librustc: Disallow &mut loans from overlapping with any other loans

Author: pcwalton

src/librustc/middle/borrowck/check_loans.rs

@@ -296,12 +296,11 @@ impl check_loan_ctxt {
         }
 
         match (old_loan.mutbl, new_loan.mutbl) {
-            (m_const, _) | (_, m_const) |
-            (m_mutbl, m_mutbl) | (m_imm, m_imm) => {
+            (m_const, _) | (_, m_const) | (m_imm, m_imm) => {
                 /*ok*/
             }
 
-            (m_mutbl, m_imm) | (m_imm, m_mutbl) => {
+            (m_mutbl, m_mutbl) | (m_mutbl, m_imm) | (m_imm, m_mutbl) => {
                 self.bccx.span_err(
                     new_loan.cmt.span,
                     fmt!("loan of %s as %s \
@@ -418,8 +417,8 @@ impl check_loan_ctxt {
 
         for self.walk_loans_of(ex.id, lp) |loan| {
             match loan.mutbl {
-              m_mutbl | m_const => { /*ok*/ }
-              m_imm => {
+              m_const => { /*ok*/ }
+              m_mutbl | m_imm => {
                 self.bccx.span_err(
                     ex.span,
                     fmt!("%s prohibited due to outstanding loan",

src/librustc/middle/borrowck/loan.rs

@@ -251,7 +251,7 @@ impl LoanContext {
         // Variant components: the base must be immutable, because
         // if it is overwritten, the types of the embedded data
         // could change.
-        do self.loan(cmt_base, m_imm).chain |_ok| {
+        do self.loan(cmt_base, m_imm).chain |_| {
             // can use static, as in loan_stable_comp()
             self.issue_loan(cmt, ty::re_static, req_mutbl)
         }

src/libstd/sort.rs

@@ -630,9 +630,15 @@ impl<T: Copy Ord> MergeState<T> {
                 dest -= 1; c2 -= 1; len2 -= 1;
                 if len2 == 1 { break_outer = true; break; }
 
-                let tmp_view = vec::mut_view(tmp, 0, len2);
-                let count2 = len2 - gallop_left(&const array[c1],
-                                                tmp_view, len2-1);
+                let count2;
+                {
+                    let tmp_view = vec::mut_view(tmp, 0, len2);
+                    count2 = len2 - gallop_left(&const array[c1],
+                                                tmp_view,
+                                                len2-1);
+                    // Make tmp_view go out of scope to appease borrowck.
+                }
+
                 if count2 != 0 {
                     dest -= count2; c2 -= count2; len2 -= count2;
                     copy_vec(array, dest+1, tmp, c2+1, count2);

src/test/run-pass/alt-implicit-copy-unique.rs

@@ -12,7 +12,7 @@ fn main() {
     let x = ~{mut a: ~10, b: ~20};
     match x {
       ~{a: ref mut a, b: ref b} => {
-        assert **a == 10; (*x).a = ~30; assert **a == 30;
+        assert **a == 10; *a = ~30; assert **a == 30;
       }
     }
 }