Internal compiler error (traits & associated consts) #56870
Description
Internal compiler error happens compiling weird code with traits and associated consts.
I tried this code:
use std::fmt::Debug;
pub trait Foo<T> {
const FOO: *const u8;
}
impl <T: Debug> Foo<T> for Debug {
const FOO: *const u8 = <T as Debug>::fmt as *const u8;
}
pub trait Bar {
const BAR: *const u8;
}
pub trait Baz {
type Data: Debug;
}
pub struct BarStruct<S: Baz>(S);
impl<S: Baz> Bar for BarStruct<S> {
const BAR: *const u8 = <Debug as Foo<<S as Baz>::Data>>::FOO;
}
struct AnotherStruct;
#[derive(Debug)]
struct SomeStruct;
impl Baz for AnotherStruct {
type Data = SomeStruct;
}
fn main() {
let _x = <BarStruct<AnotherStruct> as Bar>::BAR;
}I expected to see this happen: compiler not to crash
Instead, this happened: compiler crashed with:
error: internal compiler error: src/librustc_traits/normalize_erasing_regions.rs:53: could not fully normalize `for<'r, 's, 't0> fn(&'r <S as Baz>::Data, &'s mut std::fmt::Formatter<'t0>) -> std::result::Result<(), std::fmt::Error>`
thread 'main' panicked at 'Box<Any>', src/librustc_errors/lib.rs:600:9
query stack during panic:
#0 [normalize_ty_after_erasing_regions] normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All }, value: for<'r, 's, 't0> fn(&'r <S as Baz>::Data, &'s mut std::fmt::Formatter<'t0>) -> std::result::Result<(), std::fmt::Error> }`
#1 [const_eval_raw] const-evaluating `<(dyn std::fmt::Debug + 'static) as Foo<T>>::FOO`
--> src/main.rs:22:26
|
22 | const BAR: *const u8 = <Debug as Foo<<S as Baz>::Data>>::FOO;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#2 [optimized_mir] processing `<BarStruct<S> as Bar>::BAR`
#3 [const_eval_raw] const-evaluating `<BarStruct<S> as Bar>::BAR`
--> src/main.rs:34:12
|
34 | let _x = <BarStruct<AnotherStruct> as Bar>::BAR;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#4 [optimized_mir] processing `main`
#5 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to previous error
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Playground nightly: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=59adf803ef87a6d4b1251408811542dd
Playground stable: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=59adf803ef87a6d4b1251408811542dd