librustc: De-`@mut` the borrow check's root map

src/librustc/middle/borrowck/gather_loans/lifetime.rs

@@ -279,7 +279,9 @@ fn check_root(&self,
         // Add a record of what is required
         let rm_key = root_map_key {id: cmt_deref.id, derefs: derefs};
         let root_info = RootInfo {scope: root_scope, freeze: opt_dyna};
-        self.bccx.root_map.insert(rm_key, root_info);
+
+        let mut root_map = self.bccx.root_map.borrow_mut();
+        root_map.get().insert(rm_key, root_info);
 
         debug!("root_key: {:?} root_info: {:?}", rm_key, root_info);
         Ok(())

src/librustc/middle/borrowck/mod.rs

@@ -20,6 +20,7 @@
 use util::common::stmt_set;
 use util::ppaux::{note_and_explain_region, Repr, UserString};
 
+use std::cell::RefCell;
 use std::hashmap::{HashSet, HashMap};
 use std::ops::{BitOr, BitAnd};
 use std::result::{Result};
@@ -413,10 +414,10 @@ pub struct RootInfo {
     freeze: Option<DynaFreezeKind> // Some() if we should freeze box at runtime
 }
 
-pub type root_map = @mut HashMap<root_map_key, RootInfo>;
+pub type root_map = @RefCell<HashMap<root_map_key, RootInfo>>;
 
 pub fn root_map() -> root_map {
-    return @mut HashMap::new();
+    return @RefCell::new(HashMap::new());
 }
 
 pub enum DynaFreezeKind {

src/librustc/middle/const_eval.rs

@@ -19,6 +19,7 @@
 use syntax::visit::Visitor;
 use syntax::ast::*;
 
+use std::cell::RefCell;
 use std::hashmap::{HashMap, HashSet};
 
 //
@@ -119,7 +120,7 @@ fn variant_expr(variants: &[ast::P<ast::variant>], id: ast::NodeId) -> Option<@E
             }
         }
         let maps = astencode::Maps {
-            root_map: @mut HashMap::new(),
+            root_map: @RefCell::new(HashMap::new()),
             method_map: @mut HashMap::new(),
             vtable_map: @mut HashMap::new(),
             write_guard_map: @mut HashSet::new(),
@@ -169,7 +170,7 @@ pub fn lookup_const_by_id(tcx: ty::ctxt,
             }
         }
         let maps = astencode::Maps {
-            root_map: @mut HashMap::new(),
+            root_map: @RefCell::new(HashMap::new()),
             method_map: @mut HashMap::new(),
             vtable_map: @mut HashMap::new(),
             write_guard_map: @mut HashSet::new(),

src/librustc/middle/trans/_match.rs

@@ -1112,7 +1112,8 @@ fn pats_require_rooting(bcx: @Block,
     m.iter().any(|br| {
         let pat_id = br.pats[col].id;
         let key = root_map_key {id: pat_id, derefs: 0u };
-        bcx.ccx().maps.root_map.contains_key(&key)
+        let root_map = bcx.ccx().maps.root_map.borrow();
+        root_map.get().contains_key(&key)
     })
 }
 

src/librustc/middle/trans/write_guard.rs

@@ -45,9 +45,12 @@ pub fn root_and_write_guard(datum: &Datum,
     //
     // (Note: root'd values are always boxes)
     let ccx = bcx.ccx();
-    bcx = match ccx.maps.root_map.find(&key) {
-        None => bcx,
-        Some(&root_info) => root(datum, bcx, span, key, root_info)
+    bcx = {
+        let root_map = ccx.maps.root_map.borrow();
+        match root_map.get().find(&key) {
+            None => bcx,
+            Some(&root_info) => root(datum, bcx, span, key, root_info)
+        }
     };
 
     // Perform the write guard, if necessary.