panic: `!source_term.clone().has_escaping_bound_vars()`

struct X;

trait Trait {
    fn foo<'a, const N: &'a X = isize>() {}
} 

~/.rustup/toolchains/master/bin/rust-analyzer highlight < code.rs

thread 'main' (1323284) panicked at src/tools/rust-analyzer/crates/hir-ty/src/next_solver/infer/relate/generalize.rs:231:9:
assertion failed: !source_term.clone().has_escaping_bound_vars()
stack backtrace:
   0:     0x7fe870c2a3a6 - <<std[1982baa743927e99]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[f465834d8a4f5c90]::fmt::Display>::fmt
   1:     0x7fe87120d912 - core[f465834d8a4f5c90]::fmt::write
   2:     0x7fe870c3f4fc - <std[1982baa743927e99]::sys::stdio::unix::Stderr as core[f465834d8a4f5c90]::io::write::Write>::write_fmt
   3:     0x7fe870bfbfda - std[1982baa743927e99]::panicking::default_hook::{closure#0}
   4:     0x7fe870c1ca43 - std[1982baa743927e99]::panicking::default_hook
   5:     0x7fe870c1ceab - std[1982baa743927e99]::panicking::panic_with_hook
   6:     0x7fe870bfc0c4 - std[1982baa743927e99]::panicking::panic_handler::{closure#0}
   7:     0x7fe870bf2a29 - std[1982baa743927e99]::sys::backtrace::__rust_end_short_backtrace::<std[1982baa743927e99]::panicking::panic_handler::{closure#0}, !>
   8:     0x7fe870bfd9ed - __rustc[163072274320cfb5]::rust_begin_unwind
   9:     0x7fe86d6deafc - core[f465834d8a4f5c90]::panicking::panic_fmt
  10:     0x7fe86de7bcf2 - core[f465834d8a4f5c90]::panicking::panic
  11:     0x563b061e1cd5 - <hir_ty[26e24694bccb7328]::next_solver::infer::InferCtxt>::instantiate_ty_var::<ra_ap_rustc_type_ir[2d2ad0764abf9d15]::relate::solver_relating::SolverRelating<hir_ty[26e24694bccb7328]::next_solver::infer::InferCtxt, hir_ty[26e24694bccb7328]::next_solver::interner::DbInterner>>
  12:     0x563b065a0d01 - <ra_ap_rustc_type_ir[2d2ad0764abf9d15]::relate::solver_relating::SolverRelating<hir_ty[26e24694bccb7328]::next_solver::infer::InferCtxt, hir_ty[26e24694bccb7328]::next_solver::interner::DbInterner> as ra_ap_rustc_type_ir[2d2ad0764abf9d15]::relate::TypeRelation<hir_ty[26e24694bccb7328]::next_solver::interner::DbInterner>>::tys
  13:     0x563b062ffe45 - <hir_ty[26e24694bccb7328]::next_solver::infer::InferCtxt as ra_ap_rustc_type_ir[2d2ad0764abf9d15]::relate::solver_relating::RelateExt>::relate::<hir_ty[26e24694bccb7328]::next_solver::ty::Ty>
  14:     0x563b064caf7c - <hir_ty[26e24694bccb7328]::infer::InferenceContext>::demand_eqtype
  15:     0x563b0640e8de - <salsa[4a2c27948d016988]::function::IngredientImpl<<hir_ty[26e24694bccb7328]::infer::InferenceResult>::for_anon_const::_::for_anon_const__Configuration_>>::execute
  16:     0x563b063eb112 - <salsa[4a2c27948d016988]::function::IngredientImpl<<hir_ty[26e24694bccb7328]::infer::InferenceResult>::for_anon_const::_::for_anon_const__Configuration_>>::fetch
  17:     0x563b061fec8c - <std[1982baa743927e99]::thread::local::LocalKey<salsa[4a2c27948d016988]::attach::Attached>>::with::<salsa[4a2c27948d016988]::attach::attach<&hir_ty[26e24694bccb7328]::infer::InferenceResult, dyn hir_ty[26e24694bccb7328]::db::HirDatabase, <hir_ty[26e24694bccb7328]::infer::InferenceResult>::for_anon_const::for_anon_const_::{closure#0}>::{closure#0}, &hir_ty[26e24694bccb7328]::infer::InferenceResult>
  18:     0x563b05e06a53 - <hir[7ad85eaab5b2b40e]::source_analyzer::SourceAnalyzer>::new_generic_def_
  19:     0x563b05e28596 - <hir[7ad85eaab5b2b40e]::semantics::SemanticsImpl>::analyze_impl
  20:     0x563b05e3a147 - <hir[7ad85eaab5b2b40e]::semantics::SemanticsImpl>::resolve_path_with_subst
  21:     0x563b06c42070 - <ide_db[4c988ca8a3b6339d]::defs::NameRefClass>::classify
  22:     0x563b067a6d0f - ide[30ad0f08913b17a1]::syntax_highlighting::highlight
  23:     0x563b067e14ce - ide[30ad0f08913b17a1]::syntax_highlighting::html::highlight_as_html_with_config
  24:     0x563b06747e9c - <ide[30ad0f08913b17a1]::Analysis>::highlight_as_html
  25:     0x563b071f9dc2 - <rust_analyzer[36ea474561c7f7a2]::cli::flags::Highlight>::run
  26:     0x563b0742e1d4 - rust_analyzer[fad7725dce625749]::main
  27:     0x563b0742a443 - std[1982baa743927e99]::sys::backtrace::__rust_begin_short_backtrace::<fn() -> core[f465834d8a4f5c90]::result::Result<std[1982baa743927e99]::process::ExitCode, anyhow[20561770c327b098]::Error>, core[f465834d8a4f5c90]::result::Result<std[1982baa743927e99]::process::ExitCode, anyhow[20561770c327b098]::Error>>
  28:     0x563b0742c1a2 - std[1982baa743927e99]::rt::lang_start::<core[f465834d8a4f5c90]::result::Result<std[1982baa743927e99]::process::ExitCode, anyhow[20561770c327b098]::Error>>::{closure#0}
  29:     0x7fe87241b513 - std[1982baa743927e99]::rt::lang_start_internal
  30:     0x563b07444c68 - main
  31:     0x7fe86ba27741 - <unknown>
  32:     0x7fe86ba27879 - __libc_start_main
  33:     0x563b05d27699 - <unknown>
  34:                0x0 - <unknown>

rust-analyzer 1.99.0-nightly (c188565 2026-07-22)

Reproduce the panic with the reported Rust snippet and the rust-analyzer highlight < code.rs command. Start at crates/hir-ty/src/next_solver/infer/relate/generalize.rs:231, then trace the highlighted type-inference path; done means the command no longer panics for this input.