Handle patterns within closures

[roxelo]

Using the following test:

#![feature(capture_disjoint_fields)]

fn main() {
    let _z = 9;
    let t = (String::new(), String::new());

    let _c = ||  {
          let (_t1, _) = t;
    };
}

The relevant log output is as follows:

DEBUG rustc_typeck::check::upvar RFC2229 = upvar.rs Initialized delegate InferBorrowKind
DEBUG rustc_typeck::expr_use_visitor RFC2229 = expr_use_visitor.rs walk_pat introduce fake_read
DEBUG rustc_typeck::check::upvar RFC2229 = upvar.rs Adding fake read PlaceWithHirId { hir_id: HirId { owner: DefId(0:3 ~ rox[317d]::main), local_id: 20 }, place: Place { base_ty: (std::string::String, std
DEBUG rustc_typeck::check::upvar RFC2229 = upvar.rs write results out to typeck_results
DEBUG rustc_typeck::check::writeback RFC2229 = writeback.rs call visit_fake_read_map()
DEBUG rustc_typeck::check::writeback RFC2229 = writeback.rs visit_fake_reads_map
DEBUG rustc_mir_build::thir::cx::expr RFC2229 = Closure expr.rs ExprKind::Closure
DEBUG rustc_mir_build::thir::cx::expr RFC2229 = closure_fake_read {DefId(0:4 ~ rox[317d]::main::{closure#0}): [Place { base_ty: (std::string::String, std::string::String), base: Upvar(UpvarId(HirId { owner: DefId(0:3 ~ rox[317d]::main), local_id: 17 };`t`;DefId(0:4 ~ rox[317d]::main::{closure#0}))), projections: [] }]}
DEBUG rustc_mir_build::build::expr::as_rvalue RFC2229 = as_rvalue.rs ExprKind::Closure
DEBUG rustc_mir_build::build::expr::as_rvalue RFC2229 = as_rvalue.rs Place { base_ty: (std::string::String, std::string::String), base: Upvar(UpvarId(HirId { owner: DefId(0:3 ~ rox[317d]::main), local_id: 17 };`t`;DefId(0:4 ~ rox[317d]::main::{closure#0}))), projections: [] }
DEBUG rustc_mir_build::build::expr::as_rvalue RFC2229 = as_rvalue pushing following fake_read HirId { owner: DefId(0:3 ~ rox[317d]::main), local_id: 17 }
DEBUG rustc_mir_build::build::expr::as_rvalue RFC2229 = as_rvalue pushing following mir_place _2
DEBUG rustc_mir_build::build::expr::as_rvalue RFC2229 = as_rvalue.rs ExprKind::Closure fake_read processing over

[arora-aman]

Just things that I feel need to chage. Will do nits later

[arora-aman]

There are two fake read causes. One ForLet and one ForMatch. We probably should capture the correct one. I don't think it will be too much work to do that, but I think if this works fine for now, we should delay that until we fix bugs/ we get close to getting this to work.

[arora-aman]

initial set of comments

[arora-aman]

Did you get a chance to try HashSet, because in case of

let c = || {
   let (t1, _) = t;
   let (_, t2) = t;
}

we will introduce 2 fake reads, when one should suffice

[arora-aman]

Note to self: Read this logic properly

[arora-aman]

is this needed?

[roxelo]

Yes,

error[E0603]: module `as_place` is private
  --> compiler/rustc_mir_build/src/build/mod.rs:2:25
   |
2  | use crate::build::expr::as_place::PlaceBuilder;
   |                         ^^^^^^^^ private module
   |
note: the module `as_place` is defined here
  --> compiler/rustc_mir_build/src/build/expr/mod.rs:65:1
   |
65 | mod as_place;
   | ^^^^^^^^^^^^^

error[E0603]: module `as_place` is private
  --> compiler/rustc_mir_build/src/build/matches/mod.rs:8:25
   |
8  | use crate::build::expr::as_place::PlaceBuilder;
   |                         ^^^^^^^^ private module
   |
note: the module `as_place` is defined here
  --> compiler/rustc_mir_build/src/build/expr/mod.rs:65:1
   |
65 | mod as_place;
   | ^^^^^^^^^^^^^

error[E0603]: module `as_place` is private
  --> compiler/rustc_mir_build/src/build/matches/simplify.rs:15:25
   |
15 | use crate::build::expr::as_place::PlaceBuilder;
   |                         ^^^^^^^^ private module
   |
note: the module `as_place` is defined here
  --> compiler/rustc_mir_build/src/build/expr/mod.rs:65:1
   |
65 | mod as_place;
   | ^^^^^^^^^^^^^

error[E0603]: module `as_place` is private
  --> compiler/rustc_mir_build/src/build/matches/test.rs:8:25
   |
8  | use crate::build::expr::as_place::PlaceBuilder;
   |                         ^^^^^^^^ private module
   |
note: the module `as_place` is defined here
  --> compiler/rustc_mir_build/src/build/expr/mod.rs:65:1
   |
65 | mod as_place;
   | ^^^^^^^^^^^^^

error[E0603]: module `as_place` is private
  --> compiler/rustc_mir_build/src/build/matches/util.rs:1:25
   |
1  | use crate::build::expr::as_place::PlaceBuilder;
   |                         ^^^^^^^^ private module
   |
note: the module `as_place` is defined here
  --> compiler/rustc_mir_build/src/build/expr/mod.rs:65:1
   |
65 | mod as_place;
   | ^^^^^^^^^^^^^

error: aborting due to 5 previous errors

[roxelo]

Opened PR on rust-lang rust-lang#82536