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incorrect FromEnv predicates around supertraits #49953
Description
The predicates for supertraits look wrong, as you can see from this example:
#![feature(rustc_attrs)]
#![allow(dead_code)]
trait Foo { }
#[rustc_dump_program_clauses] //~ ERROR program clause dump
trait Bar: Foo { }I see this:
error: program clause dump
--> lower_env1.rs:16:1
|
16 | #[rustc_dump_program_clauses] //~ ERROR program clause dump
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: Implemented(Self: Bar) :- FromEnv(Self: Bar).
= note: FromEnv(Self: Bar) :- FromEnv(Self: Bar).
But I expect FromEnv(Self: Foo) :- FromEnv(Self: Bar).
cc @rust-lang/wg-traits
Activity
scalexm commentedon Apr 13, 2018
Could it be because of the fact that for the moment, we unconditionally skip the first predicate (because it’s supposed to be
Self: Bar)? Maybe in that case we are actually skipping theSelf: Foopredicate?scalexm commentedon Apr 13, 2018
cc @tmandry
tmandry commentedon Apr 13, 2018
Yeah I strongly suspect you are correct @scalexm. It looks like that hack doesn't work in all cases. I'm working to remove the
Self: Foofrompredicates_ofso the hack isn't necessary, but if we want a fix now, it should be possible to run through all the predicates and filter out the one that matchesSelf: Foo. I'll try to submit one of those fixes tomorrow, if possible.scalexm commentedon Oct 2, 2018
Closed by #51895.