Add MirBorrowckCtxt::new.

It is boilerplate-y , but it also factors out some icky duplication of
field setting at the two call sites, so I think it's worth it.

Author: nnethercote

compiler/rustc_borrowck/src/lib.rs

@@ -266,30 +266,21 @@ fn do_mir_borrowck<'tcx>(
         use rustc_middle::mir::visit::Visitor;
 
         let promoted_body = &promoted[idx];
-        let mut promoted_mbcx = MirBorrowckCtxt {
-            infcx: &infcx,
+        let mut promoted_mbcx = MirBorrowckCtxt::new(
+            &infcx,
             param_env,
-            body: promoted_body,
-            move_data: &move_data,
-            location_table: &location_table, // no need to create a real one for the promoted, it is not used
+            promoted_body,
+            &move_data,
+            &location_table, // no need to create a real one for the promoted, it is not used
             movable_coroutine,
-            fn_self_span_reported: Default::default(),
             locals_are_invalidated_at_exit,
-            access_place_error_reported: Default::default(),
-            reservation_error_reported: Default::default(),
-            uninitialized_error_reported: Default::default(),
-            regioncx: &regioncx,
-            used_mut: Default::default(),
-            used_mut_upvars: SmallVec::new(),
-            borrow_set: &borrow_set,
-            upvars: &[],
-            local_names: IndexVec::from_elem(None, &promoted_body.local_decls),
-            region_names: RefCell::default(),
-            next_region_name: RefCell::new(1),
-            polonius_output: None,
-            move_errors: Vec::new(),
+            &regioncx,
+            &borrow_set,
+            &[],                                                   // upvars
+            IndexVec::from_elem(None, &promoted_body.local_decls), // local_names
+            None,                                                  // polonius_output
             diags,
-        };
+        );
         MoveVisitor { ctxt: &mut promoted_mbcx }.visit_body(promoted_body);
         promoted_mbcx.report_move_errors();
         diags = promoted_mbcx.diags;
@@ -307,30 +298,21 @@ fn do_mir_borrowck<'tcx>(
         }
     }
 
-    let mut mbcx = MirBorrowckCtxt {
-        infcx: &infcx,
+    let mut mbcx = MirBorrowckCtxt::new(
+        &infcx,
         param_env,
         body,
-        move_data: &move_data,
-        location_table: &location_table,
+        &move_data,
+        &location_table,
         movable_coroutine,
         locals_are_invalidated_at_exit,
-        fn_self_span_reported: Default::default(),
-        access_place_error_reported: Default::default(),
-        reservation_error_reported: Default::default(),
-        uninitialized_error_reported: Default::default(),
-        regioncx: &regioncx,
-        used_mut: Default::default(),
-        used_mut_upvars: SmallVec::new(),
-        borrow_set: &borrow_set,
-        upvars: tcx.closure_captures(def),
+        &regioncx,
+        &borrow_set,
+        tcx.closure_captures(def), // upvars
         local_names,
-        region_names: RefCell::default(),
-        next_region_name: RefCell::new(1),
         polonius_output,
-        move_errors: Vec::new(),
         diags,
-    };
+    );
 
     // Compute and report region errors, if any.
     mbcx.report_region_errors(nll_errors);
@@ -584,6 +566,49 @@ struct MirBorrowckCtxt<'a, 'infcx, 'tcx> {
     move_errors: Vec<MoveError<'tcx>>,
 }
 
+impl<'a, 'infcx, 'tcx> MirBorrowckCtxt<'a, 'infcx, 'tcx> {
+    fn new(
+        infcx: &'infcx BorrowckInferCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+        body: &'a Body<'tcx>,
+        move_data: &'a MoveData<'tcx>,
+        location_table: &'a LocationTable,
+        movable_coroutine: bool,
+        locals_are_invalidated_at_exit: bool,
+        regioncx: &'a RegionInferenceContext<'tcx>,
+        borrow_set: &'a BorrowSet<'tcx>,
+        upvars: &'tcx [&'tcx ty::CapturedPlace<'tcx>],
+        local_names: IndexVec<Local, Option<Symbol>>,
+        polonius_output: Option<Box<PoloniusOutput>>,
+        diags: diags::BorrowckDiags<'infcx, 'tcx>,
+    ) -> Self {
+        MirBorrowckCtxt {
+            infcx,
+            param_env,
+            body,
+            move_data,
+            location_table,
+            movable_coroutine,
+            locals_are_invalidated_at_exit,
+            access_place_error_reported: Default::default(),
+            reservation_error_reported: Default::default(),
+            fn_self_span_reported: Default::default(),
+            uninitialized_error_reported: Default::default(),
+            used_mut: Default::default(),
+            used_mut_upvars: SmallVec::new(),
+            regioncx,
+            borrow_set,
+            upvars,
+            local_names,
+            region_names: RefCell::default(),
+            next_region_name: RefCell::new(1),
+            polonius_output,
+            diags,
+            move_errors: Vec::new(),
+        }
+    }
+}
+
 // Check that:
 // 1. assignments are always made to mutable locations (FIXME: does that still really go here?)
 // 2. loans made in overlapping scopes do not conflict