Change:
: Same in 1.52.0-nightly, same in 1.51.0. : <details<summary<strongBacktrace</strong</summary<p</p</detailsGood luck! <3
This happens on top of too much code for me to take the time to minimalize this issue, sorry. Though I'll try to file the fixing patch.
Wait! I made it! This issue revolves around L.31. Comment to see the ice go away. Interestingly, comment L.40 (or the whole impl L.37-45) to see ice go away as well. Commenting L.47-56 does not make ice go away. Commenting L.13-22 should raise another error (as L.31 is supposed to go there), but doesn't. Actually, the real fix is to replace L.31 with: Have fun!
Minimized with , then a bit by hand: <details<summaryDetails</summary<pIcemelter version: v0.2.0 label +S-bug-has-mcve </p</details
fixed by . we previously used to eagerly error but did not consider them as part of the cache key. So using a cache key from an evaluation with different can result in buggy behavior

Discussion:
<ins> // ICE: failed to get layout for [type error] // issue: rust-lang/rust#92979 use std::fs; use std::fs::File; use std::io::Read; use std::convert::TryInto; fn get_file_as_byte_vec(filename: &String) -> Vec<u8> { let mut f = File::open(&filename).expect("no file found"); let metadata = fs::metadata(&filename).expect("unable to read metadata"); let mut buffer = vec![0; metadata.len() as usize]; f.read(&mut buffer).expect("buffer overflow"); buffer } fn demo<T, const N: usize>(v: Vec<T>) -> [T; N] { v.try_into() .unwrap_or_else(|v: Vec<T>| panic!("Expected a Vec of length {} but it was {}", N, v.len())) } fn main() { // Specify filepath let file: &String = &String::from("SomeBinaryDataFileWith4ByteHeaders_f32s_and_u32s"); // Read file into a vector of bytes let file_data = get_file_as_byte_vec(file); // Print length of vector and first few values let length = file_data.len(); println!("The read function read {} bytes", length); println!("The first few bytes:"); for i in 0..20{ println!("{}", file_data[i]); } // Manually count just to make sure let mut n: u64 = 0; for data in file_data{ n += 1; } println!("We counted {} bytes", n); assert!(n as usize == length, "Manual counting does not equal len method"); // Simulation parameters const N: usize = 49627502;                // Number of Particles const bs: f64 = 125.0;                  // Box Size const HEADER_INCREMENT: u64 = 4*1; // Initialize index and counter variables let (mut j, mut pos, mut vel, mut id, mut mass): (u64, u64, u64, u64, u64) = (0, 0, 0, 0, 0); // Unpack Position Data j += HEADER_INCREMENT; let mut position: Vec<f32> = Vec::new(); while position.len() < N*3 { let p: Vec<u8> = Vec::new(); for item in 0i8..4 { let item = item; p.push(file_data[j as usize]); j += 1; } &mut position[position.len()] = f32::from_be_bytes(demo(p)); //~^ ERROR invalid left-hand side of assignment } // Ensure position data is indeed position by checking values for p in position { assert!((p > 0.) & (p < 125.), "Not in box") } } </ins>

<ins> error[E0070]: invalid left-hand side of assignment --> $DIR/failed-to-get-layout-for-type-error-ice-92979.rs:69:39 | LL |         &mut position[position.len()] = f32::from_be_bytes(demo(p)); |         ----------------------------- ^ |         | |         cannot assign to this expression | help: consider dereferencing here to assign to the mutably borrowed value | LL |         *&mut position[position.len()] = f32::from_be_bytes(demo(p)); |         + error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0070`. </ins>

<ins> // ICE argument to function with "rust-call" ABI is not a tuple // issue: rust-lang/rust#81974 #![feature(unboxed_closures)] #![feature(fn_traits)] use std::collections::HashMap; use std::hash::Hash; struct CachedFun<A, B> { cache: HashMap<A, B>, fun: fn(&mut CachedFun<A, B>, A) -> B, } impl<A: Eq + Hash, B> CachedFun<A, B> { fn new(fun: fn(&mut Self, A) -> B) -> Self { CachedFun { cache: HashMap::new(), fun, } } } impl<A, B> FnOnce<A> for CachedFun<A, B> //~^ ERROR type parameter to bare `FnOnce` trait must be a tuple where A: Eq + Hash + Clone, B: Clone, { type Output = B; extern "rust-call" fn call_once(mut self, a: A) -> Self::Output { //~^ ERROR functions with the "rust-call" ABI must take a single non-self tuple argument self.call_mut(a) //~^ ERROR `A` is not a tuple } } impl<A, B> FnMut<A> for CachedFun<A, B> //~^ ERROR type parameter to bare `FnMut` trait must be a tuple where A: Eq + Hash + Clone, B: Clone, { extern "rust-call" fn call_mut(&mut self, a: A) -> Self::Output { //~^ ERROR functions with the "rust-call" ABI must take a single non-self tuple argument self.cache.get(&a).map(|a| a.clone()).unwrap_or_else(|| { let b = (self.fun)(self, a.clone()); self.cache.insert(a, b.clone()); b }) } } fn main() -> () { let pesce = |y: &mut CachedFun<i32, i32>, x| x + 1; let cachedcoso = CachedFun::new(pesce); cachedcoso.call_once(1); //~^ ERROR `i32` is not a tuple } </ins>

<ins> error[E0059]: type parameter to bare `FnOnce` trait must be a tuple --> $DIR/rust-call-abi-not-a-tuple-ice-81974.rs:24:12 | LL | impl<A, B> FnOnce<A> for CachedFun<A, B> |            ^^^^^^^^^ the trait `Tuple` is not implemented for `A` | note: required by a bound in `FnOnce` --> $SRC_DIR/core/src/ops/function.rs:LL:COL help: consider further restricting this bound | LL |     A: Eq + Hash + Clone + std::marker::Tuple, |                          ++++++++++++++++++++ error[E0059]: type parameter to bare `FnMut` trait must be a tuple --> $DIR/rust-call-abi-not-a-tuple-ice-81974.rs:38:12 | LL | impl<A, B> FnMut<A> for CachedFun<A, B> |            ^^^^^^^^ the trait `Tuple` is not implemented for `A` | note: required by a bound in `FnMut` --> $SRC_DIR/core/src/ops/function.rs:LL:COL help: consider further restricting this bound | LL |     A: Eq + Hash + Clone + std::marker::Tuple, |                          ++++++++++++++++++++ error[E0277]: functions with the "rust-call" ABI must take a single non-self tuple argument --> $DIR/rust-call-abi-not-a-tuple-ice-81974.rs:31:5 | LL |     extern "rust-call" fn call_once(mut self, a: A) -> Self::Output { |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Tuple` is not implemented for `A` | help: consider further restricting this bound | LL |     A: Eq + Hash + Clone + std::marker::Tuple, |                          ++++++++++++++++++++ error[E0277]: functions with the "rust-call" ABI must take a single non-self tuple argument --> $DIR/rust-call-abi-not-a-tuple-ice-81974.rs:44:5 | LL |     extern "rust-call" fn call_mut(&mut self, a: A) -> Self::Output { |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Tuple` is not implemented for `A` | help: consider further restricting this bound | LL |     A: Eq + Hash + Clone + std::marker::Tuple, |                          ++++++++++++++++++++ error[E0277]: `A` is not a tuple --> $DIR/rust-call-abi-not-a-tuple-ice-81974.rs:33:23 | LL |         self.call_mut(a) |              -------- ^ the trait `Tuple` is not implemented for `A` |              | |              required by a bound introduced by this call | note: required by a bound in `call_mut` --> $SRC_DIR/core/src/ops/function.rs:LL:COL help: consider further restricting this bound | LL |     A: Eq + Hash + Clone + std::marker::Tuple, |                          ++++++++++++++++++++ error[E0277]: `i32` is not a tuple --> $DIR/rust-call-abi-not-a-tuple-ice-81974.rs:57:26 | LL |     cachedcoso.call_once(1); |                --------- ^ the trait `Tuple` is not implemented for `i32` |                | |                required by a bound introduced by this call | note: required by a bound in `call_once` --> $SRC_DIR/core/src/ops/function.rs:LL:COL error: aborting due to 6 previous errors Some errors have detailed explanations: E0059, E0277. For more information about an error, try `rustc --explain E0059`. </ins>

<ins> // ICE Where clause `Binder(..)` was applicable to `Obligation(..)` but now is not // issue: rust-lang/rust#84727 struct Cell<Fg, Bg = Fg> { foreground: Color<Fg>, //~^ ERROR cannot find type `Color` in this scope background: Color<Bg>, //~^ ERROR cannot find type `Color` in this scope } trait Over<Bottom, Output> { fn over(self) -> Output; } impl<TopFg, TopBg, BottomFg, BottomBg, NewFg, NewBg> Over<Cell<BottomFg, BottomBg>, Cell<NewFg, NewBg>> for Cell<TopFg, TopBg> where Self: Over<Color<BottomBg>, Cell<NewFg>>, //~^ ERROR cannot find type `Color` in this scope { fn over(self) -> Cell<NewFg> { //~^ ERROR mismatched types self.over(); } } impl<'b, TopFg, TopBg, BottomFg, BottomBg> Over<&Cell<BottomFg, BottomBg>, ()> for Cell<TopFg, TopBg> where Cell<TopFg, TopBg>: Over<Cell<BottomFg>, Cell<BottomFg>>, { fn over(self) -> Cell<NewBg> { //~^ ERROR cannot find type `NewBg` in this scope self.over(); } } pub fn main() {} </ins>

<ins> error[E0412]: cannot find type `Color` in this scope --> $DIR/trait-selection-ice-84727.rs:5:17 | LL |     foreground: Color<Fg>, |                 ^^^^^ not found in this scope error[E0412]: cannot find type `Color` in this scope --> $DIR/trait-selection-ice-84727.rs:7:17 | LL |     background: Color<Bg>, |                 ^^^^^ not found in this scope error[E0412]: cannot find type `Color` in this scope --> $DIR/trait-selection-ice-84727.rs:18:16 | LL |     Self: Over<Color<BottomBg>, Cell<NewFg>>, |                ^^^^^ not found in this scope error[E0412]: cannot find type `NewBg` in this scope --> $DIR/trait-selection-ice-84727.rs:32:27 | LL |     fn over(self) -> Cell<NewBg> { |                           ^^^^^ not found in this scope | help: you might be missing a type parameter | LL | impl<'b, TopFg, TopBg, BottomFg, BottomBg, NewBg> Over<&Cell<BottomFg, BottomBg>, ()> |                                          +++++++ error[E0308]: mismatched types --> $DIR/trait-selection-ice-84727.rs:21:22 | LL |     fn over(self) -> Cell<NewFg> { |        ----          ^^^^^^^^^^^ expected `Cell<NewFg>`, found `()` |        | |        implicitly returns `()` as its body has no tail or `return` expression LL | LL |         self.over(); |                    - help: remove this semicolon to return this value | = note: expected struct `Cell<NewFg>` found unit type `()` error: aborting due to 5 previous errors Some errors have detailed explanations: E0308, E0412. For more information about an error, try `rustc --explain E0308`. </ins>