Generic compilation struggle

[hasbonahad]

Code

I have not yet successfully reproduced the bug but I have a direction. it seems the compile has some struggles with how to deal with generic that are phantomdata. in this case Exact is phantomdata

pub fn get_exact_storage( storage: Self) -> Result<Storage< 2, Float, Exact>, Self>{
      if storage.seeds.len() == 4{
          return Ok(Self{ seeds: storage.seeds, state: PhantomData });
      }
      Err(storage)
  }

when I changed it to this it has compiled successfully
(Self is Storage< 2, Float, UnExact>)

pub fn get_exact_storage( storage: Self) -> Result<Storage< 2, Float, UnExact>, Self>{
      if storage.seeds.len() == 4{
          return Ok(Self{ seeds: storage.seeds, state: PhantomData });
      }
      Err(storage)
  }

I have also tried to reproduce the bug with this simple code but I have to compile

use std::marker::PhantomData;

struct A;
struct B;

struct Foo<T>{

    _marker: PhantomData<T>
}

impl Foo<A>{

    pub fn some_func(value: Self, number:i32) -> Result<Foo<A>, Foo<B>>{
        if number == 0{
            return Ok(value );
        }
        Err(Foo { _marker: PhantomData })
    }
}

Meta

rustc 1.77.2 (25ef9e3 2024-04-09)
binary: rustc
commit-hash: 25ef9e3
commit-date: 2024-04-09
host: x86_64-pc-windows-msvc
release: 1.77.2
LLVM version: 17.0.6

Error output

compiler\rustc_middle\src\ty\generic_args.rs:907:9: expected type for `Float/#0` (Float/#0/0) but found Const(2_usize) when substituting, args=[2_usize, Float/#0, storage::Exact]

thread 'rustc' panicked at /rustc/25ef9e3d85d934b27d9dada2f9dd52b1dc63bb04\compiler\rustc_errors\src\lib.rs:932:30:
Box<dyn Any>
stack backtrace:
   0:     0x7ffef5c72902 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h708c0e6d07ee75bc
   1:     0x7ffef5ca5a5d - core::fmt::write::ha562f117fc8493e6
   2:     0x7ffef5c68f91 - <std::io::IoSliceMut as core::fmt::Debug>::fmt::h73b3c4d73d82ca2e
   3:     0x7ffef5c7272a - std::sys_common::backtrace::lock::h300ba94956ddd24a
   4:     0x7ffef5c75ac9 - std::panicking::default_hook::hc9d04f0d76a9742b
   5:     0x7ffef5c75785 - std::panicking::default_hook::hc9d04f0d76a9742b
   6:     0x7ffed51db863 - <tracing_subscriber[c0eceff03426eead]::fmt::format::Writer>::write_fmt
   7:     0x7ffef5c760d3 - std::panicking::rust_panic_with_hook::h05ca8ac23cc77c65
   8:     0x7ffed65f20d8 - rustc_errors[10ae28232b989578]::add_elided_lifetime_in_path_suggestion
   9:     0x7ffed65f2019 - rustc_errors[10ae28232b989578]::add_elided_lifetime_in_path_suggestion
  10:     0x7ffed65ff069 - <rustc_errors[10ae28232b989578]::registry::Registry>::try_find_description
  11:     0x7ffed66033d5 - <rustc_errors[10ae28232b989578]::diagnostic_builder::BugAbort as rustc_errors[10ae28232b989578]::diagnostic_builder::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7ffed649563c - <core[d4e1671815e8b4a5]::option::Option<rustc_middle[3a1ce97b5b0524ba]::mir::terminator::Terminator> as rustc_middle[3a1ce97b5b0524ba]::mir::visit::MirVisitable>::apply
  13:     0x7ffed64d008b - rustc_middle[3a1ce97b5b0524ba]::util::bug::bug_fmt
  14:     0x7ffed64cf6fd - rustc_middle[3a1ce97b5b0524ba]::ty::util::is_doc_notable_trait
  15:     0x7ffed64cf6ca - rustc_middle[3a1ce97b5b0524ba]::ty::util::is_doc_notable_trait
  16:     0x7ffed64cff82 - rustc_middle[3a1ce97b5b0524ba]::util::bug::bug_fmt
  17:     0x7ffed6518797 - <rustc_middle[3a1ce97b5b0524ba]::ty::generic_args::GenericArg as rustc_middle[3a1ce97b5b0524ba]::ty::context::Lift>::lift_to_tcx
  18:     0x7ffed5047713 - <rustc_middle[3a1ce97b5b0524ba]::ty::Ty>::walk
  19:     0x7ffed40f6e1f - <rustc_middle[3a1ce97b5b0524ba]::ty::print::pretty::FmtPrinter as rustc_middle[3a1ce97b5b0524ba]::ty::print::Printer>::print_def_path
  20:     0x7ffed64a31ab - <rustc_middle[3a1ce97b5b0524ba]::ty::print::pretty::FmtPrinter as rustc_middle[3a1ce97b5b0524ba]::ty::print::pretty::PrettyPrinter>::print_value_path
  21:     0x7ffed54e66cb - <rustc_hir_typeck[d09ebf2a634d1509]::coercion::CollectRetsVisitor as rustc_hir[b6886131bf44f6e3]::intravisit::Visitor>::visit_expr
  22:     0x7ffed54aa944 - <rustc_hir[b6886131bf44f6e3]::hir_id::HirId as rustc_hir_typeck[d09ebf2a634d1509]::writeback::Locatable>::to_span
  23:     0x7ffed5446dd6 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::emit_type_mismatch_suggestions
  24:     0x7ffed544d639 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::emit_coerce_suggestions
  25:     0x7ffed545a0c0 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::blame_specific_expr_if_possible
  26:     0x7ffed430032d - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::check_call
  27:     0x7ffed4310d32 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::demand_eqtype
  28:     0x7ffed432d529 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::demand_eqtype
  29:     0x7ffed4312071 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::demand_eqtype
  30:     0x7ffed434a74f - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::check_struct_path
  31:     0x7ffed431106a - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::demand_eqtype
  32:     0x7ffed431223e - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::demand_eqtype
  33:     0x7ffed434a896 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::check_struct_path
  34:     0x7ffed431106a - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::demand_eqtype
  35:     0x7ffed432d529 - <rustc_hir_typeck[d09ebf2a634d1509]::fn_ctxt::FnCtxt>::demand_eqtype
  36:     0x7ffed42f1980 - rustc_hir_typeck[d09ebf2a634d1509]::typeck
  37:     0x7ffed42ece2e - rustc_hir_typeck[d09ebf2a634d1509]::typeck
  38:     0x7ffed4ad089f - <rustc_query_impl[910689ae0041c04b]::plumbing::QueryCtxt as rustc_query_system[9a9d032e0d04d659]::query::QueryContext>::load_side_effects
  39:     0x7ffed4ac943f - rustc_query_impl[910689ae0041c04b]::query_callbacks
  40:     0x7ffed4ba49a1 - <rustc_query_impl[910689ae0041c04b]::plumbing::QueryCtxt as rustc_query_system[9a9d032e0d04d659]::query::QueryContext>::load_side_effects
  41:     0x7ffed4b45e32 - <rustc_query_impl[910689ae0041c04b]::plumbing::QueryCtxt as rustc_query_system[9a9d032e0d04d659]::query::QueryContext>::load_side_effects
  42:     0x7ffed447bc6f - rustc_hir_analysis[dc08ae6b29e9a3a]::check::check::check_abi
  43:     0x7ffed3b572ea - rustc_hir_analysis[dc08ae6b29e9a3a]::check_crate
  44:     0x7ffed138e807 - rustc_interface[6562ac5350621f0c]::passes::analysis
  45:     0x7ffed3dd8c4d - rustc_query_impl[910689ae0041c04b]::profiling_support::alloc_self_profile_query_strings
  46:     0x7ffed3e0e239 - rustc_query_impl[910689ae0041c04b]::profiling_support::alloc_self_profile_query_strings
  47:     0x7ffed3e398d8 - rustc_query_impl[910689ae0041c04b]::profiling_support::alloc_self_profile_query_strings
  48:     0x7ffed3e10f72 - rustc_query_impl[910689ae0041c04b]::profiling_support::alloc_self_profile_query_strings
  49:     0x7ffed13406fb - rustc_driver_impl[5927ec3c421e5c5e]::args::arg_expand_all
  50:     0x7ffed133f469 - rustc_driver_impl[5927ec3c421e5c5e]::args::arg_expand_all
  51:     0x7ffed13584b1 - <rustc_middle[3a1ce97b5b0524ba]::ty::SymbolName as core[d4e1671815e8b4a5]::fmt::Debug>::fmt
  52:     0x7ffed136385f - <rustc_middle[3a1ce97b5b0524ba]::ty::SymbolName as core[d4e1671815e8b4a5]::fmt::Debug>::fmt
  53:     0x7ffed1360bf8 - <rustc_middle[3a1ce97b5b0524ba]::ty::SymbolName as core[d4e1671815e8b4a5]::fmt::Debug>::fmt
  54:     0x7ffef5c8803c - std::sys::pal::windows::thread::Thread::new::h51a32cdc9f29bad5
  55:     0x7fff52be7344 - BaseThreadInitThunk
  56:     0x7fff53c426b1 - RtlUserThreadStart

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 1.77.2 (25ef9e3d8 2024-04-09) running on x86_64-pc-windows-msvc

note: compiler flags: --crate-type lib -C opt-level=3 -C embed-bitcode=no

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

query stack during panic:
#0 [typeck] type-checking `storage::<impl at src\storage.rs:49:1: 51:25>::get_exact_storage`
#1 [analysis] running analysis passes on this crate
end of query stack

[brownie-in-motion]

@hasbonahad could you provide some more context for the snippet that's causing the crash? Having some trouble reproducing.

[hasbonahad]

@hasbonahad could you provide some more context for the snippet that's causing the crash? Having some trouble reproducing.

I have some problems with reproducing the bug with simpler examples.

I could only make this bug\crush happen by using this code.

I have my own Perlin noise lib. the lib has Storage like this

struct Exact;
struct UnExact;

struct Stroage<const Size: usize , Float, State>{
    _marker: phantomdata<State>, 
    ...
}

impl<Float> for Storage<2, Float, UnExact>{
  pub fn get_exact_storage( storage: Self) -> Result<Storage< 2, Float, Exact>, Self>{
        if storage.seeds.len() == 4{
            return Ok(Self{ seeds: storage.seeds, state: PhantomData });
        }
        Err(storage)
    }
}

it has unsecessfuly compiled when the function get_exact_storage has a return something relatable with Storage< 2, Float, Exact>.

[brownie-in-motion]

I was able to reproduce on 1.77, but it seems okay on 1.78.0.

struct X {}
struct Y {}

struct Foo<const N: usize, T, U>{
    data: Option<(T, U)>,
}

impl<T> Foo<0, T, X>{
  fn f() -> Foo<0, T, Y>{
      Self { data: None }
  }
}

fn main() {}