From fc0b466fd47ebe7f40a08276cbb26ef1f5657fce Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Sun, 22 Dec 2013 14:17:48 -0800
Subject: [PATCH] librustc: De-`@mut` `all_loans` in the borrow checker

---
 .../middle/borrowck/gather_loans/mod.rs        | 16 ++++++++++------
 src/librustc/middle/borrowck/mod.rs            | 18 ++++++++++--------
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/src/librustc/middle/borrowck/gather_loans/mod.rs b/src/librustc/middle/borrowck/gather_loans/mod.rs
index 7cf07b38d30b..36e35760400d 100644
--- a/src/librustc/middle/borrowck/gather_loans/mod.rs
+++ b/src/librustc/middle/borrowck/gather_loans/mod.rs
@@ -26,6 +26,7 @@ use middle::ty;
 use util::common::indenter;
 use util::ppaux::{Repr};
 
+use std::cell::RefCell;
 use syntax::ast;
 use syntax::ast_util::id_range;
 use syntax::codemap::Span;
@@ -68,7 +69,7 @@ struct GatherLoanCtxt<'a> {
     bccx: &'a BorrowckCtxt,
     id_range: id_range,
     move_data: @move_data::MoveData,
-    all_loans: @mut ~[Loan],
+    all_loans: @RefCell<~[Loan]>,
     item_ub: ast::NodeId,
     repeating_ids: ~[ast::NodeId]
 }
@@ -103,11 +104,11 @@ impl<'a> visit::Visitor<()> for GatherLoanCtxt<'a> {
 pub fn gather_loans(bccx: &BorrowckCtxt,
                     decl: &ast::fn_decl,
                     body: ast::P<ast::Block>)
-                    -> (id_range, @mut ~[Loan], @move_data::MoveData) {
+                    -> (id_range, @RefCell<~[Loan]>, @move_data::MoveData) {
     let mut glcx = GatherLoanCtxt {
         bccx: bccx,
         id_range: id_range::max(),
-        all_loans: @mut ~[],
+        all_loans: @RefCell::new(~[]),
         item_ub: body.id,
         repeating_ids: ~[body.id],
         move_data: @MoveData::new()
@@ -511,9 +512,9 @@ impl<'a> GatherLoanCtxt<'a> {
                     self.mark_loan_path_as_mutated(loan_path);
                 }
 
-                let all_loans = &mut *self.all_loans; // FIXME(#5074)
+                let all_loans = self.all_loans.borrow();
                 Loan {
-                    index: all_loans.len(),
+                    index: all_loans.get().len(),
                     loan_path: loan_path,
                     cmt: cmt,
                     mutbl: req_mutbl,
@@ -531,7 +532,10 @@ impl<'a> GatherLoanCtxt<'a> {
         // let loan_path = loan.loan_path;
         // let loan_gen_scope = loan.gen_scope;
         // let loan_kill_scope = loan.kill_scope;
-        self.all_loans.push(loan);
+        {
+            let mut all_loans = self.all_loans.borrow_mut();
+            all_loans.get().push(loan);
+        }
 
         // if loan_gen_scope != borrow_id {
             // FIXME(#6268) Nested method calls
diff --git a/src/librustc/middle/borrowck/mod.rs b/src/librustc/middle/borrowck/mod.rs
index dd886b3054e8..61e5d1f25fe7 100644
--- a/src/librustc/middle/borrowck/mod.rs
+++ b/src/librustc/middle/borrowck/mod.rs
@@ -133,16 +133,18 @@ fn borrowck_fn(this: &mut BorrowckCtxt,
             // Check the body of fn items.
             let (id_range, all_loans, move_data) =
                 gather_loans::gather_loans(this, decl, body);
-            let mut loan_dfcx =
-                DataFlowContext::new(this.tcx,
-                                     this.method_map,
-                                     LoanDataFlowOperator,
-                                     id_range,
-                                     all_loans.len());
-            for (loan_idx, loan) in all_loans.iter().enumerate() {
+
+            let all_loans = all_loans.borrow();
+            let mut loan_dfcx = DataFlowContext::new(this.tcx,
+                                                     this.method_map,
+                                                     LoanDataFlowOperator,
+                                                     id_range,
+                                                     all_loans.get().len());
+            for (loan_idx, loan) in all_loans.get().iter().enumerate() {
                 loan_dfcx.add_gen(loan.gen_scope, loan_idx);
                 loan_dfcx.add_kill(loan.kill_scope, loan_idx);
             }
+
             loan_dfcx.propagate(body);
 
             let flowed_moves = move_data::FlowedMoveData::new(move_data,
@@ -152,7 +154,7 @@ fn borrowck_fn(this: &mut BorrowckCtxt,
                                                               body);
 
             check_loans::check_loans(this, &loan_dfcx, flowed_moves,
-                                     *all_loans, body);
+                                     *all_loans.get(), body);
         }
     }