Add InferCtxt::with_opaque_type_inference to get_body_with_borrowck_facts

[willcrichton]

mir_borrowck uses with_opaque_type_inference before calling do_mir_borrowck:

rust/compiler/rustc_borrowck/src/lib.rs

Line 132 in 0eabf25

let opt_closure_req = tcx.infer_ctxt().with_opaque_type_inference(def.did).enter(|infcx| {

However get_body_with_borrowck_facts does not. Therefore I get an ICE eg when calling this function on the bodies of an async function as described here: https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/.E2.9C.94.20ICE.20when.20using.20get_body_with_borrowck_facts.20with.20async

This change fixes that bug.

r? @nikomatsakis

[oli-obk]

r? @oli-obk

ah, yea I missed this call site.

independently of that, I am not convinced anymore that this is the right way to do this, it may cause problems with global caching, as it's not information tracked in the ParamEnv. But that is something I need to investigate.

@bors r+ rollup

[bors]

📌 Commit 549a68b has been approved by oli-obk