Fixes rust-lang#67639 `Instance.ty` assumes that we are in a fully monomorphic context (e.g. codegen), and can therefore use an empty `ParamEnv` when performing normalization. Howver, the MIR constant evaluator code ends up calling `Instance.ty` as a result of us attemptign to 'speculatively' const-evaluate generic functions during const propagation. As a result, we may end up with projections involving type parameters (e.g. <T as MyTrait>::Bar>) in the type we are trying to normalize. Normalization expects us to have proper predicates in the `ParamEnv` for such projections, and will ICE if we don't. This commit adds a new method `Instance.ty_env`, which takes a `ParamEnv` for use during normalization. The MIR const-evaluator code is changed to use this method, passing in the proper `ParamEnv` for the context at hand.

Commits

Commits on Jan 5, 2020

Fix ICE involving calling Instance.ty during const evaluation

Change 'panic!' to 'bug!'

Run rustfmt

s/projections/params/

Rename Instance.ty to Instance.monomorphic_ty

Fix typo

Use Instance.ty_env instead of Instance.monomorphic_ty in interpreter

Fix ICE involving calling `Instance.ty` during const evaluation