add borrows to NLL MIR dumps

Author: lqd

compiler/rustc_borrowck/src/lib.rs

@@ -229,7 +229,7 @@ fn do_mir_borrowck<'tcx>(
 
     // Dump MIR results into a file, if that is enabled. This let us
     // write unit-tests, as well as helping with debugging.
-    nll::dump_nll_mir(&infcx, body, &regioncx, &opt_closure_req);
+    nll::dump_nll_mir(&infcx, body, &regioncx, &opt_closure_req, &borrow_set);
 
     // We also have a `#[rustc_regions]` annotation that causes us to dump
     // information.

compiler/rustc_borrowck/src/nll.rs

@@ -223,6 +223,7 @@ pub(super) fn dump_nll_mir<'tcx>(
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,
     closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
+    borrow_set: &BorrowSet<'tcx>,
 ) {
     if !dump_enabled(infcx.tcx, "nll", body.source.def_id()) {
         return;
@@ -254,6 +255,18 @@ pub(super) fn dump_nll_mir<'tcx>(
                         )?;
                         writeln!(out, "|")?;
                     }
+
+                    if borrow_set.len() > 0 {
+                        writeln!(out, "| Borrows")?;
+                        for (borrow_idx, borrow_data) in borrow_set.iter_enumerated() {
+                            writeln!(
+                                out,
+                                "| {:?}: issued at {:?} in {:?}",
+                                borrow_idx, borrow_data.reserve_location, borrow_data.region
+                            )?;
+                        }
+                        writeln!(out, "|")?;
+                    }
                 }
 
                 PassWhere::BeforeLocation(_) => {}