmt_nightly::visitor::FmtVisitor::visit_item
  35: rustfmt_nightly::reorder::<impl rustfmt_nightly::visitor::FmtVisitor>::visit_items_with_reordering
  36: rustfmt_nightly::visitor::FmtVisitor::walk_mod_items
  37: rustfmt_nightly::visitor::FmtVisitor::format_separate_mod
  38: rustfmt_nightly::formatting::format_project
  39: scoped_tls::ScopedKey<T>::set
  40: rustc_ap_rustc_ast::attr::with_session_globals
  41: rustfmt_nightly::Session<T>::format
  42: rustfmt::format_and_emit_report
  43: rustfmt::execute
  44: rustfmt::main
  45: std::rt::lang_start::{{closure}}
  46: std::rt::lang_start_internal
  47: main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
[Error - 8:13:42 PM] Request textDocument/formatting failed.
  Message: rustfmt exited with:
                           Status: exit code: 101
                           stdout: 
  Code: -32900 

To Reproduce

git clone https://github.com/virtualritz/polyhedron-operators.git
cargo fmt

Meta

• rustfmt version: rustfmt 1.4.19-nightly (cef1c0d5 2020-07-21)
• From where did you install rustfmt: rustup
• How do you run rustfmt: cargo fmt

[calebcartwright]

thank you for the report @virtualritz. However, I believe this is a duplicate of #4355 and would rather close and track in one place. Will hold off on closing this for a bit in case you feel this is a different underlying issue and want to make that case.

[virtualritz]

Yes, totally looks like a duplicate. Sorry about the noise, didn't see #4355 even though I tried searching for this.

[calebcartwright]

No worries! Thanks again for reaching out